Abstracts

RATIONALE: Anterior temporal lobectomy (ATL) is an effective intervention for treating medically refractory temporal lobe epilepsy, but patients who undergo this procedure may be placed at risk for post-surgical memory decline. This study is designed to demonstrate that non-invasive, state-of-the-art assessment techniques are sufficient to maximize the accurate prediction of post-surgical memory decline after ATL, potentially rendering relatively higher-risk procedures obsolete for this purpose. The objective of this presentation is to provide clinicians with information about predictive relationships between pre-operative evaluations and post-operative memory outcome for use when counseling patients about potential risks of ATL.
METHODS: This IRB-approved study involved a retrospective analysis of data archived as part of the standard clinical care of 22 left ATL and 29 right ATL patients. Patients were administered the Wechsler Memory Scales-Third Edition (WMS-III) before and approximately six months after surgery. All 51 patients evidenced left-hemisphere language dominance, and 78% were seizure-free after surgery. Patients were divided into two groups: those demonstrating memory decline (test-retest scores below the 15th percentile of non-surgical epilepsy controls) versus those with stable memory. A series of exploratory logistic regression analyses with side of surgery, pre-operative neuropsychological data, volumetric analyses of MRI scans, and Wada test results entered as dependent variables determined the relative contributions of these factors to the accurate prediction of memory decline.
RESULTS: In contrast to previous findings in the literature, side of surgery was not a significant predictor of memory outcome as measured by the WMS-III; right ATL and left ATL patients demonstrated similar rates of memory decline. For verbal memory measures, hippocampal atrophy contralateral to the seizure focus and poor memory scores on the Wada test after ipsilateral injection were associated with memory decline after surgery. For visual memory measures, strong baseline visual memory was associated with post-operative memory decline, but a poor memory score on the Wada test after ipsilateral injection predicted a good memory outcome after surgery.
CONCLUSIONS: Contrary to expectation, the Wada procedure predicts memory outcome following ATL above and beyond side of surgery, MRI volumetric analyses, and baseline memory. The ability of the contralateral hemisphere to independently support memory is significantly related to post-operative memory decline. Hippocampal volumes also help to predict verbal memory outcome, whereas pre-operative neuropsychological measures are associated with visual memory changes. These exploratory results support recent research in the literature that suggests both the functional adequacy and functional reserve models may contribute to understanding memory decline after ATL. Results also indicate that findings based on previous neuropsychological test measures may not be generalizable to newer methods of assessing memory.
[Supported by: This project was supported by the Epilepsy Foundation.]