gms | German Medical Science

Objective: MTLE is the most common form of pharmacoresistant focal epilepsy in adults and SAH is a safe and well-recognized surgical procedure for its treatment. One of the procedural risks are visual field deficits due to damage of the optic radiation (OR), the so-called Meyer's Loop. Here we compare the transsylvian and the subtemporal approach with regard to VFDs both clinically and with Diffusion Tensor Imaging (DTI).

Method: Overall, 65 consecutive patients with MTLE underwent temporal resections. Pre- and postoperative visual fields and MRIs were performed. DTI data was processed with FSL tools and probabilistic tractography of the OR was carried out using previously described ROIs.

Results: A total of 56 patients with SAH had pre- and postoperative perimetry data and were evaluated for this study (33-transsylvian, 23-subtemporal approach). Eight patients (24.2%) from the transsylvian approach group showed no VFDs and 3 (10%) had unspecific changes, whereas the remaining 22 exhibited some form of visual field impairment related to surgery (66.7%). Interestingly, only 12 patients (52.1%) with subtemporal approach showed surgery related VFDs. Thus, 10 patients (43.2%) from the latter group had no VFD. The analysis of the DTI-data is not yet included and further correlation with VFDs is in process. There was no significant difference in seizure outcome between the two groups.

Conclusions: The subtemporal approach reduces the risk for VFDs in patients, who undergo SAH. DTI-based tractography can accurately delineate the optic radiation and may help to avoid VFDs in the future by choosing the most appropriate surgical approach.