title: EEG-fMRI correlation patterns in the presurgical evaluation of focal epilepsy: a comparison with electrocorticographic data and surgical outcome measures.
abstract: EEG-correlated functional MRI (EEG-fMRI) visualizes brain regions associated with interictal epileptiform discharges (IEDs). This technique images the epileptiform network, including multifocal, superficial and deeply situated cortical areas. To understand the role of EEG-fMRI in presurgical evaluation, its results should be validated relative to a gold standard. For that purpose, EEG-fMRI data were acquired for a heterogeneous group of surgical candidates (n=16) who were later implanted with subdural grids and strips (ECoG). The EEG-fMRI correlation patterns were systematically compared with brain areas involved in IEDs ECoG, using a semi-automatic analysis method, as well as to the seizure onset zone, resected area, and degree of seizure freedom. In each patient at least one of the EEG-fMRI areas was concordant with an interictally active ECoG area, always including the early onset area of IEDs in the ECoG data. This confirms that EEG-fMRI reflects a pattern of onset and propagation of epileptic activity. At group level, 76% of the BOLD regions that were covered with subdural grids, were concordant with interictally active ECoG electrodes. Due to limited spatial sampling, 51% of the BOLD regions were not covered with electrodes and could, therefore, not be validated. From an ECoG perspective it appeared that 29% of the interictally active ECoG regions were missed by EEG-fMRI and that 68% of the brain regions were correctly identified as inactive with EEG-fMRI. Furthermore, EEG-fMRI areas included the complete seizure onset zone in 83% and resected area in 93% of the data sets. No clear distinction was found between patients with a good or poor surgical outcome: in both patient groups, EEG-fMRI correlation patterns were found that were either focal or widespread. In conclusion, by comparison of EEG-fMRI with interictal invasive EEG over a relatively large patient population we were able to show that the EEG-fMRI correlation patterns are spatially accurate at the level of neurosurgical units (i.e. anatomical brain regions) and reflect the underlying network of IEDs. Therefore, we expect that EEG-fMRI can play an important role for the determination of the implantation strategy.
authors: Department of Research and Development, Kempenhaeghe, Sterkselseweg 65, 5591 VE Heeze, The Netherlands; Department of Physics and Medical Technology, VU University Medical Center, De Boelelaan 1118,1081 HZ Amsterdam, The Netherlands.
authors: Petra J
authors: PJ
authors: van Houdt
authors: Department of Physics and Medical Technology, VU University Medical Center, De Boelelaan 1118,1081 HZ Amsterdam, The Netherlands.
authors: Jan C
authors: JC
authors: de Munck
authors: Department of Clinical Neurophysiology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors: Frans S S
authors: FSS
authors: Leijten
authors: Department of Clinical Neurophysiology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
authors: Geertjan J M
authors: GJM
authors: Huiskamp
authors: Department of Neurology, Kempenhaeghe, Sterkselseweg 65, 5591 VE Heeze, The Netherlands.
authors: Albert J
authors: AJ
authors: Colon
authors: Department of Research and Development, Kempenhaeghe, Sterkselseweg 65, 5591 VE Heeze, The Netherlands.
authors: Paul A J M
authors: PAJM
authors: Boon
authors: Department of Clinical Physics, Kempenhaeghe, Sterkselseweg 65, 5591 VE , The Netherlands. Electronic address: ossenblokp@kempenhaeghe.nl.
authors: Pauly P W
authors: PPW
authors: Ossenblok
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology / Q000601:surgery; D002648:Child; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D064847:Multimodal Imaging; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult