Motor function performance in individuals with RYR1-related myopathies

Introduction The objective of this study was to obtain a 6-month natural history of motor function performance in individuals with RYR1- related myopathy (RYR1-RM) by using the Motor Function Measure-32 (MFM-32) and graded functional tests (GFT) while facilitating preparation for interventional trials. Methods In total, 34 participants completed the MFM-32 and GFTs at baseline and 6-month visits. Results Motor deficits according to MFM-32 were primarily observed in the standing and transfers domain (D1; mean 71%). Among the GFTs, participants required the most time to ascend/descend stairs (>7.5 s). Functional movement, determined by GFT grades, was strongly correlated with MFM-32 (D1; r >= 0.770, P < 0.001). Motor Function Measure-32 and GFT scores did not reflect any change in performance between baseline and 6-month visits. Discussion The MFM-32 and GFTs detected motor impairment in RYR1-RM, which remained stable over 6 months. Thus, these measures may be suitable for assessing change in motor function in response to therapeutic intervention. Muscle Nerve 60: 80-87, 2019