PERI-ROLANDIC AND FRONTOPARIETAL COMPONENTS OF SCALP-RECORDED GIANT SEPS IN CORTICAL MYOCLONUS

Scalp topography of giant SEPs to median nerve stimulation was studied in 4 patients with cortical myoclonus of various etiology. The positi ve peak (P30) at the contralateral parietal area was simultaneously ac companied by a negative peak at the frontal area(N30), and at least on e of these two peaks was enhanced in 2 patients. Another positive peak (P25) and a negative peak (N35) were also identified at the peri-rola ndic area with different latency from P30 and N30, respectively, in al l patients. N35 was enhanced in 3 patients, and P25 in 2 patients. It is concluded that, as seen in normal subjects, tangential (P30-N30) an d radial (P25 and N35) components of SEPs are most likely distinguisha ble in giant SEPs, and that either one or both of those components is enhanced in different ways depending on the patients.