Abstracts

Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS) is the most refractory form of partial epilepsy that is amenable to surgical treatment. However, even in the most rigorously selected candidates, small but significant numbers of patients are not rendered seizure free. We used surface-based anatomical mapping to detect features of hippocampal anatomy that correlated with surgical outcomes in epilepsy patients who had undergone surgery for MTLE with HS. We mapped and compared 3D hippocampal atrophy profiles in MTLE patients who were seizure free (SF) after surgery with those who had not attained seizure freedom (NSF). 3D averaged anatomical surface models of the hippocampus were derived from preoperative T1-weighted MRI scans of 30 SF and 10 NSF patients and mapped using semi-automated image analysis. The hippocampal asymmetry maps in the NSF outcome group showed lesser degrees of asymmetry compared to the SF group along the entire hippocampal axis without regional specificity (p[lt]0.0001 by permutation). Comparison of mean hippocampal volumes between the two groups showed that the NSF group had significantly greater hippocampal atrophy bilaterally (p[lt]0.0001). However, the contralateral hippocampal atrophy map showed maximal deficit in the anterior and lateral aspects of the hippocampus while the ipsilateral side showed more diffuse changes (Figure1, ipsilateral p[lt]0.01; contralateral p[lt]0.002 by permutation). MRI-based surface modeling revealed patients with NSF surgical outcome have a significantly greater bilateral regional specific hippocampal atrophy profile compared to SF group. These regions of atrophy may indicate areas of increased epileptogenecity, contributing to poorer surgical outcomes.[figure1] (Supported by grants from the Epilepsy Foundation Clinical Research Training Fellowship, National EpiFellows Foundation Fritz E. Dreifuss Award (to J.J.L. and J.E.), National Institute for Biomedical Imaging and Bioengineering, the National Center for Research Resources, and the National Institute on Aging (to P.M.T.: R21 EB01651, R21 RR019771, P50 AG016570; to A.W.T.: P41 RR13642 and M01 RR00865 (GCRC).)