Benign neonatal sleep myoclonus: our experience of 15 Japanese cases.

PURPOSE: Benign neonatal sleep myoclonus is a non-epileptic movement disorder that may mimic neonatal seizures. The aim of this study was to clarify the clinical manifestations and outcomes in Japanese infants with benign neonatal sleep myoclonus.

METHODS

We reviewed the clinical manifestations and outcomes in 15 consecutive patients with benign neonatal sleep myoclonus (males: 10), including three paired familial cases, referred to our center between 1996 and 2011. The diagnosis of benign neonatal sleep myoclonus was based on a neonatal onset, characteristic myoclonic jerks that occurred during sleep, and normal electroencephalogram findings.

RESULTS

All were healthy full-term neonates at birth. The age at onset ranged from 1 to 18 days (median: 7 days). Prior to referral to our center (3-8 weeks), two infants had been placed on antiepileptic drugs, without effects. During the clinical course, the myoclonic jerks resolved by 6 months in 14 of the 15 patients. On follow-up (final evaluation, mean: 38 months), all but one patient (speech delay) showed normal development. None developed epilepsy. Of note, migraine occurred after 5 years of age in three children, including one who developed cyclic vomiting syndrome, evolving to migraine. Another boy developed cyclic vomiting syndrome, a precursor of migraine, before 1 year, and was being followed. A high incidence of migraine was observed in five (42%) of 12 parents whose detailed family history was available.

CONCLUSION

Our study suggests that benign neonatal sleep myoclonus is related to migraine. With the high rate of familial cases, further genetic study, including migraine-related gene analysis, is necessary to determine the underlying mechanism responsible for benign neonatal sleep myoclonus.