Abstracts

Rationale: The claustrum is a small subcortical grey matter structure with multimodal integration and diffuse connectivity, which may play an important role in epilepsy. The claustrum is difficult to visualize and measure in vivo using conventional Magnetic Resonance Imaging (MRI), and there is limited information about potential volumetric changes in disease states. Here, we used 7 Tesla (7T) MR images from patients with focal epilepsy and controls to manually segment and to quantify the volume of the claustrum.  Methods: High resolution T1 multi-echo magnetization-prepared rapid gradient-echo (meMPRAGE). Following bias correction, automatic segmentation files were created using FreeSurfer (v6.00). Manual segmentation of the claustrum (Figure.1) was performed by a single person, blinded to the group or clinical history, using Freeview. Volumetric measures were then extracted for statistical analysis. Mann-Whitney U Test, followed by controlling for false discovery rate, was used to compare cortical and subcortical volumes between subjects and controls, as well as laterality index (LI) calculated for each patient as a measure of asymmetry.  Results: Sixteen patients and eleven unmatched controls were included. Based on available clinical and post-surgical results, the seizure focus was in the left temporal lobe in seven, left frontal in two, and right temporal in three patients. The exact focus could not be determined in one patient, but was determined to be left sided. In all groups, the right claustrum was larger than left, shown in Figure.2. The left-to-right asymmetry only reached significance in those with a left-sided focus (p=0.011). The differences between median claustral volumes in patients (L: 502mm3R: 656mm3) and controls (L: 634 mm3, R:703 mm3) did not reach statistical significance. Median LI for claustral volumes was -0.08 in controls and -0.11 in patients (p=1.0). No other differences were found after false discovery rate was adjusted for.  Conclusions: There were no significant differences in 7T MRI in vivo measurements of claustral volumes in focal epilepsy patients compared to controls. The asymmetry between the left and right side of the claustra was only significantly different in patients with left-sided epilepsy. Adequately powered studies will be required to confirm this finding. Additionally, this provides a foundation for future research into structural connectivity in epilepsy.  Funding: AES/TS Alliance (Taha Gholipour)