Abstract
INTRODUCTION: In this study we determined the reliability and validity of electrical impedance myography (EIM) in facioscapulohumeral muscular dystrophy (FSHD). METHODS: We performed a prospective study of EIM on 16 bilateral limb and trunk muscles in 35 genetically defined and clinically affected FSHD patients (reliability testing on 18 patients). Summary scores based on body region were derived. Reactance and phase (50 and 100 kHz) were compared with measures of strength, FSHD disease severity, and functional outcomes. RESULTS: Participants were mostly men, mean age 53.0 years, and included a full range of severity. Limb and trunk muscles showed good to excellent reliability [intraclass correlation coefficients (ICC) 0.72-0.99]. Summary scores for the arm, leg, and trunk showed excellent reliability (ICC 0.89-0.98). Reactance was the most sensitive EIM parameter to a broad range of FSHD disease metrics. CONCLUSIONS: EIM is a reliable measure of muscle composition in FSHD that offers the possibility to serially evaluate affected muscles. Muscle Nerve 54: 696-701, 2016.