Detection of epileptogenic zones in people with epilepsy using optimized EEG-fMRI

Concurrent electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) have been used to assist in the presurgical localization of seizure foci in people with epilepsy. Our study aimed to examine the clinical feasibility of an optimized concurrent EEG-fMRI protocol.

The optimized protocol employed a fast-fMRI sequence (sampling rate = 10 Hz) with a spare arrangement, which allowed a time window of 1.9 s for EEG recording without radio frequency noise. Patients with a diagnosis of drug-resistant epilepsy who were candidates for surgical intervention were enrolled and underwent concurrent EEG-fMRI studies to map fMRI blood oxygen level-dependent (BOLD) signal changes related to interictal epileptiform discharges. The BOLD signals were compared to those in the epileptogenic zone determined by resective cavities or radiofrequency thermocoagulation lesions. Postoperative seizure outcomes were classified according to the ILAE classification.

The EEG-related BOLD results indicated that 15 of the 19 patients (78.9 %) had concordant findings in the epileptogenic zone determined by surgical intervention. The percentage of patients who achieved good surgical outcomes was significantly greater in the concordant group than in the discordant group (n = 9, 60.0 % vs. n = 0, 0 %, p = 0.033).

Using fast MRI scan, the optimized protocol provides satisfactory accuracy (78.9 %) for detecting epileptogenic zones. A concordant BOLD signal and epileptogenic zone can predict good surgical outcomes.