DYNAMIC CHANGES OF FOCAL HYPOMETABOLISM IN RELATION TO EPILEPTIC ACTIVITY

The interictal hypometabolism in patients with focal epilepsy is usual ly regarded as stationary. In this study we investigated to which exte nt the hypometabolism may depend on the activity of the epileptic focu s. In focal penicillin-induced epilepsy in rats the epileptic focus is hypermetabolic. This focus is accompanied by hypometabolism in widesp read areas of adjacent cerebral cortex. The experiments revealed that these metabolic alterations are transient. Data from a patient experie ncing a focal seizure during PET scanning gave similar results. They s howed that the transition from interictal to ictal activity was accomp anied by the development of a hypermetabolic epileptic focus and the d ynamic enlargement of the surrounding hypometabolism. Both, the experi mental and clinical data provide evidence that the cerebral hypometabo lism may vary in size depending on the activity of the epileptic focus . It is hypothesized that in human PET studies the large interictal hy pometabolism may prevent the identification of hyperactive interictal epileptic foci due to the partial volume effects resulting from the li mited spatial resolution of PET cameras.