Abstracts

Rationale: Diffusion tensor tractography (DTT), an application of diffusion MR imaging, has been utilized in studies of anatomical differences in patients with psychiatric and behavioral conditions, as well as in temporal lobe epilepsy and other neurologic conditions. However, the clinical application of diffusion tensor imaging and tractography has not been well established in the treatment of epilepsy. Here we present a case where DTT identified an aberrant connection from a large focal cortical dysplasia to the epileptic focus on EEG, and was useful in planning epilepsy surgery. This use of DTT in guiding epilepsy surgery has not been previously reported, and presents a new application for this noninvasive technology.Methods: Diffusion tensor imaging and tractography was performed on a 2 year old girl with right frontal cortical dysplasia and refractory epilepsy since infancy. Continuous long term video telemetry showed seizure onset in the right frontal and midline central areas, more medial to the identified MRI lesion, which was mainly in the right inferior frontal gyrus on MRI. Results: Diffusion tensor imaging and tractography applied to region of dysplasia revealed aberrant white matter fiber tract connections between the frontal cortical dysplasia in the right inferior frontal gyrus and the apparently normal appearing right superior frontal gyrus, as seen on conventional MRI. This aberrant connection explained the discrepancy between the MRI lesion in the right inferior frontal gyrus and the focus of EEG seizure onset in the right superior frontal gyrus, including the medial aspects. Incorporating all data including MRI with DTT and continuous video EEG telemetry, subdural EEG electrodes were placed over the lateral and medial right frontal and parietal lobes. Seizure onset on continuous video EEG telemetry with subdural electrodes mapped to the lateral and inferior right frontal areas. Resection of the right frontal cortical dysplasia and multiple subpial transections of the right motor area correlating to aberrant white matter tracts were performed. Intraoperative corticography allowed for preservation of motor and sensory cortex. Pathology revealed cellular atypia and mild disorientation of pyramidal cells, consistent with cortical dysplasia. Patient recovered well, with only a few residual seizures in postoperative period, all of which were of milder semiology than prior seizures. Conclusions: This is the first documented report of DTT data assisting epilepsy surgery planning. From our case, DTT may identify an epileptic network which expands beyond the primary structural MRI lesion through aberrant white matter connections. The use of DTT in planning epilepsy surgery for focal cortical malformations, especially with discordant EEG findings, presents a novel and helpful application for this new technology.