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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., (Copyright © 2024 International Federation of Clinical Neurophysiology. All rights reserved.)

Objective : This study aimed to reveal the diagnostic utility of Gold Coast (GC) criteria in Japanese patients with amyotrophic lateral sclerosis (ALS) by comparing the sensitivity/specificity with revised El Escorial (R-EE) and Awaji criteria, because its utility has not been studied in Asian ALS. Methods : Consecutive 639 patients (529 with ALS and 110 with ALS mimics), who were suspected of ALS and referred to three Japanese ALS centers, were enrolled. Diagnostic accuracy and characteristics of false positive and negative in GC criteria were compared with those of the Awaji and R-EE criteria. Patients were categorized as definite, probable or possible ALS according to each criterion. Results : The sensitivity of GC criteria (96.8%, 95% confidence interval [CI]: 95.3-98.3%) was higher than that of Awaji (89.6%, 95% CI: 87.0-92.2%) and R-EEC (89.2, 95% CI: 86.6-91.8%) criteria (both, p  < 0.001). The specificity was also higher with GC criteria (77.3%, 95% CI: 69.5-85.1%) than Awaji (65.5%, 95% CI: 56.6-74.4%) and R-EEC (66.4, 95% CI: 57.6-75.2%) criteria (both, p  < 0.01). Using GC criteria, patients with cervical spondylosis and Parkinson's syndrome tended to be diagnosed with ALS (i.e. "false positive"). Additionally, ALS patients diagnosed only by GC criteria less frequently had upper motor neuron (UMN) signs, compared with the other two criteria. Conclusion : Gold Coast criteria improve diagnostic accuracy for ALS in an Asian population, especially in patients with subtle UMN signs.

Neuromuscular ultrasound has become an integral part of the diagnostic workup of neuromuscular diseases in neurology. Neuromuscular ultrasound can detect nerve enlargement, selective muscle damage, and fasciculation easily and non-invasively, which allows differentiation between auto-immune/inflammatory and degenerative/hereditary diseases. It is significant and essential for all neurologists to master the neuromuscular ultrasound technique.

Introduction/aims: In amyotrophic lateral sclerosis (ALS), the impact of motor neuron dysfunction on the motor unit (MU) firing pattern remains to be elucidated. The aim of this study was to clarify the characteristics of the MU firing rate and its association with clinical factors in ALS patients using high-density surface electromyography (HDSEMG) and MU decomposition analysis., Methods: Nineteen ALS patients and 20 controls prospectively underwent HDSEMG recording of the vastus lateralis muscle during ramp-up (30% of maximum voluntary contraction) and sustained (10% of maximal voluntary contraction for 60 seconds) contractions on performing isometric knee extension. After decomposition analysis, instantaneous firing rates (IFRs) of individually identified MUs were calculated. Comparison of IFRs and clinical variables between ALS patients and controls and analysis of the correlation between individual mean IFR and clinical variables in ALS patients were performed., Results: The number of identified MUs was lower in ALS patients than in controls (P = .017). Mean IFRs of MUs (i.e., mean MU firing rates) were higher in ALS patients than in controls at some force levels on ramp-up contraction (P < .05) and at 50 to 60 seconds during sustained contraction (9.1 [ALS] vs 8.3 [controls] pulses per second; P = .036). There was no correlation between the clinical parameters and mean IFR of each patient., Discussion: ALS patients had a higher MU firing rate during muscle contraction at a low force level. Noninvasive assessment of the MU firing rate by HDSEMG can detect a motor neuronal hyperexcitable state in ALS patients., (© 2023 Wiley Periodicals LLC.)

To clarify the natural courses, medical conditions, and problems in daily life and medical care of the patients with Charcot-Marie-Tooth disease (CMT) in Japan, we have developed a patient registration system (CMT Patient Registry (CMTPR)). We analyzed data of questionnaires from 303 patients (males: 162, females: 141, mean age: 45.9 years old) who registered for CMTPR. The age of onset was less than 15 years old in 45% and more than 60 years old in 5% of the patients. Genetic testing was performed in 65%, and about half of the patients with genetic testing had a duplication of the PMP22 gene. Seventy-six percent of the patients had regular visits to medical facilities. Five percent of patients had no history of hospital visits. Fifteen percent of all patients needed assistance with daily activities due to motor function impairment in the upper extremities, and 25% required assistance due to lower limb impairment. There were no significant differences in the need for assistance by gender or age. Of the 267 adult patients, 18% had difficulty working due to reasons related to the disease, although none of the junior patients reported any problem attending school. This was the first nationwide epidemiological study with healthcare and welfare information on patients with CMT in Japan. We hope the results of this study will lead to better welfare and medical care in CMT patients.

Objective: To elucidate the utility of the proximal to distal compound muscle action potential (CMAP) duration ratio to distinguish between demyelinating Charcot-Marie-Tooth disease (CMT) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) compared with nerve ultrasound., Methods: Thirty-nine demyelinating CMT patients and 19 CIDP patients underwent nerve conduction studies (NCS) and nerve ultrasound. NCS parameters including CMAP duration ratio calculated by dividing the value at the proximal site by that at the distal site and nerve cross-sectional area (CSA) measured by ultrasound were compared between the two groups. The diagnostic sensitivity and specificity of each parameter were analysed., Results: CMT patients showed a significantly lower CMAP duration ratio than CIDP patients (p < 0.05). The area under the curve (AUC) value of the CMAP duration ratio exceeded 0.95 when CMT was considered "positive", and a cut-off value of 1.13 resulted in high diagnostic sensitivity and specificity (84.6 and 100 % for median nerve, 97.4 and 85.7 % for ulnar nerve, respectively), whereas the AUC value of nerve CSA ranged from 0.70 to 0.81., Conclusions: The CMAP duration ratio could effectively distinguish between demyelinating CMT and CIDP., Significance: Adding the CMAP duration ratio to a routine NCS may improve the accuracy of the diagnosis of demyelinating CMT., Competing Interests: Conflict of interest None of the authors have potential conflicts of interest to be disclosed., (Copyright © 2022 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objective: Myasthenia gravis (MG) is an antibody-mediated inflammatory disease affecting post-synaptic membranes of neuromuscular junctions, and objective biomarkers of MG disease activity are lacking. Pentraxin 3 (PTX3) is an acute-phase inflammatory glycoprotein in the same family as C-reactive protein that is associated with disease activity in several autoimmune disorders. Thus, we investigated whether circulating PTX3 is a useful biomarker of MG activity., Methods: Serum PTX3 was measured in 40 patients with MG who were positive for anti-acetylcholine receptor antibody, and in 30 healthy and disease controls, using a commercial enzyme-linked immunosorbent assay kit. In patients with MG, the correlation of serum PTX3 levels with disease severity scales at serum sampling, including MG Foundation of America (MGFA) classification, MG activity of daily living (MG-ADL) score, and quantitative MG (QMG) score, were investigated., Results: Although there was no significant difference in serum PTX3 between the MG and control groups (mean, 3346 pg/mL in MG group vs. 2870 pg/mL in control group, P = 0.56), serum PTX3 moderately correlated with all disease severity scores (MGFA classification: Spearman's ρ = 0.53, P = 0.0004; MG-ADL score: Spearman's ρ = 0.45, P = 0.004; QMG score: Spearman's ρ = 0.50, P = 0.004)., Conclusion: Our results suggest that circulating PTX3 may reflect the extent of neuromuscular junction damage and might be involved in the pathogenesis of MG., Competing Interests: Conflict of interest All authors have no conflicts of interest to declare., (Copyright © 2022 Elsevier B.V. All rights reserved.)