FMRI Correlates of Interictal Epileptic Activity in Patients with Idiopathic Benign Focal Epilepsy of Childhood. A Simultanous EEG- Functional MRI Study

The localization of the epileptic zone or related brain regions plays an important role in patients with focal epilepsy. So far there are no established non-invasive methods that allow such diagnostic procedure, especially in children with idiopathic focal epilepsy. Our aim was to demonstrate EEG-correlated functional MRI (EEG-fMRI) as a feasible method in children and to correlate our data with clinical and EEG findings. Using simultaneous EEG-fMRI in a 3 Tesla MR scanner (Siemens Trio, Erlangen) we detected blood oxygen level-dependent (BOLD) signal changes related to spontaneous interictal epileptic activity. We studied 10 children with typical or atypical benign focal epilepsy of childhood (BFE) or benign epileptic activity of childhood. This is the largest published patient number examined by these methods so far. EEG artefacts were subtracted offline and epileptic activity discharges were marked after visual inspection using the analyzer software (Brain Products, Munich). These discharges were used as regressors for event-related fMRI analysis in SPM2. In the seven children with interictal epileptic activity (IED) during EEG-fMRI we found IED related activation or deactivation in the perisylvian, central and frontal regions in seven children. One child showed additional bilateral occipital fMRI activation. FMRI activation represented the affected brain areas in accordance to EEG localization. Additionally to former reports our results indicated that frontal brain areas are functionally disturbed during IED corresponding to clinical neuropsychological findings in BFE. We conclude that EEG-fMRI is a useful diagnostic tool to localize epileptic activity and functionally disturbed brain regions in children. Further studies are required to differentiate between BFE subtypes and to identify fMRI signatures of specific syndromes.