Is epileptogenic cortex truly hypometabolic on interictal positron emission tomography?

Positron emission tomography (PET) of glucose metabolism is often applied f or the localization of epileptogenic brain regions, but hypometabolic areas are often larger than or can miss epileptogenic cortex in nonlesional neoc ortical epilepsy. The present study is a three-dimensional brain surface an alysis designed to demonstrate the functional relation between glucose PET abnormalities and epileptogenic cortical regions. Twelve young patients (me an age, 10.8 years) with intractable epilepsy of neocortical origin underwe nt chronic intracranial electroencephalographic monitoring. The exact locat ion of the subdural electrodes was determined on high-resolution three-dime nsional reconstructed magnetic resonance imaging scan volumes. The electrod es were classified according to their locations over cortical areas, which were defined as hypometabolic, normometabolic, or at the border between hyp ometabolic and normal cortex (metabolic "border zones") based on interictal glucose PET. Electrodes with seizure onset were located over metabolic bor der zones significantly more frequently than over hypometabolic or normomet abolic regions. Seizure spread electrodes also more frequently overlay meta bolic border zones than hypometabolic regions. These findings suggest that cortical areas with hypometabolism should be interpreted as regions mostly not involved in seizure activity, although epileptic activity commonly occu rs in the surrounding cortex. This feature of hypometabolic cortex is remar kably similar to that of structural brain lesions surrounded by epileptogen ic cortex. Cortical areas bordering hypometabolic regions can be highly epi leptogenic and should be carefully assessed in presurgical evaluations.