Congenital muscular dystrophies

To determine the minimal clinically important difference (MCID) for the motor function measure (MFM-32) in congenital muscular dystrophy and congenital myopathy patient an observational, retrospective, multicentric study was conducted on 85 congenital muscular dystrophy or congenital myopathy patients, aged 5 to 22 years at the national institute of neurological disorders and stroke of the national institutes of health and 2 French departments of paediatric physical medicine and rehabilitation. Data were collected if at least 2 MFMs were performed (MFM1 and MFM2) within 8 to 36 months of each other and if during MFM2 parents or patients were asked to provide their perceived change in functional status or strength since MFM1. Patients were divided in 3 groups according to their overall assessment of disease evolution: deterioration, stability or improvement. Absolute score changes between MFM1 and MFM2 total score (TS) and each subscore (D1, D2 and D3) were calculated for each patient. The mean score change of each group of patient reported disease evolution was provided and then groups were compared to determine if the difference was statistically significant. The MCID was calculated. Mean scores changes for D1, D2 and TS improved for patients reporting improvement (respectively 2,4±5,6; 2,1±13,3 and 2,5±7,2) and declined for patients reporting deterioration (-3,2±8,1; -1,3±15,7 and -1,3±7,2) or stability (-1,2±7,4; -2,2±10,5 and -1,5±10). The mean score for D3 was stable or improved in all patients, even if they reported an overall deterioration. The MCID was consecutively calculated for D1, D2 and TS. When designing clinical trials in congenital onset neuromuscular diseases, the use of MCID for MFM should be considered as a chief outcome measure to determine if a given intervention effects not only statistically significant change but also clinically meaningful improvements.