Wisconsin Card Sorting performance in patients with temporal lobe epilepsy: Clinical and neuroanatomical correlates

Purpose: A sizable proportion of patients with temporal lobe epilepsy (TLE) display impairments on tests of executive function. Previous studies have suggested several factors that may explain such performance, including the presence of hippocampal sclerosis, electrophysiological disruption to extra temporal regions, and early age of seizure onset. However, no clear determi nants have been found that consistently explain such executive dysfunction. The present study investigated the contribution of several clinical variab les and temporal lobe neuroanatomic features to performance on the Wisconsi n Card Sorting Test (WCST) in a series of patients with TLE. Methods: Eighty-nine patients with lateralized TLE (47 left, 42 right) were examined. Seventy-two patients from this series underwent anterior tempora l lobectomy (ATL). Regression analysis was used to examine the effects of a ge, education, age at seizure onset, seizure duration, seizure laterality, history of secondary generalized seizures, and MRI-based volumes of the rig ht and left hippocampi on preoperative WCST performance (number of categori es completed, perseverative errors). Further univariate analyses examined w hether the presence of bilateral hippocampal sclerosis, mesial temporal lob e abnormalities beyond the hippocampus, or temporal neocortical abnormaliti es affected preoperative WCST performance. In addition, we examined whether becoming seizure free after ATL affected change in WCST performance. Results: Overall regression analysis was not significant. However, an exami nation of individual partial correlations revealed that patients with a his tory of secondary generalized seizures performed more poorly on the preoper ative WCST than did patients without such history. In addition, patients wh o were seizure free after ATL did not exhibit better WCST outcome than pati ents who did not become seizure free. The presence of bilateral hippocampal sclerosis, extrahippocampal mesial temporal atrophy, or temporal neocortic al lesions did not affect WCST performance. Conclusions: These results indicate that the presence of temporal lobe stru ctural abnormalities do not significantly affect executive function as meas ured by the WCST. The present study does suggests that the critical determi nants of WCST performance in patients with TLE lie outside the temporal lob e and likely relate to metabolic disruption to frontostriatal neural networ k systems.