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Shin-Yi Lin C, Howells J, Rutkove S, Nandedkar S, Neuwirth C, Noto YI, Shahrizaila N, Whittaker RG, Bostock H, Burke D, Tankisi H. Neurophysiological and imaging biomarkers of lower motor neuron dysfunction in motor neuron diseases/amyotrophic lateral sclerosis: IFCN handbook chapter. Clin Neurophysiol 2024; 162:91-120. [PMID: 38603949 DOI: 10.1016/j.clinph.2024.03.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 02/07/2024] [Accepted: 03/12/2024] [Indexed: 04/13/2024]
Abstract
This chapter discusses comprehensive neurophysiological biomarkers utilised in motor neuron disease (MND) and, in particular, its commonest form, amyotrophic lateral sclerosis (ALS). These encompass the conventional techniques including nerve conduction studies (NCS), needle and high-density surface electromyography (EMG) and H-reflex studies as well as novel techniques. In the last two decades, new methods of assessing the loss of motor units in a muscle have been developed, that are more convenient than earlier methods of motor unit number estimation (MUNE),and may use either electrical stimulation (e.g. MScanFit MUNE) or voluntary activation (MUNIX). Electrical impedance myography (EIM) is another novel approach for the evaluation that relies upon the application and measurement of high-frequency, low-intensity electrical current. Nerve excitability techniques (NET) also provide insights into the function of an axon and reflect the changes in resting membrane potential, ion channel dysfunction and the structural integrity of the axon and myelin sheath. Furthermore, imaging ultrasound techniques as well as magnetic resonance imaging are capable of detecting the constituents of morphological changes in the nerve and muscle. The chapter provides a critical description of the ability of each technique to provide neurophysiological insight into the complex pathophysiology of MND/ALS. However, it is important to recognise the strengths and limitations of each approach in order to clarify utility. These neurophysiological biomarkers have demonstrated reliability, specificity and provide additional information to validate and assess lower motor neuron dysfunction. Their use has expanded the knowledge about MND/ALS and enhanced our understanding of the relationship between motor units, axons, reflexes and other neural circuits in relation to clinical features of patients with MND/ALS at different stages of the disease. Taken together, the ultimate goal is to aid early diagnosis, distinguish potential disease mimics, monitor and stage disease progression, quantify response to treatment and develop potential therapeutic interventions.
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Affiliation(s)
- Cindy Shin-Yi Lin
- Faculty of Medicine and Health, Central Clinical School, Brain and Mind Centre, University of Sydney, Sydney 2006, Australia.
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Seward Rutkove
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Sanjeev Nandedkar
- Natus Medical Inc, Middleton, Wisconsin, USA and Medical College of Wisconsin, Milwaukee, WI, USA
| | - Christoph Neuwirth
- Neuromuscular Diseases Unit/ALS Clinic, Kantonsspital, St. Gallen, Switzerland
| | - Yu-Ichi Noto
- Department of Neurology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Nortina Shahrizaila
- Division of Neurology, Department of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia
| | - Roger G Whittaker
- Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University., Newcastle Upon Tyne, United Kingdom
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom
| | - David Burke
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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Strunge K, Bostock H, Howells J, Cengiz B, Samusyte G, Koltzenburg M, Tankisi H. Caffeine and cortical excitability, as measured with paired-pulse transcranial magnetic stimulation. Muscle Nerve 2024; 69:206-212. [PMID: 38124685 DOI: 10.1002/mus.28027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 11/27/2023] [Accepted: 12/12/2023] [Indexed: 12/23/2023]
Abstract
INTRODUCTION/AIMS The transcranial magnetic stimulation tests of short-interval intracortical inhibition (SICI) by both conventional amplitude measurements (A-SICI) and threshold-tracking (T-SICI) are important methods to investigate intracortical inhibitory circuits, and T-SICI has been proposed to aid the diagnosis of amyotrophic lateral sclerosis. Beverages containing caffeine are widely consumed, and caffeine has been reported to affect cortical excitability. The aim of this study was to determine whether these SICI tests are affected by caffeine. METHODS Twenty-four healthy subjects (13 females, 11 males, aged from 19 to 31, mean: 26.2 ± 2.4 years) were studied in a single fixed-dose randomized double-blind placebo-controlled cross-over trial of 200 mg caffeine or placebo ingested as chewing gum. A-SICI and T-SICI, using parallel tracking (T-SICIp), were performed before and after chewing gum. RESULTS There was no significant change in SICI parameters after placebo in A-SICI (p > .10) or T-SICIp (p > .30), and no significant effect of caffeine was found on A-SICI (p > .10) or T-SICIp (p > .50) for any of the interstimulus intervals. DISCUSSION There is no need for caffeine abstention before measurements of SICI by either the T-SICI or A-SICI measurements.
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Affiliation(s)
- Kristine Strunge
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Hospital of Lithuanian University of Health Sciences Kauno Klinikos, Kaunas, Lithuania
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, London, UK
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
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Boran HE, Alaydın HC, Kılınç H, Tankişi H, Samusyte G, Howells J, Koltzenburg M, Cengiz B. Long-interval afferent inhibition measurement using two different methods: Normative values, repeatability and reliability. Neurophysiol Clin 2024; 54:102940. [PMID: 38382141 DOI: 10.1016/j.neucli.2023.102940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 12/20/2023] [Accepted: 12/20/2023] [Indexed: 02/23/2024] Open
Abstract
BACKGROUND The mechanism of Short-Latency Afferent Inhibition (SAI) is relatively well understood. In contrast, Long-Latency Afferent Inhibition (LAI) has not been as extensively studied as SAI, and its underlying mechanism remains unclear. OBJECTIVE/HYPOTHESIS This study had two primary objectives: first, to determine the optimal ISIs for LAI measured by amplitude changes (A-LAI) using high-resolution ISI ranges; and second, to compare measurements of LAI by threshold-tracking (T-LAI). METHODS Twenty-eight healthy volunteers (12 males aged 24- 45 years) participated in the study. Paired peripheral electrical and transcranial magnetic stimulation (TMS) stimuli (TS1mv) were applied at varying (ISIs)- 100, 200, 250, 300, 350, 400, 450, 500, 550, 600, 700, 800, 900, 1000 ms. RESULTS Both A-LAI and T-LAI showed that LAI decreased progressively from a peak at 200 or 250 ms to 1000 ms. Using the A-LAI method, pronounced inhibition was observed at three specific ISIs: 100 ms, 250 ms and 450 ms. When A-LAI values were converted to equivalent threshold changes, they did not differ significantly from T-LAI. Reliability at distinguishing individuals, as indicated by intraclass correlation coefficient (ICC) was greater for A-LAI, with a peak value of 0.82 at 250 ms. CONCLUSION(S) The study demonstrates that ISIs of 100 ms and 250 ms can be reliably used in amplitude measurement LAI. The study demonstrates that both LAI measurements record a similar decline of inhibition with increasing ISI.
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Affiliation(s)
- Hürrem Evren Boran
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500 Ankara, Turkey; Gazi University Neuropsychiatry of Education, Research and Application Center, Ankara, Turkey; NOROM, Neuroscience and Neurotechnology Center of Excellence, Ankara, Turkey
| | - Halil Can Alaydın
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500 Ankara, Turkey
| | - Hasan Kılınç
- Gazi University Neuropsychiatry of Education, Research and Application Center, Ankara, Turkey
| | - Hatice Tankişi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Ginte Samusyte
- Department of Neurology, Lithuanian University of Health Sciences, Hospital Kauno klinikos Kaunas, Lithuania; Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Martin Koltzenburg
- Department of Clinical and Movement Neuroscience, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom; Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG London, United Kingdom; Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500 Ankara, Turkey; Gazi University Neuropsychiatry of Education, Research and Application Center, Ankara, Turkey; NOROM, Neuroscience and Neurotechnology Center of Excellence, Ankara, Turkey.
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Tankisi H, Pia H, Strunge K, Howells J, Cengiz B, Samusyte G, Koltzenburg M, Fuglsang-Frederiksen A, Bostock H. Three different short-interval intracortical inhibition methods in early diagnosis of amyotrophic lateral sclerosis. Amyotroph Lateral Scler Frontotemporal Degener 2023; 24:139-147. [PMID: 35899374 DOI: 10.1080/21678421.2022.2101926] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Objectives: To compare the utility of conventional amplitude measurements of short-interval intracortical inhibition (A-SICI) with two threshold-tracking (T-SICI) methods, as aids to early diagnosis of amyotrophic lateral sclerosis (ALS). The new parallel threshold-tracking method (T-SICIp) was compared with the previously used serial tracking method (T-SICIs). Methods: 112 consecutive patients referred with the suspicion of ALS and 40 healthy controls were prospectively included. Based on clinical follow-up, patients were divided into 67 patients with motor neuron disease (MND) comprising progressive muscular atrophy (PMA) as well as ALS, and 45 patient controls. SICI was recorded from first dorsal interosseus muscle using the three different protocols. Results: MND patients had significantly reduced T-SICIp, T-SICIs and A-SICI, compared with healthy controls and patient controls, while healthy and patient controls were similar. Paradoxically, T-SICIp was least affected in MND patients with the most upper motor neuron (UMN) signs (Spearman ρ = 0.537, P < 0.0001) whereas there was no correlation for T-SICIs or A-SICI. T-SICIp also provided the best discrimination between patient controls and MND as determined by the receiver operating characteristic (ROC) curves. For patients with no UMN signs, area under ROC curve for 2-3ms inter-stimulus intervals was 0.931 for T-SICIp, 0.771 for T-SICIs and 0.786 for A-SICI. Conclusions: SICI is a sensitive measure for detection of cortical involvement in ALS patients. T-SICIp has higher sensitivity and specificity than T-SICIs and A-SICI, particularly in patients without any upper motor neuron signs.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Hossein Pia
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Kristine Strunge
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom, and
| | - Anders Fuglsang-Frederiksen
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London, United Kingdom
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Cengiz B, Boran HE, Alaydın HC, Tankisi H, Samusyte G, Howells J, Koltzenburg M, Bostock H. Short latency afferent inhibition: comparison between threshold-tracking and conventional amplitude recording methods. Exp Brain Res 2022; 240:1241-1247. [PMID: 35192042 DOI: 10.1007/s00221-022-06327-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 02/05/2022] [Indexed: 11/04/2022]
Abstract
Short-latency afferent inhibition (SAI), which is conventionally measured as a reduction in motor evoked potential amplitude (A-SAI), is of clinical interest as a potential biomarker for cognitive impairment. Since threshold-tracking has some advantages for clinical studies of short-interval cortical inhibition, we have compared A-SAI with a threshold-tracking alternative method (T-SAI). In the T-SAI method, inhibition was calculated by tracking the required TMS intensity for the targeted MEP amplitude (200 uV) both for the test (TMS only) and paired (TMS and peripheral stimulation) stimuli. A-SAI and T-SAI were recorded from 31 healthy subjects using ten stimuli at each of 12 inter-stimulus intervals, once in the morning and again in the afternoon. There were no differences between morning and afternoon recordings. When A-SAI was normalized by log conversion it was closely related to T-SAI. Between subjects, variability was similar for the two techniques, but within-subject variability was significantly smaller for normalized A-SAI. Conventional amplitude measurements appear more sensitive for detecting changes within-subjects, such as in interventional studies, but threshold-tracking may be as sensitive as detecting abnormal SAI in a patient.
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Affiliation(s)
- Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey.
| | - H Evren Boran
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - Halil Can Alaydın
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Martin Koltzenburg
- Department of Clinical and Movement Neuroscience, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK.,Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK
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Tankisi H, Cengiz B, Samusyte G, Howells J, Koltzenburg M, Bostock H. Short interval intracortical inhibition: Variability of amplitude and threshold-tracking measurements with 6 or 10 stimuli per point. Neurophysiol Clin 2022; 52:170-173. [PMID: 35000804 DOI: 10.1016/j.neucli.2021.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/18/2021] [Accepted: 11/16/2021] [Indexed: 10/19/2022] Open
Abstract
Reduced short-interval intracortical inhibition (SICI) in motor neuron disease has been demonstrated by amplitude changes (A-SICI) and threshold-tracking (T-SICI) using 10 stimuli per inter-stimulus interval (ISI). To test whether fewer stimuli would suffice, A-SICI and T-SICI were recorded twice from 30 healthy subjects using 6 and 10 stimuli per ISI. Using fewer stimuli increased mean A-SICI variances by 23.8% but the 7.3% increase in T-SICI variance was not significant. We conclude that our new parallel threshold-tracking SICI protocol, with 6 stimuli per ISI, can reduce time and stimulus numbers by 40% without appreciable loss of accuracy.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500 Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Martin Koltzenburg
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom; Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG London, United Kingdom
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom.
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Carroll AS, Howells J, Lin CS, Park SB, Simon N, Reilly MM, Vucic S, Kiernan MC. Differences in nerve excitability properties across upper limb sensory and motor axons. Clin Neurophysiol 2021; 136:138-149. [DOI: 10.1016/j.clinph.2021.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/16/2021] [Accepted: 12/07/2021] [Indexed: 11/24/2022]
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Kariyawasam DST, D'Silva AM, Herbert K, Howells J, Carey K, Kandula T, Farrar MA, Lin CSY. Axonal excitability changes in children with spinal muscular atrophy treated with nusinersen. J Physiol 2021; 600:95-109. [PMID: 34783018 DOI: 10.1113/jp282249] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 11/05/2021] [Indexed: 11/08/2022] Open
Abstract
Spinal muscular atrophy (SMA) is associated with developmental disruption of motor axons in ventral roots of the spinal cord alongside motor axon degeneration. The pathogenesis of peripheral axonal change during development is pertinent to understand treatment response. Nerve excitability techniques, stimulating the median motor nerve at the wrist, were utilised to investigate axonal change during neurodevelopment in 24 children with SMA, compared with 71 age-matched controls. Longitudinal axonal response to nusinersen treatment in 18 children was also investigated. Significant differences in axonal development were noted in the youngest children with SMA, signified by reduced compound muscle action potential (CMAP) (P = 0.030), higher axonal threshold (P = 0.016), rheobase (minimal current amplitude of infinite duration, required to generate an action potential) (P = 0.012) and greater changes in depolarising and hyperpolarising threshold electrotonus. Subexcitability increased in all children with SMA, compared to controls. With treatment, nerve excitability changes were observed prominently in young children, with increases in CMAP, reduction in axonal threshold, fanning-in of threshold electrotonus, increase in resting current-threshold slope and reduction in subexcitability. Whilst motor axons continue to mature in SMA, developmental delays in passive and active membrane properties occur especially in early childhood. Concurrently, motor axons actively undergo degeneration. Nusinersen restores the developmental trajectory of motor axons reducing degeneration, especially in children with early treatment initiation. Our findings move the field forward in understanding the developmental aspect of childhood-onset motor neurone diseases and changes in axonal function associated with disease modification. KEY POINTS: Pathomechanisms in spinal muscular atrophy involve concurrent neurodevelopmental and neurodegenerative processes. The greatest delays in maturation of the passive and active properties of the peripheral motor axon are seen in early childhood. Nusinersen facilitates developmental recovery of the motor axon whilst also reducing neurodegeneration. Axonal dysfunction is reversed with SMN repletion particularly when intervention occurs early in development.
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Affiliation(s)
- Didu S T Kariyawasam
- Department of Neurology, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia.,School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Arlene M D'Silva
- School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Karen Herbert
- Department of Physiotherapy, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Kate Carey
- School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Tejaswi Kandula
- Department of Neurology, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia
| | - Michelle A Farrar
- Department of Neurology, Randwick, Sydney Children's Hospital, Sydney, New South Wales, Australia.,School of Women's and Children's Health, University of New South Wales Medicine and Health, University of New South Wales, Sydney, New South Wales, Australia
| | - Cindy Shin-Yi Lin
- Translational Research Collective, Faculty of Medicine and Health, Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia
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Tankisi H, Howells J, Cengiz B, Samusyte G, Koltzenburg M, Bostock H. Conventional and Threshold-Tracking Transcranial Magnetic Stimulation Tests for Single-handed Operation. J Vis Exp 2021. [PMID: 34459814 DOI: 10.3791/62787] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Most single-pulse transcranial magnetic stimulation (TMS) parameters (e.g., motor threshold, stimulus-response function, cortical silent period) are used to examine corticospinal excitability. Paired-pulse TMS paradigms (e.g., short- and long-interval intracortical inhibition (SICI/LICI), short-interval intracortical facilitation (SICF), and short- and long-latency afferent inhibition (SAI/LAI)) provide information about intracortical inhibitory and facilitatory networks. This has long been done by the conventional TMS method of measuring changes in the size of the motor-evoked potentials (MEPs) in response to stimuli of constant intensity. An alternative threshold-tracking approach has recently been introduced whereby the stimulus intensity for a target amplitude is tracked. The diagnostic utility of threshold-tracking SICI in amyotrophic lateral sclerosis (ALS) has been shown in previous studies. However, threshold-tracking TMS has only been used in a few centers, in part due to the lack of readily available software but also perhaps due to uncertainty over its relationship to conventional single- and paired-pulse TMS measurements. A menu-driven suite of semi-automatic programs has been developed to facilitate the broader use of threshold-tracking TMS techniques and to enable direct comparisons with conventional amplitude measurements. These have been designed to control three types of magnetic stimulators and allow recording by a single operator of the common single- and paired-pulse TMS protocols. This paper shows how to record a number of single- and paired-pulse TMS protocols on healthy subjects and analyze the recordings. These TMS protocols are fast and easy to perform and can provide useful biomarkers in different neurological disorders, particularly neurodegenerative diseases such as ALS.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital;
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery; Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology
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Tankisi H, Nielsen CSZ, Howells J, Cengiz B, Samusyte G, Koltzenburg M, Blicher JU, Møller AT, Pugdahl K, Fuglsang-Frederiksen A, de Carvalho M, Bostock H. Early diagnosis of amyotrophic lateral sclerosis by threshold tracking and conventional transcranial magnetic stimulation. Eur J Neurol 2021; 28:3030-3039. [PMID: 34233060 PMCID: PMC9291110 DOI: 10.1111/ene.15010] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 06/30/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE Short-interval intracortical inhibition by threshold tracking (T-SICI) has been proposed as a diagnostic tool for amyotrophic lateral sclerosis (ALS) but has not been compared directly with conventional amplitude measurements (A-SICI). This study compared A-SICI and T-SICI for sensitivity and clinical usefulness as biomarkers for ALS. METHODS In all, 104 consecutive patients referred with suspicion of ALS were prospectively included and were subsequently divided into 62 patients with motor neuron disease (MND) and 42 patient controls (ALS mimics) by clinical follow-up. T-SICI and A-SICI recorded in the first dorsal interosseus muscle (index test) were compared with recordings from 53 age-matched healthy controls. The reference standard was the Awaji criteria. Clinical scorings, conventional nerve conduction studies and electromyography were also performed on the patients. RESULTS Motor neuron disease patients had significantly reduced T-SICI and A-SICI compared with the healthy and patient control groups, which were similar. Sensitivity and specificity for discriminating MND patients from patient controls were high (areas under the receiver operating characteristic curves 0.762 and 0.810 for T-SICI and A-SICI respectively at 1-3.5 ms). Paradoxically, T-SICI was most reduced in MND patients with the fewest upper motor neuron (UMN) signs (Spearman ρ = 0.565, p = 4.3 × 10-6 ). CONCLUSIONS Amplitude-based measure of cortical inhibition and T-SICI are both sensitive measures for the detection of cortical involvement in MND patients and may help early diagnosis of ALS, with T-SICI most abnormal before UMN signs have developed. The gradation in T-SICI from pathological facilitation in patients with minimal UMN signs to inhibition in those with the most UMN signs may be due to progressive degeneration of the subset of UMNs experiencing facilitation.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | | | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, London, UK.,Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Jakob U Blicher
- Department of Neurology, Aarhus University Hospital, Aarhus, Denmark.,Centre of Functionally Integrated Neuroscience, Aarhus University, Aarhus, Denmark
| | - Anette T Møller
- Department of Neurology, Aarhus University Hospital, Aarhus, Denmark
| | - Kirsten Pugdahl
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | | | - Mamede de Carvalho
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Univeridade de Lisboa, Lisbon, Portugal.,Department of Neurosciences and Mental Health, Hospital de Santa Maria, Centro Hospitalar Universitário de Lisboa Norte, Lisbon, Portugal
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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11
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Agarwal S, Highton-Williamson E, Caga J, Howells J, Dharmadasa T, Matamala JM, Ma Y, Shibuya K, Hodges JR, Ahmed RM, Vucic S, Kiernan MC. Motor cortical excitability predicts cognitive phenotypes in amyotrophic lateral sclerosis. Sci Rep 2021; 11:2172. [PMID: 33500476 PMCID: PMC7838179 DOI: 10.1038/s41598-021-81612-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Accepted: 12/30/2020] [Indexed: 12/31/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are well-recognised as an extended disease spectrum. This study hypothesised that cortical hyperexcitability, an early pathophysiological abnormality in ALS, would distinguish cognitive phenotypes, as a surrogate marker of pathological disease burden. 61 patients with ALS, matched for disease duration (pure motor ALS, n = 39; ALS with coexistent FTD, ALS-FTD, n = 12; ALS with cognitive/behavioural abnormalities not meeting FTD criteria, ALS-Cog, n = 10) and 30 age-matched healthy controls. Cognitive function on the Addenbrooke's cognitive examination (ACE) scale, behavioural function on the motor neuron disease behavior scale (MiND-B) and cortical excitability using transcranial magnetic stimulation (TMS) were documented. Cortical resting motor threshold (RMT), lower threshold indicating hyperexcitability, was lower in ALS-FTD (50.2 ± 6.9) compared to controls (64.3 ± 12.6, p < 0.005), while ALS-Cog (63.3 ± 12.7) and ALS (60.8 ± 13.9, not significant) were similar to controls. Short interval intracortical inhibition (SICI) was reduced across all ALS groups compared to controls, indicating hyperexcitability. On receiver operating characteristic curve analysis, RMT differentiated ALS-FTD from ALS (area under the curve AUC = 0.745, p = 0.011). The present study has identified a distinct pattern of cortical excitability across cognitive phenotypes in ALS. As such, assessment of cortical physiology may provide more precise clinical prognostication in ALS.
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Affiliation(s)
- Smriti Agarwal
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia. .,Neurology Unit, A5, Box 165, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0QQ, UK.
| | | | - Jashelle Caga
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - James Howells
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - José M Matamala
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - Yan Ma
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - Kazumoto Shibuya
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - John R Hodges
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - Rebekah M Ahmed
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - Steve Vucic
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre and Sydney Medical School, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, NSW, Australia
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12
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Ørskov S, Bostock H, Howells J, Pugdahl K, Fuglsang-Frederiksen A, Nielsen CSZ, Cengiz B, Samusyte G, Koltzenburg M, Tankisi H. Comparison of figure-of-8 and circular coils for threshold tracking transcranial magnetic stimulation measurements. Neurophysiol Clin 2021; 51:153-160. [PMID: 33468370 DOI: 10.1016/j.neucli.2021.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/05/2021] [Accepted: 01/05/2021] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVES The transcranial magnetic stimulation (TMS) technique of threshold-tracking short-interval intracortical inhibition (T-SICI) has been proposed as a diagnostic tool for amyotrophic lateral sclerosis (ALS). Most of these studies have used a circular coil, whereas a figure-of-8 coil is usually recommended for paired-pulse TMS measurements. The aim of this study was to compare figure-of-8 and circular coils for T-SICI in the upper limb, with special attention to reproducibility, and the pain or discomfort experienced by the subjects. METHODS Twenty healthy subjects (aged: 45.5 ± 6.7, mean ± SD, 9 females, 11 males) underwent two examinations with each coil, in morning and afternoon sessions on the same day, with T-SICI measured at interstimulus intervals (ISIs) from 1-7 ms. After each examination the subjects rated degree of pain/discomfort from 0 to 10 using a numerical rating scale (NRS). RESULTS Mean T-SICI was higher for the figure-of-8 than for the circular coil at ISI of 2 ms (p < 0.05) but did not differ at other ISIs. Intra-subject variability did not differ between coils, but mean inhibition from 1-3.5 ms was less variable between subjects with the figure-of-8 coil (SD 7.2% vs. 11.2% RMT, p < 0.05), and no such recordings were without inhibition (vs. 6 with the circular coil). The subjects experienced less pain/discomfort with the figure-of-8 coil (mean NRS: 1.9 ± 1.28 vs 2.8 ± 1.60, p < 0.005). DISCUSSION The figure-of-8 coil may have better applicability in patients, due to the lower incidence of lack of inhibition in healthy subjects, and the lower experience of pain or discomfort.
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Affiliation(s)
- Søren Ørskov
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Hugh Bostock
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, United Kingdom
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Kirsten Pugdahl
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | | | | | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, United Kingdom; Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.
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13
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Makker PGS, Keating BA, Lees JG, Burke D, Howells J, Moalem-Taylor G. Electrophysiological investigation of motor axonal excitability in a mouse model of nerve constriction injury. J Peripher Nerv Syst 2021; 26:99-112. [PMID: 33432642 DOI: 10.1111/jns.12430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/19/2020] [Accepted: 12/30/2020] [Indexed: 11/29/2022]
Abstract
Peripheral nerve injuries caused by focal constriction are characterised by local nerve ischaemia, axonal degeneration, demyelination, and neuroinflammation. The aim of this study was to understand temporal changes in the excitability properties of injured motor axons in a mouse model of nerve constriction injury (NCI). The excitability of motor axons following unilateral sciatic NCI was studied in male C57BL/6J mice distal to the site of injury at the acute (6 hours-1 week) and chronic (up to 20 weeks) phases of injury, using threshold tracking. Multiple measures of nerve excitability, including strength-duration properties, threshold electrotonus, current-threshold relationship, and recovery cycle were examined using the automated nerve excitability protocol (TRONDNF). Acutely, injured motor axons developed a pattern of excitability characteristic of ischemic depolarisation. In most cases, the sciatic nerve became transiently inexcitable. When a liminal compound muscle action potential could again be recorded, it had an increase in threshold and latency, compared to both pre-injury baseline and sham-injured groups. These axons showed a greater threshold change in response to hyperpolarising threshold electrotonus and a significant upward shift in the recovery cycle. Mathematical modelling suggested that the changes seen in chronically injured axons involve shortened internodes, reduced myelination, and exposed juxtaparanodal fast K+ conductances. The findings of this study demonstrate long-term changes in motor excitability following NCI (involving alterations in axonal properties and ion channel activity) and are important for understanding the mechanisms of neurapraxic injuries and traumatic mononeuropathies.
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Affiliation(s)
- Preet G S Makker
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - Brooke A Keating
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - Justin G Lees
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - David Burke
- Central Clinical School, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - James Howells
- Central Clinical School, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - Gila Moalem-Taylor
- Translational Neuroscience Facility, School of Medical Sciences, The University of New South Wales (UNSW), Sydney, New South Wales, Australia
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14
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Tankisi H, Cengiz B, Howells J, Samusyte G, Koltzenburg M, Bostock H. Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared. Brain Stimul 2020; 14:22-32. [PMID: 33166726 DOI: 10.1016/j.brs.2020.11.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 10/28/2020] [Accepted: 11/01/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Short-interval intracortical inhibition (SICI), as measured by threshold-tracking as a function of inter-stimulus interval (ISI), has been proposed as a useful biomarker for amyotrophic lateral sclerosis (ALS), but its relationship to conventional amplitude measurements has not been established. METHODS Serial tracking of SICI at increasing ISIs from 1 to 7 ms (T-SICIs) was compared in 50 healthy control subjects with the same ISIs tracked in parallel (T-SICIp), and with conventional amplitude measurements (A-SICI). For T-SICIp and A-SICI, pairs of conditioning and test stimuli with different ISIs were pseudo-randomised and interspersed with test-alone stimuli given at regular intervals. Thresholds were estimated by regression of log peak-to-peak amplitude on stimulus. RESULTS T-SICIp and A-SICI were closely related: a ten-fold reduction in amplitude corresponding to an approximately 18% increase in threshold. Threshold increases were greater for T-SICIs than for T-SICIp at 3.5-5 ms (P < 0.001). This divergence depended on the initial settings and whether ISIs were progressively increased or decreased, and was attributed to the limitations of the serial tracking protocol. SICI variability between subjects was greatest for T-SICIs estimates and least for A-SICI, and only A-SICI estimates revealed a significant decline in inhibition with age. CONCLUSIONS The serial tracking protocol did not accurately show the dependence of inhibition on ISI. Randomising ISIs gives corresponding SICI measures, whether tracking thresholds or measuring amplitude measurements. SICI variability suggested that A-SICI measurements may be the most sensitive to loss of inhibition.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical and Movement Neuroscience, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom; Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, United Kingdom
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom.
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15
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Kariyawasam D, D'Silva A, Howells J, Herbert K, Geelan-Small P, Lin CSY, Farrar MA. Motor unit changes in children with symptomatic spinal muscular atrophy treated with nusinersen. J Neurol Neurosurg Psychiatry 2020; 92:jnnp-2020-324254. [PMID: 33106369 PMCID: PMC7803907 DOI: 10.1136/jnnp-2020-324254] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 08/10/2020] [Accepted: 09/02/2020] [Indexed: 12/13/2022]
Abstract
OBJECTIVES To elucidate the motor unit response to intrathecal nusinersen in children with symptomatic spinal muscular atrophy (SMA) using a novel motor unit number estimation technique. METHODS MScanFit MUNE studies were sequentially undertaken from the abductor pollicis brevis muscle after stimulation of the median nerve in a prospective cohort of symptomatic children with SMA, undergoing intrathecal treatment with nusinersen at a single neuromuscular centre from June 2017 to August 2019. Electrophysiological measures included compound muscle action potential (CMAP), motor unit number estimation (MUNE), motor unit number contributing to 50%-100% of CMAP (N50) and measures of collateral reinnervation including largest single motor unit potential (LSMUP) and amplitude of the smallest unit contributing to N50 (A50). RESULTS Twenty children (median age 99 months, range 4-193) were followed for a median of 13.8 (4-33.5) months. Therapeutic intervention was an independent and significant contributor to an increase in CMAP (p = 0.005), MUNE (p = 0.001) and N50 (p = 0.04). The magnitude of this electrophysiological response was increased in children with shorter disease durations (p<0.05). Electrophysiological changes delineated children who were functionally stable from those who attained clinically significant gains in motor function. INTERPRETATION Nusinersen therapy facilitated functional innervation in SMA through recovery of smaller motor units. Delineation of biomechanisms of therapeutic response may be the first step in identifying potential novel targets for disease modification in this and other motor neuropathies. MScanFit MUNE techniques may have a broader role in establishing biomarkers of therapeutic response in similar adult-onset diseases.
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Affiliation(s)
- Didu Kariyawasam
- Neurology, Sydney Children's Hospital Randwick, Randwick, New South Wales, Australia
- School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Arlene D'Silva
- School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Karen Herbert
- Physiotherapy, Syndey Children's Hospital, Randwick, Sydney, New South Wales, Australia
| | - Peter Geelan-Small
- Mark Wainwright Analytical Centre, University of New South Wales, Sydney, New South Wales, Australia
| | - Cindy Shin-Yi Lin
- Central Clinical School, Faculty of Medicine and Health, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales, Australia
| | - Michelle Anne Farrar
- Neurology, Sydney Children's Hospital Randwick, Randwick, New South Wales, Australia
- School of Women's and Children's Health, UNSW Medicine, University of New South Wales, Sydney, New South Wales, Australia
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16
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Dharmadasa T, Howells J, Matamala JM, Simon NG, Burke D, Vucic S, Kiernan MC. Cortical inexcitability defines an adverse clinical profile in amyotrophic lateral sclerosis. Eur J Neurol 2020; 28:90-97. [PMID: 32902860 PMCID: PMC7820947 DOI: 10.1111/ene.14515] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 09/02/2020] [Indexed: 12/11/2022]
Abstract
Background and purpose In amyotrophic lateral sclerosis, studies using threshold‐tracking transcranial magnetic stimulation (TMS) have identified corticomotoneuronal dysfunction as a key pathogenic mechanism. Some patients, however, display no motor response at maximal TMS intensities, termed here an ‘inexcitable’ motor cortex. The extent to which this cortical difference impacts clinical outcomes remains unclear. The aim of this study was to determine the clinical profile of patients with inexcitability to TMS. Methods Motor cortex excitability was evaluated using TMS. Patients in whom a motor evoked potential could not be recorded in one or more limbs at maximal TMS intensities were classified as four‐limb or partially inexcitable. Demographic information, clinical variables and survival data were analysed. Results From 133 patients, 40 were identified with inexcitability. Patients with four‐limb inexcitability were younger (P = 0.03) and had lower‐limb disease onset (64%), greater functional disability (P < 0.001) and faster disease progression (P = 0.02), particularly if inexcitability developed within 1 year of symptoms (P < 0.01). Patients with partial inexcitability had higher resting motor thresholds compared to the excitable cohort (P < 0.01), but averaged short‐interval intracortical inhibition was similar (P = 0.5). Mean survival was reduced if inexcitability involved all limbs within 12 months of symptom onset (P = 0.04). Conclusion Amyotrophic lateral sclerosis patients with inexcitability of all four limbs to TMS have a distinct clinical profile of younger age and lower‐limb onset. Importantly, these patients display a more malignant disease trajectory, with faster progression, greater functional disability and reduced survival when occurring in early disease. This measure may provide an important prognostic marker in amyotrophic lateral sclerosis.
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Affiliation(s)
- T Dharmadasa
- Brain and Mind Centre, University of Sydney, Sydney, NSW, Australia
| | - J Howells
- Brain and Mind Centre, University of Sydney, Sydney, NSW, Australia
| | - J M Matamala
- Brain and Mind Centre, University of Sydney, Sydney, NSW, Australia
| | - N G Simon
- St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - D Burke
- Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - S Vucic
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
| | - M C Kiernan
- Brain and Mind Centre, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
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17
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Howells J, Coyle C, Archer C. P-113 Supportive medication in advanced biliary tract cancers with ABC-02 regimen. Ann Oncol 2020. [DOI: 10.1016/j.annonc.2020.04.195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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18
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Makker PGS, White D, Lees JG, Parmar J, Goldstein D, Park SB, Howells J, Moalem-Taylor G. Acute changes in nerve excitability following oxaliplatin treatment in mice. J Neurophysiol 2020; 124:232-244. [PMID: 32519566 DOI: 10.1152/jn.00260.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxaliplatin chemotherapy produces acute changes in peripheral nerve excitability in humans by modulating voltage-gated Na+ channel activity. However, there are few animal studies of oxaliplatin-induced neuropathy that demonstrate similar changes in excitability. In the present study, we measured the excitability of motor and sensory caudal nerve in C57BL/6 mice after oxaliplatin injections either systemically (intraperitoneal) or locally (intramuscular at the base of the tail). As opposed to intraperitoneal administration of oxaliplatin, a single intramuscular injection of oxaliplatin produced changes in both motor and sensory axons. In motor axons, oxaliplatin caused a greater change in response to long-lasting depolarization and an upward shift in the recovery cycle, particularly at 24 h [depolarizing threshold electrotonus (TEd) 10-20 ms, P = 0.0095; TEd 90-100 ms, P = 0.0056) and 48 h (TEd 10-20 ms, P = 0.02; TEd 90-100 ms, P = 0.04) posttreatment. Oxaliplatin treatment also stimulated the production of afterdischarges in motor axons. These changes were transient and showed dose dependence. Mathematical modeling demonstrated that these changes could be accounted for by slowing inactivation of voltage-gated Na+ channels by 73.3% and reducing fast K+ conductance by 47% in motor axons. In sensory axons, oxaliplatin caused an increase in threshold, a reduction in peak amplitude, and greater threshold changes to strong hyperpolarizing currents on days 4 and 8. Thus, local administration of oxaliplatin produced clinically relevant changes in nerve excitability in mice and may provide an alternative approach for the study of acute oxaliplatin-induced neurotoxicity.NEW & NOTEWORTHY We present a novel mouse model of acute oxaliplatin-induced peripheral neurotoxicity that is comparable to clinical observations. Intramuscular injection of oxaliplatin produced acute changes in motor nerve excitability that were attributable to alterations in Na+ and K+ channel activity. Conversely, we were unable to show any significant changes in nerve excitability with systemic intraperitoneal injections of oxaliplatin. This study suggests that local intramuscular injection is a valid approach for modelling oxaliplatin-induced peripheral neuropathy in animals.
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Affiliation(s)
- Preet G S Makker
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - Daniel White
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - Justin G Lees
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - Jasneet Parmar
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales (UNSW), Sydney, New South Wales, Australia
| | - David Goldstein
- Department of Medical Oncology, Prince of Wales Hospital, Randwick, New South Wales, Australia.,Prince of Wales Clinical School, UNSW, New South Wales, Australia
| | - Susanna B Park
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - James Howells
- Central Clinical School, Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - Gila Moalem-Taylor
- Translational Neuroscience Facility, School of Medical Sciences, University of New South Wales (UNSW), Sydney, New South Wales, Australia
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19
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Howells J, Sangari S, Matamala JM, Kiernan MC, Marchand-Pauvert V, Burke D. Interrogating interneurone function using threshold tracking of the H reflex in healthy subjects and patients with motor neurone disease. Clin Neurophysiol 2020; 131:1986-1996. [PMID: 32336595 DOI: 10.1016/j.clinph.2020.03.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/21/2020] [Accepted: 03/15/2020] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The excitability of the lower motoneurone pool is traditionally tested using the H reflex and a constant-stimulus paradigm, which measures changes in the amplitude of the reflex response. This technique has limitations because reflex responses of different size must involve the recruitment or inhibition of different motoneurones. The threshold-tracking technique ensures that the changes in excitability occur for an identical population of motoneurones. We aimed to assess this technique and then apply it in patients with motor neurone disease (MND). METHODS The threshold-tracking approach was assessed in 17 healthy subjects and 11 patients with MND. The soleus H reflex was conditioned by deep peroneal nerve stimulation producing reciprocal Ia and so-called D1 and D2 inhibitions, which are believed to reflect presynaptic inhibition of soleus Ia afferents. RESULTS Threshold tracking was quicker than the constant-stimulus technique and reliable, properties that may be advantageous for clinical studies. D1 inhibition was significantly reduced in patients with MND. CONCLUSIONS Threshold tracking is useful and may be preferable under some conditions for studying the excitability of the motoneurone pool. The decreased D1 inhibition in the patients suggests that presynaptic inhibition may be reduced in MND. SIGNIFICANCE Reduced presynaptic inhibition could be evidence of an interneuronopathy in MND. It is possible that the hyperreflexia is a spinal pre-motoneuronal disorder, and not definitive evidence of corticospinal involvement in MND.
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Affiliation(s)
- James Howells
- Brain & Mind Centre, The University of Sydney, N.S.W. 2006, Australia
| | - Sina Sangari
- Sorbonne Université, INSERM, CNRS, Laboratoire d'Imagerie Biomédicale, LIB, F-75006 Paris, France
| | - José Manuel Matamala
- Department of Neurological Science and Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Matthew C Kiernan
- Brain & Mind Centre, The University of Sydney, N.S.W. 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital and The University of Sydney, N.S.W. 2006, Australia
| | | | - David Burke
- Department of Neurology, Royal Prince Alfred Hospital and The University of Sydney, N.S.W. 2006, Australia.
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20
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Dharmadasa T, Matamala JM, Howells J, Vucic S, Kiernan MC. Early focality and spread of cortical dysfunction in amyotrophic lateral sclerosis: A regional study across the motor cortices. Clin Neurophysiol 2020; 131:958-966. [DOI: 10.1016/j.clinph.2019.11.057] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/13/2019] [Accepted: 11/18/2019] [Indexed: 11/15/2022]
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21
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Mahoney CJ, Highton-Williamson E, Howells J, Ahmed R, Huynh W, Kiernan MC. 11. Neurophysiological correlates of impaired cognition in Amyotrophic Lateral Sclerosis. Clin Neurophysiol 2020. [DOI: 10.1016/j.clinph.2019.11.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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22
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van den Bos MA, Higashihara M, Howells J, Parvathi Menon, Geevasinga N, Kiernan MC, Vucic S. 13. Transcallosal dysfunction an early marker of ALS. Clin Neurophysiol 2020. [DOI: 10.1016/j.clinph.2019.11.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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23
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Farrar MA, Tomlinson SE, Howells J, Lin CSYI, Carey K, Park SB, Hollingsworth G, Lawson JA, Kiernan MC, Berkovic SF, Burke D, Scheffer IE. 009 Axonal excitability properties in dravet’s syndrome reflect effect of loss of sodium channels. J Neurol Neurosurg Psychiatry 2019. [DOI: 10.1136/jnnp-2019-anzan.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
IntroductionMutations in SCN1A encoding the Nav1.1 subunit of the neuronal sodium channel underlie the devastating epilepsy of Dravet’s syndrome.1 The mechanism by which Nav1.1 dysfunction causes seizures is not clear. In vitro and in silico channel evaluation can support mutation pathogenicity but cannot define the in vivo impact of channel dysfunction. Axonal excitability studies can show the pattern of single-channel dysfunction in disorders where the channel is peripherally expressed.2 This study was undertaken to determine whether axonal excitability studies could detect changes in Dravet’s patients related to the condition or due to medication effect.MethodsPatients with Dravet’s syndrome were recruited from clinics in Sydney and Melbourne and axonal excitability studies were performed. Excitability results were analysed in 3 age groups and compared to age-matched normal controls.ResultsTwenty six patients (ages 2–46) were studied. Findings were most pronounced in patients aged 20–46 (n=7) with 6.9% greater increase in threshold during hyperpolarization(p=0.1), 7.6% greater threshold decrease on depolarization(p=0.005) and, in the recovery cycle, 19.7% reduction in superexcitability(p=0.002) and 26% reduction in subexcitability(p=0.03). Axonal excitability studies resembled previously published changes seen in patients with sodium channel blockade caused by acute tetrodotoxin poisoning.3ConclusionsChanges in excitability of axonal membrane in Dravet’s syndrome are consistent with a decrease in sodium channel function. As the affected channel in Dravet’s syndrome is not peripherally expressed, the effect seen is likely due to the heavy anticonvulsant regime required to control epilepsy, combined with a progressive loss of sodium channel function that occurs with age.ReferencesMeisler MH, O’Brien JE, Sharkey LM. Sodium channel gene family: epilepsy mutations, gene interactions and modifier effects. J Physiol 2010;588:1841–1848.Tomlinson SE, Howells J, Burke D. In vivo assessment of neurological channelopathies: Application of peripheral nerve excitability studies. Neuropharmacology. 2018 Apr;132:98–107.Kiernan MC, Isbister GK, Lin CS, Burke D, Bostock H. Acute tetrodotoxin-induced neurotoxicity after ingestion of puffer fish. Ann Neurol 2005;57:339–48.
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Howells J, Khoury E, Hack J, Yeoh C, Rahimi S. Expression of MMR in women high grade carcinoma of unknown primary. Ann Oncol 2019. [DOI: 10.1093/annonc/mdz155.394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Bos MVD, Howells J, Higashihara M, Geevasinga N, Kiernan M, Vucic S. 018 Role of transcallosal inhibition in disease spread in ALS. J Neurol Psychiatry 2019. [DOI: 10.1136/jnnp-2019-anzan.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
IntroductionThere is substantial evidence for the cortical origin of amyotrophic lateral sclerosis (ALS). Impaired function of the corpus callosum has been demonstrated in ALS patients and may play a role in disease spread, potentially mediating the spread of cortical hyperexcitability between hemispheres. We assessed transcallosal inhibition, utilising the threshold tracking transcranial magnetic stimulation (TMS) technique to assess transcallosal inhibition and related the changes to disease involvement.MethodsThreshold tracking TMS was undertaken in 15 ALS patients and results were compared to 16 healthy controls. Interhemispheric inhibition was assessed using a figure of eight coil over each hemisphere across interstimulus intervals ranging from 8 to 40ms.ResultsTranscallosal inhibition was reduced in ALS patients (0.9 ± 1.0%) when compared to controls (6.6 ± 1.0%, P=0.03). Importantly differences in transcallosal inhibition between hemispheres were evident in ALS patients. Specifically, transcallosal inhibition projecting from the motor cortex contralateral to disease onset (0.9 ± 1.0%) was significantly lower when compared to projection form the ipsilateral motor cortex (3.2 ± 1.0%, P=0.036). Abnormalities of transcallosal inhibition correlated with upper motor neurone dysfunction and greater functional disability in ALS.ConclusionAbnormalities of transcallosal inhibition were demonstrated in ALS patients and were associated with clinical features. Consequently, dysfunction of transcallosal fibres may contribute to development of cortical hyperexcitability, a pathogenic mechanism in ALS. Strategies aimed at modulating dysfunction may prove therapeutically useful in ALS.
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Garg N, Park SB, Howells J, Vucic S, Yiannikas C, Mathey EK, Nguyen T, Noto Y, Barnett MH, Krishnan AV, Spies J, Bostock H, Pollard JD, Kiernan MC. Conduction block in immune-mediated neuropathy: paranodopathy versus axonopathy. Eur J Neurol 2019; 26:1121-1129. [PMID: 30882969 DOI: 10.1111/ene.13953] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 03/11/2019] [Indexed: 12/15/2022]
Abstract
BACKGROUND AND PURPOSE Conduction block is a pathognomonic feature of immune-mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). METHODS A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments. RESULTS Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons. CONCLUSIONS The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody-mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.
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Affiliation(s)
- N Garg
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - S B Park
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - J Howells
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - S Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital, University of Sydney, Sydney, NSW, Australia
| | - C Yiannikas
- Department of Neurology, Concord and Royal North Shore Hospitals, University of Sydney, Sydney, NSW, Australia
| | - E K Mathey
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - T Nguyen
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Y Noto
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - M H Barnett
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - A V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - J Spies
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - H Bostock
- MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, UK.,Institute of Neurology, University College London, London, UK
| | - J D Pollard
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - M C Kiernan
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW, Australia
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Geevasinga N, Howells J, Menon P, van den Bos M, Shibuya K, Matamala JM, Park SB, Byth K, Kiernan MC, Vucic S. Amyotrophic lateral sclerosis diagnostic index: Toward a personalized diagnosis of ALS. Neurology 2019; 92:e536-e547. [PMID: 30709964 DOI: 10.1212/wnl.0000000000006876] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 09/28/2018] [Indexed: 01/08/2023] Open
Abstract
OBJECTIVE The aim of the study was to assess the utility of a novel amyotrophic lateral sclerosis (ALS) diagnostic index (ALSDI). METHODS A prospective multicenter study was undertaken on patients presenting with suspected ALS. The reference standard (Awaji criteria) was applied to all patients at recruitment. Patients were randomly assigned to a training (75%) and a test (25%) cohort. The ALSDI was developed in the training cohort and its diagnostic utility was subsequently assessed in the test cohort. RESULTS A total of 407 patients were recruited, with 305 patients subsequently diagnosed with ALS and 102 with a non-ALS mimicking disorder. The ALSDI reliably differentiated ALS from neuromuscular disorders in the training cohort (area under the curve 0.92, 95% confidence interval 0.89-0.95), with ALSDI ≥4 exhibiting 81.6% sensitivity, 89.6% specificity, and 83.5% diagnostic accuracy. The ALSDI diagnostic utility was confirmed in the test cohort (area under the curve 0.90, 95% confidence interval 0.84-0.97), with ALSDI ≥4 exhibiting 83.3% sensitivity, 84% specificity, and 83.5% diagnostic accuracy. In addition, the diagnostic utility of the ALSDI was confirmed in patients who were Awaji negative at recruitment and in those exhibiting a predominantly lower motor neuron phenotype. CONCLUSION The ALSDI reliably differentiates ALS from mimicking disorders at an early stage in the disease process. CLASSIFICATION OF EVIDENCE This study provides Class I evidence that for patients with suspected ALS, the ALSDI distinguished ALS from neuromuscular mimicking disorders.
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Affiliation(s)
- Nimeshan Geevasinga
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - James Howells
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Parvathi Menon
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Mehdi van den Bos
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Kazumoto Shibuya
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - José Manuel Matamala
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Susanna B Park
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Karen Byth
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Matthew C Kiernan
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia
| | - Steve Vucic
- From Westmead Clinical School (N.G., P.M., M.v.d.B., S.V.), Brain and Mind Center (J.H., K.S., J.M.M., S.B.P., M.C.K.), and NHMRC Clinical Trials Centre (K.B.), University of Sydney; and Westmead Hospital (K.B.), Research and Education Network, Sydney, Australia.
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Balata H, Hayton C, Barber P, Duerden R, Evison M, Greaves M, Howells J, Irion K, Karunaratne D, Leonard C, Mellor S, Newton T, Sawyer R, Sharman A, Smith E, Taylor B, Walsham A, Whittaker J, Chaudhuri N, Booton R, Crosbie P. Prevalence of incidental interstitial lung disease in the Manchester lung cancer screening pilot. Lung Cancer 2019. [DOI: 10.1016/s0169-5002(19)30103-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Czesnik D, Howells J, Bartl M, Veiz E, Ketzler R, Kemmet O, Walters AS, Trenkwalder C, Burke D, Paulus W. I h contributes to increased motoneuron excitability in restless legs syndrome. J Physiol 2018; 597:599-609. [PMID: 30430565 DOI: 10.1113/jp275341] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 10/18/2018] [Indexed: 12/17/2022] Open
Abstract
KEY POINTS Restless legs patients complain about sensory and motor symptoms leading to sleep disturbances. Symptoms include painful sensations, an urge to move and involuntary leg movements. The responsible mechanisms of restless legs syndrome are still not known, although current studies indicate an increased neuronal network excitability. Reflex studies indicate the involvement of spinal structures. Peripheral mechanisms have not been investigated so far. In the present study, we provide evidence of increased hyperpolarization-activated cyclic nucleotide-gated (HCN) channel-mediated inward rectification in motor axons. The excitability of sensory axons was not changed. We conclude that, in restless legs syndrome, an increased HCN current in motoneurons may play a pathophysiological role, such that these channels could represent a valuable target for pharmaceutical intervention. ABSTRACT Restless legs syndrome is a sensorimotor network disorder. So far, the responsible pathophysiological mechanisms are poorly understood. In the present study, we provide evidence that the excitability of peripheral motoneurons contributes to the pathophysiology of restless legs syndrome. In vivo excitability studies on motor and sensory axons of the median nerve were performed on patients with idiopathic restless legs syndrome (iRLS) who were not currently on treatment. The iRLS patients had greater accommodation in motor but not sensory axons to long-lasting hyperpolarization compared to age-matched healthy subjects, indicating greater inward rectification in iRLS. The most reasonable explanation is that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels open at less hyperpolarized membrane potentials, a view supported by mathematical modelling. The half-activation potential for HCN channels (Bq) was the single best parameter that accounted for the difference between normal controls and iRLS data. A 6 mV depolarization of Bq reduced the discrepancy between the normal control model and the iRLS data by 92.1%. Taken together, our results suggest an increase in the excitability of motor units in iRLS that could enhance the likelihood of leg movements. The abnormal axonal properties are consistent with other findings indicating that the peripheral system is part of the network involved in iRLS.
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Affiliation(s)
- Dirk Czesnik
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - James Howells
- Brain & Mind Centre, The University of Sydney, Sydney, NSW, Australia
| | - Michael Bartl
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Elisabeth Veiz
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Rebecca Ketzler
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Olga Kemmet
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
| | - Arthur S Walters
- Division of Sleep Medicine, School of Medicine, Medical Center North, Vanderbilt University, Nashville, TN, USA
| | - Claudia Trenkwalder
- Clinic of Neurosurgery, University Medical Center, Paracelsus Klinik Kassel, Göttingen, Germany
| | - David Burke
- Royal Prince Alfred Hospital and The University of Sydney, Sydney, NSW, Australia
| | - Walter Paulus
- Department of Clinical Neurophysiology, Medical School Göttingen, University of Göttingen, Göttingen, Germany
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Vucic S, van den Bos M, Menon P, Howells J, Dharmadasa T, Kiernan MC. Utility of threshold tracking transcranial magnetic stimulation in ALS. Clin Neurophysiol Pract 2018; 3:164-172. [PMID: 30560220 PMCID: PMC6275211 DOI: 10.1016/j.cnp.2018.10.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 10/17/2018] [Accepted: 10/29/2018] [Indexed: 12/21/2022] Open
Abstract
Upper motor neuron [UMN] and lower motor neuron [LMN] dysfunction, in the absence of sensory features, is a pathognomonic feature of amyotrophic lateral sclerosis [ALS]. Although the precise mechanisms have yet to be elucidated, one leading hypothesis is that UMN precede LMN dysfunction, which is induced by anterograde glutamatergic excitotoxicity. Transcranial magnetic stimulation (TMS) is a neurophysiological tool that provides a non-invasive and painless assessment of cortical function. Threshold tracking methodologies have been recently adopted for TMS, whereby changes in threshold rather than motor evoked potential (MEP) amplitude serve as outcome measures. This technique is reliable and provides a rapid assessment of cortical function in ALS. Utilisng the threshold tracking TMS technique, cortical hyperexcitability was demonstrated as an early feature in sporadic ALS preceding the onset of LMN dysfunction and possibly contributing to disease spread. Separately, cortical hyperexcitability was reported to precede the clinical onset of familial ALS. Of further relevance, the threshold tracking TMS technique was proven to reliably distinguish ALS from mimicking disorders, even in the presence of a comparable degree of LMN dysfunction, suggesting a diagnostic utility of TMS. Taken in total, threshold tracking TMS has provided support for a cortical involvement at the earliest detectable stages of ALS, underscoring the utility of the technique for probing the underlying pathophysiology. The present review will discuss the physiological processes underlying TMS parameters, while further evaluating the pathophysiological and diagnostic utility of threshold tracking TMS in ALS.
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Affiliation(s)
- Steve Vucic
- Western Clinical School, University of Sydney, Sydney, Australia
| | | | - Parvathi Menon
- Western Clinical School, University of Sydney, Sydney, Australia
| | - James Howells
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
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Howells J, Matamala JM, Park SB, Garg N, Vucic S, Bostock H, Burke D, Kiernan MC. In vivo evidence for reduced ion channel expression in motor axons of patients with amyotrophic lateral sclerosis. J Physiol 2018; 596:5379-5396. [PMID: 30175403 DOI: 10.1113/jp276624] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/31/2018] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS The progressive loss of motor units in amyotrophic lateral sclerosis (ALS) is initially compensated for by the reinnervation of denervated muscle fibres by surviving motor axons. A disruption in protein homeostasis is thought to play a critical role in the pathogenesis of ALS. The changes in surviving motor neurons were studied by comparing the nerve excitability properties of moderately and severely affected single motor axons from patients with ALS with those from single motor axons in control subjects. A mathematical model indicated that approximately 99% of the differences between the ALS and control units could be explained by a non-selective reduction in the expression of all ion channels. These changes in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron. ABSTRACT Amyotrophic lateral sclerosis (ALS) is characterised by a progressive loss of motor units and the reinnervation of denervated muscle fibres by surviving motor axons. This reinnervation preserves muscle function until symptom onset, when some 60-80% of motor units have been lost. We have studied the changes in surviving motor neurons by comparing the nerve excitability properties of 31 single motor axons from patients with ALS with those from 21 single motor axons in control subjects. ALS motor axons were classified as coming from moderately or severely affected muscles according to the compound muscle action potential amplitude of the parent muscle. Compared with control units, thresholds were increased, and there was reduced inward and outward rectification and greater superexcitability following a conditioning impulse. These abnormalities were greater in axons from severely affected muscles, and were correlated with loss of fine motor skills. A mathematical model indicated that 99.1% of the differences between the moderately affected ALS and control units could be explained by a reduction in the expression of all ion channels. For the severely affected units, modelling required, in addition, an increase in the current leak through and under the myelin sheath. This might be expected if the anchoring proteins responsible for the paranodal seal were reduced. We conclude that changes in axonal excitability identified in ALS patients are best explained by a failure in the supply of ion channel and other membrane proteins from the diseased motor neuron, a conclusion consistent with recent animal and in vitro human data.
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Affiliation(s)
- James Howells
- Brain & Mind Centre, University of Sydney, Sydney, Australia
| | | | - Susanna B Park
- Brain & Mind Centre, University of Sydney, Sydney, Australia
| | - Nidhi Garg
- Brain & Mind Centre, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
| | - Steve Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital and University of Sydney, Sydney, Australia
| | - Hugh Bostock
- MRC Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.,Institute of Neurology, UCL, Queen Square, London, WC1N 3BG, UK
| | - David Burke
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
| | - Matthew C Kiernan
- Brain & Mind Centre, University of Sydney, Sydney, Australia.,Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia
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Garg N, Park SB, Howells J, Noto YI, Vucic S, Yiannikas C, Tomlinson SE, Huynh W, Simon NG, Mathey EK, Spies J, Pollard JD, Krishnan AV, Kiernan MC. Anti-MAG neuropathy: Role of IgM antibodies, the paranodal junction and juxtaparanodal potassium channels. Clin Neurophysiol 2018; 129:2162-2169. [PMID: 30144659 DOI: 10.1016/j.clinph.2018.07.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 06/12/2018] [Accepted: 07/15/2018] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To improve understanding of disease pathophysiology in anti-myelin-associated glycoprotein (anti-MAG) neuropathy to guide further treatment approaches. METHODS Anti-MAG neuropathy patients underwent clinical assessments, nerve conduction and excitability studies, and ultrasound assessment. RESULTS Patients demonstrated a distinctive axonal excitability profile characterised by a reduction in superexcitability [MAG: -14.2 ± 1.6% vs healthy controls (HC): -21.8 ± 1.2%; p < 0.01] without alterations in most other excitability parameters. Mathematical modelling of nerve excitability recordings suggested that changes in axonal function could be explained by a 72.5% increase in juxtaparanodal fast potassium channel activation and an accompanying hyperpolarization of resting membrane potential (by 0.3 mV) resulting in a 94.2% reduction in discrepancy between anti-MAG data and the healthy control model. Superexcitability changes correlated strongly with clinical and neurophysiological parameters. Furthermore, structural assessments demonstrated a proximal pattern of nerve enlargement (C6 nerve root cross-sectional area: 15.9 ± 8.1 mm2 vs HC: 9.1 ± 2.3 mm2; p < 0.05). CONCLUSIONS The imaging and neurophysiological results support the pathogenicity of anti-MAG IgM. Widening between adjacent loops of paranodal myelin due to antibodies would expand the pathway from the node to the juxtaparanode, increasing activation of juxtaparanodal fast potassium channels, thereby impairing saltatory conduction. SIGNIFICANCE Potassium channel blockers may prove beneficial in restoring conduction closer to its normal state and improving nerve function in anti-MAG neuropathy.
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Affiliation(s)
- Nidhi Garg
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Susanna B Park
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - James Howells
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Yu-Ichi Noto
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Steve Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital, The University of Sydney, NSW, Australia.
| | - Con Yiannikas
- Department of Neurology, Concord and Royal North Shore Hospitals, The University of Sydney, NSW, Australia.
| | - Susan E Tomlinson
- Sydney Medical School, University of Sydney, Sydney, Australia; Department of Neurology, St Vincent's Hospital, Sydney, Australia.
| | - William Huynh
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Neil G Simon
- St Vincent's Clinical School, University of New South Wales, NSW, Australia.
| | - Emily K Mathey
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Judith Spies
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - John D Pollard
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, NSW, Australia.
| | - Matthew C Kiernan
- Brain and Mind Centre, Sydney Medical School, The University of Sydney, 94 Mallett St, Camperdown, NSW 2050, Australia.
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Balata H, Blandin Knight S, Barber P, Colligan D, Crosbie EJ, Duerden R, Elton P, Evison M, Greaves M, Howells J, Irion K, Karunaratne D, Kirwan M, Macnab A, Mellor S, Miller C, Newton T, Novasio J, Sawyer R, Sharman A, Slevin K, Smith E, Taylor B, Taylor S, Tonge J, Walsham A, Waplington S, Whittaker J, Booton R, Crosbie PAJ. Targeted lung cancer screening selects individuals at high risk of cardiovascular disease. Lung Cancer 2018; 124:148-153. [PMID: 30268454 DOI: 10.1016/j.lungcan.2018.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 08/03/2018] [Accepted: 08/06/2018] [Indexed: 01/13/2023]
Abstract
BACKGROUND Cardiovascular disease (CVD) is a major cause of morbidity and mortality in populations eligible for lung cancer screening. The aim of this study was to determine whether a brief CV risk assessment, delivered as part of a targeted community-based lung cancer screening programme, was effective in identifying individuals at high risk who might benefit from primary prevention. METHODS The Manchester Lung Screening Pilot consisted of annual low dose CT (LDCT) over 2 screening rounds, targeted at individuals in deprived areas at high risk of lung cancer (age 55-74 and 6-year risk ≥1.51%, using PLCOM2012 risk model). All participants of the second screening round were eligible to take part in the study. Ten-year CV risk was estimated using QRISK2 in participants without CVD and compared to age (±5 years) and sex matched Health Survey for England (HSE) controls; high risk was defined as QRISK2 score ≥10%. Coronary artery calcification (CAC) was assessed on LDCT scans and compared to QRISK2 score. RESULTS Seventy-seven percent (n=920/1,194) of screening attendees were included in the analysis; mean age 65.6 ± 5.4 and 50.4% female. QRISK2 and lung cancer risk (PLCOM2012) scores were correlated (r = 0.26, p < 0.001). Median QRISK2 score was 21.1% (IQR 14.9-29.6) in those without established CVD (77.6%, n = 714/920), double that of HSE controls (10.3%, IQR 6.6-16.2; n = 714) (p < 0.001). QRISK2 score was significantly higher in those with CAC (p < 0.001). Screening attendees were 10-fold more likely to be classified high risk (OR 10.2 [95% CI 7.3-14.0]). One third (33.7%, n = 310/920) of all study participants were high risk but not receiving statin therapy for primary CVD prevention. DISCUSSION Opportunistic CVD risk assessment within a targeted lung cancer screening programme is feasible and is likely to identify a very large number of individuals suitable for primary prevention.
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Affiliation(s)
- H Balata
- Manchester Thoracic Oncology Centre, North West Lung Centre, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - S Blandin Knight
- Manchester Thoracic Oncology Centre, North West Lung Centre, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - P Barber
- Manchester Thoracic Oncology Centre, North West Lung Centre, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - D Colligan
- Manchester Health and Care Commissioning, Manchester, UK
| | - E J Crosbie
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - R Duerden
- Department of Radiology, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - P Elton
- Greater Manchester Health & Social Care Partnership, Manchester, UK
| | - M Evison
- Manchester Thoracic Oncology Centre, North West Lung Centre, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - M Greaves
- Department of Radiology, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - J Howells
- Department of Radiology, Royal Preston Hospital, Preston, UK
| | - K Irion
- Department of Radiology, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, Manchester, UK
| | - D Karunaratne
- Department of Radiology, Manchester Royal Infirmary, Manchester University NHS Foundation Trust, Manchester, UK
| | - M Kirwan
- Thoracic Oncology Research Hub (TORCH), Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - A Macnab
- Department of Cardiology, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - S Mellor
- Department of Radiology, Royal Blackburn Hospital, Blackburn, UK
| | - C Miller
- Department of Cardiology, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - T Newton
- Department of Radiology, Royal Blackburn Hospital, Blackburn, UK
| | - J Novasio
- Department of Radiology, The Christie NHS Foundation Trust, Manchester, UK
| | - R Sawyer
- Department of Radiology, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - A Sharman
- Department of Radiology, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - K Slevin
- Thoracic Oncology Research Hub (TORCH), Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - E Smith
- Department of Radiology, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - B Taylor
- Department of Radiology, The Christie NHS Foundation Trust, Manchester, UK
| | - S Taylor
- Manchester Health and Care Commissioning, Manchester, UK
| | - J Tonge
- Manchester Health and Care Commissioning, Manchester, UK
| | - A Walsham
- Department of Radiology, Salford Royal NHS Foundation Trust, Salford, UK
| | - S Waplington
- Manchester Health and Care Commissioning, Manchester, UK
| | - J Whittaker
- Department of Radiology, Stockport NHS Foundation Trust, Stockport, UK
| | - R Booton
- Manchester Thoracic Oncology Centre, North West Lung Centre, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK
| | - P A J Crosbie
- Manchester Thoracic Oncology Centre, North West Lung Centre, Manchester University NHS Foundation Trust, Southmoor Road, Wythenshawe, UK; Division of Cancer Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.
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Makker PGS, Matamala JM, Park SB, Lees JG, Kiernan MC, Burke D, Moalem‐Taylor G, Howells J. A unified model of the excitability of mouse sensory and motor axons. J Peripher Nerv Syst 2018; 23:159-173. [DOI: 10.1111/jns.12278] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Revised: 06/13/2018] [Accepted: 06/13/2018] [Indexed: 11/29/2022]
Affiliation(s)
- Preet G. S. Makker
- School of Medical SciencesUniversity of New South Wales Sydney Australia
| | | | - Susanna B. Park
- Brain and Mind CentreThe University of Sydney Sydney Australia
| | - Justin G. Lees
- School of Medical SciencesUniversity of New South Wales Sydney Australia
| | - Matthew C. Kiernan
- Brain and Mind CentreThe University of Sydney Sydney Australia
- Royal Prince Alfred HospitalThe University of Sydney Sydney Australia
| | - David Burke
- Royal Prince Alfred HospitalThe University of Sydney Sydney Australia
| | - Gila Moalem‐Taylor
- School of Medical SciencesUniversity of New South Wales Sydney Australia
| | - James Howells
- Brain and Mind CentreThe University of Sydney Sydney Australia
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Garg N, Park SB, Howells J, Yiannikas C, Vucic S, Noto YI, Krishnan AV, Spies J, Mathey EK, Pollard JD, Kiernan MC. 004 Mechanisms of nerve dysfunction in inflammatory neuropathies. J Neurol Neurosurg Psychiatry 2018. [DOI: 10.1136/jnnp-2018-anzan.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
IntroductionImmune-mediated neuropathies are a cause of disability and an immense cost to the healthcare system. They include chronic inflammatory demyelinating polyneuropathy (CIDP), multifocal motor neuropathy (MMN) and the neuropathy associated with IgM antibodies against myelin-associated glycoprotein (MAG). CIDP is extremely heterogeneous with marked variability in treatment responsiveness. Patients with MMN often respond to treatment but progressive weakness and wasting typically ensues over time. No therapy has consistently proven effective in anti-MAG neuropathy. The present series of studies were undertaken to improve understanding of disease mechanisms in these neuropathies, a critical step before targeted treatment approaches can be developed.MethodsPatients fulfilling Peripheral Nerve Society criteria for CIDP or MMN and patients positive for anti-MAG IgM underwent comprehensive clinical assessments, neurophysiology, serological testing and structural assessments.ResultsThe patient cohort consisted of 80 patients (51 CIDP, 14 MMN, 15 MAG). 6% of CIDP patients tested positive for anti-neurofascin 155 (NF155) and 4% for anti-contactin 1 IgG4. Anti-NF155 neuropathy was characterised by diffuse nerve enlargement and an axonal excitability profile consistent with severe disruption of the paranodal seal. CIDP patients testing negative for IgG4 antibodies also demonstrated significant nerve enlargement compared with healthy subjects. Axonal excitability profiles differed in those with and without median nerve conduction block. MMN was characterised by patchy nerve enlargement, marked increases in super-excitability and enlarged motor unit size. In contrast, anti-MAG neuropathy patients demonstrated a proximal pattern of nerve enlargement and an axonal excitability profile characterised by reduced super-excitability consistent with increased juxta-paranodal fast potassium channel conductance.ConclusionPatterns of nerve enlargement and neurophysiological profiles differ in the immune-mediated neuropathies providing insights into molecular mechanisms. These results provide templates that can guide treatment approaches. The combination of directed autoantibody assays and measures of axonal function can be used to monitor disease progression and therapeutic response.
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Dharmadasa T, Matamala JM, Howells J, Vucic S, Kiernan M. S151. Assessing lower limb cortical function with threshold tracking transcranial magnetic stimulation. Clin Neurophysiol 2018. [DOI: 10.1016/j.clinph.2018.04.511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Matamala JM, Howells J, Dharmadasa T, Trinh T, Ma Y, Vucic S, Burke D, Kiernan M. F147. Absolute and relative reliability of short-interval intracortical inhibition measured by threshold tracking transcranial magnetic stimulation. Clin Neurophysiol 2018. [DOI: 10.1016/j.clinph.2018.04.310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Van den Bos MAJ, Menon P, Howells J, Geevasinga N, Kiernan MC, Vucic S. Physiological Processes Underlying Short Interval Intracortical Facilitation in the Human Motor Cortex. Front Neurosci 2018; 12:240. [PMID: 29695952 PMCID: PMC5904283 DOI: 10.3389/fnins.2018.00240] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 03/27/2018] [Indexed: 11/24/2022] Open
Abstract
Short interval intracortical facilitation (SICF) may be elicited by a paired pulse transcranial magnetic stimulation (TMS) paradigm, whereby a suprathreshold first stimulus (S1) precedes a perithreshold second stimulus (S2). Other facilitatory circuits can be probed by TMS such as intracranial facilitation, however the cortical contributions to these circuits may lie partially outside of M1. SICF as such represents a unique analog to M1 inhibitory circuits such as short interveal intracortical circuits. The aim of the present study was to provide insight into the physiological processes underlying the development of SICF using the threshold tracking TMS technique which was recently demonstrated to have significant reliability. TMS studies were undertaken on 35 healthy controls, using either a 90 mm circular and 70 mm figure of eight coil, and one of two targets (0.2 and 1.0 mV) tracked. The motor evoked potential (MEP) responses were recorded from the abductor pollicis brevis. SICF was consistently evident between interstimulus intervals (ISI) of 1–5 ms (P < 0.001), with two peaks occurring ISIs 1.5 and 3 ms when using the circular coil. A significant SICF reduction (F = 5.631, P < 0.05) was evident with the higher tracking target, while SICF increased when stimulating with the figure of eight coil. While there was a correlation between SICF and CSP duration, there was no relationship between SICF and SICI or ICF. Age appeared to have no influence on SICF, SICI, or ICF. Findings from the present work suggest that SICF appears to be mediated by I-wave facilitation.
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Affiliation(s)
| | - Parvathi Menon
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
| | - James Howells
- Brain and Mind Center, University of Sydney, Sydney, NSW, Australia
| | | | | | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
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Matamala JM, Howells J, Dharmadasa T, Huynh W, Park SB, Burke D, Kiernan MC. Excitability of sensory axons in amyotrophic lateral sclerosis. Clin Neurophysiol 2018; 129:1472-1478. [PMID: 29661595 DOI: 10.1016/j.clinph.2018.03.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 02/22/2018] [Accepted: 03/11/2018] [Indexed: 12/11/2022]
Abstract
OBJECTIVE To evaluate the excitability of sensory axons in patients with amyotrophic lateral sclerosis (ALS). METHODS Comprehensive sensory nerve excitability studies were prospectively performed on 28 sporadic ALS patients, compared to age-matched controls. Sensory nerve action potentials were recorded from digit 2 following median nerve stimulation at the wrist. Disease severity was measured using motor unit number estimation (MUNE), the revised ALS Functional Rating Scale (ALSFRS-R) and the MRC scale. RESULTS There were no significant differences in standard and extended measures of nerve excitability between ALS patients and controls. These unchanged excitability measures included accommodation to long-lasting hyperpolarization and the threshold changes after two supramaximal stimuli during the recovery cycle. Excitability parameters did not correlate with MUNE, ALSFRS-R, APB MRC scale or disease duration. CONCLUSIONS This cross-sectional study has identified normal axonal membrane properties in myelinated sensory axons of ALS patients. Previously described sensory abnormalities could be the result of axonal fallout, possibly due to a ganglionopathy, or to involvement of central sensory pathways rostral to gracile and cuneate nuclei. SIGNIFICANCE These results demonstrate the absence of generalized dysfunction of the membrane properties of sensory axons in ALS in the face of substantial deficits in motor function.
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Affiliation(s)
| | - James Howells
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - William Huynh
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - David Burke
- Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia; Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
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Howells J, Trinh T, Burke D, Kiernan MC. 13. Threshold-tracking TMS without an MEP. Clin Neurophysiol 2018. [DOI: 10.1016/j.clinph.2017.12.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Garg N, Park SB, Howells J, Noto YI, Yiannikas C, Krishnan AV, Spies J, Pollard JD, Vucic S, Bostock H, Kiernan MC. 1. Axonal function in inflammatory neuropathy: The importance of conduction block. Clin Neurophysiol 2018. [DOI: 10.1016/j.clinph.2017.12.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Agarwal S, Highton-Williamson E, Matamala JM, Caga J, Howells J, Vucic S, Ahmed RM, Kiernan MC. 9. Upper motor neuron dysfunction and neuropsychological profile in PLS: Another entrant on the ALS-FTD spectrum. Clin Neurophysiol 2018. [DOI: 10.1016/j.clinph.2017.12.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Li T, Howells J, Lin C, Garg N, Kiernan M, Park S. 8. Predicting motor disorders from nerve excitability studies. Clin Neurophysiol 2018. [DOI: 10.1016/j.clinph.2017.12.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Howells J, Bostock H, Park SB, Kiernan MC, Burke D. Tracking small sensory nerve action potentials in human axonal excitability studies. J Neurosci Methods 2018; 298:45-53. [DOI: 10.1016/j.jneumeth.2018.02.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 01/08/2018] [Accepted: 02/08/2018] [Indexed: 10/18/2022]
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Matamala JM, Howells J, Dharmadasa T, Trinh T, Ma Y, Lera L, Vucic S, Burke D, Kiernan MC. Inter-session reliability of short-interval intracortical inhibition measured by threshold tracking TMS. Neurosci Lett 2018; 674:18-23. [PMID: 29501687 DOI: 10.1016/j.neulet.2018.02.065] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 02/28/2018] [Accepted: 02/28/2018] [Indexed: 12/14/2022]
Abstract
Paired-pulse transcranial magnetic stimulation (TMS) using fixed test stimuli suffers from marked variability of the motor evoked potential (MEP) amplitude. Threshold tracking TMS (TT-TMS) was introduced to overcome this problem. The aim of this work was to describe the absolute and relative reliability of short-interval intracortical inhibition (SICI) using TT-TMS. Cortical excitability studies were performed on twenty-six healthy subjects over three sessions (two recordings on the same day and one seven days apart), with MEPs recorded over abductor pollicis brevis. Reliability was established by calculating the standard error of the measurements (SEm), minimal detectable change (MDC) and intraclass correlation coefficient (ICC). Resting motor threshold and averaged SICI presented the lowest SEm and highest ICCs. SICI at 1 ms showed a higher SEm than SICI at 3 ms, suggesting different physiological processes, but averaging SICI over a number of intervals greatly increases the reproducibility. The variability was lower for tests undertaken at the same time of day seven days apart compared to tests performed on the same day, and in both instances the ICC for averaged SICI was ≥0.81. The MDC in averaged SICI was reduced from 6.7% to 2% if the number of subjects was increased from one to eleven. In conclusion, averaged SICI is the most reproducible variable across paired-pulse TT-TMS measures, showing an excellent ICC. It is recommended that, in longitudinal studies, testing be performed at the same time of day and that changes in cortical excitability should be measured and averaged over a number of interstimulus intervals to minimise variability.
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Affiliation(s)
| | - James Howells
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Terry Trinh
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Yan Ma
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia
| | - Lydia Lera
- Institute of Nutrition and Food Technology, University of Chile, Santiago, 7830490, Chile
| | - Steve Vucic
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia; Western Clinical School, University of Sydney, Sydney, NSW 2145, Australia
| | - David Burke
- Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney, Sydney, NSW 2050, Australia; Sydney Medical School, University of Sydney, Sydney, NSW 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital, Sydney, NSW 2050, Australia
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Garg N, Park SB, Yiannikas C, Vucic S, Howells J, Noto YI, Mathey EK, Pollard JD, Kiernan MC. Neurofascin-155 IGG4 Neuropathy: Pathophysiological Insights, Spectrum of Clinical Severity and Response To treatment. Muscle Nerve 2017; 57:848-851. [DOI: 10.1002/mus.26010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 10/31/2017] [Accepted: 11/07/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Nidhi Garg
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
- Department of Neurology, Royal Prince Alfred Hospital; The University of Sydney; NSW Australia
| | - Susanna B. Park
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
| | - Con Yiannikas
- Department of Neurology, Concord and Royal North Shore Hospitals; The University of Sydney; NSW Australia
| | - Steve Vucic
- Departments of Neurology and Neurophysiology, Westmead Hospital; The University of Sydney; NSW Australia
| | - James Howells
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
| | - Yu-Ichi Noto
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
| | - Emily K. Mathey
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
| | - John D. Pollard
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
- Department of Neurology, Royal Prince Alfred Hospital; The University of Sydney; NSW Australia
| | - Matthew C. Kiernan
- Brain and Mind Centre, Sydney Medical School; The University of Sydney; 94 Mallett Street Camperdown, NSW 2050 Australia
- Department of Neurology, Royal Prince Alfred Hospital; The University of Sydney; NSW Australia
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Kandula T, Farrar M, Park S, Howells J, Carey K, Lin C. Maturation of motor and sensory axonal biophysical properties occurs in parallel from early childhood. J Neurol Sci 2017. [DOI: 10.1016/j.jns.2017.08.3609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Garg N, Howells J, Yiannikas C, Vucic S, Krishnan AV, Spies J, Bostock H, Mathey EK, Pollard JD, Park SB, Kiernan MC. Motor unit remodelling in multifocal motor neuropathy: The importance of axonal loss. Clin Neurophysiol 2017; 128:2022-2028. [DOI: 10.1016/j.clinph.2017.07.414] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 06/27/2017] [Accepted: 07/18/2017] [Indexed: 12/13/2022]
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Boland‐Freitas R, Lee J, Howells J, Liang C, Corbett A, Nicholson G, Ng K. Sarcolemmal excitability in the myotonic dystrophies. Muscle Nerve 2017; 57:595-602. [DOI: 10.1002/mus.25962] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 08/25/2017] [Accepted: 09/02/2017] [Indexed: 01/21/2023]
Affiliation(s)
- Robert Boland‐Freitas
- Department of Neurology and NeurophysiologyRoyal North Shore HospitalReserve RoadSt Leonards New South Wales Australia
- Department of NeurologyBlacktown HospitalBlacktown New South Wales Australia
| | - James Lee
- Department of Neurology and NeurophysiologyRoyal North Shore HospitalReserve RoadSt Leonards New South Wales Australia
| | - James Howells
- Sydney Medical SchoolCamperdown New South Wales Australia
| | - Christina Liang
- Department of Neurology and NeurophysiologyRoyal North Shore HospitalReserve RoadSt Leonards New South Wales Australia
| | - Alastair Corbett
- Department of NeurologyConcord HospitalConcord New South Wales Australia
| | - Garth Nicholson
- Department of Molecular MedicineConcord HospitalConcord New South Wales Australia
| | - Karl Ng
- Department of Neurology and NeurophysiologyRoyal North Shore HospitalReserve RoadSt Leonards New South Wales Australia
- Sydney Medical SchoolCamperdown New South Wales Australia
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Kanagaratnam M, Pendleton C, Souza DA, Pettit J, Howells J, Baker MD. Diuretic-sensitive electroneutral Na + movement and temperature effects on central axons. J Physiol 2017; 595:3471-3482. [PMID: 28213919 PMCID: PMC5451713 DOI: 10.1113/jp273963] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 02/13/2017] [Indexed: 01/26/2023] Open
Abstract
Key points Optic nerve axons get less excitable with warming. F‐fibre latency does not shorten at temperatures above 30°C. Action potential amplitude falls when the Na+‐pump is blocked, an effect speeded by warming. Diuretics reduce the rate of action potential fall in the presence of ouabain. Our data are consistent with electroneutral entry of Na+ occurring in axons and contributing to setting the resting potential.
Abstract Raising the temperature of optic nerve from room temperature to near physiological has effects on the threshold, refractoriness and superexcitability of the shortest latency (fast, F) nerve fibres, consistent with hyperpolarization. The temperature dependence of peak impulse latency was weakened at temperatures above 30°C suggesting a temperature‐sensitive process that slows impulse propagation. The amplitude of the supramaximal compound action potential gets larger on warming, whereas in the presence of bumetanide and amiloride (blockers of electroneutral Na+ movement), the action potential amplitude consistently falls. This suggests a warming‐induced hyperpolarization that is reduced by blocking electroneutral Na+ movement. In the presence of ouabain, the action potential collapses. This collapse is speeded by warming, and exposure to bumetanide and amiloride slows the temperature‐dependent amplitude decline, consistent with a warming‐induced increase in electroneutral Na+ entry. Blocking electroneutral Na+ movement is predicted to be useful in the treatment of temperature‐dependent symptoms under conditions with reduced safety factor (Uhthoff's phenomenon) and provide a route to neuroprotection. Optic nerve axons get less excitable with warming. F‐fibre latency does not shorten at temperatures above 30°C. Action potential amplitude falls when the Na+‐pump is blocked, an effect speeded by warming. Diuretics reduce the rate of action potential fall in the presence of ouabain. Our data are consistent with electroneutral entry of Na+ occurring in axons and contributing to setting the resting potential.
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Affiliation(s)
- Meneka Kanagaratnam
- Neuroscience and Trauma centre, Blizard Institute, Queen Mary University of London, 4 Newark Street, Whitechapel, London, E1 2AT, UK
| | - Christopher Pendleton
- Neuroscience and Trauma centre, Blizard Institute, Queen Mary University of London, 4 Newark Street, Whitechapel, London, E1 2AT, UK
| | - Danilo Almeida Souza
- Neuroscience and Trauma centre, Blizard Institute, Queen Mary University of London, 4 Newark Street, Whitechapel, London, E1 2AT, UK
| | - Joseph Pettit
- Neuroscience and Trauma centre, Blizard Institute, Queen Mary University of London, 4 Newark Street, Whitechapel, London, E1 2AT, UK
| | - James Howells
- Brain and Mind Research Institute, University of Sydney, 94 Mallet Street, Camperdown, NSW, 2050, Australia
| | - Mark D Baker
- Neuroscience and Trauma centre, Blizard Institute, Queen Mary University of London, 4 Newark Street, Whitechapel, London, E1 2AT, UK
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