Comparative Sleep Disturbances in Myotonic Dystrophy Types 1 and 2

PURPOSE OF REVIEW: To update current knowledge regarding sleep disturbances and myotonic dystrophies so as to better understand if sleep symptoms may help in the early recognition of the two genetic subtypes: myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2). RECENT FINDINGS: Sleep-disordered breathing (SDB), restless legs syndrome, periodic limb movements in sleep, hypersomnia, and REM sleep dysregulation are frequently described in DM1 patients. SDB does not always explain hypersomnia, but a central dysregulation of sleep-wake modulation is reported mainly in DM1. Sleep apnea, restless legs syndrome, and REM sleep without atonia have been reported in single case reports and small case series of DM2. DM2 is less prevalent and more recently described than DM1, with a milder phenotype than DM1. The most frequent sleep disorders in DM1 are hypersomnia, SDB, periodic limb movements, and a narcoleptic-like phenotype, whereas restless legs syndrome, SDB, and REM sleep without atonia seem to be the most frequent sleep disorders in DM2. Comparative sleep studies are strongly required to delineate the sleep phenotype of myotonic dystrophies.