Benign neonatal sleep myoclonus. A differential diagnosis of neonatal seizures.

OBJECTIVE: To describe 10 infants with benign neonatal sleep myoclonus.

DESIGN: Patient series, representing the experience of one pediatric neurologist.

SETTING: Referral-based Pediatric Neurology Service at a Children's Hospital.

PATIENTS: Sequential sample of 10 neonates referred for assessment of seizures and found to have benign neonatal sleep myoclonus. Neonates who did not have the events of concern during electroencephalography or in whom electroencephalography was not done were excluded even if the clinical features suggested the entity.

RESULTS: Our patients met the criteria for the diagnosis. The myoclonus often increased with gentle restraint. The amplitude and duration of events mimicked convulsive status epilepticus and serial seizures in four neonates. In two of them the myoclonus worsened in spite of anticonvulsant therapy, decreasing substantially when such treatment was stopped.

CONCLUSION: Benign neonatal sleep myoclonus, an entity characterized by (1) neonatal onset, (2) myoclonic jerks only during sleep, (3) abrupt and consistent cessation with arousal, (4) absence of concomitant electrographic changes suggestive of seizures, and (5) good outcome must be included in the differential diagnosis of neonatal seizures.