Intraoperative Ultrasound-Assisted 3D-Electrocorticography for resection of type II focal cortical dysplasias

Objective: Type II focal cortical dysplasias (FCDII) present a clear-cut anatomo-electro-clinical profile and are associated with optimal surgical outcome when completely resected. Alongside presurgical planning and neuroimaging, intraoperative electrocorticography (ECoG) can aid in delineating FCDII boundaries. We report outcomes from patients undergoing FCDII resection using 3D-ECoG with an intracerebral electrode guided by intraoperative ultrasound (ioUS). Methods: Patients with suspected FCDII underwent 3D-ECoG during surgery to record intracerebral interictal epileptiform discharges (IEDs) classified as: 1) rhythmic spikes (RS), and 2) periodic bursts of polyspikes (PBOP). Results: Ten patients (5 male, 5 female; median age 19.5 years, median epilepsy duration 16 years) were included. Bottom-of-sulcus dysplasia (BOSD) was found in 60 %. 3D-ECoG identified RS in 30 % and PBOP in 70 %. Total IED removal was achieved in 60 %. Histopathology revealed FCDII in 80 %, while 20 % had a diagnosis of “no definite FCD on histopathology”. After a median 24-month follow-up, 90 % achieved ILAE class 1 outcome (seizure free), 10 % had class 2 (only auras). No major complications occurred. Conclusions: IoUS-assisted 3D-ECoG is a safe procedure for intraoperative delineation of FCDII, supporting complete resection. Significance: Integrating IoUS with 3D-ECoG can offer substantial benefits for surgical management of FCDII- related epilepsy.