Electroencephalography/functional MRI in human epilepsy: what it currently can and cannot do

Abstract

Simultaneous recording of electroencephalogram and functional MRI is being increasingly applied to the investigation of normal cerebral processes and disorders, particularly epilepsies. We will summarize recent epilepsy-related studies and appraise the clinical and scientific value of EEG/fMRI. Interictal and ictal EEG/fMRI can provide helpful information in the presurgical evaluation of epilepsy. At present, EEG/fMRI cannot supercede any of the current methods because validation studies are lacking, informative results are only obtained in some patients, and haemodynamic activation and deactivation patterns are not always of localizing value. EEG/fMRI data often identify distributed brain areas and can help to generate concepts of epileptogenic networks both in individual patients and groups with particular epilepsy syndromes. Clinically, EEG/fMRI studies may influence further investigations such as more detailed structural imaging or the planning of intracranial electrophysiological studies by generating hypotheses about the location of epileptic foci. Validation studies are underway to determine whether such clinical applications are appropriate. EEG/fMRI can also assess epileptogenic networks and changes in brain state, leading to a new dimension of understanding of dynamic cerebral processes in health and disease.