Scalp topography of somatosensory evoked potentials in juvenile myoclonic epilepsy of Janz

Abnormality enlarged somatosensory evoked potentials following stimulation of median nerves (namely P25 and N33 central components) were found by means of two-channel equipement in patients suffering from juvenile myoclonic epilepsy (JME) (Salas-Puig J. et al. Epilepsia, 33 (3): 527-530, 1992). We studied scalp topography of somatosensory evoked potentials (SEP-MAP) following stimulation of median nerves in 10 JME patients (1M-9F, mean = 23.7 ± 11.2 yrs, mean height = 158.9 ± 4.3 cm) and in 10 healthy volunteers (1M-9F, mean age = 18.6 ± 9.2 yrs, mean height = 158.5 ± 8.4 cm). Data for mapping were collected using 16 recording channels, reference was A1 + A2, bandpass 1-100 Hz, stimulation rate 1 c/sec, acquisition time 150 ms. Student's t test between groups was performed on averaged mean maps and their standard deviations of each component (parietal N20, P27, P45, N60, P100, central P22, N33 and frontal N30 waves) by using the significance probability mapping method. Z-score between control group and single patient was also performed with respect to each SEP-MAP component. No significant intergroup differences were observed. However, 3 out of 10 patients had significantly enlarged central (P22, N33, P45) and frontal (N30) components. These data indicate that functional abnormalities of precentral cortex may be observed in some patients suffering from JME.