Needle electromyography and histopathologic correlation in myopathies.

Area of Science:

• Neurology
• Clinical Neurophysiology

Background:

• Needle electromyography (EMG) is crucial for diagnosing myopathies.
• EMG findings can guide muscle biopsy interpretation.

Purpose of the Study:

• To correlate specific needle EMG findings with muscle biopsy results.
• To determine the diagnostic accuracy of EMG findings for myopathic changes.

Main Methods:

• Retrospective chart review of 218 patients undergoing muscle biopsy.
• Correlation of needle EMG findings with pathologic muscle biopsy results (inflammation, necrosis, splitting, vacuolar changes).
• Calculation of sensitivity, specificity, and predictive values for EMG findings.

Main Results:

• Short-duration motor unit potentials (MUPs) showed high sensitivity (83%-94%) but low specificity (34%-49%) for pathologic changes.
• Fibrillation potentials were moderately sensitive (65%-74%) and specific (58%-81%) for inflammation, necrosis, splitting, or vacuolar changes.
• Absence of fibrillation potentials had high negative predictive value (82%-93%) for certain myopathic changes.

Conclusions:

• Fibrillation potentials and short-duration MUPs are predictive of muscle fiber necrosis, splitting, and vacuolar changes, common in inflammatory myopathies and muscular dystrophies.
• The absence of fibrillation potentials suggests alternative myopathologic conditions, such as congenital myopathies.