DYNAMIC [F-18] FLUORODEOXYGLUCOSE POSITRON-EMISSION-TOMOGRAPHY AND HYPOMETABOLIC ZONES IN SEIZURES - REDUCED CAPILLARY INFLUX

We performed dynamic [F-18]fluorodeoxyglucose ([F-18]FDG) positron emi ssion tomographic (PET) analyses in 8 patients. Rate constants of infl ux (K-1), efflux (k(2)*), phosphorylation (k(3)*), and dephosphorylat ion (k(4)) were derived for the regions of interest (ROIs), which inc luded (1) the hypometabolic epileptogenic regions and (2) the homologo us regions in the contralateral hemispheres. In addition, the four con stants were determined from at least one clearly defined (control) ROI from the same plane and its homologous contralateral ROI. Influx (K-1 ) in the epileptogenic region was reduced in comparison with the cont ralateral ROI. Reductions in influx (K-1), which averaged 18 +/- 13% (mean +/- SD), [F-18]FDG phosphorylation (k(3)) (25 +/- 20%), and bra in glucose utilization rates (26 +/- 10%) were observed in the epilept ogenic region. Reductions in efflux were not statistically significant (k(2) = 13 +/- 28%) but were comparable in magnitude to the average reduction in K-1. No ipsilateral versus contralateral differences wer e seen for any rate constants measured outside the epileptogenic regio n, Influx correlated highly with phosphorylation in the epileptogenic region. Our data suggest that the hypometabolic epileptogenic focus se en in [F-18]FDG-PET studies is also a region of reduced blood-brain ba rrier glucose transporter activity and that reductions in phosphorylat ion are proportional to reductions in [(18)]FDG influx.