FRONTAL INHIBITORY SPIKE COMPONENT ASSOCIATED WITH EPILEPTIC NEGATIVEMYOCLONUS

The aim of this study was to characterize paroxysmal EEG activities as sociated with epileptic negative myoclonus (ENM) in an epileptic patie nt presenting with ENM. ENM was predominant in the right upper limb an d was correlated to a spike in the left central region. Spikes associa ted with ENM (SaENM) and spikes unrelated to ENM (SuENM) were identifi ed by the temporal relation between the left central spike and the EMG silent period in the right wrist extensor. SaENM showed a significant ly longer duration than SuENM (128 +/- 27 msec versus 92 +/- 21 msec, respectively; P < 0.01). SaENM and SuENM were submitted to spike avera ging and topographic mapping. Spike averaging was performed averaging the EEG 640 msec before and after the peak of the spike. Both averaged SaENM and SuENM consisted of a negative spike with highest amplitude at C3 and similar topographic characteristics. The discriminant featur e between the two types of spikes was the presence, in averaged SaENM, of a second smaller negative spike, 40 msec after the peak of the spi ke at C3, whose maxima were distributed over the left frontal region. We labeled this second spike as ENM-related component. We conclude tha t, in our patient, ENM was associated with a frontal cortical potentia l suggesting the involvement of frontal areas in the generation of neg ative myoclonus.