[Negative myoclonus; a simple partial seizure].

Negative myoclonus in a 4-year-old boy was analyzed by polygraphic study, which lead to the diagnosis of simple partial seizure. He had irregularly trembling movements of right upper limb when he held some objects with his right hand. There were also coarse trembling movements in his body and lower limbs while sitting or standing. Polygraphic recording showed that the involuntary movements were caused by intermittent inhibition of muscle contraction associated with electrical silence on EMG and spikes in the left central area on EEG.