Propriospinal myoclonus at the sleep-wake transition: a new type of parasomnia

STUDY OBJECTIVES: To describe the clinical, neurophysiological, and polysomnographic characteristics of propriospinal myoclonus (PSM) at the sleep-wake transition. DESIGN: Patients referred for insomnia due to myoclonic activity arising during relaxed wakefulness preceding sleep, or complaining of muscular jerks also during intrasleep wakefulness and upon awakening in the morning were considered. SETTING: All patients underwent EEG-EMG recordings during wakefulness and night sleep. Back-averaging of the EEG activity preceding the jerks was performed. Somatosensory evoked potentials (SEPs), transcranial magnetic stimulation (TMS) and spinal and cranial MRI were also done. PARTICIPANTS: Four patients were studied all affected with involuntary jerks arising when falling asleep, and one with jerks also during sleep and upon awakening in the morning. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Polysomnographic investigations revealed jerks arising during the sleep-wake transition period. Myoclonic activity was neurophysiologically documented to be of the propriospinal type. SEPs, TMS and MRI were normal CONCLUSIONS: PSM may have a peculiar relationship with the state of vigilance and represent a sleep-wake transition disorder. In this regard we consider PSM a new type of parasomnia.