Abstracts

Rationale: Cognitive difficulties have frequently been noted in individuals with epilepsy, but the relation of cognitive function to brain structure at the time of illness onset is unclear. If predictive MRI-based biomarkers can be identified, such metrics may aid the prediction of health outcomes and facilitate the implementation of early interventions. In order to examine potential structural biomarkers, we investigated the relationship between select brain structural features and performance on measures of processing speed, working memory, attention and executive function, in individuals with newly diagnosed focal epilepsy. Methods: Participants were from The Human Epilepsy Project (HEP) and included 73 individuals with focal epilepsy and 39 healthy controls matched on sex, age and education level. Individuals in the epilepsy group underwent cognitive testing using the following Cogstate test battery subtests: Detection Test, One-Back Test, Identification Test and the Groton Maze Learning Test. All participants completed an MRI scan and the following values were extracted: cerebral white matter volume, total intracranial volume, hippocampal volume, dorsolateral prefrontal cortex volume and caudate nuclei volume. Because the control group did not complete cognitive testing, normative data for the Cogstate measures were obtained from a sample of 73 individuals that was matched on age and sex with the epilepsy group. We hypothesized that patients with epilepsy would perform worse than controls on the cognitive measures and that there would be structural differences on the selected structural MRI variables between epilepsy and control groups. We examined the relationship between the brain volumetric variables and cognitive performance (i.e., attention, processing speed, working memory and executive function) in the group with newly diagnosed focal epilepsy. Results: Although there were no group differences in processing speed, the epilepsy group exhibited significantly weaker working memory, attention and executive functioning, as compared to the normative group. Contrary to expectations, there were no significant differences between the epilepsy group and the control group on any of the brain volumetric variables and no relationship between those structural variables and cognitive performance was identified in the epilepsy sample. Conclusions: Findings suggest that although newly diagnosed focal epilepsy may be associated with specific cognitive weaknesses, it is not associated with significant volumetric reductions within the areas examined here. This contrasts with past studies that focused primarily on medically refractory chronic epilepsy and temporal lobe epilepsy populations. Ongoing seizures and other chronic effects, such as long-term medication use, may be contributors to the previously observed structural abnormalities in patients with focal epilepsy. Funding: Epilepsy Study Consortium (ESCI), a non-profit organization accelerating development of new epilepsy therapies; ESCI is supported by industry, philanthropy and foundations.