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Introduction: Friedreich's Ataxia (FA) is a devastating, progressive, neurodegenerative disease. Objective measures that detect changes in neurological function in FA patients are needed to facilitate therapeutic clinical trials. The purpose of this pilot study was to analyze longitudinal changes in gait and balance in subjects with FA using the GAITRite Walkway System ® and Biodex Balance System™, respectively, and to test the ability of these measures to detect change over time compared to the Friedreich's Ataxia Rating Scale (FARS)., Methods: This was a 24-month longitudinal study comparing ambulatory FA subjects with age- and gender-matched, healthy controls. Eight FA subjects and 8 controls were tested at regular intervals using the GAITRite and Biodex Balance systems and the FARS., Results: In the FA group, comfortable and fast gait velocity declined 8.0% and 13.9% after 12 months and 24.1% and 30.3% after 24 months, respectively. Postural stability indices increased in FA subjects an average of 41% from baseline to 24 months, representing a decline in balance. Subjects with FA also demonstrated a 17.7% increase in FARS neurological exam scores over 24 months. There were no changes in gait or balance variables in controls. In the FA group, multiple gait and balance measures correlated significantly with FARS neurological exam scores., Conclusions: The GAITRite and Biodex Balance systems provided objective and clinically relevant measures of functional decline in subjects with FA that correlated significantly with performance measures in the FARS. Gait velocity may be an important objective measure to identify disease progression in adults with FA., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Autoimmune myasthenia gravis (MG) is the prototypic, antibody-mediated neuromuscular disease and is characterized by a decrease in the number of functional acetylcholine receptors (AChR) within the muscle end plate zone of the neuromuscular junction (NMJ). Although the pathophysiology of AChR-mediated myasthenia gravis has been extensively studied over the last 40 years since its original description by Patrick and Lindstrom (Science 180:871-872, 1973), less is known about the much more recently described muscle-specific kinase (MuSK) antibody-mediated MG. MuSK-MG has features clinically distinct from Ach-R MG, as well as a different pattern of response to treatment and a unique immunopathogenesis.

Background: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting upper and lower motor neurons in the CNS and leading to paralysis and death. There are currently no effective treatments for ALS due to the complexity and heterogeneity of factors involved in motor neuron degeneration. A complex of interrelated effectors have been identified in ALS, yet systemic factors indicating and/or reflecting pathological disease developments are uncertain. The purpose of the study was to identify humoral effectors as potential biomarkers during disease progression., Methods: Thirteen clinically definite ALS patients and seven non-neurological controls enrolled in the study. Peripheral blood samples were obtained from each ALS patient and control at two visits separated by 6 months. The Revised ALS Functional Rating Scale (ALSFRS-R) was used to evaluate overall ALS-patient functional status at each visit. Eleven humoral factors were analyzed in sera. Cytokine levels (GM-CSF, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, and TNF-α) were determined using the Bio-Rad Bio-Plex® Luminex 200 multiplex assay system. Nitrite, a breakdown product of NO, was quantified using a Griess Reagent System. Glutathione (GSH) concentrations were measured using a Glutathione Fluorometric Assay Kit., Results: ALS patients had ALSFRS-R scores of 30.5 ± 1.9 on their first visit and 27.3 ± 2.7 on the second visit, indicating slight disease progression. Serum multiplex cytokine panels revealed statistically significant changes in IL-2, IL-5, IL-6, and IL-8 levels in ALS patients depending on disease status at each visit. Nitrite serum levels trended upwards in ALS patients while serum GSH concentrations were drastically decreased in sera from ALS patients versus controls at both visits., Conclusions: Our results demonstrated a systemic pro-inflammatory state and impaired antioxidant system in ALS patients during disease progression. Increased levels of pro-inflammatory IL-6, IL-8, and nitrite and significantly decreased endogenous antioxidant GSH levels could identify these humoral constituents as systemic biomarkers for ALS. However, systemic changes in IL-2, IL-5, and IL-6 levels determined between visits in ALS patients might indicate adaptive immune system responses dependent on current disease stage. These novel findings, showing dynamic changes in humoral effectors during disease progression, could be important for development of an effective treatment for ALS.

Introduction: Numerous methods for motor unit number estimation (MUNE) have been developed. The objective of this article is to summarize and compare the major methods and the available data regarding their reproducibility, validity, application, refinement, and utility., Methods: Using specified search criteria, a systematic review of the literature was performed. Reproducibility, normative data, application to specific diseases and conditions, technical refinements, and practicality were compiled into a comprehensive database and analyzed., Results: The most commonly reported MUNE methods are the incremental, multiple-point stimulation, spike-triggered averaging, and statistical methods. All have established normative data sets and high reproducibility. MUNE provides quantitative assessments of motor neuron loss and has been applied successfully to the study of many clinical conditions, including amyotrophic lateral sclerosis and normal aging., Conclusions: MUNE is an important research technique in human subjects, providing important data regarding motor unit populations and motor unit loss over time., (© 2014 American Association of Neuromuscular and Electrodiagnostic Medicine.)

Introduction: The purpose of this study was to measure and analyze motor unit number estimation (MUNE) values longitudinally in spinal muscular atrophy (SMA)., Methods: Sixty-two children with SMA types 2 and 3 were observed prospectively for up to 42 months. Longitudinal electrophysiological data were collected, including compound motor action potential (CMAP), single motor unit action potential (SMUP), and MUNE., Results: Significant motor neuron loss and compensatory collateral reinnervation were noted at baseline. Over time, there was a significant mean increase in MUNE (4.92 units/year, P = 0.009), a mean decrease in SMUP amplitude (-6.32 μV/year, P = 0.10), and stable CMAP amplitude., Conclusions: The unexpected longitudinal results differ from findings in amyotrophic lateral sclerosis studies, perhaps indicating that compensatory processes in SMA involve new motor unit development. A better understanding of the mechanisms of motor unit decline and compensation in SMA is important for assessing novel therapeutic strategies and for providing key insights into disease pathophysiology., (Copyright © 2013 Wiley Periodicals, Inc.)

Objectives: To report and associate acute cerebral infarctions in 2 young, previously healthy siblings with use of the street drug known as "spice" (a synthetic marijuana product, also known as "K2"), which they independently smoked before experiencing acute embolic-appearing ischemic strokes., Methods: We present history, physical examination, laboratory data, cerebrovascular imaging, echocardiogram, ECG, and hospital course of these patients., Results: We found that in both siblings spice was obtained from the same source. The drug was found to contain the schedule I synthetic cannabinoid JWH-018. Full stroke workup was unrevealing of a stroke etiology; urine drug screen was positive for marijuana., Conclusions: We found that our 2 patients who smoked the street drug spice had a temporal association with symptoms of acute cerebral infarction. This association may be confounded by contaminants in the product consumed (i.e., marijuana or an unidentified toxin) or by an unknown genetic mechanism. The imaging of both patients suggests an embolic etiology, which is consistent with reports of serious adverse cardiac events with spice use, including tachyarrhythmias and myocardial infarctions.

Background: To undertake a systematic review of the available data for oral and intravenous topotecan in adults with relapsed small cell lung cancer (SCLC) for whom re-treatment with the first line regimen is not considered appropriate., Methods: We searched six databases from 1980 up to March 2009 for relevant trials regardless of language or publication status. Relevant studies included any randomised trial of any chemotherapeutic treatment against any comparator in this licensed indication. Where possible we used opposite quantitative methods. Where meta-analysis was considered unsuitable for some or all of the data, we employed a narrative synthesis method. For indirect comparisons we used the method of Bucher et al., where available data allowed it, otherwise we used narrative descriptions., Results: Seven unique studies met the inclusion criteria, four of which could be used in our analyses. These included one study comparing oral topotecan plus best supportive care (BSC) to BSC alone, one study comparing intravenous topotecan to cyclophosphamide, adriamycin and vincristine (CAV), and two studies comparing oral topotecan with intravenous topotecan. All four studies appear to be well conducted and with low risk of bias. Oral topotecan plus BSC has advantages over BSC alone in terms of survival (hazard ratio = 0.61; 95% CI, 0.43 to 0.87) and quality of life (EQ-5 D difference: 0.15; 95% CI, 0.05 to 0.25). Intravenous topotecan was at least as effective as CAV in the treatment of patients with recurrent small-cell lung cancer and resulted in improved quality-of-life with respect to several symptoms. CAV was associated with significantly less grade 4 thrombocytopenia compared with IV topotecan (risk ratio = 5.83; 95% CI, 2.35 to 14.42). Survival (hazard ratio = 0.98; 95% CI, 0.77 to 1.25) and response (pooled risk ratio = 1.04; 95% CI, 0.58 to 1.85) data were similar for the oral and IV topotecan groups. Symptom control was also very similar between the trials and between the oral and IV groups. Toxicity data showed a significant difference in favour of oral topotecan for neutropenia (pooled risk ratio = 0.65; 95% CI, 0.47 to 0.89). Indirect evidence showed that oral topotecan was at least as good as or better than CAV on all outcomes (survival, response rates, toxicities, and symptoms) that allowed indirect comparisons, with the only exception being grade four thrombocytopenia which occurred less often on CAV treatment., Conclusions: Concerning topotecan both the oral and intravenous options have similar efficacy, and patient preference may be a decisive factor if the choice would be between the two formulations. The best trial evidence for decision making, because it was tested versus best supportive care, exists for oral topotecan. Indirectly, because we have two head-to-head comparisons of oral versus intravenous topotecan, and one comparison of intravenous topotecan versus CAV in similar patients as in the trial against best supportive care, one might infer that IV topotecan and CAV could also be superior to best supportive care, and that oral topotecan has similar effects to CAV with possibly better symptom control. From the evidence discussed above, it is evident that oral topotecan has similar efficacy to IV topotecan (direct comparison) and CAV (indirect comparison). There is no further evidence base of direct or possible indirect comparisons for other comparators than CAV of either oral or IV topotecan.

Two patients with atypical Friedreich ataxia (heterozygotes for a GAA expansion and a G130V point mutation) experienced modest proprioceptive improvements in their extremities within a month of taking varenicline (Chantix), a drug approved for smoking cessation.

Objective: Randomized, blinded trial of intramuscular gene transfer using plasmid vascular endothelial growth factor (VEGF) to treat diabetic polyneuropathy., Methods: Diabetic patients with polyneuropathy were randomized to receive a VEGF-to-placebo ratio of 3:1. Three sets of injections were given at eight standardized sites adjacent to the sciatic, peroneal, and tibial nerves of one leg. Primary outcomes were change in symptom score at 6 months and a prespecified overall clinical and electrophysiological improvement score. Secondary outcomes were differences in symptoms, examination scores, visual analog pain scale, nerve conduction, and quantitative sensory testing., Results: Thirty-nine patients received plasmid VEGF and 11 received placebo. Mean symptom score improved in both legs at 6 months, favoring VEGF over placebo (-1.2 +/- 0.5 vs -0.9 +/- 0.5; p < 0.01 after adjustment for change in the untreated leg) and compared with the untreated leg (-0.7 +/- 0.5; p = 0.02). The region of sensory loss and visual analog pain scale improved in the treated group (-1.5 vs -0.5; p = 0.01). Twelve of 39 VEGF versus 2 of 11 placebo patients met criterion for overall improvement. Other measures including nerve conduction potentials did not improve. There were 84 adverse events in VEGF patients, and 22 were serious; there were 51 events in placebo patients, and 2 were serious., Interpretation: Intramuscular plasmid VEGF gene transfer improved diabetic neuropathic symptoms, meeting primary end-point criteria for efficacy but not affecting most secondary measures. Treatment was associated with more serious adverse events that did not reach statistical significance. These results are not conclusive but may justify further clinical study.

We prospectively studied 64 patients with motor neuron disease (amyotrophic lateral sclerosis (ALS), familial ALS (fALS), progressive muscular atrophy (PMA) and primary lateral sclerosis (PLS)) using multiple point stimulation motor unit number estimation (MUNE), transcranial magnetic stimulation (TMS), proton magnetic resonance spectroscopic imaging (1H MRSI), diffusion tensor imaging (MRDTI), and clinical measures at baseline and every 3 months thereafter for 15 months. Substantial differences in MUNE were noted among the motor neuron disease subgroups (P = 0.0005) and mean values for each motor neuron disease subgroup were significantly lower vs. controls (ALS = 76, fALS = 80, PMA = 29, and PLS = 174) vs. the normal control average (267). MUNE correlated well with % FVC (r = 0.32; P = 0.01), manual muscle testing (r = 0.52; P < 0.0005), grip strength (r = 0.34; P = 0.007), and pinch strength (r = 0.49; P < 0.0005). Overall, MUNE showed the greatest significant change over time of any measure, clinical or otherwise, tested in this study (-2.35 linear trend % change per month, mean). MUNE clearly delineates lower motor neuron dysfunction, strongly correlates with important clinical functions (such as strength and respiration) and is a highly sensitive marker of disease progression over time. These features make MUNE an important tool for both the study of the pathophysiology of the motor neuron diseases, as well as an important measure for incorporation into future clinical trials.

The parkinsonian variant of multiple system atrophy (MSA-P) can be difficult to differentiate from Parkinson's disease (PD). This Practice Point commentary discusses a multicenter study performed by the European MSA Study Group that sought to determine whether certain clinical features could serve as 'red flags', or warning signs, to assist in the early diagnosis of MSA-P. The study included 57 patients with probable MSA-P and 116 patients with probable PD. The presence of two out of six red-flag categories yielded 98.3% specificity and 84.2% sensitivity for a diagnosis of MSA-P as opposed to PD. In 13 of 17 patients with possible MSA-P who later progressed to probable MSA-P, use of the red-flag categories would have accelerated the diagnosis of probable MSA-P by an average of 15.9 months. Although this study has several limitations, the identified red-flag categories may be useful as supportive criteria in diagnosing probable MSA-P.

Objective: To investigate the value of objective biomarkers for upper (UMN) and lower (LMN) motor neuron involvement in ALS., Methods: We prospectively studied 64 patients with ALS and its subsets using clinical measures, proton MR spectroscopic imaging ((1)H MRSI), diffusion tensor imaging, transcranial magnetic stimulation, and the motor unit number estimation (MUNE) at baseline and every 3 months for 15 months and compared them with control subjects., Results: (1)H MRSI measures of the primary motor cortex N-acetyl-aspartate (NAA) concentration were markedly reduced in ALS (p = 0.009) and all UMN syndromes combined (ALS, familial ALS [fALS], and primary lateral sclerosis; p = 0.03) vs control values. Central motor conduction time to the tibialis anterior was prolonged in ALS (p < 0.0005) and combined UMN syndromes (p = 0.001). MUNE was lower in ALS (p < 0.0005) and all LMN syndromes combined (ALS, fALS, and progressive muscular atrophy; p = 0.001) vs controls. All objective markers correlated well with the ALS Functional Rating Scale-Revised, finger and foot tapping, and strength testing, suggesting these markers related to disease activity. Regarding changes over time, MUNE changed rapidly, whereas neuroimaging markers changed more slowly and did not significantly differ from baseline., Conclusions: (1)H MR spectroscopic imaging measures of the primary motor cortex N-acetyl-aspartate (NAA) concentration and ratio of NAA to creatine, central motor conduction time to the tibialis anterior, and motor unit number estimation significantly differed between ALS, its subsets, and control subjects, suggesting they have potential to provide insight into the pathobiology of these disorders.

Electrodiagnostic studies are a critical tool for the identification and study of peripheral neuropathy, enabling definition of the pathophysiologic type of nerve injury, its distribution, severity, and the degree of motor or sensory nerve involvement. These data help to differentiate the varieties of neuropathy from other neuromuscular diseases. Nerve conduction studies and electromyography, although widely performed, are complex techniques and are subject to a wide range of artifacts, which can result in missed or erroneous diagnoses. Without proper education, training, and experience in neuromuscular disease and the techniques of electrodiagnosis and careful attention to potential sources of error, the critical information needed to properly diagnose and treat patients with neuropathy is unreliable and may lead to wasted resources and patient injury.

Objective: To describe a patient with multifocal motor neuropathy with conduction block who had annual clinical and physiological examinations for 18 years but declined treatment for personal reasons., Design: Case report., Setting: Collaboration between 2 academic tertiary care hospitals. Patient One patient with multifocal motor neuropathy with conduction block., Results: At age 44 years, there was weakness and wasting of the left biceps with conduction block in the left musculocutaneous and right ulnar nerves. The left median nerve was inexcitable. The right median, ulnar, and left peroneal nerves developed axonal change (loss of distal compound muscle action potential amplitude) at years 5, 12, and 13. By 2005, new weakness had appeared in 20 muscles (16 in the arms); he could not use a keyboard, button buttons, or write his name. Nerves that initially showed conduction block became inexcitable over the course of the illness., Conclusions: Multifocal motor neuropathy with conduction block is a disease that may be "only" slowly progressive but is not always benign. Nerves showing conduction block may develop axonal change. Better markers for this disease are needed.

Background: Mitochondrial DNA point mutations are especially deleterious to tissues with high energy demand, including the peripheral nervous system. Neuropathy has been associated with several mitochondrial diseases, including MELAS (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes)., Objective: To evaluate nerve conduction in a genotypically and phenotypically homogeneous group of patients with MELAS and the A3243G mutation., Design: We studied 30 patients with MELAS and the A3243G mutation using neurophysiological techniques, medical history questionnaires, laboratory tests, and a standardized neurological examination., Results: Twenty-three subjects (77%) had abnormal nerve conduction measures. Symptoms suggestive of neuropathy were present in only half of the patients, but almost all had decreased reflexes or distal sensory findings on examination. Nerve conduction abnormalities were predominantly axonal and sensory and mainly present in the legs. Patients with nerve conduction abnormalities tended to be older and were more likely male., Conclusions: Peripheral nerve impairment is common in those with MELAS and the A3243G mutation, and may be subclinical. Male sex and older age may add to the genetic disposition to develop neuropathy.

Aims: The appearance of peripheral neuropathy is the dose-limiting toxicity in many chemotherapy protocols, and glutamine has been proposed as a potentially neuroprotective agent in patients receiving paclitaxel., Materials and Methods: In this non-randomised study, we assessed neurologic signs and symptoms, and changes in nerve-conduction studies in 46 consecutive patients given high-dose paclitaxel either with (n=17) or without (n=29) glutamine. Neurological assessments and electrodiagnostic studies were carried out at baseline and at least 2 weeks (median 32 days) after treatment., Results: Patients who received glutamine developed significantly less weakness (P = 0.02), less loss of vibratory sensation (P = 0.04) and less toe numbness (P = 0.004) than controls. The per cent change in the compound motor action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes after paclitaxel treatment was lower in the glutamine group, but this finding was not statistically significant in these small groups., Conclusions: In this study, serial neurologic assessment of patient symptoms and signs seemed to be a better indicator of a possible glutamine effect than sensory- or motor-nerve-conduction studies. Prospective randomised trials are needed to clarify the effect of glutamine on paclitaxel and other types of chemotherapy-induced neuropathy.

Over the last decade, motor unit number estimation (MUNE) methods have been applied with increasing frequency to the study of amyotrophic lateral sclerosis. MUNE is the ideal tool for the assessment of diseases in which the primary defect is motor unit loss, as it enables quantitation and tracking of motor unit numbers while simultaneously gauging countervailing collateral reinervation. These properties make it particularly useful for assessing the effects of both neuroprotective therapies and therapies designed to enhance collateral reinervation, not only in animal models but also in the living patient. Previous studies have supplied important natural history information, confirming an average 50% loss of motor units for every six months of disease progression, and newer pathophysiological investigations are providing unique insight into motor unit behavior in the face of progressive anterior horn cell death. More recent efforts have incorporated MUNE into ongoing, multi-center clinical trials as a putative early biomarker, with encouraging results. As MUNE methods continue to be refined and disseminated, they are proving to be useful and unique tools for the study of motor neuron disease.

During 2003, numerous research advances in both clinical neuromuscular disease and in the basic pathophysiology of these disorders were published and/or presented. In this review, we present a few categorical highlights of the year, discussing a new potential treatment of McArdle's disease, proposed new diagnostic criteria for the inflammatory myopathies and their clinical implications, the emerging anti-MuSK antibody syndrome in patients with myasthenia gravis, potential new therapies for the most common hereditary neuropathy (Charcot-Marie-Tooth type 1A), the successful pharmacologic manipulation and its therapeutic implications of the genetic mechanisms underlying spinal muscular atrophy, and several emerging therapeutic strategies in amyotrophic lateral sclerosis. As these reports indicate, clinical and basic research in neuromuscular disease continues to yield important and clinically relevant insights, which are now being rapidly translated into new clinical trials showing therapeutic promise for diseases previously thought untreatable.

Since its introduction 30 years ago, MUNE techniques have increasingly been refined and applied to a wide variety of neuromuscular disorders. Differences of opinion remain among MUNE investigators as to which method is best; however, statistical and MPS MUNE are currently the most widely used. Numerous methodologic issues remain, including the development of detailed universal standards for each technique and the implementation of modifications for the enhancement of reproducibility. These issues are the subjects of ongoing investigation. Despite technical variability, the MUNE values obtained using different methods show good agreement in studies of normal subjects and in patients with a variety of neurogenic processes. MUNE has been applied most successfully to patients with amyotrophic lateral sclerosis and to animal models of motor neuron disease, providing significant insight into the pathophysiology of these disorders. These techniques are increasingly being incorporated into clinical therapeutic trials. MUNE offers promise in the study of neuromuscular disease, enabling the collection of novel data in the living patient unobtainable by any other method.

We studied 22 patients with dystonia to determine the normal range of values for the extensor digitorum brevis (EDB) test, and to determine its sensitivity and specificity in detecting resistance to botulinum toxin type A (BTX-A). Three compound muscle action potentials (CMAPs) elicited by peroneal nerve stimulation were averaged before and 2 weeks after injection of 20 units of BTX-A into the EDB. Amplitude and area ratios were calculated by dividing the averaged postinjection CMAP by the averaged preinjection CMAP values. The difference in means of this ratio between clinically sensitive and resistant subjects was statistically significant (P < 0.002). A normal range of <0.45 for each ratio was determined by adding two standard deviations to the ratio mean of 14 clinically sensitive subjects. Four of five resistant patients had values outside the normal range. The EDB test is a simple quantitative method of detecting resistance to BTX-A, with a sensitivity of 80% and specificity of 94%., (Copyright 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 828-831, 2002)

Carpal tunnel syndrome (CTS) is a frequent and underdiagnosed complication of pregnancy. Conservative therapies are common initial measures, but data on the course of improvement are limited. We report a case of pregnancy-associated CTS with unusually detailed serial electrophysiologic studies before and after wrist splinting. Physiologic measures reached a nadir and then rapidly improved following conservative therapy, paralleling clinical improvement. Responses took between 6 and 20 months postpartum to approach baseline values., (Copyright 2002 Wiley Periodicals, Inc.)

Objectives: To determine the number of motor units (MUNEs) in the anterior tibial muscle of normal subjects for comparison with those of severely paretic or paralytic muscles of critically ill patients in intensive care units., Results: The mean MUNE for 24 normal subjects (194 +/- 5; mean +/- standard deviation) was similar to that of the 22 patients with critical illness (184 +/- 10). However, both the mean amplitude of the evoked compound muscle action potential (CMAP) and of the single motor unit action potential (S-MUAP) among patients were approximately one third of those in normal subjects., Conclusion: Critically ill patients in this study demonstrated normal MUNEs with reduced CMAP and S-MUAP amplitudes in the setting of severe clinical weakness, suggestive of predominantly myopathic injury. MUNE may provide a valuable tool for distinguishing between neuropathy and myopathy in critically ill patients.

Since its introduction 30 years ago, MUNE technologies have been increasingly refined and applied to a wide variety of neuromuscular disorders. Differences of opinion remain among MUNE investigators as to which method should be used; however, statistical and MPS MUNE currently enjoy the most widespread use. A number of methodological issues remain, including the development of detailed universal standards for each technique and modifications for the further enhancement of reproducibility. These issues are the subject of ongoing investigation. However, despite technical variability, the MUNE values obtained with different methods show good agreement, both in studies of healthy subjects and in patients with a variety of neurogenic processes. MUNE has been most successfully applied to patients with ALS and in animal models of motor neuron disease, providing significant insight into the pathophysiology of these disorders. These techniques are being increasingly incorporated into clinical therapeutic trials. MUNE is a technology offering important promise in the study of neuromuscular disease, enabling the collection of novel data in the living patient unobtainable by any other method.

As the number of new transgenic mouse models of human neuromuscular disease continues to increase, the development of sophisticated electrophysiologic techniques for assessing the peripheral nervous system in these models has become important. Neuromuscular junction (NMJ) dysfunction, in particular, is often not detectable by morphologic or other techniques. To enable sensitive testing of murine NMJ function, we developed and tested a method for stimulated single fiber electromyography (S-SFEMG) in the gastrocnemius muscles of anesthetized mice. Jitter was assessed by measuring the mean consecutive latency difference (MCD) of single fiber responses to sciatic nerve stimulation at 2 HZ. Mean MCD values in normothermic mice were in the range of 6-8 micros for different strains, with no MCD values exceeding 25 micros. Reduced core temperature (to 29 degrees--30 degrees C) resulted in increased jitter, whereas intubation and mechanical ventilation of mice did not alter these values. Intraperitoneal and intravenous injection of vecuronium, however, resulted in progressively increased jitter followed by blocking in continuously monitored fibers. These observations validate the utility of S-SFEMG in mice as an index of NMJ function under a variety of physiologic conditions, and suggest that a high safety factor for neuromuscular transmission exists at mouse NMJs., (Copyright 2001 John Wiley & Sons, Inc.)

Motor unit number estimation (MUNE) techniques have evolved substantially over the past decade and have been applied, with increasing frequency, to the study of amyotrophic lateral sclerosis (ALS). As major clinical therapeutic trials in motor neuron disease continue to appear, the need for a clear quantitative method of following motor unit physiology in the living subject grows ever more pressing. In this article, we review the major modern techniques of MUNE and the data supporting their reproducibility and utility in patients with ALS, with particular attention to their role in evaluating the efficacy of new therapeutic interventions.

We elicited three single motor unit action potentials (S-MUAPs) via multiple point stimulation and subjected them to repetitive stimulation (RS) in 3 healthy subjects. We tracked each S-MUAP and its RS trains over two separate sessions as well as the compound motor action potential (CMAP) RS trains obtained from the same muscle following whole nerve stimulation. Repetitive axonal stimulation yields consistent results when carefully performed with minimal variation in each S-MUAP RS train from session to session, providing previously unobtainable data regarding neuromuscular junction function in the same single motor unit over time. In this small, normative sample, no significant correlation between S-MUAP and CMAP RS responses was observed.