Is the left cerebral hemisphere more prone to epileptogenesis than the right?

Purpose. To determine if there is evidence that the left cerebral hemispher e is more prone to epileptogenesis than the right hemisphere. Methods. We examined 532 patients with localization-related epilepsy, as do cumented by long-term EEG-video monitor studies. We identified those with i nterictal epileptiform patterns on EEG confined to one hemisphere, those wi th clinical seizures that arose only from one side, and individuals with ne uropsychological deficits lateralizing more to one cerebral hemisphere than the other. These data were then related to the handedness of the subjects. Results. For left-handed patients, interictal discharges were significantly more likely to be confined to the left side, seizures more frequently aros e from only the left hemisphere, and neuropsychological deficits lateralize d more often to the left brain. In contrast, for right-handed subjects, the re were no significant differences in unilateral localization of either int erictal discharges or of seizure onsets, nor did neuropsychological deficit s lateralize more often to one side or the other. Although, as a group, lef t-handers had an earlier age of onset of epilepsy than right-handers, the l ateralizing EEG and neuropsychological patterns seen in left-handers were n ot related to age of onset of epilepsy, febrile seizures, family history of either epilepsy or left-handed ness, or other risk factors. Conclusion. In localization-related epilepsy, there is a significant associ ation of left-handedness with left hemispheric lateralization of epileptifo rm EEG patterns and neuropsychological deficits. These findings do not clea rly reflect a greater left than right cerebral hemispheric vulnerability to epileptogensis, except possibly in left-handers.