A sporadic case of benign myoclonus epilepsy of adult onset: its clinical aspects and electroencephalographic, polygraphic study

A sporadic case of myoclonus epilepsy of adult onset with a benign course is presented. Its clinical implications were discussed symptomatologically and nosologically. EEG findings consisted of the slowing of basic activity, characteristic polyspike and wave discharges or other paroxysmal patterns and photomyoclonic response (PMR). The PMR was well evoked by flashes of 6-21 Hz and of yellow or red color. Clinical similarities of this case to those of hereditary myoclonus epilepsy without progressive dementia and cerebellar ataxia, and pathognomonic characteristics of electrophysiological findings indicated that the myoclonic epilepsy syndrome might share basic properties, which are state-dependent, but independent of underlying neuropathology or heredity. During sleep, paroxysmal discharges with spike(s) significantly decreased in slow-wave sleep and almost recovered in REM sleep. This finding suggests that the brain stem may be responsible for the epileptogeneity in this case.