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Stikvoort García DJL, Goedee HS, van Eijk RPA, van Schelven LJ, van den Berg LH, Sleutjes BTHM. Revisiting distinct nerve excitability patterns in patients with amyotrophic lateral sclerosis. Brain 2024; 147:2842-2853. [PMID: 38662766 DOI: 10.1093/brain/awae131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 03/29/2024] [Accepted: 04/08/2024] [Indexed: 08/02/2024] Open
Abstract
Amyotrophic lateral sclerosis is a devastating neurodegenerative disease, characterized by loss of central and peripheral motor neurons. Although the disease is clinically and genetically heterogeneous, axonal hyperexcitability is a commonly observed feature that has been suggested to reflect an early pathophysiological step linked to the neurodegenerative cascade. Therefore, it is important to clarify the mechanisms causing axonal hyperexcitability and how these relate to the clinical characteristics of patients. Measures derived directly from a nerve excitability recording are frequently used as study end points, although their biophysical basis is difficult to deduce. Mathematical models can aid in the interpretation but are reliable only when applied to group-averaged recordings. Consequently, model estimates of membrane properties cannot be compared with clinical characteristics or treatment effects in individual patients, posing a considerable limitation in heterogeneous diseases, such as amyotrophic lateral sclerosis. To address these challenges, we revisited nerve excitability using a new pattern analysis-based approach (principal component analysis). We evaluated disease-specific patterns of excitability changes and established their biophysical origins. Based on the observed patterns, we developed new compound measures of excitability that facilitate the implementation of this approach in clinical settings. We found that excitability changes in amyotrophic lateral sclerosis patients (n = 161, median disease duration = 11 months) were characterized by four unique patterns compared with controls (n = 50, age and sex matched). These four patterns were best explained by changes in resting membrane potential (modulated by Na+/K+ currents), slow potassium and sodium currents (modulated by their gating kinetics) and refractory properties of the nerve. Consequently, we were able to show that altered gating of slow potassium channels was associated with, and predictive of, the rate of progression of the disease on the amyotrophic lateral sclerosis functional rating scale. Based on these findings, we designed four composite measures that capture these properties to facilitate implementation outside this study. Our findings demonstrate that changes in nerve excitability in patients with amyotrophic lateral sclerosis are dominated by four distinct patterns, each with a distinct biophysical origin. Based on this new approach, we provide evidence that altered slow potassium-channel function might play a role in the rate of disease progression. The magnitudes of these patterns, quantified using a similar approach or our new composite measures, have potential as efficient measures to study membrane properties directly in amyotrophic lateral sclerosis patients, and thus aid prognostic stratification and trial design.
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Affiliation(s)
| | - H Stephan Goedee
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, 3584CX, The Netherlands
| | - Ruben P A van Eijk
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, 3584CX, The Netherlands
- Biostatistics and Research Support, Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, Universiteitsweg 100, 3584CX, Utrecht, The Netherlands
| | - Leonard J van Schelven
- Department of Medical Technology and Clinical Physics, University Medical Centre Utrecht, 3584CX, Utrecht, The Netherlands
| | - Leonard H van den Berg
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, 3584CX, The Netherlands
| | - Boudewijn T H M Sleutjes
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, 3584CX, The Netherlands
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Otani R, Shibuya K, Suzuki YI, Suichi T, Morooka M, Aotsuka Y, Ogushi M, Kuwabara S. Effects of motor cortical and peripheral axonal hyperexcitability on survival in amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry 2024; 95:730-736. [PMID: 38418214 DOI: 10.1136/jnnp-2023-333039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 02/13/2024] [Indexed: 03/01/2024]
Abstract
BACKGROUND Increased 'cortical' and 'peripheral' excitability are reportedly associated with shorter survival in amyotrophic lateral sclerosis (ALS) patients, suggesting that hyperexcitability contributes to motor neuron death. However, whether upper or lower motor function has a greater impact on survival is unclear. We aimed to investigate the component that strongly impacts the prognosis of ALS. METHODS A total of 103 consecutive patients with ALS who underwent cortical (threshold tracking transcranial magnetic stimulation (TMS)) and motor nerve excitability tests were included. Motor cortical excitability was evaluated using short-interval intracortical inhibition (SICI) during TMS. Motor axonal excitability was assessed using the strength-duration time constant (SDTC). Survival time was defined as the time from examination to death or tracheostomy. RESULTS Compared with healthy subjects, patients with ALS had lower SICI and longer SDTC (p<0.05), indicating increased excitability of cortical motor neurons and motor axons. According to the SICI and SDTC findings, patients were divided into the following four groups: 'cortical high and peripheral high (high-high)', 'high-low', 'low-high' and 'low-low' groups. In Kaplan-Meier curves, the 'high-high' and 'low-high' groups showed significantly shorter survival than the other groups. Multivariate analysis revealed that increased cortical (HR=5.3, p<0.05) and peripheral (HR=20.0, p<0.001) excitability were significantly associated with shorter survival. CONCLUSIONS In patients with ALS, both motor cortical and peripheral hyperexcitability independently affected survival time, with peripheral hyperexcitability having a greater impact on shorter survival. The modulation of neuronal/axonal excitability is a potential therapeutic target for ALS.
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Affiliation(s)
- Ryo Otani
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Kazumoto Shibuya
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Yo-Ichi Suzuki
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Tomoki Suichi
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Marie Morooka
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Yuya Aotsuka
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Moeko Ogushi
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
| | - Satoshi Kuwabara
- Neurology, Chiba University Graduate School of Medicine School of Medicine, Chiba, Japan
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3
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Lugg A, Schindle M, Sivak A, Tankisi H, Jones KE. Nerve excitability measured with the TROND protocol in amyotrophic lateral sclerosis: a systematic review and meta-analysis. J Neurophysiol 2023; 130:1480-1491. [PMID: 37910562 DOI: 10.1152/jn.00174.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 10/30/2023] [Accepted: 10/31/2023] [Indexed: 11/03/2023] Open
Abstract
This meta-analysis assessed the 30+ nerve excitability indices generated by the TROND protocol to identify potential biomarkers for amyotrophic lateral sclerosis (ALS). A comprehensive search was conducted in multiple databases to identify human studies that tested median motor axons. Forest plot analyses were performed using a random-effects model to determine the pooled effect (Z-score), heterogeneity (I2), and Cohen's d for potential biomarker identification. Out of 2,866 studies, 23 studies met the inclusion criteria, incorporating data from 719 controls and 942 patients with ALS. Seven indices emerged as potential biomarkers: depolarizing threshold electrotonus (TEd) 90-100 ms, strength-duration time constant (SDTC), superexcitability, TEd 40-60 ms, resting I/V slope, 50% depolarizing I/V, and subexcitability (ranked by the magnitude of the difference between patients and controls from largest to smallest). In a sensitivity analysis focusing on patients with larger compound muscle action potentials (CMAPs), only four indices were potential biomarkers: TEd 10-20 ms, TEd 90-100 ms, superexcitability, and SDTC. Among the extensive range of 30+ excitability indices generated by the TROND protocol, we have identified seven indices that effectively differentiate patients with ALS from healthy controls. Furthermore, a smaller subset of four indices shows promise as potential biomarkers when the CMAP remains relatively large. However, most studies were considered to be at moderate risk of bias due to case-control designs and absence of sensitivity and specificity calculations, underscoring the need for more prospective diagnostic test-accuracy studies with appropriate disease controls.NEW & NOTEWORTHY This meta-analysis uncovers seven potential axonal excitability biomarkers for lower motor neuron pathology in ALS, shedding light on ion channel dysfunction. The identified dysfunction aligns with the primary pathology-protein homeostasis disruption. These biomarkers could fill a gap to detect presymptomatic spread of the disease in the spinal cord and monitor treatments targeting protein homeostasis and limiting spread, toward enhancing patient care.
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Affiliation(s)
- Anna Lugg
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Mason Schindle
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Allison Sivak
- University of Alberta Library, Edmonton, Alberta, Canada
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Kelvin E Jones
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
- Neuroscience and Mental Health Institute, Edmonton, Alberta, Canada
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Stikvoort García DJL, Sleutjes BTHM, van Schelven LJ, Goedee HS, van den Berg LH. Diagnostic accuracy of nerve excitability and compound muscle action potential scan derived biomarkers in amyotrophic lateral sclerosis. Eur J Neurol 2023; 30:3068-3078. [PMID: 37354059 DOI: 10.1111/ene.15954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 06/26/2023]
Abstract
BACKGROUND AND PURPOSE The lack of reliable early biomarkers still causes substantial diagnostic delays in amyotrophic lateral sclerosis (ALS). The aim was to assess the diagnostic accuracy of a novel electrophysiological protocol in patients with suspected motor neuron disease (MND). METHODS Consecutive patients with suspected MND were prospectively recruited at our tertiary referral centre for MND in Utrecht, The Netherlands. Procedures were performed in accordance with the Standards for Reporting of Diagnostic Accuracy. In addition to the standard diagnostic workup, an electrophysiological protocol of compound muscle action potential (CMAP) scans and nerve excitability tests was performed on patients' thenar muscles. The combined diagnostic yield of nerve excitability and CMAP scan based motor unit number estimation was compared to the Awaji and Gold Coast criteria and their added value was determined. RESULTS In all, 153 ALS or progressive muscular atrophy patients, 63 disease controls and 43 healthy controls were included. Our electrophysiological protocol had high diagnostic accuracy (area under the curve [AUC] 0.85, 95% confidence interval [95% CI] 0.80-0.90), even in muscles with undetectable axon loss (AUC 0.78, 95% CI 0.70-0.85) and in bulbar-onset patients (AUC 0.85, 95% CI 0.73-0.95). Twenty-four of 33 (73%) ALS patients who could not be diagnosed during the same visit were correctly identified, as well as 8/13 (62%) ALS patients not meeting the Gold Coast criteria and 49/59 (83%) ALS patients not meeting the Awaji criteria during this first visit. CONCLUSIONS Our practical and non-invasive electrophysiological protocol may improve early diagnosis in clinically challenging patients with suspected ALS. Routine incorporation may boost early diagnosis, enhance patient selection and generate baseline measures for clinical trials.
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Affiliation(s)
- D J L Stikvoort García
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
| | - B T H M Sleutjes
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
| | - L J van Schelven
- Department of Medical Technology and Clinical Physics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - H S Goedee
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
| | - L H van den Berg
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
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Jørgensen HS, Jensen DB, Dimintiyanova KP, Bonnevie VS, Hedegaard A, Lehnhoff J, Moldovan M, Grondahl L, Meehan CF. Increased Axon Initial Segment Length Results in Increased Na + Currents in Spinal Motoneurones at Symptom Onset in the G127X SOD1 Mouse Model of Amyotrophic Lateral Sclerosis. Neuroscience 2020; 468:247-264. [PMID: 33246068 DOI: 10.1016/j.neuroscience.2020.11.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 10/22/2020] [Accepted: 11/10/2020] [Indexed: 12/13/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease preferentially affecting motoneurones. Transgenic mouse models have been used to investigate the role of abnormal motoneurone excitability in this disease. Whilst an increased excitability has repeatedly been demonstrated in vitro in neonatal and embryonic preparations from SOD1 mouse models, the results from the only studies to record in vivo from spinal motoneurones in adult SOD1 models have produced conflicting findings. Deficits in repetitive firing have been reported in G93A SOD1(high copy number) mice but not in presymptomatic G127X SOD1 mice despite shorter motoneurone axon initial segments (AISs) in these mice. These discrepancies may be due to the earlier disease onset and prolonged disease progression in G93A SOD1 mice with recordings potentially performed at a later sub-clinical stage of the disease in this mouse. To test this, and to explore how the evolution of excitability changes with symptom onset we performed in vivo intracellular recording and AIS labelling in G127X SOD1 mice immediately after symptom onset. No reductions in repetitive firing were observed showing that this is not a common feature across all ALS models. Immunohistochemistry for the Na+ channel Nav1.6 showed that motoneurone AISs increase in length in G127X SOD1 mice at symptom onset. Consistent with this, the rate of rise of AIS components of antidromic action potentials were significantly faster confirming that this increase in length represents an increase in AIS Na+ channels occurring at symptom onset in this model.
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Affiliation(s)
- H S Jørgensen
- Department of Neuroscience, University of Copenhagen, Denmark
| | - D B Jensen
- Department of Neuroscience, University of Copenhagen, Denmark
| | | | - V S Bonnevie
- Department of Neuroscience, University of Copenhagen, Denmark
| | - A Hedegaard
- Department of Neuroscience, University of Copenhagen, Denmark
| | - J Lehnhoff
- Department of Neuroscience, University of Copenhagen, Denmark
| | - M Moldovan
- Department of Neuroscience, University of Copenhagen, Denmark
| | - L Grondahl
- Department of Neuroscience, University of Copenhagen, Denmark
| | - C F Meehan
- Department of Neuroscience, University of Copenhagen, Denmark.
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Nakagawa Y, Yamada S. A novel hypothesis on metal dyshomeostasis and mitochondrial dysfunction in amyotrophic lateral sclerosis: Potential pathogenetic mechanism and therapeutic implications. Eur J Pharmacol 2020; 892:173737. [PMID: 33220280 DOI: 10.1016/j.ejphar.2020.173737] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Revised: 10/27/2020] [Accepted: 11/09/2020] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by motor dysfunctions resulting from the loss of upper (UMNs) and lower (LMNs) motor neurons. While ALS symptoms are coincidental with pathological changes in LMNs and UMNs, the causal relationship between the two is unclear. For example, research on the extra-motor symptoms associated with this condition suggests that an imbalance of metals, including copper, zinc, iron, and manganese, is initially induced in the sensory ganglia due to a malfunction of metal binding proteins and transporters. It is proposed that the resultant metal dyshomeostasis may promote mitochondrial dysfunction in the satellite glial cells of these sensory ganglia, causing sensory neuron disturbances and sensory symptoms. Sensory neuron hyperactivation can result in LMN impairments, while metal dyshomeostasis in spinal cord and brain stem parenchyma induces mitochondrial dysfunction in LMNs and UMNs. These events could prompt intracellular calcium dyshomeostasis, pathological TDP-43 formation, and reactive microglia with neuroinflammation, which in turn activate the apoptosis signaling pathways within the LMNs and UMNs. Our model suggests that the degeneration of LMNs and UMNs is incidental to the metal-induced changes in the spinal cord and brain stem. Over time psychiatric symptoms may appear as the metal dyshomeostasis and mitochondrial dysfunction affect other brain regions, including the reticular formation, hippocampus, and prefrontal cortex. It is proposed that metal dyshomeostasis in combination with mitochondrial dysfunction could be the underlying mechanism responsible for the initiation and progression of the pathological changes associated with both the motor and extra-motor symptoms of ALS.
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Affiliation(s)
- Yutaka Nakagawa
- Center for Pharma-Food Research (CPFR), Division of Pharmaceutical Sciences, Graduate School of Integrative Pharmaceutical and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
| | - Shizuo Yamada
- Center for Pharma-Food Research (CPFR), Division of Pharmaceutical Sciences, Graduate School of Integrative Pharmaceutical and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan
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7
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Gatto RG, Weissmann C, Amin M, Finkielsztein A, Sumagin R, Mareci TH, Uchitel OD, Magin RL. Assessing neuraxial microstructural changes in a transgenic mouse model of early stage Amyotrophic Lateral Sclerosis by ultra-high field MRI and diffusion tensor metrics. Animal Model Exp Med 2020; 3:117-129. [PMID: 32613171 PMCID: PMC7323706 DOI: 10.1002/ame2.12112] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Revised: 02/28/2020] [Accepted: 03/22/2020] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVE Cell structural changes are one of the main features observed during the development of amyotrophic lateral sclerosis (ALS). In this work, we propose the use of diffusion tensor imaging (DTI) metrics to assess specific ultrastructural changes in the central nervous system during the early neurodegenerative stages of ALS. METHODS Ultra-high field MRI and DTI data at 17.6T were obtained from fixed, excised mouse brains, and spinal cords from ALS (G93A-SOD1) mice. RESULTS Changes in fractional anisotropy (FA) and linear, planar, and spherical anisotropy ratios (CL, CP, and CS, respectively) of the diffusion eigenvalues were measured in white matter (WM) and gray matter (GM) areas associated with early axonal degenerative processes (in both the brain and the spinal cord). Specifically, in WM structures (corpus callosum, corticospinal tract, and spinal cord funiculi) as the disease progressed, FA, CL, and CP values decreased, whereas CS values increased. In GM structures (prefrontal cortex, hippocampus, and central spinal cord) FA and CP decreased, whereas the CL and CS values were unchanged or slightly smaller. Histological studies of a fluorescent mice model (YFP, G93A-SOD1 mouse) corroborated the early alterations in neuronal morphology and axonal connectivity measured by DTI. CONCLUSIONS Changes in diffusion tensor shape were observed in this animal model at the early, nonsymptomatic stages of ALS. Further studies of CL, CP, and CS as imaging biomarkers should be undertaken to refine this neuroimaging tool for future clinical use in the detection of the early stages of ALS.
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Affiliation(s)
- Rodolfo G. Gatto
- Department of BioengineeringUniversity of Illinois at ChicagoChicagoILUSA
| | - Carina Weissmann
- Instituto de Fisiología Biologia Molecular y Neurociencias‐IFIBYNE‐CONICETUniversity of Buenos AiresBuenos AiresArgentina
| | - Manish Amin
- Department of BiochemistryNational High Magnetic Field LaboratoryUniversity of FloridaGainesvilleFLUSA
| | - Ariel Finkielsztein
- Department of PathologySchool of MedicineNorthwestern UniversityChicagoILUSA
| | - Ronen Sumagin
- Department of PathologySchool of MedicineNorthwestern UniversityChicagoILUSA
| | - Thomas H. Mareci
- Department of BiochemistryNational High Magnetic Field LaboratoryUniversity of FloridaGainesvilleFLUSA
| | - Osvaldo D. Uchitel
- Instituto de Fisiología Biologia Molecular y Neurociencias‐IFIBYNE‐CONICETUniversity of Buenos AiresBuenos AiresArgentina
| | - Richard L. Magin
- Department of BioengineeringUniversity of Illinois at ChicagoChicagoILUSA
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Bonnevie VS, Dimintiyanova KP, Hedegaard A, Lehnhoff J, Grøndahl L, Moldovan M, Meehan CF. Shorter axon initial segments do not cause repetitive firing impairments in the adult presymptomatic G127X SOD-1 Amyotrophic Lateral Sclerosis mouse. Sci Rep 2020; 10:1280. [PMID: 31992746 PMCID: PMC6987224 DOI: 10.1038/s41598-019-57314-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 12/19/2019] [Indexed: 12/13/2022] Open
Abstract
Increases in axonal sodium currents in peripheral nerves are some of the earliest excitability changes observed in Amyotrophic Lateral Sclerosis (ALS) patients. Nothing is known, however, about axonal sodium channels more proximally, particularly at the action potential initiating region - the axon initial segment (AIS). Immunohistochemistry for Nav1.6 sodium channels was used to investigate parameters of AISs of spinal motoneurones in the G127X SOD1 mouse model of ALS in adult mice at presymptomatic time points (~190 days old). In vivo intracellular recordings from lumbar spinal motoneurones were used to determine the consequences of any AIS changes. AISs of both alpha and gamma motoneurones were found to be significantly shorter (by 6.6% and 11.8% respectively) in G127X mice as well as being wider by 9.8% (alpha motoneurones). Measurements from 20–23 day old mice confirmed that this represented a change during adulthood. Intracellular recordings from motoneurones in presymptomatic adult mice, however, revealed no differences in individual action potentials or the cells ability to initiate repetitive action potentials. To conclude, despite changes in AIS geometry, no evidence was found for reduced excitability within the functional working range of firing frequencies of motoneurones in this model of ALS.
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Affiliation(s)
- V S Bonnevie
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark
| | - K P Dimintiyanova
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark
| | - A Hedegaard
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark
| | - J Lehnhoff
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark
| | - L Grøndahl
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark
| | - M Moldovan
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark
| | - C F Meehan
- Department of Neuroscience, University of Copenhagen, Panum Institute, Blegdamsvej 3, DK-2200, Copenhagen N, Denmark.
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Kiernan MC, Bostock H, Park SB, Kaji R, Krarup C, Krishnan AV, Kuwabara S, Lin CSY, Misawa S, Moldovan M, Sung J, Vucic S, Wainger BJ, Waxman S, Burke D. Measurement of axonal excitability: Consensus guidelines. Clin Neurophysiol 2019; 131:308-323. [PMID: 31471200 DOI: 10.1016/j.clinph.2019.07.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 12/12/2022]
Abstract
Measurement of axonal excitability provides an in vivo indication of the properties of the nerve membrane and of the ion channels expressed on these axons. Axonal excitability techniques have been utilised to investigate the pathophysiological mechanisms underlying neurological diseases. This document presents guidelines derived for such studies, based on a consensus of international experts, and highlights the potential difficulties when interpreting abnormalities in diseased axons. The present manuscript provides a state-of-the-art review of the findings of axonal excitability studies and their interpretation, in addition to suggesting guidelines for the optimal performance of excitability studies.
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Affiliation(s)
- Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia.
| | - Hugh Bostock
- UCL Queen Square Institute of Neurology, London WC1N 3BG, United Kingdom
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Ryuji Kaji
- National Utano Hospital, 8-Narutaki Ondoyamacho, Ukyoku, Kyoto 616-8255, Japan
| | - Christian Krarup
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Satoshi Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Cindy Shin-Yi Lin
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Sonoko Misawa
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Mihai Moldovan
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Jiaying Sung
- Taipei Medical University, Wanfang Hospital, Taipei, Taiwan
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Western Clinical School, University of Sydney, Australia
| | - Brian J Wainger
- Department of Neurology and Anesthesiology, Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Stephen Waxman
- Department of Neurology, Yale Medical School, New Haven, CT 06510, USA; Neurorehabilitation Research Center, Veterans Affairs Hospital, West Haven, CT 06516, USA
| | - David Burke
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
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Chipika RH, Finegan E, Li Hi Shing S, Hardiman O, Bede P. Tracking a Fast-Moving Disease: Longitudinal Markers, Monitoring, and Clinical Trial Endpoints in ALS. Front Neurol 2019; 10:229. [PMID: 30941088 PMCID: PMC6433752 DOI: 10.3389/fneur.2019.00229] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Accepted: 02/22/2019] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) encompasses a heterogeneous group of phenotypes with different progression rates, varying degree of extra-motor involvement and divergent progression patterns. The natural history of ALS is increasingly evaluated by large, multi-time point longitudinal studies, many of which now incorporate presymptomatic and post-mortem assessments. These studies not only have the potential to characterize patterns of anatomical propagation, molecular mechanisms of disease spread, but also to identify pragmatic monitoring markers. Sensitive markers of progressive neurodegenerative change are indispensable for clinical trials and individualized patient care. Biofluid markers, neuroimaging indices, electrophysiological markers, rating scales, questionnaires, and other disease-specific instruments have divergent sensitivity profiles. The discussion of candidate monitoring markers in ALS has a dual academic and clinical relevance, and is particularly timely given the increasing number of pharmacological trials. The objective of this paper is to provide a comprehensive and critical review of longitudinal studies in ALS, focusing on the sensitivity profile of established and emerging monitoring markers.
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Affiliation(s)
| | - Eoin Finegan
- Computational Neuroimaging Group, Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Stacey Li Hi Shing
- Computational Neuroimaging Group, Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Orla Hardiman
- Computational Neuroimaging Group, Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Peter Bede
- Computational Neuroimaging Group, Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
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Agarwal S, Koch G, Hillis AE, Huynh W, Ward NS, Vucic S, Kiernan MC. Interrogating cortical function with transcranial magnetic stimulation: insights from neurodegenerative disease and stroke. J Neurol Neurosurg Psychiatry 2019; 90:47-57. [PMID: 29866706 DOI: 10.1136/jnnp-2017-317371] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 05/07/2018] [Accepted: 05/07/2018] [Indexed: 12/11/2022]
Abstract
Transcranial magnetic stimulation (TMS) is an accessible, non-invasive technique to study cortical function in vivo. TMS studies have provided important pathophysiological insights across a range of neurodegenerative disorders and enhanced our understanding of brain reorganisation after stroke. In neurodegenerative disease, TMS has provided novel insights into the function of cortical output cells and the related intracortical interneuronal networks. Characterisation of cortical hyperexcitability in amyotrophic lateral sclerosis and altered motor cortical function in frontotemporal dementia, demonstration of cholinergic deficits in Alzheimer's disease and Parkinson's disease are key examples where TMS has led to advances in understanding of disease pathophysiology and potential mechanisms of propagation, with the potential for diagnostic applications. In stroke, TMS methodology has facilitated the understanding of cortical reorganisation that underlie functional recovery. These insights are critical to the development of effective and targeted rehabilitation strategies in stroke. The present review will provide an overview of cortical function measures obtained using TMS and how such measures may provide insight into brain function. Through an improved understanding of cortical function across a range of neurodegenerative disorders, and identification of changes in neural structure and function associated with stroke that underlie clinical recovery, more targeted therapeutic approaches may now be developed in an evolving era of precision medicine.
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Affiliation(s)
- Smriti Agarwal
- Brain and Mind Centre, University of Sydney, and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Giacomo Koch
- Non-Invasive Brain Stimulation Unit, Neurologia Clinica e Comportamentale, Fondazione Santa Lucia IRCCS, Rome, Italy.,Stroke Unit, Department of Neuroscience, Policlinico Tor Vergata, Rome, Italy
| | - Argye E Hillis
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Cognitive Science, Johns Hopkins University, Baltimore, Maryland, USA
| | - William Huynh
- Brain and Mind Centre, University of Sydney, and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Nick S Ward
- Sobell Department of Motor Neuroscience, UCL Institute of Neurology, University College London, London, UK.,UCL Partners Centre for Neurorehabilitation, UCL Institute of Neurology, University College London, London, UK.,The National Hospital for Neurology and Neurosurgery, London, UK
| | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney, and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
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12
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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] [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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13
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Gatto RG, Li W, Magin RL. Diffusion tensor imaging identifies presymptomatic axonal degeneration in the spinal cord of ALS mice. Brain Res 2017; 1679:45-52. [PMID: 29175489 DOI: 10.1016/j.brainres.2017.11.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 11/14/2017] [Accepted: 11/18/2017] [Indexed: 12/11/2022]
Abstract
Extensive pathological evidence indicates that axonal degeneration represents an early and critical event in amyotrophic lateral sclerosis (ALS). Unfortunately, few MRI studies have focused in the early detection of white matter (WM) alterations in the spinal cord region. To unveil these WM changes, we performed high resolution diffusion tensor imaging (DTI) and correlated the results with histological analysis of adjacent slices taken from the spinal cords of presymptomatic mice. The DTI studies demonstrated a significant reduction in fractional anisotropy (FA) as well as axial diffusivities (AD) and an increase in radial diffusivity (RD), predominantly at lower segments of the spinal cord. Increases in FA and a reduction in AD and RD were observed in spinal cord (SC) gray matter (GM). Diffusion changes are associated with early and progressive alterations in axonal connectivity following a distal to proximal progression. Histological data tagging neuronal, axonal and glial cell markers demonstrated presymptomatic alterations in spinal cord WM and GM. This study demonstrates that DTI methods are optimal preclinical imaging tools to detect structural anomalies in WM and GM spinal cord during early stages of the disease.
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Affiliation(s)
- Rodolfo G Gatto
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA.
| | - Weiguo Li
- Department of Bioengineering, University of Illinois at Chicago, School of Engineering, Chicago, IL 60612, USA
| | - Richard L Magin
- Department of Bioengineering, University of Illinois at Chicago, School of Engineering, Chicago, IL 60612, USA
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14
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Stephanova DI, Kossev A. Temperature effects on accommodative processes in simulated amyotrophic lateral sclerosis in the physiological range. J Integr Neurosci 2017; 16:319-333. [PMID: 28891518 DOI: 10.3233/jin-170022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The present study investigates the temperature dependence of electrotonic potentials in mathematically-simulated myelinated axons with one of three increasingly-severe type of amyotrophic lateral sclerosis (ALS) pathology, termed as ALS1, ALS2 and ALS3, respectively, in the physiological range (30-37∘C). These potentials were elicited by long-lasting (100 ms) subthreshold polarizing current stimuli (±40% of the threshold). Numerical solutions were computed using our temperature-dependent multi-layered model. The results showed the following trends: (i) in ALS1, polarizing electrotonic potentials were normal; (ii) in ALS2 and ALS3, action potentials were elicited in the early parts of the depolarizing electrotonic potentials, and (iii) in ALS3, spontaneous discharges were elicited after the termination of applied hyperpolarizing stimuli (i.e., post-anodal excitation). The ionic currents underlying electrotonic potentials in the ALS1 case were attributable to the activation of potassium fast (Kf+) and slow (Ks+) channels in the nodal and internodal axolemma beneath the myelin sheath. By contrast, in ALS2 and ALS3, the depolarizing stimuli activated the classical "transient" Na+ channels in the nodal and internodal axolemma beneath the myelin sheath eliciting action potential generation. These results obtained were closer to those observed in hypothermia (⩽25∘C) than in hyperthermia (⩾40∘C).
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Affiliation(s)
- D I Stephanova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. Bl 21, Sofia 1113, Bulgaria
| | - A Kossev
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. Bl 21, Sofia 1113, Bulgaria
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15
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de Carvalho M, Kiernan MC, Swash M. Fasciculation in amyotrophic lateral sclerosis: origin and pathophysiological relevance. J Neurol Neurosurg Psychiatry 2017; 88:773-779. [PMID: 28490504 DOI: 10.1136/jnnp-2017-315574] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 03/20/2017] [Accepted: 03/29/2017] [Indexed: 12/11/2022]
Abstract
This review considers the origin and significance of fasciculations in neurological practice, with an emphasis on fasciculations in amyotrophic lateral sclerosis (ALS), and in benign fasciculation syndromes. Fasciculation represents a brief spontaneous contraction that affects a small number of muscle fibres, causing a flicker of movement under the skin. While an understanding of the role of fasciculation in ALS remains incomplete, fasciculations derive from ectopic activity generated in the motor system. A proximal origin seems likely to contribute to the generation of fasciculation in the early stages of ALS, while distal sites of origin become more prominent later in the disease, associated with distal motor axonal sprouting as part of the reinnervation response that develops secondary to loss of motor neurons. Fasciculations are distinct from the recurrent trains of axonal firing described in neuromyotonia. Fasciculation without weakness, muscle atrophy or increased tendon reflexes suggests a benign fasciculation syndrome, even when of sudden onset. Regardless of origin, fasciculations often present as the initial abnormality in ALS, an early harbinger of dysfunction and aberrant firing of motor neurons.
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Affiliation(s)
- Mamede de Carvalho
- Department of Neurosciences and Mental Health, Hospital de Santa Maria-CHLN, Lisbon, Portugal.,Institute of Physiology-IMM, Faculty of Medicine, University of Lisbon, Lisbon, Portugal
| | - Matthew C Kiernan
- Bushell Chair of Neurology, Sydney Medical School, University of Sydney, Brain & Mind Centre, University of Sydney, Sydney, NSW, Australia
| | - Michael Swash
- Institute of Physiology-IMM, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.,Department of Neurology, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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16
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Maglemose R, Hedegaard A, Lehnhoff J, Dimintiyanova KP, Moldovan M, Grøndahl L, Meehan CF. Potassium channel abnormalities are consistent with early axon degeneration of motor axons in the G127X SOD1 mouse model of amyotrophic lateral sclerosis. Exp Neurol 2017; 292:154-167. [PMID: 28322742 DOI: 10.1016/j.expneurol.2017.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 02/21/2017] [Accepted: 03/14/2017] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disease, which selectively affects upper and lower motoneurones. The underlying pathophysiology of the disease is complex but electrophysiological studies of peripheral nerves in ALS patients as well as human autopsy studies indicate that a potassium channel dysfunction/loss is present early in the symptomatic phase. It remains unclear to what extent potassium channel abnormalities reflect a specific pathogenic mechanism in ALS. The aim of this study was therefore to investigate the temporal changes in the expression and/or function of potassium channels in motoneurones in the adult G127X SOD1 mouse model of ALS, a model which has a very long presymptomatic phase. Evidence from animal models indicates that the early progressive motoneurone dysfunction and degeneration can be largely compensated by motor unit remodeling, delaying the clinical symptom onset. Experiments were therefore performed both before and after symptom onset. Immunohistochemistry of motor axons in the ventral roots of G127X SOD1 mice, was used to investigate juxta-paranodal Kv1.2 potassium channels along with nodal Nav1.6 and the paranodal scaffolding protein Caspr. This allowed an investigation of changes in the distribution of Kv1.2 relative to the general structure of the nodal-paranodal-juxta-paranodal complex. This revealed that the motor axons in the ventral roots of presymptomatic G127X SOD1 mice, already show a disruption in juxta-paranodal Kv1.2 potassium channels. The axonal Kv1.2 disruption was preceded by abnormalities in the distribution of the paranodal scaffolding protein Caspr with the nodal arrangement of Nav1.6 appearing relatively preserved even in symptomatic mice. These changes were accompanied by axon swelling and a slowing of conduction in the peripheral motor axons in symptomatic mice. In vivo electrophysiological intracellular recordings of individual spinal motoneurones revealed that central potassium channel function was preserved or even enhanced with higher amplitude and longer duration after-hyperpolarisations in the G127X SOD1 mice. Our data suggest that the potassium channel abnormalities observed in presymptomatic G127X, rather than representing a specific pathophysiological mechanism targeting potassium channels, most likely reflect early axonal degenerative changes, consistent with the "dying-back" phenomenon observed in other ALS models.
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Affiliation(s)
- Rikke Maglemose
- Centre for Neuroscience, Copenhagen University, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Anne Hedegaard
- Centre for Neuroscience, Copenhagen University, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Janna Lehnhoff
- Centre for Neuroscience, Copenhagen University, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | | | - Mihai Moldovan
- Centre for Neuroscience, Copenhagen University, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Lillian Grøndahl
- Centre for Neuroscience, Copenhagen University, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Claire Francesca Meehan
- Centre for Neuroscience, Copenhagen University, Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
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17
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Stephanova DI, Kossev A. Theoretical predication of temperature effects on accommodative processes in simulated amyotrophic lateral sclerosis during hypothermia and hyperthermia. J Integr Neurosci 2017; 15:553-569. [PMID: 28100104 DOI: 10.1142/s0219635216500308] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Electrotonic potentials allow the accommodative processes to long-lasting subthreshold polarizing stimuli to be assessed. The present study investigates such potentials in previously simulated cases of amyotrophic lateral sclerosis, termed as ALS1, ALS2 and ALS3, respectively, when the temperature is changed during hypothermia ([Formula: see text]C) and hyperthermia ([Formula: see text]C). The ALS cases are modeled as three progressively severe uniform axonal dysfunctions along the human motor nerve fiber which is simulated by our temperature-dependent multi-layered numerical model. The results show that the polarizing electrotonic potentials in the ALS1 case are quite similar to those in the normal case during hypothermia. Their defining currents are caused by the activation of potassium fast (K[Formula: see text]) and slow (K[Formula: see text]) channels in the nodal and internodal axolemma beneath the myelin sheath. Except in the ALS3 case at 20[Formula: see text]C, where the accommodative processes are blocked by depolarizing stimuli, in the ALS2 and ALS3 cases during hypothermia these stimuli activate the classical "transient" Na[Formula: see text] channels in the nodal and internodal axolemma beneath the myelin sheath. And this leads to action potential generations during the early parts of electrotonic responses in all compartments along the fiber length. Only in the ALS3 case after the termination of long-lasting subthreshold hyperpolarizing stimuli, action potential generations are obtained in the late parts of electrotonic potentials along the fiber length. In comparison to the normal case, in the gradually severe ALS cases, the depolarizing electrotonic potentials gradually increase, while the hyperpolarizing electrotonic potentials gradually decrease during hyperthermia. However, the repetitive firings are not obtained in these polarizing electrotonic potentials. The results show that the accommodative processes to depolarizing stimuli in the ALS3 case are more likely to be blocked during hypothermia than hyperthermia. The results also show that the polarizing electrotonic potentials in the three simulated ALS cases are specific indicators for the motor nerve disease ALS during hypothermia and hyperthermia.
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Affiliation(s)
- D I Stephanova
- 1 Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. Bl 21, Sofia 1113, Bulgaria
| | - A Kossev
- 1 Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. Bl 21, Sofia 1113, Bulgaria
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18
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Park SB, Kiernan MC, Vucic S. Axonal Excitability in Amyotrophic Lateral Sclerosis : Axonal Excitability in ALS. Neurotherapeutics 2017; 14:78-90. [PMID: 27878516 PMCID: PMC5233634 DOI: 10.1007/s13311-016-0492-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Axonal excitability testing provides in vivo assessment of axonal ion channel function and membrane potential. Excitability techniques have provided insights into the pathophysiological mechanisms underlying the development of neurodegeneration and clinical features of amyotrophic lateral sclerosis (ALS) and related neuromuscular disorders. Specifically, abnormalities of Na+ and K+ conductances contribute to development of membrane hyperexcitability in ALS, thereby leading to symptom generation of muscle cramps and fasciculations, in addition to promoting a neurodegenerative cascade via Ca2+-mediated processes. Modulation of axonal ion channel function in ALS has resulted in significant symptomatic improvement that has been accompanied by stabilization of axonal excitability parameters. Separately, axonal ion channel dysfunction evolves with disease progression and correlates with survival, thereby serving as a potential therapeutic biomarker in ALS. The present review provides an overview of axonal excitability techniques and the physiological mechanisms underlying membrane excitability, with a focus on the role of axonal ion channel dysfunction in motor neuron disease and related neuromuscular diseases.
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Affiliation(s)
- Susanna B Park
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | | | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, Australia.
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19
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Iwai Y, Shibuya K, Misawa S, Sekiguchi Y, Watanabe K, Amino H, Kuwabara S. Axonal Dysfunction Precedes Motor Neuronal Death in Amyotrophic Lateral Sclerosis. PLoS One 2016; 11:e0158596. [PMID: 27383069 PMCID: PMC4934877 DOI: 10.1371/journal.pone.0158596] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 06/18/2016] [Indexed: 12/20/2022] Open
Abstract
Wide-spread fasciculations are a characteristic feature in amyotrophic lateral sclerosis (ALS), suggesting motor axonal hyperexcitability. Previous excitability studies have shown increased nodal persistent sodium conductances and decreased potassium currents in motor axons of ALS patients, both of the changes inducing hyperexcitability. Altered axonal excitability potentially contributes to motor neuron death in ALS, but the relationship of the extent of motor neuronal death and abnormal excitability has not been fully elucidated. We performed multiple nerve excitability measurements in the median nerve at the wrist of 140 ALS patients and analyzed the relationship of compound muscle action potential (CMAP) amplitude (index of motor neuronal loss) and excitability indices, such as strength-duration time constant, threshold electrotonus, recovery cycle and current-threshold relationships. Compared to age-matched normal controls (n = 44), ALS patients (n = 140) had longer strength-duration time constant (SDTC: a measure of nodal persistent sodium current; p < 0.05), greater threshold changes in depolarizing threshold electrotonus (p < 0.05) and depolarizing current threshold relationship (i.e. less accommodation; (p < 0.05), greater superexcitability (a measure of fast potassium current; p < 0.05) and reduced late subexcitability (a measure of slow potassium current; p < 0.05), suggesting increased persistent sodium currents and decreased potassium currents. The reduced potassium currents were found even in the patient subgroups with normal CMAP (> 5mV). Regression analyses showed that SDTC (R = -0.22) and depolarizing threshold electrotonus (R = -0.22) increased with CMAP decline. These findings suggest that motor nerve hyperexcitability occurs in the early stage of the disease, and precedes motor neuronal loss in ALS. Modulation of altered ion channel function could be a treatment option for ALS.
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Affiliation(s)
- Yuta Iwai
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Kazumoto Shibuya
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Sonoko Misawa
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Yukari Sekiguchi
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Keisuke Watanabe
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Hiroshi Amino
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Satoshi Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
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20
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de Carvalho M, Swash M. Lower motor neuron dysfunction in ALS. Clin Neurophysiol 2016; 127:2670-81. [DOI: 10.1016/j.clinph.2016.03.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 02/08/2016] [Accepted: 03/01/2016] [Indexed: 12/11/2022]
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21
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Noto YI, Shibuya K, Vucic S, Kiernan MC. Novel therapies in development that inhibit motor neuron hyperexcitability in amyotrophic lateral sclerosis. Expert Rev Neurother 2016; 16:1147-54. [DOI: 10.1080/14737175.2016.1197774] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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22
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23
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Sleutjes BTHM, Maathuis EM, van Doorn PA, Blok JH, Visser GH. Electrically evoked multiplet discharges are associated with more marked clinical deterioration in motor neuron disease. Muscle Nerve 2015; 53:222-6. [PMID: 25960042 DOI: 10.1002/mus.24700] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/06/2015] [Indexed: 12/12/2022]
Abstract
INTRODUCTION The aim of this study was to determine whether electrically evoked multiplet discharges (MDs) are related to severity of clinical deterioration in motor neuron disease (MND). METHODS Stimulated high-density surface electromyographic (HDsEMG) recordings were performed in thenar muscles. Data were collected from 31 MND patients. MDs from the HDsEMG recordings were determined at baseline. ALSFRS-R scores were obtained at baseline and at a maximum of 16 weeks follow-up. RESULTS The presence of MDs was associated with progressive deterioration of ALSFRS-R score (P = 0.02) and fine motor function (FMF) (P < 0.001). Patients who had a higher number of motor units that generated MDs (r = 0.61, P < 0.001) and patients who had a higher number of MDs (as percentage of applied stimuli) (r = 0.59, P = 0.001) had a more severe decline in FMF. CONCLUSIONS Electrically evoked MDs are associated with more marked clinical deterioration in patients with MND.
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Affiliation(s)
- Boudewijn T H M Sleutjes
- Department of Clinical Neurophysiology, University Medical Centre Rotterdam, P.O. Box 2040, 3000, CA Rotterdam, The Netherlands
| | - Ellen M Maathuis
- Department of Clinical Neurophysiology, University Medical Centre Rotterdam, P.O. Box 2040, 3000, CA Rotterdam, The Netherlands
| | - Pieter A van Doorn
- Department of Neurology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Joleen H Blok
- Department of Clinical Neurophysiology, University Medical Centre Rotterdam, P.O. Box 2040, 3000, CA Rotterdam, The Netherlands.,Department of Clinical Physics, Máxima Medical Centre Veldhoven, Veldhoven, The Netherlands
| | - Gerhard H Visser
- Department of Clinical Neurophysiology, University Medical Centre Rotterdam, P.O. Box 2040, 3000, CA Rotterdam, The Netherlands.,Department of Clinical Neurophysiology, SEIN Heemstede, Heemstede, The Netherlands
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24
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Chen X, Shang HF. New developments and future opportunities in biomarkers for amyotrophic lateral sclerosis. Transl Neurodegener 2015; 4:17. [PMID: 26425343 PMCID: PMC4589120 DOI: 10.1186/s40035-015-0040-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 09/20/2015] [Indexed: 02/05/2023] Open
Abstract
Modern technology has improved the ability to probe effectively the underlying biology of ALS by examination of genomic, proteomic and physiological changes in patients with ALS, as well as to monitor functional and structural changes during the course of disease. While effective treatments for ALS are lacking, the discovery of sensitive biomarkers to disease activity offers clinicians tools for rapid diagnosis and insights into the pathophysiology of ALS. The ultimate aim is to lessen reliance on clinical measures and survival as trial endpoints and broaden the therapeutic options for patients with this disease.
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Affiliation(s)
- Xueping Chen
- Department of Neurology, West China Hospital, Sichuan University, 610041 Chengdu, Sichuan China
| | - Hui-Fang Shang
- Department of Neurology, West China Hospital, Sichuan University, 610041 Chengdu, Sichuan China
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25
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Mancuso R, Navarro X. Amyotrophic lateral sclerosis: Current perspectives from basic research to the clinic. Prog Neurobiol 2015; 133:1-26. [PMID: 26253783 DOI: 10.1016/j.pneurobio.2015.07.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 07/30/2015] [Accepted: 07/31/2015] [Indexed: 02/07/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive degeneration of upper and lower motoneurons, leading to muscle weakness and paralysis, and finally death. Considerable recent advances have been made in basic research and preclinical therapeutic attempts using experimental models, leading to increasing clinical and translational research in the context of this disease. In this review we aim to summarize the most relevant findings from a variety of aspects about ALS, including evaluation methods, animal models, pathophysiology, and clinical findings, with particular emphasis in understanding the role of every contributing mechanism to the disease for elucidating the causes underlying degeneration of motoneurons and the development of new therapeutic strategies.
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Affiliation(s)
- Renzo Mancuso
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain
| | - Xavier Navarro
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
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Menezes MP, Farrar MA, Webster R, Antony J, O'Brien K, Ouvrier R, Kiernan MC, Burns J, Vucic S. Pathophysiology of motor dysfunction in a childhood motor neuron disease caused by mutations in the riboflavin transporter. Clin Neurophysiol 2015; 127:911-918. [PMID: 26092362 DOI: 10.1016/j.clinph.2015.05.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 05/19/2015] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Brown-Vialetto-Van Laere (BVVL) syndrome is a progressive motor and sensory neuronopathy secondary to mutations in SLC52A2 encoding the riboflavin transporter type 2 (RFVT2). The phenotype is characterized by early childhood onset hearing loss and sensory ataxia followed by progressive upper limb weakness, optic atrophy, bulbar weakness and respiratory failure. To gain further insight into disease pathophysiology and response to riboflavin supplementation, the present study investigated whether axonal ion channel or membrane abnormalities were a feature of BVVL. METHODS Axonal excitability studies and clinical assessments were prospectively undertaken on six patients with BVVL secondary to riboflavin transporter deficiency type 2 (age range 10-21 years) at baseline and after 12 months of riboflavin (1000 mg daily) therapy. RESULTS At baseline, depolarizing and hyperpolarizing threshold electrotonus was 'fanned out' and superexcitability was increased, while the resting current-threshold gradient and refractoriness were significantly reduced in BVVL patients when compared to controls. Mathematical modeling suggested that functional alterations of myelin underlay these findings with an increase in myelin permeability. Riboflavin therapy resulted in partial normalization of the axonal excitability findings, paralleled by maintenance of muscle strength. CONCLUSIONS The present study established that abnormalities in myelin permeability at the paranode was a feature of BVVL and were partially normalized with riboflavin therapy. SIGNIFICANCE This study reveals a novel pathophysiological process for motor nerve dysfunction in BVVL. It also indicates that nerve excitability studies may be further developed in larger cohorts as a potential biomarker to identify treatment response for BVVL patients.
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Affiliation(s)
- Manoj P Menezes
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Discipline of Paediatrics and Child Health, The Children's Hospital at Westmead Clinical School, The University of Sydney, Sydney, Australia; Department of Neurology, The Children's Hospital at Westmead, Sydney, Australia
| | - Michelle A Farrar
- Discipline of Paediatrics, School of Women's and Children's Health, UNSW Medicine, The University of New South Wales, Sydney, Australia; Neurosciences Research Australia, Sydney, Australia; Department of Neurology, Sydney Children's Hospital, Sydney, Australia.
| | - Richard Webster
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Department of Neurology, The Children's Hospital at Westmead, Sydney, Australia
| | - Jayne Antony
- Department of Neurology, The Children's Hospital at Westmead, Sydney, Australia
| | - Katherine O'Brien
- Department of Audiology, The Children's Hospital at Westmead, Sydney, Australia
| | - Robert Ouvrier
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Discipline of Paediatrics and Child Health, The Children's Hospital at Westmead Clinical School, The University of Sydney, Sydney, Australia; Department of Neurology, The Children's Hospital at Westmead, Sydney, Australia
| | - Matthew C Kiernan
- Neurosciences Research Australia, Sydney, Australia; Sydney Medical School, Brain & Mind Research Institute, University of Sydney, Sydney, Australia
| | - Joshua Burns
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia; Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network, Sydney, Australia; Sydney Arthritis and Musculoskeletal Research Network, The University of Sydney, Sydney, Australia
| | - Steve Vucic
- Department of Neurology, Westmead Hospital and Western Clinical School, University of Sydney, Sydney, Australia
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Shibuya K, Misawa S, Kimura H, Noto YI, Sato Y, Sekiguchi Y, Iwai Y, Mitsuma S, Beppu M, Watanabe K, Fujimaki Y, Tsuji Y, Shimizu T, Mizuno T, Nakagawa M, Sawaguchi K, Hanaoka H, Kuwabara S. A single blind randomized controlled clinical trial of mexiletine in amyotrophic lateral sclerosis: Efficacy and safety of sodium channel blocker phase II trial. Amyotroph Lateral Scler Frontotemporal Degener 2015; 16:353-8. [DOI: 10.3109/21678421.2015.1038277] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Simon NG, Turner MR, Vucic S, Al-Chalabi A, Shefner J, Lomen-Hoerth C, Kiernan MC. Quantifying disease progression in amyotrophic lateral sclerosis. Ann Neurol 2014; 76:643-57. [PMID: 25223628 PMCID: PMC4305209 DOI: 10.1002/ana.24273] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 09/12/2014] [Accepted: 09/12/2014] [Indexed: 12/28/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) exhibits characteristic variability of onset and rate of disease progression, with inherent clinical heterogeneity making disease quantitation difficult. Recent advances in understanding pathogenic mechanisms linked to the development of ALS impose an increasing need to develop strategies to predict and more objectively measure disease progression. This review explores phenotypic and genetic determinants of disease progression in ALS, and examines established and evolving biomarkers that may contribute to robust measurement in longitudinal clinical studies. With targeted neuroprotective strategies on the horizon, developing efficiencies in clinical trial design may facilitate timely entry of novel treatments into the clinic.
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Affiliation(s)
- Neil G Simon
- Department of Neurology, University of California, San Francisco, San Francisco, CA; Prince of Wales Clinical School, University of New South Wales, Randwick, Australia; Neuroscience Research Australia, Barker St, Randwick, Australia
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Sleutjes BTHM, Montfoort I, van Doorn PA, Visser GH, Blok JH. Increased supernormality in patients with multiplet discharges: Evidence for a common pathophysiological mechanism behind multiplets and fasciculations. Clin Neurophysiol 2014; 126:1440-5. [PMID: 25468238 DOI: 10.1016/j.clinph.2014.10.145] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 10/16/2014] [Accepted: 10/21/2014] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To determine whether there is a relation between electrically evoked multiplet discharges (MDs) and motor axonal excitability properties. We hypothesized that electrically evoked MDs share their underlying pathophysiological mechanism with fasciculations. METHODS High-density surface EMG and motor nerve excitability recordings of the thenar muscles were performed in 22 patients with motor neuron disease (MND) in their differential diagnosis and who were referred for EMG examination. RESULTS Supernormality (hyperexcitable phase following the refractory period) was significantly increased in patients with MDs (n=10) compared to patients without MDs (n=12) (25.5% vs 17.0%; p=0.02). Depolarizing threshold electrotonus differed significantly between both groups as well (TEdpeak, 76.6% vs 66.6%, p<0.01; TEd90-100ms, 51.7% vs 44.3%, p<0.01) CONCLUSIONS: Our findings imply that the same pathophysiological excitability changes are involved in generating MDs and fasciculations. Yet, MDs may be quantified more easily, and may be more specific for abnormal distal excitability than fasciculations, because fasciculations may originate along the motor axon as well as in the neuron cell body. SIGNIFICANCE MDs are potentially useful as objective measure of increased distal axonal excitability at individual motor unit level and might complement clinical studies in MND.
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Affiliation(s)
| | | | - Pieter A van Doorn
- Department of Neurology, Erasmus MC, University Medical Centre Rotterdam, The Netherlands
| | - Gerhard H Visser
- Department of Clinical Neurophysiology, The Netherlands; Department of Clinical Neurophysiology, SEIN Heemstede, The Netherlands
| | - Joleen H Blok
- Department of Clinical Neurophysiology, The Netherlands; Department of Clinical Physics, Reinier de Graaf Hospital Delft, The Netherlands
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Sato A, Sakai N, Shinbo J, Hashidate H, Igarashi S, Kakita A, Yamazaki M. [An autopsy case of amyotrophic lateral sclerosis with prominent muscle cramps, fasciculation, and high titer of anti-voltage gated potassium channel (VGKC) complex antibody]. Rinsho Shinkeigaku 2014; 54:32-7. [PMID: 24429646 DOI: 10.5692/clinicalneurol.54.32] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The patient was a 55-year-old male who had prominent fasciculation and muscle cramps. Muscle weakness and atrophy of the trunk, respiratory system, and extremities gradually progressed. On the basis of these features, we diagnosed this patient as having amyotrophic lateral sclerosis (ALS), however, the upper motor neuron signs were not significant. Following the detection of the anti-voltage gated potassium channel (VGKC) complex antibody at 907.5 pM (normal < 100 pM) and repetitive discharge in a nerve conduction study, immunotherapy with intravenous immunoglobulin, methylprednisolone (mPSL), double filtration plasmapheresis (DFPP), ciclosporin, and rituximab was introduced. mPSL and DFPP showed only tentative effectiveness for fasciculation and muscle cramps, respectively. Thereafter, muscle weakness progressed. The patient died of type II respiratory failure at the age of 57 years, about 2 years after the onset of the disease. At autopsy, a histopathological diagnosis of ALS with lower-motor-predominant degeneration was made. Characteristic cellular features, including Bunina bodies in the remaining lower motor neurons and phosphorylated TAR DNA-binding protein 43-kDa (pTDP-43)-immunopositive inclusions in both upper and lower motor neuron systems, were evident. At present, an immunological role of the anti-VGKC complex antibody in the development of cramp-fasciculation syndrome has been speculated. In this ALS patient, the antibodies might be associated with pathomechanisms underlying the characteristic symptoms.
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Affiliation(s)
- Aki Sato
- Department of Neurology, Niigata City General Hospital
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Liang C, Ng K. Comparing axonal excitability in past polio to amyotrophic lateral sclerosis. Muscle Nerve 2014; 50:602-4. [PMID: 24752543 DOI: 10.1002/mus.24265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2014] [Indexed: 11/06/2022]
Abstract
INTRODUCTION Poliomyelitis causes selective destruction of anterior horn cells and usually has a stable disease course post-infection. We assessed the excitability characteristics in patients with a stable course after past poliomyelitis and compared them with changes described in amyotrophic lateral sclerosis (ALS). METHODS The excitability characteristics of motor and sensory nerves were studied in 10 subjects with stable past poliomyelitis. RESULTS Motor rheobase was increased, but there were no significant changes in strength-duration properties or depolarizing threshold electrotonus, as have been seen in previous studies of ALS. CONCLUSIONS There is minimal change in axonal excitability properties in patients with stable past poliomyelitis. The results may signify sufficient compensation in the stable state of the disease. Increased subexcitability in 1 subject with demonstrable hyperexcitability may represent compensation for increased ectopic activity rather than a different process in surviving motor neurons. Muscle Nerve 50: 602-604, 2014.
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Affiliation(s)
- Christina Liang
- Department of Neurology and Clinical Neurophysiology, Royal North Shore Hospital, Sydney, St Leonards, New South Wales, 2065, Australia
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Arnold R, Kwai NC, Krishnan AV. Mechanisms of axonal dysfunction in diabetic and uraemic neuropathies. Clin Neurophysiol 2013; 124:2079-90. [DOI: 10.1016/j.clinph.2013.04.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 04/12/2013] [Accepted: 04/13/2013] [Indexed: 12/13/2022]
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Vucic S, Lin CSY, Cheah BC, Murray J, Menon P, Krishnan AV, Kiernan MC. Riluzole exerts central and peripheral modulating effects in amyotrophic lateral sclerosis. ACTA ACUST UNITED AC 2013; 136:1361-70. [PMID: 23616585 DOI: 10.1093/brain/awt085] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Riluzole, a benzothiazole derivative, has been shown to be effective in prolonging survival in amyotrophic lateral sclerosis. The mechanisms by which riluzole exerts neuroprotective effects in amyotrophic lateral sclerosis remains to be fully elucidated, although inhibition of glutamatergic transmission and modulation of Na+ channel function have been proposed. In an attempt to determine the mechanisms by which riluzole exerts neuroprotective effects, in particular to dissect the relative contributions of inhibition of glutamatergic transmission and Na+ channel modulation, the present study utilized a combination of cortical and peripheral axonal excitability approaches to monitor changes in excitability and function in patients with amyotrophic lateral sclerosis. Cortical assessment was undertaken by utilising the threshold tracking transcranial magnetic stimulation (TMS) technique and combined with peripheral axonal excitability studies in 25 patients with amyotrophic lateral sclerosis. Studies were performed at baseline and repeated when patients were receiving riluzole 100 mg/day. At the time of second testing all patients were tolerating the medication well. Motor evoked potential and compound muscle action potential responses were recorded over the abductor pollicis brevis muscle. At baseline, features of cortical hyperexcitability were evident in patients with amyotrophic lateral sclerosis, indicated by marked reduction in short interval intracortical inhibition (P < 0.001) and cortical silent period duration (P < 0.001), as well as an increase in the motor evoked potential amplitude (P < 0.01). Riluzole therapy partially normalized cortical excitability by significantly increasing short interval intracortical inhibition (short interval intracortical inhibitionbaseline 0.5 ± 1.8%; short interval intracortical inhibitionON riluzole 7.9 ± 1.7%, P < 0.01). In contrast, riluzole did not exert any modulating effect on cortical silent period duration (P = 0.45) or motor evoked potential amplitude (P = 0.31). In terms of peripheral nerve function, axonal excitability studies established that, relative to control subjects, patients with amyotrophic lateral sclerosis had significant increases in depolarizing threshold electrotonus [amyotrophic lateral sclerosisbaseline TEd (90-100 ms) 49.1 ± 1.8%; controlsTEd (90-100 ms) 45.2 ± 0.6%, P < 0.01] and superexcitability (amyotrophic lateral sclerosisbaseline 30.1 ± 2.3%; control subjects 23.4 ± 1.0%, P < 0.01) at baseline. Following institution of riluzole therapy there was a significant reduction in superexcitability (amyotrophic lateral sclerosisbaseline 30.1 ± 2.3%; amyotrophic lateral sclerosisON riluzole 27.3 ± 2.3%, P < 0.05) and refractoriness at 2 ms (amyotrophic lateral sclerosisbaseline 98.7 ± 10.7%; amyotrophic lateral sclerosisON riluzole 67.8 ± 9.3%, P < 0.001). In conclusion, the present study has established that riluzole exerts effects on both central and peripheral nerve function, interpreted as partial normalization of cortical hyperexcitability and reduction of transient Na+ conductances. Taken together, these findings suggest that the neuroprotective effects of riluzole in amyotrophic lateral sclerosis are complex, with evidence of independent effects across both compartments of the nervous system.
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Affiliation(s)
- Steve Vucic
- Neuroscience Research Australia, Barker Street, Randwick, Sydney, NSW 2031, Australia
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Bae JS, Simon NG, Menon P, Vucic S, Kiernan MC. The puzzling case of hyperexcitability in amyotrophic lateral sclerosis. J Clin Neurol 2013; 9:65-74. [PMID: 23626643 PMCID: PMC3633193 DOI: 10.3988/jcn.2013.9.2.65] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 08/24/2012] [Accepted: 08/24/2012] [Indexed: 12/11/2022] Open
Abstract
The development of hyperexcitability in amyotrophic lateral sclerosis (ALS) is a well-known phenomenon. Despite controversy as to the underlying mechanisms, cortical hyperexcitability appears to be closely related to the interplay between excitatory corticomotoneurons and inhibitory interneurons. Hyperexcitability is not a static phenomenon but rather shows a pattern of progression in a spatiotemporal aspect. Cortical hyperexcitability may serve as a trigger to the development of anterior horn cell degeneration through a 'dying forward' process. Hyperexcitability appears to develop during the early disease stages and gradually disappears in the advanced stages of the disease, linked to the destruction of corticomotorneuronal pathways. As such, a more precise interpretation of these unique processes may provide new insight regarding the pathophysiology of ALS and its clinical features. Recently developed technologies such as threshold tracking transcranial magnetic stimulation and automated nerve excitability tests have provided some clues about underlying pathophysiological processes linked to hyperexcitability. Additionally, these novel techniques have enabled clinicians to use the specific finding of hyperexcitability as a useful diagnostic biomarker, enabling clarification of various ALS-mimic syndromes, and the prediction of disease development in pre-symptomatic carriers of familial ALS. In terms of nerve excitability tests for peripheral nerves, an increase in persistent Na+ conductances has been identified as a major determinant of peripheral hyperexcitability in ALS, inversely correlated with the survival in ALS. As such, the present Review will focus primarily on the puzzling theory of hyperexcitability in ALS and summarize clinical and pathophysiological implications for current and future ALS research.
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Affiliation(s)
- Jong Seok Bae
- Department of Neurology, College of Medicine, Inje University, Busan, Korea. ; Neuroscience Research Australia, Sydney, Australia
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Dengler R, Petri S. Changes in motor axon K(+) conductance in ALS. Primary or secondary to motor neuron degeneration? Clin Neurophysiol 2012; 123:2326-7. [PMID: 22901336 DOI: 10.1016/j.clinph.2012.07.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2012] [Revised: 07/11/2012] [Accepted: 07/19/2012] [Indexed: 11/30/2022]
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