SOMATOSENSORY-EVOKED POTENTIALS IN ADULTS WITH CORTICAL DYSGENESIS AND EPILEPSY

Cortical dysgenesis (CD) is a well-recognised cause of epilepsy, but i ts functional anatomy is not fully understood. We recorded cortical so matosensory evoked potentials (SEPs) in 13 adult patients with epileps y and various CDs excluding diffuse gyral malformations as diagnosed b y MRI. The CD involved the perirolandic/perisylvian region in 7 patien ts. Six patients had neurological signs but only 3 had sensory dysfunc tion (astereognosis). As compared with 12 control subjects, SEPs were considered definitely abnormal in 7 patients (including the 6 with neu rological signs) and equivocally abnormal in 2. The abnormalities rang ed from defects affecting single components to absence of all potentia ls of cortical origin in one patient with hemiparesis and astereognosi s. In this case it appears that gross sensory function must have been mediated by subcortical structures or through diffuse cortical project ions. The initial cortical potentials (N20/P20) were absent in 6 patie nts, 5 of whom had CD intones involving or bordering on the primary se nsory cortex. Parietal potentials following N20 were absent or attenua ted in 4 patients and of abnormally wide distribution, spreading to fr ontal, midline and ipsilateral electrodes, in 3 frontal components fol lowing P20 were absent, attenuated, delayed or distorted by abnormal s pread of the parietal activity in 5 patients. Five patients with unila teral CD showed definite or equivocal SEP abnormalities to stimulation of both arms, suggesting there may be more widespread disturbance of cortical organisation and/or synaptogenesis, beyond the resolution of present day neuroimaging. (C) 1997 Elsevier Science Ireland Ltd.