Post-Anoxic Reticular Reflex Myoclonus in a Child and Proposed Classification of Post-Anoxic Myoclonus.

OBJECTIVE: We describe a child with post-anoxic myoclonus of the reticular reflex type and discuss the classification of post-anoxic myoclonus. PATIENT DESCRIPTION: A nine-year-old boy with severe hypoxic-ischemic encephalopathy due to submersion developed early epileptic spasms followed by stimulus sensitive multifocal generalized myoclonus and later dystonia. Video electromyography (EMG) polygraphy performed before treatment demonstrated that the discharges associated with the myoclonus lasted less than 50 milliseconds. Cortical myoclonus was excluded by jerk-locked averaging using arm muscles, which showed no cortical correlates. The recruitment order on EMG polygraphy was consistent with a brainstem generator for the myoclonus, characteristic of reticular reflex myoclonus. Both myoclonus and dystonia responded to clonazepam. He remains in a persistent vegetative state. CONCLUSIONS: Reticular reflex myoclonus can be demonstrated by detailed neurophysiological assessment in children as in adults, and it has a similar poor prognosis in children. Post-anoxic myoclonus can have several mechanisms and should not be considered synonymous with Lance-Adams myoclonus.