Lateralization of the epileptogenic focus by computerized EEG study and neuropsychological evaluation

The localization of the epileptogenic focus relies on different factors. In patients with partial seizures, asymmetries in EEG background activity were measured by a statistical evaluation of spectral data. Neurophysiological results were compared with neuropsychological findings and MRI. Fifteen of 22 patients showed asymmetries in EEG background activity. The most prominent abnormality was a statistically significant increase of slow activity observed in 59% of cases. Delta asymmetry coincided with the site of lesions, evidenced by MRI, in 83% of patients; with the site of decreased beta activity in 60% and with the maximum level of spiking activity in 58% of cases. Neuropsychological tests showed a lateralization of the hemispheric function which coincided with delta asymmetry in 33% of patients. These results suggest that the EEG background activity, when compared with other parameters, may represent a useful method in lateralizing the epileptogenic focus.