BILATERAL MAGNETIC-RESONANCE IMAGING-DETERMINED HIPPOCAMPAL ATROPHY AND VERBAL MEMORY BEFORE AND AFTER TEMPORAL LOBECTOMY

We investigated pre- and postoperative verbal memory in temporal lobec tomy patients who had volumetrically symmetric hippocampi. Pre- and po stoperative verbal memory data based on the Logical Memory subtest of the Wechsler Memory Scale-Revised (WMS-R) were obtained from 15 left a nd 18 right temporal lobectomy patients. The difference between hippoc ampal volumes (R/L) was between -0.1 and 0.3 cm(3), which is indetermi nate for lateralizing hippocampal atrophy. Patients were divided into four groups based on side of operation and combined hippocampal volume expressed as a function of total intracranial volume (R + L volume/to tal intracranial volume). Patients with a combined hippocampal volume that was smaller than any combined hippocampal value of a normal contr ol group were defined as bilaterally atrophic. Left temporal lobectomy patients demonstrated the expected decrease in verbal memory postoper atively regardless of whether the volumetrically symmetric hippocampi were nonatrophic or atrophic, Left temporal lobectomy patients with bi laterally atrophic hippocampi, however, had the poorest verbal memory before and after operation. Right temporal lobectomy patients tended t o have improved verbal memory after operation whether or not the volum etrically symmetric hippocampi were atrophic. We conclude that side of operation is a more potent predictor of verbal memory outcome than is hippocampal atrophy when hippocampi are bilaterally symmetric and tha t left temporal lobectomy patients with bilateral atrophy may be at ri sk for greater functional deficits after operation.