Abstracts

Rationale: Epilepsy is known to have debilitating consequences on cognitive abilities. This study compares neuropsychological performance and explores the functional correlates of memory.Methods: We studied 22 left focus epilepsy patients (10 Males; age 7-12) and 22 age-matched healthy controls (8 Males). Participants underwent comprehensive neuropsychological testing of intellectual, memory, and reading abilities. Functional imaging was also conducted using whole brain 3T fMRI (EPI BOLD) with a reading task employing a box car design. Data was analyzed using multivariate analysis of variance (MANOVA), regression analyses, and correlational tests. Imaging data was analyzed with SPM2 using a hippocampal mask as a functional marker for the ongoing memory requirements that are needed to read successfully.Results: Patients performed worse than healthy controls across measures of intelligence (p<.05), memory (p<.01), and reading (p<.01); however, average patient performance fell within the low average range compared to high or above average performance for healthy controls. Older age of onset correlated with higher IQ (p < .05) and taking fewer medications correlated with better verbal memory (p< .05). After accounting for variance due to IQ, regression analyses revealed that patients’ visual memory skills are worse than healthy controls (p<.01), and a trend towards poorer reading abilities was also revealed (p=.08). Better reading abilities correlated with greater left lateralization of hippocampal activation (p<.05) for healthy controls. In contrast, there was a trend towards better reading abilities correlating with greater right lateralization of hippocampal activation (p=.09). Activation of hippocampus did not correlate with memory measures.Conclusions: Left hemisphere epilepsy is associated with adverse cognitive effects particularly in visual memory and reading skills. This is consistent with the crowding hypothesis that visually based skills are impacted at the cost of preserving language functions. Functional imaging results indicate that activation of hippocampal structures during a reading task differentially correlates with reading performance. Healthy controls who have greater left lateralization of the hippocampus also have better reading abilities whereas patients who invoke the right hippocampus have better reading abilities. This patient pattern may represent a compensatory strategy and further supports the hypothesis that patients need to recruit right hemisphere structures for language tasks. Hippocampal activation during this reading task likely represents semantic retrieval.