The current status of neuroimaging for epilepsy

Neuroimaging research continues apace and is being applied to further understanding of the epilepsies, and improve clinical management.

Structural imaging has become more sensitive with developments of MRI hardware, acquisition and postprocessing methods. Tractography is being used to define critical pathways prior to surgery. Functional MRI for language lateralization is now a clinical tool. PET studies with specific ligands reveal neurochemical changes associated with specific epilepsy syndromes.

MRI at 3T with FLAIR and multiple channel coils identifies and clarifies relevant abnormalities in 20% of patients with previously unremarkable scans. Voxel-based analysis of diffusion scans may identify abnormalities in group comparisons. Identification of relevant abnormalities using voxel-based methods in individual patients requires a careful balance of sensitivity and specificity, and has a 10-30% yield. The PROPELLER sequence improves the detail of hippocampal anatomy and correlation with histological slices shows the pathological basis of MRI signal changes. Tractography has shown the connections of the language cortex and visualizes specific tracts. Electroencephalograms with simultaneous functional MRI and perfusion have shown that perfusion changes are a major determinant of changes in blood-oxygen-level-dependent signal. Functional MRI of language and memory are becoming used as a predictor of deficits as a result of temporal lobe resection.Increased uptake of the PET tracer 11C-alpha-methyl tryptophan shows promise for localizing epileptogenic malformations of cortical development. Abnormalities of 5HT-1A receptor ligands have been reported in temporal lobe epilepsy, with controversial association with depression. Dopamine uptake abnormalities have been noted in autosomal dominant nocturnal frontal lobe epilepsy.