Abstracts

Rationale: To determine if abnormal memory performance in children with medically resistant partial epilepsy correlates with decreased temporal lobe cortical thickness and hippocampal volumes. Methods: Children who underwent surgical resection for medically resistant epilepsy and who had a neuropsychological evaluation prior to surgery and high resolution MRI were retrospectively identified for this study. Volumetric analysis and cortical thickness studies were performed using FreeSurfer version 4.0. Volumes and cortical thickness were compared to a cohort of healthy controls (n=39, 2-16 years (mean 8.5 ± 4.5), 17M:20F). Data collected included: age of epilepsy onset, duration of epilepsy, history of status epilepticus, number of anti-convulsant medications, MRI abnormalities, IQ, side of surgical resection and surgical pathology. Memory impairment was defined as performance below 1.5 SDs on standardized memory scales; for each case, the percentage of tests in the impaired range was calculated for verbal and visual memory tests. Children were administered a variety of memory scales, including tests from the Children’s Memory Scale, the Wide Range Assessment of Memory and Learning, the California Verbal Learning Test - Children’s Edition, the Rey Osterrieth Complex Figure Test, and the Wechsler Memory Scale Third Edition. Results: 21 children (11 M; 10 F) ages 4-17 years (10.8 ± 3.7) at the time of surgery were included in the study. The mean age of seizure onset was 6.3 ± 3.6 years (history of status, 5) and duration was 5 ± 3.4 years. Left temporal mean cortical thickness (3.27 mm) was significantly thinner than control data (3.51mm) (p <0.01) and did correlate with a longer duration of epilepsy prior to surgery (p<0.01) but not with temporal or extra-temporal epilepsy, a history of status or side of the surgical resection. Right temporal mean cortical thickness was not different from control data. Thinning of the left temporal cortex was associated with a higher percent of impaired verbal memory scores (p<0.03) but not visual memory scores. Abnormal memory scores did not correlate with decreased hippocampal volumes. Neither cortical thickness nor hippocampal volume correlated with full scale IQ. Conclusions: Left temporal mean cortical thickness is significantly thinner in children with medically refractory partial epilepsy and is associated with a longer duration prior to surgery and decreased verbal memory. Further studies are necessary to better elucidate the temporal relationship between cortical thickness and memory changes in children with medically refractory partial epilepsy.