Organization of the epileptogenic zone and signal analysis at seizure onset in patients with drug-resistant epilepsy due to focal cortical dysplasia with mTOR pathway gene mutations - an SEEG study.

Epilepsy surgery in genetic drug-resistant epilepsy is a debated subject as more histological and molecular data are available. We retrospectively collected data from focal drug-resistant epilepsy patients that underwent stereo-electroencephalography (SEEG) invasive recordings. Patients with non-lesional brain imaging or in whom a first epilepsy surgery failed to control seizures were selected. We computed and displayed the intracranial ictal onset activity pattern on structural imaging. Patients underwent epilepsy gene panel testing, next generation sequencing - NGS. Of 113 patients, 13 underwent genetic testing and in 6 patients a mechanistic target of rapamycin pathway gene germline mutation (mTOR) was identified. Brain imaging was non-lesional except for one patient in whom two abnormalities suggestive of focal cortical dysplasia (FCD) were found. Patients underwent tailored brain surgery based on SEEG data, tissue analysis revealed FCD and postsurgical outcome was favorable. Our findings are similar to previous case series suggesting that epilepsy surgery can be a treatment option in patients with mTOR pathway mutation. In patients with mTOR pathway mutation, the post-surgical outcome is favorable if complete resection of the epileptogenic zone is performed. Electrophysiological seizure onset patterns in FCDs associated with mTOR pathway mutations display low-voltage fast activity as previously described.