Abstracts

Rationale: Quantitative diffusion tensor imaging (DTI) analysis is not yet routinely used in the presurgical evaluation of patients with epilepsy. However, white matter alterations in epileptogenic zone (EZ) have been evaluated by studies using DTI. The goal of our study was to assess whether quantitative DTI methods could improve EZ localization in individual patients with temporal lobe epilepsy (TLE). Methods: DTI images of two adult patients with refractory TLE who underwent depth electrode implantation to assess intracranial electroencephalography (icEEG) were studied. We compared two different methods, i.e., an automated probabilistic native space based approach using the software of TRActs Constrained by UnderLying Anatomy (TRACULA) and a manual deterministic technique in which tracts were seeded from intracranial EEG electrode sites using TrackVis. We measured the fractional anisotropy (FA) of the tracts. Seizure onset zone (SOZ) was defined by icEEG. Two age and gender matched healthy controls were also included.  Results: In both patients the cingulum contralateral to the SOZ was found to have increased FA compared to controls using automated tractography. Case 1 had unilateral neocortical TLE with frontal opercular SOZ. In this patient, automated tractography found that the entire superior longitudinal fasciculus (slf) ipsilateral to the SOZ had lower FA compared to the control. In case 2 of unilateral mesial TLE and extensive bilateral seizure spread, the temporal bundle of the slf tract in both hemispheres and the forceps minor of the corpus callosum showed markedly decreased FA compared to the control. Using manual tractography, we found in both patients that the mean FA of tracts located at electrode sites of the SOZ were lower compared to the mean FA of tracts located at non-SOZ sites. However, this was not seen at the corresponding tracts of control subjects. Conclusions: DTI alterations seemed to correspond to the patients’ EZ and seizure spread. Quantitative DTI might help in presurgical evaluation of individual patients with epilepsy. Future studies should focus on standardizing tractography methods and defining normal reference for outcome parameters. Funding: I.O. received the Otfried-Foerster research grant from the German Epilepsy Society.  J.E.Jr. was supported by the NS033310 and NS100054 NIH grants.