2024 Workshop Handout Bundle-W55B EDX Approach to Myopathies Needle EMG of Unusual Muscles Elie Naddaf

W55B EDX Approach to Myopathies Needle EMG of Unusual Muscles Elie Naddaf

Pdf Summary

This document, authored by Dr. Elie Naddaf, provides an insight into the electrodiagnostic (EDX) approach to evaluating myopathies, particularly focusing on needle electromyography (EMG) of unusual muscles. The introduction emphasizes the pivotal role EDX plays in confirming myopathy, distinguishing it from neuropathy, identifying specific myopathy types, assessing disease activity, and selecting muscles for biopsy. The document then outlines common classifications of myopathies, dividing them into acquired (e.g., immune-mediated, toxic, metabolic, infectious) and hereditary, explaining the complexity and overlap of presentations.<br /><br />A critical component of myopathy evaluation in EDX is identifying the clinical phenotype, as myopathies exhibit different patterns of muscle weakness (diffuse, cranio-bulbar, axial, proximal, or distal). Proximal myopathies are more common, whereas distal and axial myopathies can be underdiagnosed. Axial myopathies, for instance, affect vital muscles and are often missed due to sampling errors in an EDX lab.<br /><br />Overlap presentations further complicate the EDX approach, with patients presenting concurrent myopathy and neuropathy or neuromuscular transmission defects.<br /><br />The document recommends a standardized approach for conducting EDX tests, emphasizing that testing the most affected muscles yields the highest diagnostic accuracy. Routine nerve conduction studies and needle EMG play central roles. Needle EMG protocols are suggested, particularly highlighting the examination of axial muscles like thoracic paraspinals and less commonly-examined muscles such as infraspinatus and pectoralis major.<br /><br />When interpreting needle EMG findings, particular attention is given to the presence of fibrillation potentials and myotonic discharges, though these findings must be carefully interpreted due to their wide clinical implications. The document underlines the importance of selecting an appropriate muscle for biopsy to avoid sampling error.<br /><br />To mitigate the complexity in diagnosing myopathies, the text suggests adopting a systematic approach, sampling extensively, and being descriptive without forcing findings into predefined categories.<br /><br />A concise bibliography is provided for further reading on myopathies, their classification, and management.

Keywords

electrodiagnostic

myopathies

needle electromyography

EDX

muscle biopsy

clinical phenotype

nerve conduction studies

ncs

fibrillation potentials

myotonic discharges

systematic approach

nerve conduction studies

nerve conduction study

ncs