Abstracts

Rationale: Approximately 30% of patients with epilepsy are drug-resistant (DRE), and long-standing refractory epilepsy is associated with a variety of neuropsychologic deficits. Adult patients with drug-resistant frontal lobe epilepsy (FLE) show a general pattern of cognitive dysfunction, especially in the functions related to the frontal lobe such as executive functions and attention, which are influenced by the duration and age at onset of epilepsy. Long-standing FLE can also be associated with MRI changes outside the frontal lobes, typically detected by volumetric analysis of MRI images. In this study we examined longitudinal changes in hippocampal volume in pediatric refractory FLE patients, whether these changes are correlated with overall cognitive performance and memory scores and whether these trends are dependent on epilepsy lateralization.

Methods: We examined patients with refractory frontal lobe epilepsy who underwent epilepsy surgery. We included patients who underwent more than one MRI scan during their presurgical evaluation, have no mesial temporal sclerosis (MTS) on visual inspection of the MRI and had at least one neuropsychological evaluation. MRI scans were acquired on a 3-T Philips Achieve whole body scanner. Whole-brain volumetric segmentation and cortical surface reconstruction was performed, and total volumes of the hippocampi were measured through an open-source software FreeSurfer 7.1 (https://surfer.nmr.mgh.harvard.edu). Hippocampal asymmetry index (AI) was calculated as volumes of ipsilateral hippocampus-contralateral hippocampus/sum of both hippocampi. A linear regression mode was carried out to determine changes in hippocampal volume over time and statistical analysis was performed to examine the correlation between hippocampal volumes and memory scores.

Results: 21 patients were included. Full Scale Intelligence Quotients (FSIQ) was assessed for 21 patients localized the left (n=8) and right (n=13) hemispheres. The average age at the time of the evaluation was 12.5 ± 4.2 years with an average of 6.0 ± 4.2 years since seizure onset. Only 15 had specific verbal and visual memory scores (Left n=6; right n=9). Progressive decline in FSIQ with longer duration of epilepsy was seen irrespective of epilepsy lateralization as well as in verbal and visual memory scores only in right sided FLE (Fig. 1). Progressive decline in ipsilateral hippocampal volume was seen (Fig. 2) irrespective of epilepsy lateralization that correlated with FSIQ, verbal and visual memory scores in right sided FLE and with visual memory scores in left sided FLE.

Conclusions: These preliminary findings show evidence of progressive decline in overall cognitive functions and hippocampal asymmetry in pediatric refractory FLE as well as memory scores in right sided refractory FLE. Left sided FLE showed dissociated memory scores with an unexpected, improved verbal memory that is likely due to small sample size and variability in the severity of epilepsy.

Funding: Please list any funding that was received in support of this abstract.: This study was funded through Pediatric KPRI grant and NSF-EPSCoR # 1632891.