Effects of temporal lobectomy for treatment of epilepsy on hemispheric functions ipsilateral to surgery: preliminary findings

Several studies have reported a pattern of ipsilateral deficit and contralateral improvement following temporal lobectomy. Presumably the contralateral improvement is due to cessation of commissural spread, and the ipsilateral deficit to surgical damage to that side. If, as hypothesized, the underlying mechanism is cessation of commissural spread of seizure activity, some ipsilateral improvements might also occur. This question was addressed in a small sample of left (N = 4) and right (N = 5) temporal lobectomy patients. It was found that the left-operated patients demonstrated improvements on tests reported to measure left frontal lobe function. In addition, both left- and right-operated patients improved on a dexterity test with the hand ipsilateral to the side of surgery. The ipsilateral improvement would be due to removal of an active electrically discharging focus impairing ipsilateral function and contralateral function by commissural spread. These data were interpreted to suggest that cessation of commissural spread of seizure activity can result in improvement in regions of the hemisphere ipsilateral to surgery, and that the contralateral hemispheric improvements may include psychomotor functions in addition to memory and IQ changes. Seizure control achieved by surgery may have influenced the pattern of results.