Abstracts

To identify the best predictors of postoperative verbal memory decline in patients undergoing left temporal lobe excisions for epilepsy., A retrospective analysis was carried out using data from 59 patients with left mesial temporal lobe epilepsy (TLE) who underwent en-bloc resection. Memory was measured by a standard word list-learning task (z-score for total number of words over 5 trials) administered before and after surgery. A new rating was devised for the MR images, to characterize the extent of hippocampal damage. Atrophy and signal change of the hippocampus were examined separately. Both changes were assessed on a scale: 0=no change 1=moderate atrophy/signal change, 2=severe atrophy/signal change. The average of these two factors was calculated to classify the degree (range 0 to 2) of mesiotemporal sclerosis (MTS). The Wada results included number of correctly identified items after ipsilateral injection and contralateral injection (pass/fail boundary: 67%), as well as an asymmetry score. In various multiple regression analyses, Wada test scores (injection ipsilateral, injection contralateral, asymmetry score), neuropsychological test scores before surgery, MRI scores (atrophy, increased signal change, MTS) and further risk factors such as age of onset were entered as the independent variables. The difference in the verbal memory test was the dependent variable., After surgery, 35% of the patients showed a memory decline indicated by a z-score loss of more than one point. The regression analyses revealed that the pre-operative memory test score was the strongest predictor of memory change (p[lt]0.05, adjusted R Square=0.341). Higher preoperative performance in the verbal memory task was associated with a greater risk of verbal memory decline after surgery. The second significant predictor was the MTS classification (p[lt]0.05, adjusted R Square=0.428). Greater damage to the hippocampus was associated with less decline following surgery. None of the other variables, including the Wada results and other risk factors, were significant predictors of memory outcome., The Wada test results did add to the prediction of verbal memory decline in this sample of patients in whom temporal lobe resection was considered safe with regard to the risk of amnesia (i.e., adequate memory functioning following ipsilesional injection compared to contralesional injection). Thus, the clinical data obtained routinely before surgery seems to be sufficient to predict risk of memory decline in the majority of TLE patients. However, our findings do not refute the usefulness of the Wada test for excluding from surgery those patients who are at risk for amnesia after temporal lobe resection.,