Abstracts

Rationale: Patients with epilepsy are known to have an array of changes in volume in a variety of cortical and subcortical structures. Advancements in neuroimaging techniques and their quantification allow these structures to be studied non-invasively and easily. We sought to explore these phenomena in older population, whereby we hypothesize that those with geriatric onset epilepsy (GOE; age of onset 65years or older) will display different imaging findings when compared to aged related patients with longstanding epilepsy (non-GOE; age of onset less than 65years). Methods: Following IRB approval, a retrospective study was performed identifying patients aged 65 years or older treated for epilepsy between January 2012-July 2014 and who underwent 3T volumetric MR imaging. They were divided into 2 groups, longstanding (NGOE) or geriatric onset (GOE). Using open-source software, FreeSurfer, cortical, hippocampal and thalamic volumes were measured in an automated fashion. Hippocampal and thalamic volumes were normalized for individual cortical volumes and reported as a ratio. Analysis comparing both groups with respect to seizure frequency and asymmetry indices were completed. Results: 14 patients with NGOE and 22 with GOE were included, with the NGOE group having a longer duration of epilepsy (214 yrs vs 23 yrs, p < 0.01). Older patients had smaller hemispheric volumes (p < 0.01), however no difference in hemispheric volumes was noted between groups (NGOE: 490170cc vs GOE:460140cc). Left hippocampal volumes were smaller in NGOE (0.006 vs 0.008, p=0.036) and similarly on the right (NGOE: 0.007 vs GOE:0.008, p=0.15). In GOE increased seizure frequency (greater than one seizure per month vs less than one seizure per month) was associated with smaller left hippocampal volume (0.007 vs 0.009, p=0.02), however no difference was noted in NGOE (0.006 vs 0.006, p=0.32). No difference in thalamic volume was noted (p=0.39), however in NGOE there was an appreciable asymmetry between both thalami (NGOE: 1.24 vs GOE: 1.04, p=0.11). Conclusions: Patients with GOE distinguish themselves from those age-related patients with longstanding epilepsy in terms of volumetric analysis. Despite smaller hippocampal volumes seen in NGOE, likely as a result of longstanding seizure activity, the hippocampus appears to be more susceptible to volume loss with increased seizure activity in GOE. These findings suggest the importance of seizure control in this already vulnerable age group. Further, more detailed studies are needed to fully understand these effects. Funding: None