Usefulness of Wada test in predicting seizure outcome following anterior temporal lobectomy

Abstract

To study the usefulness of the Wada test for predicting seizure outcome following anterior temporal lobectomy (ATL). From 1996 to 2002, all patients with left mesial temporal lobe epilepsy and hippocampal sclerosis (MTLE-HS) and selected patients with right MTLE-HS underwent the Wada test before ATL at our center. Patients were selected for ATL on the basis of unilateral HS on MRI and concordant electro-clinical data. Twelve-item recognition paradigm was used for Wada memory testing. Score of +1 was awarded for a correct response and -0.5 for an incorrect response. We defined Wada failure as a contralateral score of <5, ipsilateral score of >8, and difference score of <0. No patient was denied surgery based on the Wada results. Means of the three scores were compared between seizure free and non-seizure free patients. Sensitivity, specificity and receiver operator characteristic curves of various scores for predicting seizure outcome were calculated. 151 patients (129 left MTLE; mean age: 27.80±8.72 years) formed the study group. At mean postoperative follow-up of 6.4±2.0 years, 127 patients were seizure free. Mean contralateral score was lower in the seizure-free group (7.15±3.07 vs. 8.71±4.13; p<0.001) while ipsilateral and difference scores were similar between the two seizure outcome groups. Areas under the curves for contralateral, ipsilateral and difference scores for predicting seizure-free outcome were 0.49, 0.58 and 0.59, respectively, suggesting its modest usefulness in individual patients. Results remained same when the analysis was restricted to left MTLE patients. Wada test has limited usefulness for predicting seizure outcome following ATL.