Neuropsychological tests with lateralizing value in patients with temporal lobe epilepsy: Reconsidering material-specific theory

PURPOSE To assess the ability of neuropsychological tests to determine the side of seizure onset for preoperative assessment in patients with drug-resistant temporal lobe epilepsy. METHODS Twenty-nine consecutive patients diagnosed with temporal lobe epilepsy (TLE), in whom the epileptogenic focus was clearly identified and localized to either the right or left hemisphere. Patients underwent a full neuropsychological assessment as part of their pre-surgical investigation, including the Boston Naming Test (BNT) and a variety of Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) and Wechsler Memory Scale-Third Edition (WMS-III) subtests. Two multivariate analyses of variance were carried out to assess differences on memory and language measures between groups according to side of epileptogenic focus. Binary logistic regression analysis was performed to find the sets of tests that best predicted the side of seizure onset (determined by EEG and MRI). RESULTS Memory multivariate analysis of variance failed to show significant differences between the right- and left-sided groups. Among language measures, only the BNT revealed significant differences between the groups. The neuropsychological measures that best predicted the side of seizure onset were the BNT and Visual Reproduction II. CONCLUSIONS Language measures predict the side of seizure focus better than memory measures. The results of this study in a sample of drug-resistant temporal lobe epilepsy patients challenge the memory material-specific theory for the side of seizure focus.