Abstracts

Although there have been numerous previous studies reporting memory outcome following temporal lobectomy, these studies typically do not follow patients for periods greater than one-two years after surgery. Consequently, little is known about long-term (i.e., more than 2 years post-surgery) cognitive outcome following temporal lobectomy. Variables that relate to outcome, particularly long-term seizure control, have also not been studied. The current study reports on the verbal memory outcome for patients enrolled in a multi-center, prospective epilepsy surgery outcome study. A total of 80 patients who had reached the 5 year post-surgical date and for whom follow-up memory data were available are included in this report. Patients were enrolled in the multicenter study of epilepsy surgery (MSES), and underwent neuropsychological testing as part of their pre-surgical evaluation, follow-up testing at two years post-surgery, and again at 5 years following surgery. Neuropsychological evaluation included general cognitive ability (Wechsler Adult Intelligence Scale), and verbal memory testing (California Verbal Learning Test). Neuropsychological testing at baseline revealed no significant pre-operative differences in Verbal, Performance or Full Scale IQ scores between the right and left TL surgery groups. Interestingly, there was no significant difference in the baseline verbal memory testing between the right and left TL groups. Repeated measures ANOVA reveals a trend toward better verbal memory outcome among patients with at least one 3 year remission period (p=.07), regardless of side of surgery. There is no significant main effect for side of surgery, but there was a significant interaction between time, side of surgery, and seizure outcome. While patients who underwent successful right temporal lobectomy (defined as at least 3 year seizure free period during follow-up) had the best verbal memory outcome, patients undergoing right temporal lobectomy that did not have a 3 year remission had the worst memory outcome, and were comparable to the left TL group without a 3 year remission. Post-hoc analysis also revealed that 3 of the 4 groups declined between the 2 year and 5 year outcome points. These results reveal that patients undergoing temporal lobectomy continue to evidence evolving changes in cognitive function 5 years after surgery. Although seizure outcome is a key factor, other variables also play a role, including side of surgery and baseline level of function. These findings indicate that patients may remain vulnerable to verbal memory declines as long as 5 years following temporal lobectomy. (Supported by NIH Grant Number 2 R01 NS32375-06.)