gms | German Medical Science

Objective: Diagnosis and surgical treatment of cryptogenic epilepsy are difficult and challenging. Morphometric MRI voxel-based postprocessing tools can help to localize the epileptogenic zone and thus facilitate invasive diagnostics and resective surgery. The aim of the study was to report on the clinical pathway used in our department and to evaluate the surgical results based on consecutive patients, who underwent it.

Method: We developed an algorithm for the implementation of the region of interest (ROI) based on postprocessed data into the neuronavigation. This was followed by stereotactic ROI-guided implantation of depth electrodes and ROI-navigated resective surgery. Eighteen patients underwent the algorithm. Data on focus detection rate, histology and seizure outcome were collected and evaluated.

Results: All patients were initially classified as nonlesional. Reevaluation of the MRIs using the data delivered by the postprocessing analysis could however identify subtle lesions in 10 patients. The ROI-guided invasive EEG was positive in 17 patients, who were consequently referred to surgery. Despite the negative MRI findings, focal cortical dysplasia (FCD) could be found in 65% of the patients (n=11). At the last available outcome (LAO) 9 patients (50%) were completely seizure free (ILAE1).

Conclusions: Our results support the feasibility and usefulness of a robust and straightforward algorithm for the implementation of postprocessed based ROIs into the neuronavigation. This led to the stereotactic implantation of a low number of depth electrodes confirming the seizure onset hypothesis in 90% of the cases without causing any complications. Furthermore, the neuronavigated ROI-guided lesionectomy helped to perform resective surgery in this rather challenging subgroup of patients with cryptogenic epilepsy.