Wisconsin Card Sorting Test Performance in Mesial Temporal Lobe Epilepsy

Kim, Chul Ho; Lee, Sang Ahm; Yoo, Hee Jung; Kang, Joong Koo; Lee, Jung Kyo

Abstract

PURPOSE: To investigate the origin of frontal lobe dysfunction identified by the Wisconsin Card Sorting Test (WCST) in mesial temporal lobe epilepsy (MTLE).
METHODS
We included 85 patients with unilateral MTLE and 34 patients with neocortical temporal lobe epilepsy (NTLE). We included only MTLE patients who postoperatively became seizure free at least for 1 year. Comparisons were made on the WCST performance between MTLE and NTLE and between preoperative and postoperative test in MTLE. Standardized regression based (SRB) methodology was used for correcting test-retest bias.
RESULTS
1) There were no significant differences in frontal lobe dysfunction defined as more than 17 perseverative errors between MTLE (64%) and NTLE (76%). 2) No significant differences in WCST performance between MTLE and NTLE were noted, except in categories completed (p=0.05). NTLE achieved significantly fewer categories than MTLE. 3) The proportions of patients with MTLE who postoperatively showed a clinically meaningful improvement on WCST performance were higher than those who displayed a significant decline. In case of perseverative responses, 52% of patients with MTLE postoperatively showed an improvement whereas 18% displayed a decline. 4) Postoperatively, mean values of perseverative responses and total errors were significantly decreased (p<0.05). 5) Significant negative correlations were found between preoperative WCST performance and postoperative SRB change scores for WCST (r=-0.3~-0.4, p<0.05).
CONCLUSIONS
Our results could not be explained by any one of 'neural noise' or 'hippocampal' hypothesis. Our data suggest that poor WCST performance in patients with MTLE might be attributed to dysfunction of neural system including both hippocampus and frontal lobe cortex. Further studies are needed to make new hypothesis.