Relationship between EEG and positron emission tomography abnormalities inclinical epilepsy

Positron emission tomography (PET) is a relatively noninvasive neuroimaging method by means of which a large variety of human brain functions can be a ssessed. Localized neurochemical abnormalities detected by PET were found i n patients with partial epilepsy and suggested the use of this modality for localizing epileptogenic regions of the brain. The clinical usefulness of PET is determined by its sensitivity and specificity for identifying epilep togenic areas as defined by ictal surface and intracranial EEG recordings. The findings obtained from comparative EEG and glucose PET data are reviewe d with special emphasis on patients undergoing presurgical evaluation becau se of medically intractable temporal and extratemporal lobe epilepsy. The u tility of glucose PET studies for identifying regions of seizure onset is p resented, and the limited specificity of glucose metabolic abnormalities fo r the detection of various EEG patterns in clinical epilepsy is discussed. The authors review the available intracranial EEG and PET comparisons using [C-11]flumazenil (FMZ) PET, a tracer for the assessment of tau-amino-butyr ic acid/benzodiazepine receptor function. They also summarize their experie nce with [C-11]flumazenil PET in identifying cortical regions that show var ious ictal and interictal cortical EEG abnormalities in patients with extra temporal seizure origin. Finally, the authors demonstrate that further deve lopment of new PET tracers, such as alpha-[C-11]methyl-L-tryptophan, is fea sible and clinically useful and may increase the number of patients in whom PET studies can replace invasive EEG monitoring..