Background The main challenge in assessing patients with epilepsy for resective surgery is localising seizure onset. Frequently, identification of the irritative and seizure onset zones requires invasive EEG. EEG correlated functional MRI (EEG-fMRI) is a novel imaging technique which may provide localising information with regard to these regions. In patients with focal epilepsy, interictal epileptiform discharge (IED) correlated blood oxygen dependent level (BOLD) signal changes were observed in approximately 50% of patients in whom IEDs are recorded. In 70%, these are concordant with expected seizure onset defined by non-invasive electroclinical information. Assessment of clinical validity requires post-surgical outcome studies which have, to date, been limited to case reports of correlation with intracranial EEG. The value of EEG-fMRI was assessed in patients with focal epilepsy who subsequently underwent epilepsy surgery, and IED correlated fMRI signal changes were related to the resection area and clinical outcome.
Methods Simultaneous EEG-fMRI was recorded in 76 patients undergoing presurgical evaluation and the locations of IED correlated preoperative BOLD signal change were compared with the resected area and postoperative outcome.
Results 21 patients had activations with epileptic activity on EEG-fMRI and 10 underwent surgical resection. Seven of 10 patients were seizure free following surgery and the area of maximal BOLD signal change was concordant with resection in six of seven patients. In the remaining three patients, with reduced seizure frequency post-surgically, areas of significant IED correlated BOLD signal change lay outside the resection. 42 of 55 patients who had no IED related activation underwent resection.
Conclusion These results show the potential value of EEG-fMRI in presurgical evaluation.
- Epilepsy, Surgery
- Functional Imaging
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Funding This work was funded by the Medical Research Council (G0301067). This work was undertaken at UCLH/UCL who received a proportion of funding from the Department of Health's NIHR Biomedical Research Centres funding scheme and supported by a grant from the UK Medical Research Council No. G0301067. We are grateful to the Big Lottery Fund, Wolfson Trust and National Society for Epilepsy for supporting the NSE MRI scanner. HL was supported by the Deutsche Forschungsgemeinschaft (LA 1452/3-1) and the Bundesministerium für Bildung und Forshung (BMBF 01 EV 0703). SV was supported by the “Fonds de Perfectionnement” of the University Hospital of Geneva, Switzerland. JD receives funding from the Wellcome Trust (067176) and the Medical Research Council (G9805089) and the National Society for Epilepsy.
Competing interests None.
Ethics approval This study was conducted with the approval of the National Hospital for Neurology and Neurosurgery and the Institute of Neurology Joint Research Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.