Tractography of the optic radiation for vision sparing epilepsy surgery

In case of refractory localized temporal lobe epilepsy the anterior part of the temporal lobe and parts of the mesial structures can be removed with epilepsy surgery. After anterior temporal lobe resection approximately 60 to 80% of the patients become seizure free. However, a visual field deficit in the upper quadrant of the visual field is a complication that arises due to disruption of the most anterior part of the optic radiation (Meyer's loop) in up to 100% of the cases. In case of a severe visual field deficit, patients are not allowed to drive anymore after surgery. In this study we tackle the difficult task of mapping the highly curved fibers of Meyer's loop to assist the neurosurgical planning. Tractography seeding is done by fMRI for the calcarine sulcus, and manual outlining of the lateral geniculate nucleus. The fibers of the central, upper and lower visual areas could be discriminated on their specific lengths and curvatures.