A case of postanoxic encephalopathy with cortical action and brainstem reticular reflex myoclonus

A patient with postanoxic encephalopathy, with both action- and stimulus-sensitive reflex myoclonus, is described. The action myoclonus was multifocal and cortical in origin. In contrast, reflex myoclonus elicited by somaesthetic and auditory stimulation was generalised. The earliest reflex electromyograph activity was recorded in the sternocleidomastoid; myoclonic activity then spread up the brainstem and down the spinal cord, suggesting that this reflex myoclonus had its origin in the caudal brainstem. Stimulus sensitivity was greatest in the limbs. The bulbospinal motor pathways involved in the generalised reflex myoclonus were rapidly conducting, and this characteristic distinguishes this form of brainstem reflex myoclonus from that described in hyperekplexia.