Imaging epileptic activity using functional MRI

Abstract

This review concentrates on functional MRI (fMRI) methods to identify the epileptic focus, i.e. ictal and interictal fMRI. First, established clinical applications of fMRI in the field of epilepsy are briefly introduced: fMRI of sensorimotor, language and memory function can already be considered as clinically relevant tools to identify the eloquent cortex and to predict postoperative functional deficits in patients considered for epilepsy surgery. fMRI offers a valid alternative to invasive methods like the Wada test for establishing language dominance, and it is likely that it will also replace the Wada test for assessing presurgical memory function in the nearer future. Ictal fMRI (fMRI studies of epileptic seizures) will remain confined to exceptional cases due to practical limitations. The generators of interictal epileptiform discharges (IED) can be studied with EEG-correlated fMRI. Despite its technical challenges, it has proved useful to provide insights into the generation of IED in patients with focal and generalized epilepsy. In selected patients with focal IED, EEG-correlated fMRI has the potential to reproducibly identify cortical areas involved in generating IED, i.e. the irritative zone. In patients with generalizes IED, suspension of functional networks due to the IED can be demonstrated. The utility of EEG-correlated fMRI in clinical epileptology cannot be definitely determined yet.