Segmental action and stimuli-sensitive myoclonus with acute onset. A case report.

A 23-year old man developed action and stimulus-sensitive myoclonus involving neck and proximal arm muscles. The finding of abnormally long and tortuous vertebral and carotid arteries and the abrupt onset of symptomatology suggest a possible hemodynamic mechanism. The electrophysiological characters and the sensitivity to serotonin precursors are consistent with the definition of "reticular reflex myoclonus".