Paper by Invitation: Imaging Idiopathic Generalized Epilepsy

Abstract

It has been traditionally held that there is no radiological abnormality in patients with idiopathic generalized epilepsy (IGE). Sophisticated image processing and quantitative magnetic resonance imaging (MRI) studies suggest that, in some cases, there may be a subtle structural abnormality. Magnetic resonance spectroscopy indicates neuronal dysfunction with differing patterns of abnormality in the IGE sub-syndromes, and high levels of glutamate and glutamine have been suggested in the frontal lobes, and low GABA levels in the occipital lobe. Studies reflecting cerebral blood flow at the time of absences have given complex results. The principal consensus is of an increase in the thalamus and broad decreases in the neocortex, reflecting a suppression of neuronal activity, but with the possibility of some increases, that could perhaps reflect focal areas of neuronal activation. PET ligand studies with an opioid tracer have implied neocortical release of endogenous opioids at the time of serial absences. In combination with high time-resolution neurophysiological methods, static and dynamic PET studies with specific ligands have the potential to elucidate the functional anatomy and neurochemical circuits that under-lie IGE.