Abstracts

Rationale: Little is known about the long-term cognitive outcomes following pediatric epilepsy surgery. Little change is found within the first two years following surgery and the few studies of longer-term outcomes have yielded inconsistent results. This study addressed this issue by examining memory functioning in a group of surgical and nonsurgical patients at baseline and four to eleven years after. Methods: Participants were 97 patients (mean age 20.08 [SD 4.44]) with childhood-onset intractable epilepsy; 61 had undergone resective epilepsy surgery. Participants underwent neuropsychological testing at two times (prior to surgery for the surgical group and in follow-up; at comparable times for the nonsurgical group). Tests of various aspects of memory involving recall and/or recognition of stories, faces, and lists of single words or word pairs were administered. Results: 54% of the surgical and 39% of the nonsurgical patients were seizure free in the preceding 12 months (p >.05). There were no significant effects of group (surgical vs. nonsurgical). A significant group x time interaction was found for story recall; the surgical group improved over time and had better recall than the nonsurgical group (p = .043). Additionally, both groups showed significant declines over time in terms of word list recall (p = .014). A similar effect of time was found when comparing seizure-free patients and those with persistent seizures. Additionally, seizure-free patients had better story recall than patients with persistent seizures at follow-up (p=.013). Higher IQ at follow-up was the most consistent independent predictor of better memory performance at follow-up. Memory performance at baseline was independently and positively predictive of recall of stories and word pairs. Age at surgery was predictive of story recall and face recognition, in that an older age at surgery was predictive of better performance. Cessation of antiepileptic medication was associated with better performance of word list recall. Change in IQ from baseline to follow-up was positively predictive of change from baseline in all memory tasks. Laterality and site (temporal vs. extratemporal) of surgery or epilepsy focus and age of seizure onset were not independently associated with performance at follow-up or change overtime. Conclusions: Improvements over time in story recall were associated with surgery and seizure freedom. For all other measures, the results show similar memory outcomes irrespective of group (surgical vs. nonsurgical) or seizure status (seizure-free vs. persistent seizures). Although little change is observed four to eleven years after pediatric epilepsy surgery, performance at follow-up is most consistently dependent on baseline memory performance and IQ at follow-up. Funded by the Ontario Brain Institute.