Positron emission tomography receptor studies in epilepsy

Investigations with specific PET ligands that bind to specific neuro-recept ors give information on abnormalities of neurotransmission involved in the pathophysiology of the epilepsies. Data need to be interpreted in the light of optimal structural imaging. Objective voxel-based and region-based anal yses, with correction of partial volume effect, are complementary. Central benzodiazepine (cBZR) and opioid receptors have been studied most. Reduced cBZR binding is commonly seen at an epileptic focus, in a more restricted d istribution than an area of hypometabolism, and sometimes also in projectio n areas. In contrast to acquired lesions causing partial seizures, focal in creases in cBZR binding have been demonstrated in malformations of cortical development and also in areas of brain that appear normal on MAI, indicati ng the widespread nature of the abnormalities. Focal abnormalities of cBZR are also commonly found in patients with partial seizures and normal MRI. I t is not yet clear how useful these data will prove to be in presurgical ev aluation. Mu- and delta-opioid receptors have been found to be increased in temporal neocortex overlying mesial temporal epileptic foci, but with diff erent patterns of increase. Dynamic studies of the binding of 11C-diprenorp hine to opioid receptors are possible using PET, and have implied the relea se of cerebral endogenous opioids at the time of serial absences and reflex seizures induced by reading. Other tracers, that have been applied less widely, label the enzyme monoami ne oxidase type B and peripheral benzodiazepine and histamine H1 receptors.