As surgical treatments for adult and pediatric forms of
epilepsy have become more refined, methods for noninvasive localization of epileptogenic foci have become increasingly important. Detection of focal brain metabolic or flow abnormalities is now well recognized as an essential step in the presurgical evaluation of many patients with
epilepsy. Positron emission tomography (PET) scanning is most beneficial when used in the context of the total clinical evaluation of patients, including scalp EEG, invasive EEG, neuropsychologic testing, etc. Metabolic PET studies also give insight into pathophysiologic mechanisms of
epilepsy. The dynamic nature of the interictal hypometabolism observed with 18[F]FDG in some patients suggests that excitatory or inhibitory
neurotransmitters and their receptors may be involved. An exciting current application of PET scanning is the use of tracers for
neurotransmitter receptors in the study of
epilepsy patients. Mu and non-mu
opiate receptors have been extensively studied and are beginning to give new insights into this disorder. Increased labeling of
mu receptors in temporal neocortex using
11C-carfentanil has been demonstrated and, in some patients, supplements the clinical localization information from 18[F]FDG studies. Increased mu
opiate receptor number or affinity is thought to play a role in
anticonvulsant mechanisms. Specificity of increased
mu receptors is supported by the absence of significant changes in non-mu
opiate receptors. Other brain receptors are also of interest for future studies, particularly those for excitatory
neurotransmitters. Combined studies of flow, metabolism, and neuroreceptors may elucidate the factors responsible for initiation and termination of
seizures, thus improving patient treatment.