Abstracts

Wisconsin Card Sorting Test (WCST) deficits have been observed in a significant proportion of individuals with TLE, although the cause of this deficit remains unclear. Competing explanations include the epileptogenic region remotely interfering with frontal lobe functioning, consistent with the nociferous cortex hypothesis, and the hippocampus contributing directly to card-sorting performance by virtue of its role in memory. The purpose of this study was to evaluate the relationship of seizure disorder characteristics to performance on neuropsychological measures sensitive to frontal lobe integrity, while considering the possibility that memory deficits mediated observed relationships, in TLE patients for whom quantitative MRI data was available., The sample included 60 surgical candidates with TLE, after excluding those with extratemporal lesions. Hippocampal volumes were normalized by reference to total intracranial volume. All neuropsychological scores, except number of WCST categories, were converted to normative values. Potential associations between disease-related variables (i.e., laterality of seizure focus, seizure frequency, age at onset, and delayed recall on the WMS-R) and performance on measures of executive functions (i.e., WCST, Trails B, and lexical fluency) were evaluated via t-tests, correlations, and hierarchical regression analyses., WCST, Trails B, and lexical fluency scores were similar for those with left TLE and right TLE. Seizure frequency appeared unrelated to neuropsychological scores. Earlier age at onset was associated with completion of fewer categories on the WCST ([italic]p[/italic]=.021), but was otherwise unrelated to performance on measures of executive functions. Correlation analyses showed that smaller right hippocampal volume (RHipV) predicted poorer WCST performance, including completion of fewer categories ([italic]p[/italic]=.036), commission of more errors in total ([italic]p[/italic]=.016), and commission of more perseverative errors ([italic]p[/italic]=.009). RHipV improved prediction of perseverative errors, even after controlling for FSIQ ([italic]p[/italic]=.014). Higher scores on Visual Reproduction Delayed Recall (VRII) predicted improved card-sorting performance, including commission of fewer perseverative errors ([italic]p[/italic]=.018). Even after accounting for VRII, RHipV improved prediction of perseverative errors ([italic]p[/italic]=.017), with independent contributions from both variables in the final model. Hippocampal volumes were unrelated to performance on other tests sensitive to frontal lobe integrity., The findings suggest a specific association between right hippocampal atrophy and perseveration on the WCST in TLE. Delayed nonverbal recall, as measured by VRII, did not fully account for the observed relationship between right hippocampal atrophy and perseveration during card-sorting.,