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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] [Abstract] [Key Words] [MESH Headings] [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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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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Sleutjes BTHM, Stikvoort García DJL, Kovalchuk MO, Heuberger JAAC, Groeneveld GJ, Franssen H, van den Berg LH. Acute retigabine-induced effects on myelinated motor axons in amyotrophic lateral sclerosis. Pharmacol Res Perspect 2022; 10:e00983. [PMID: 35881020 PMCID: PMC9318643 DOI: 10.1002/prp2.983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 06/11/2022] [Accepted: 06/15/2022] [Indexed: 11/24/2022] Open
Abstract
Altered motor neuron excitability in patients with amyotrophic lateral sclerosis (ALS) has been suggested to be an early pathophysiological mechanism associated with motor neuron death. Compounds that affect membrane excitability may therefore have disease‐modifying effects. Through which mechanism(s), these compounds modulate membrane excitability is mostly provided by preclinical studies, yet remains challenging to verify in clinical studies. Here, we investigated how retigabine affects human myelinated motor axons by applying computational modeling to interpret the complex excitability changes in a recent trial involving 18 ALS patients. Compared to baseline, the post‐dose excitability differences were modeled well by a hyperpolarizing shift of the half‐activation potential of slow potassium (K+)‐channels (till 2 mV). These findings verify that retigabine targets slow K+‐channel gating and highlight the usefulness of computational models. Further developments of this approach may facilitate the identification of early target engagement and ultimately aid selecting responders leading to more personalized treatment strategies.
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Affiliation(s)
- Boudewijn T H M Sleutjes
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Maria O Kovalchuk
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | | | - Hessel Franssen
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Leonard H van den Berg
- Department of Neurology, Brain Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands
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Tankisi H, Bostock H, Grafe P. A test to determine the site of abnormal neuromuscular refractoriness. Clin Neurophysiol Pract 2022; 7:1-6. [PMID: 34984248 PMCID: PMC8693356 DOI: 10.1016/j.cnp.2021.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 09/18/2021] [Accepted: 11/07/2021] [Indexed: 10/26/2022] Open
Abstract
Objective The relative refractory period (RRP) of motor axons is an important parameter in nerve excitability tests of the recovery cycle (RC). Abnormalities may have a site in the axonal membrane, the neuromuscular junction, or in a dysfunction of the muscle. We aimed in this study to determine the site of abnormality, using a modified protocol of the conventional RC test, whereby an additional supramaximal stimulus is added at the same interstimulus interval as in RC recordings (RCSM). Methods Twenty-four healthy subjects aged 37.8 ± 2.4 years (mean ± SE) were examined with median nerve excitability testing using RC and RCSM protocols at normal temperature (34.1 ± 0.2 °C). The recordings were repeated in 12 subjects after selective cooling of the thenar muscle (25.2 ± 0.7 °C) and in 12 subjects after cooling the nerve trunk at the wrist (24.9 ± 0.3 °C). Results After cooling the nerve, RRP measured with RC and RCSM were prolonged similarly (medians by 1.8 ms, and 2.1 ms respectively). In contrast, cooling the muscle prolonged RRP measured with RC (by 1.3 ms), but did not significantly prolong RRP measured with RCSM. RRPs measured by RC and RCSM were significantly different when cooling was at the muscle (P = 5.10-4), but not when cooling was at the nerve (P = 0.57). Conclusions A difference between RC and RCSM indicates abnormal excitability distal to the axonal membrane under the stimulating electrode. Significance Combining RCSM with the conventional RC protocol should help to localize the site of abnormal neuromuscular refractoriness.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Peter Grafe
- Institute of Physiology, Ludwig-Maximilians University Munich, Germany
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Stikvoort García DJL, Kovalchuk MO, Goedee HS, van Schelven LJ, van den Berg LH, Franssen H, Sleutjes BTHM. Motor unit integrity in multifocal motor neuropathy: A systematic evaluation with CMAP scans. Muscle Nerve 2021; 65:317-325. [PMID: 34854491 PMCID: PMC9300115 DOI: 10.1002/mus.27469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 11/18/2021] [Accepted: 11/23/2021] [Indexed: 11/09/2022]
Abstract
Introduction/Aims Progressive axonal loss in multifocal motor neuropathy (MMN) is often assessed with nerve conduction studies (NCS), by recording maximum compound muscle action potentials (CMAPs). However, reinnervation maintains the CMAP amplitude until a significant portion of the motor unit (MU) pool is lost. Therefore, we performed more informative CMAP scans to study MU characteristics in a large cohort of patients with MMN. Methods We derived the maximum CMAP amplitude (CMAPmax), an MU number estimate (MUNE), and the largest MU amplitude stimulus current required to elicit 5%, 50%, and 95% of CMAPmax (S5, S50, S95) and relative ranges ([S95 − S5] × 100 / S50) from the scans. These metrics were compared with clinical, laboratory, and NCS results. Results Forty MMN patients and 24 healthy controls were included in the study. CMAPmax and MUNE were reduced in MMN patients (both P < .001). Largest MU amplitude as a percentage of CMAPmax was increased in MMN patients (P < .001). Disease duration and treatment duration were not associated with MUNE. Relative range was larger in patients with anti‐GM1 antibodies than in those without anti‐GM1 antibodies (P = .016) and controls (P < .001). The largest MU amplitudes were larger in patients without anti‐GM1 antibodies than in patients with anti‐GM1 antibodies (P = .037) and controls (P = .044). Discussion We found that MU loss is common in MMN and accompanied by enlarged MUs. Presence of anti‐GM1 antibodies was associated with increased relative range of MU thresholds and reduction in largest MU amplitude. Our findings indicate that CMAP scans complement routine NCS, and may have potential for practical monitoring of treatment efficacy and disease progression.
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Affiliation(s)
| | - Maria O Kovalchuk
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - H Stephan Goedee
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Leonard J van Schelven
- Department of Medical Technology and Clinical Physics, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Leonard H van den Berg
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Hessel Franssen
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Boudewijn T H M Sleutjes
- Department of Neurology, Brain Centre Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
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