Propriospinal myoclonus at sleep onset.
OBJECTIVE
To describe the clinical and polygraphic features of propriospinal myoclonus (PSM) at sleep onset.


METHODS
PSM was first described in 1997 in patients with jerks occurring in the relaxation period preceding sleep. EMG showed jerks to arise in spinally innervated muscles, propagating thereafter to rostral and caudal muscles at a low speed, typical of propriospinal pathways.


RESULTS
PSM arose when EEG alpha activity spread over the scalp and disappeared during either active wakefulness or actual sleep. In some patients EMG activity could sometimes remain localized to the abdominal muscles, propagating to other segments only in fully developed jerks. Neurological examination, brain and spinal MRI were usually normal and clonazepam afforded partial improvement. PSM has been recently observed also in restless legs syndrome, during relaxed wakefulness preceding falling asleep, coexisting with motor restlessness and sensory discomfort. PSM disappeared when spindles and K-complexes and typical Periodic Limb Movements appeared with EMG activity limited to leg muscles, without propriospinal propagation.


CONCLUSIONS
Conceivably, PSM arises in axial muscles due to some spinal generator set into motion by facilitating influences characteristic of the wake-sleep transition and then undergoes multimeric propriospinal propagation. In the International Classification of Sleep Disorders (ICSD-2), PSM is listed in chapter VII, among the "Isolated symptoms, apparently normal variants and unresolved issues".
Montagna
P
P
Department of Neurological Sciences, University of Bologna Medical School, Via Ugo Foscolo 7, 40123 Bologna, Italy. pasquale.montagna@unibo.it
Provini
F
F
Vetrugno
R
R
D000328:Adult; D000368:Aged; D002998:Clonazepam / Q000627:therapeutic use; D003937:Diagnosis, Differential; D004569:Electroencephalography; D004576:Electromyography; D006801:Humans; D008875:Middle Aged; D009207:Myoclonus / Q000175:diagnosis / Q000503:physiopathology*; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis; D012063:Relaxation / Q000502:physiology; D012148:Restless Legs Syndrome / Q000175:diagnosis; D020922:Sleep-Wake Transition Disorders / Q000175:diagnosis / Q000503:physiopathology*; D013116:Spinal Cord / Q000503:physiopathology*
D002998:Clonazepam