Motor unit number estimation: a technology and literature review.

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.

Genotype-phenotype correlations in recessive RYR1-related myopathies.

Background: RYR1 mutations are typically associated with core myopathies and are the most common overall cause of congenital myopathy. Dominant mutations are most often associated with central core disease and malignant hyperthermia, and genotype-phenotype patterns have emerged from the study of these mutations that have contributed to the understanding of disease pathogenesis. The recent availability of genetic testing for the entire RYR1 coding sequence has led to a dramatic expansion in the identification of recessive mutations in core myopathies and other congenital myopathies.

Use of supramaximal stimulation to predict facial nerve outcomes following vestibular schwannoma microsurgery: results from a decade of experience.

Object: The goal of vestibular schwannoma surgery is tumor removal and preservation of neural function. Intraoperative facial nerve (FN) monitoring has emerged as the standard of care, but its role in predicting long-term facial function remains a matter of debate. The present report seeks to describe and critically assess the value of applying current at supramaximal levels in an effort to identify patients destined for permanent facial paralysis.

Clinical and electrophysiologic variability in amyotrophic lateral sclerosis within a kindred harboring the C9ORF72 repeat expansion.

Our objective was to characterize the motor neuron disease features within a large c9FTD/ALS kindred. We analyzed clinical, electrophysiologic and neuropathologic data in a c9FTD/ALS kindred of Scandinavian ancestry. Results showed that of six family members affected, three had only ALS, two had FTD and one had FTD and ALS.

Myotonia associated with caveolin-3 mutation.

Introduction: Caveolin-3 is a major component of the caveolae in skeletal and cardiac muscle. Mutations in the caveolin-3 gene (CAV3) lead to a spectrum of clinical phenotypes including limb-girdle muscular dystrophy 1C, distal myopathy, rippling muscle disease, isolated hyperCKemia, and cardiomyopathy.

Case Report: A 24-year-old man with myalgia, muscle stiffness, and fatigue has normal strength and prominent myotonic discharges in the gastrocnemius.

Optimal stimulation settings for CMAP scan registrations.

Background: The CMAP (Compound Muscle Action Potential) scan is a non-invasive electrodiagnostic tool, which provides a quick and visual assessment of motor unit potentials as electrophysiological components that together constitute the CMAP. The CMAP scan records the electrical activity of the muscle (CMAP) in response to transcutaneous stimulation of the motor nerve with gradual changes in stimulus intensity. Large MUs, including those that result from collateral reinnervation, appear in the CMAP scan as so-called steps, i.

Electrophysiological testing of spinal accessory nerve in suspected cases of nerve transection.

Introduction: In this study we sought to determine whether standard electrophysiological testing of the spinal accessory nerve (SAN) accurately identifies patients who would benefit from surgical repair.

Methods: Sixteen consecutive patients sent for surgical evaluation of unilateral SAN injury were studied clinically and electrophysiologically.

Results: All patients demonstrated a low-amplitude SAN compound muscle action potential (CMAP) that required a higher stimulus intensity to obtain it than on the unaffected side.

Absent, unrecognized, and minimal myotonic discharges in myotonic dystrophy type 2.

The purpose of this study was to describe the frequency of absent, unrecognized, or minimal myotonic discharges (MDs) in myotonic dystrophy type 2 (DM2). We performed a retrospective review of needle electromyography (EMG) data prior to genetic diagnosis in 49 DM2 patients at the Mayo Clinic. MDs were not reported on first or repeat EMG studies (n = 8) and not found in archived recordings of 4 patients (8%); archived EMG recordings (n = 4) confirmed the absence of MDs (n = 2), including 1 patient with normal insertional activity in all muscles, and misinterpretation of MDs as slow fibrillation potentials (n = 1) and complex repetitive discharge (CRD) activity (n = 1).

Myotonic dystrophy type 2 with focal asymmetric muscle weakness and no electrical myotonia.

Genetically proven myotonic dystrophy type 2 (DM2) was found in a 61-year-old woman with creatine kinase (CK) elevation and only isolated weakness of one triceps. There was no clinical or electrical myotonia. Electromyography (EMG) showed only scattered fibrillation potentials and short duration motor unit potentials.

Clinical and electrodiagnostic correlates of peroneal intraneural ganglia.

Objective: Intraneural ganglia (IG) are an underappreciated but treatable cause of common peroneal neuropathy (CPN). This study was designed to determine if there are clinical measures that distinguish CPN caused by IG from CPN without a clear proximate cause.

Methods: Clinical and electrodiagnostic features of 22 cases of IG were compared in a case-control study to 11 cases of CPN with imaging negative for IG.

Needle electromyography.

Physiologic assessment of diseases of the motor unit from the anterior horn cells to the muscles relies on a combination of needle electromyography (EMG) and nerve conduction studies (NCS). Both require a unique combination of knowledge of peripheral nervous system anatomy, physiology, pathophysiology, diseases, techniques, and electricity is necessary. Successful, high-quality, reproducible EMG depends on the skills of a clinician in patient interaction during the physical insertion and movement of the needle while recording the electrical signals.

Anal sphincter motor unit potential (MUP) differences between sides, between rest and voluntary contraction, and between MUP analysis programs in normal subjects.

Trauma to the external anal sphincter resulting in incontinence is a relatively common disorder. Methods to detect damage include pudendal nerve conduction studies and needle EMG. We have applied a quantitative EMG technique using decomposition-enhanced software to isolate motor unit potentials (MUPs) and their surface representation from an anal probe electrode in healthy nulliparous women.

Prospective 15-year study of neuromuscular function in a cohort of patients with prior poliomyelitis.

Poliomyelitis is a monophasic illness affecting lower motor neurons and individuals may describe new problems years after the initial weakness. We have studied 38 people with the post-polio syndrome over a 15-year period assessing a number of neuromuscular measures, including motor unit number estimation (MUNE). Twenty-five individuals reported progressive weakness but there was no objective change in MUNE and other measures.

Strength, physical activity, and fasciculations in patients with ALS.

Fasciculations are a nearly universal feature in people with amyotrophic lateral sclerosis (ALS). The prognostic value of fasciculations remains uncertain. Twenty-four patients with ALS were evaluated for the effects of atrophy, limb weakness, disease duration, and physical activity on fasciculation frequency (as measured by surface electromyography and clinical counting).

Motor and somatosensory evoked potentials: their role in predicting spinal cord ischemia in patients undergoing thoracoabdominal aortic aneurysm repair with regional lumbar epidural cooling.

Background: Paraplegia is a devastating complication for patients undergoing repair of thoracoabdominal aortic aneurysms. A monitor to detect spinal cord ischemia is necessary if anesthesiologists are to intervene to protect the spinal cord during aortic aneurysm clamping.

Methods: The medical records of 60 patients who underwent thoracoabdominal aortic aneurysm repair with regional lumbar epidural cooling with evoked potential monitoring were reviewed.

Intraneural perineurioma of the radial nerve visualized by 3.0 Tesla MRI.

A progressive radial neuropathy of unknown etiology despite 1.5T magnetic resonance imaging (MRI) and surgical exploration was identified as an intraneural perineurioma by a localized Tinel's sign, an enlarged radial nerve at the spiral groove by 3.0T MRI, and a fascicular biopsy.

Electrophysiological findings in a cohort of old polio survivors.

A population-based cohort of poliomyelitis survivors was established and followed for 15 years (mean time since polio was 40 years). Over time, the cohort demonstrated a modest decline in summated compound muscle action potential amplitudes (CMAP) and a moderate decline in the summated motor unit number estimates (MUNE). There was no association between symptoms of late deterioration and magnitude of decline.

Motor unit number estimates correlate with strength in polio survivors.

Motor unit number estimation (MUNE) has been proposed as an outcome measure in clinical trials for the motor neuron diseases. One major criticism of MUNE is that it may not represent a clinically meaningful endpoint. We prospectively studied a cohort of polio survivors over a period of 15 years with respect to MUNE and strength.

Motor unit number estimates--from A to Z.

Quantitation has become an increasingly important part of clinical EMG. Most aspects of peripheral nerve and muscle function can be evaluated quantitatively using commonly available neurophysiologic methods. Because of the effects of collateral sprouting and reinnervation, techniques to measure the number of motor units supplying a muscle have been more difficult to develop.

A 15-year follow-up of neuromuscular function in patients with prior poliomyelitis.

A population-based cohort of poliomyelitis survivors was established and followed for 15 years (mean time since poliomyelitis was 40 years). Over time, the cohort demonstrated only a modest decline in function as measured by strength measurements, electrophysiologic assessments, and timed functional tasks. There was no association between symptoms of late deterioration and magnitude of decline.

Decrement in surface-recorded motor unit potentials in amyotrophic lateral sclerosis.

Background: A decrement to repetitive stimulation sometimes occurs in ALS. The ability to isolate individual surface-recorded motor unit potentials (SMUPs) indirectly allows the analysis of the decrement by comparing the effect of different rates of stimulation on the size of the isolated SMUP.

Methods: The median or ulnar nerve or both were studied in 11 patients with reduced compound muscle action potential (CMAP) amplitude.