Abstract Details

Title Correlation of Spontaneous Activity on Needle Electromyography with Pathological Changes on Muscle Biopsies

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P16 - Poster Session 16 (5:30 PM-6:30 PM)

Poster/Presentation
Number 1-014

Objective To determine whether spontaneous activity on needle electromyography (EMG) is predictive of inflammation and/or necrosis on muscle biopsy.

Background Inflammatory myopathy is a common differential diagnosis in patients presenting with weakness, of which electrodiagnostic (EDX) testing and muscle biopsy play indispensable roles in confirmation of the diagnosis. Abnormal spontaneous activities are a key finding on needle EMGs and are proposed to suggest fiber necrosis or separation due to inflammatory infiltrates on muscle biopsies. However, tissue diagnosis remains the gold standard and is required to establish the pathology. There are limited studies that describe the association between spontaneous activity and biopsy findings.

Design/Methods

A retrospective chart review of patients with suspected inflammatory myopathy who underwent muscle biopsy was performed and the pattern of abnormalities on needle EMG was correlated with pathologic findings of inflammation and muscle fiber necrosis. The sensitivities, specificities, negative predictive values (NPV) and positive predictive values (PPV) of specific spontaneous activities - fibrillation potentials, positive sharp waves (PSW), pseudomyotonia, and complex repetitive discharges (CRDs) - were determined for analysis.

Results

Fourteen patients were included, and all patients had muscle weakness. The average age was 60, and 71% were female. Correlation of the EMG findings showed that both fibrillation potentials and PSW were highly sensitive (100%) but not specific (33%). They had a PPV of 67% and NPV of 100%. In contrast, CRDs and pseudomyotonia had higher specificity (83%) than sensitivity (38%), with PPV of 75% and NPV of 50%.

Conclusions Abnormal spontaneous activities on needle EMG have been used as surrogate markers for inflammation and fiber necrosis in inflammatory myopathies. Our study suggests that fibrillation potentials and PSW are predictive of pathological findings of inflammation and necrosis, whereas the absence of CRDs and pseudomyotonia may indicate an alternative pathology.

Authors/Disclosures
Maria Kristina C. Dorotan, MD (Yale School of Medicine) PRESENTER	Dr. Dorotan has nothing to disclose.
Justin Y. Kwan, MD, FAAN (National Institutes of Health)	Dr. Kwan has received research support from National Institutes of Health. Dr. Kwan has received personal compensation in the range of $100,000-$499,999 for serving as a Employee with National Institutes of Health.

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