Electrographic study of brainstem reflex myoclonus.

A patient with post-hypoxic brainstem reflex myoclonus was examined. In spontaneous jerks electromyographic activity started in the sternocleidomastoid and spread down the spinal cord bilaterally. A similar jerk was elicited by somaesthetic or acoustic stimulation. The patient's blink reflex suggested bilateral pontine lesions at least. Thus, the pattern of muscle activation pointed to a brainstem origin of the myoclonus. Spinal conduction studies conducted during the jerks suggested that the myoclonus signal facilitated a path identical to the spinobulbospinal reflex demonstrated in animals.