Left hemispheric dominance of epileptiform discharges

Purpose: We reviewed 1,360 EEG reports for all patients studied in two different neurophysiology laboratories during 1 calendar year to determine whether epileptiform discharges have a hemispheric dominance. Methods: Both inpatients and outpatients, with or without epilepsy, were included. Results: Ninety-four records (6.9%) demonstrated generalized epileptiform activity. Of 95 EEG reports indicating spikes solely from one hemisphere, spikes arose from the left in 61 and from the right in 34. Among 50 other records with bilateral independent spikes with lateralization, 40 were left hemisphere dominant and 10 were right hemisphere dominant. Conclusions: These findings raise the possibility that the left cerebral hemisphere may generate focal epilepsy more frequently than the right.