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

Study objectives: To describe the clinical, neurophysiological, and polysom nographic characteristics of propriospinal myoclonus (PSM) at the sleep-wak e transition. Design: Patients referred for insomnia due to myoclonic activity arising du ring relaxed wakefulness preceding sleep, or complaining of muscular jerks also during intrasleep wakefulness and upon awakening in the morning were c onsidered. Setting: All patients underwent EEG-EMG recordings during wakefulness and n ight sleep. Back-averaging of the EEG activity preceding the jerks was perf ormed. Somatosensory evoked potentials (SEPs), transcranial magnetic stimul ation (TMS) and spinal and cranial MRI were also done. Participants: Four patients were studied all affected with involuntary jerk s arising when falling asleep, and one with jerks also during sleep and upo n awakening in the morning. Interventions: N/A Measurements and Results: Polysomnographic investigations revealed jerks ar ising during the sleep-wake transition period. Myoclonic activity was neuro physiologically documented to be of the propriospinal type. SEPs, TMS and M RI were normal Conclusions: PSM may have a peculiar relationship with the state of vigilan ce and represent a sleep-wake transition disorder. In this regard we consid er PSM a new type of parasomnia.