Auf der Suche nach den Urprüngen epileptischer Entladungen: fMRT/EEG bei kindlichen Epilepsiesyndromen

Simultaneous recording of EEG and blood-oxygenation level-dependent (BOLD) functional MRI (EEG-fMRI) is a new non-invasive technique that allows evaluation of haemodynamic changes in the brain correlated with interictal epileptiform discharges (IED). In idiopathic generalized epilepsies, EEG-fMRI has revealed a typical network with a significant activation in the thalamus and deactivation in brain areas of the default mode network (DMN) such as precuneus, medial prefrontal cortex and parieto-temporal junction. In epileptic encephalopathies, syndrome-specific networks have been specified: bilateral activation in insula and anterior cingulate gyrus associated with continuous spikes and waves during slow sleep, bilateral activation in putamen und brainstem associated with high-amplitude slow activity in hypsarrhythmia, bilateral activation in thalamus and brainstem associated with multifocal epileptic activity and runs of polyspikes in patients with Lennox-Gastaut syndrome, and bilateral activation in the thalamus associated with multifocal epileptic activity in patientsn with Pseudo-Lennox syndrome. In focal epilepsies, the EEG-fMRI has revealed not only neurometabolic changes in brain regions corresponding to the IED localization, but also in functionally significant brain areas on remote of epileptic activity. In most cases, the technique has identified an extended network of activation which has to be validated by other localization methods such as video-EEG monitoring, PET, ictal SPECT. The addition of EEG source imaging (ESI) may allow the identification of areas of IED generation and propagation and therefore enhance the interpretation of fMRI results. In summary, EEG-fMRI has been shown as a powerful technique to characterize epileptic networks. Even after 15 years of intensive research, however, methodical work is still necessary to increase the value of the method for clinical praxis.