Electroencephalography-functional magnetic resonance imaging can better identify the epileptogenic focus, resulting in a direct impact on patient management and surgery decision-making.
Graeme Jackson, MD, BSc
Results of a retrospective analysis of electroencephalography-functional magnetic resonance imaging (EEG-fMRI) show that the imaging modality can help with identifying the epileptogenic focus in difficult cases of pharmacoresistant focal epilepsy, which may be associated with better post-surgery seizure outcomes.
Investigators examined 118 EEG-fMRI studies conducted from 2003 to 2018 in patients with focal epilepsy who were referred from the Comprehensive Epilepsy Program at the Florey Institute of Neuroscience and Mental Health in Australia. Specifically, the investigators assessed the success of each study, clinical utility of the results, when epilepsy surgery was performed, and the postoperative outcome. EEG-fMRI studies were performed while patients were outpatients, or during inpatient video-EEG monitoring.
Ultimately, EEG-fMRI studies were included for 118 patients, including 79 cases scanned on the 3T GE Signa and 39 on the 3T Siemens Trio/ Skyra. There was a total of 39 interictal epileptiform discharges (IEDs) observed in the study, 22 from inpatients and 17 from outpatients. In total, 21 of 22 (96%) inpatients had IEDs recorded during the EEG-fMRI study, compared to just 5 of the 17 (29%) outpatients (P < .0001).
Of the 118 studies examined, 59 (50%) were deemed to be successful in terms of the data being of good quality and interictal epileptiform discharges were recorded. Among the 118 patients, 57 (48%) elected to have epilepsy surgery. In 10 of those cases, the decision to have surgery was directly influenced by the EEG-fMRI results. In addition, the EEG-fMRI results influenced 4 of the 10 patients to proceed to intracranial video-EEG to validate thee findings.
Over 1 year follow-up, all 10 patients whose EEG-fMRI scan results influenced their surgery had good seizure outcomes.
Precisely locating the epileptogenic focus is critical for successful epilepsy surgery, and can help reduce the incidence of repeat resections. EEG-fMRI is well established and can be performed in a tertiary care hospital environment, making it an accessible tool for clinical decision-making. The investigators believe that controlled clinical trials are needed to understand the overall benefit of EEG-fMRI and its impact on patient outcomes.
Kawalczyk MA, Omidvarnia A, Abbott DF, et al. Clinical benefit of EEG-fMRI in difficult-to-localize focal epilepsy: A single institution retrospective review. Epilepsia. Published online December 2, 2019. Doi:: 10.1111/epi.16399.