Objective: Most types of neuromuscular diseases are known to be associated with a high risk of sleep-disordered breathing. We performed a prospective study in a well individualized group of muscular disorders, congenital muscular dystrophies (CMD), to characterize the frequency of sleep-disordered breathing and thereby to determine the potential usefulness of sleep studies in such patients. Methods: Twenty CMD children (12 F, 8 M, aged 4-17 years) were included. Using overnight polysomnography, we determined the following parameters: sleep stages, sleep latency, sleep efficiency index, wake time duration, total sleep time (TST), apnea/hypopnea index (AHI), arterial blood oxygen saturation, and nocturnal paroxysmal EEG activity. Results: As compared to healthy controls, we detected in our study group frequent awakenings, a decreased TST (mean 448 +/- 44.4 min) and a decreased REM duration (mean 11.5 +/- 3.5% of TST). Significant increase in wake time duration (28-90 min) and decrease in REM duration were observed in 12 patients. An apnea/hypopnea syndrome was detected in 13 patients (65%) with central apneas in 8, obstructive apneas in 2 and 3 mixed apneas in 3 patients. AHI was >10 in 3 cases, < 10 > 5 in 4 cases and were concomitant with blood oxygen de-saturation in four cases. NPA were detected in 10 patients ranging from 10 to 40% of TST. Interpretation: Our results confirm the high incidence of sleep disordered breathing in children with CMD, and thereby, the usefulness of overnight polysomnography recordings in such patients. Crown Copyright (C) 2012 Published by Elsevier Ltd on behalf of European Paediatric Neurology Society. All rights reserved.