Functional neuroimaging with positron emission tomography.

Epilepsy research using positron emission tomography (PET) has provided considerable new information about ictal and interictal dysfunctions in human epilepsy. Neuroreceptor mapping with PET ligands has revealed altered central benzodiazepine receptor and opiate receptor densities in partial epilepsies interictally, and regional increases in endogenous opioid peptide concentrations during absence seizures. Imaging of perfusion and glucose metabolism during cognitive processing has shown interictal abnormalities of regional activation in partial and generalized epilepsies. The diagnostically robust patterns of interictal glucose hypometabolism are not adequately explained by macrostructural and microstructural alterations in temporal lobe epilepsy. Current investigations of the pathophysiology of interictal hypometabolism must address ultrastructural and neurochemical factors. Clinical PET in presurgical evaluation of medically refractory epilepsies remains an active area of research, but remarkably little antiepileptic drug research has exploited PET techniques.