Epileptic Activity Increases Cerebral Amino Acid Transport Assessed by 18 F-Fluoroethyl-l-Tyrosine Amino Acid PET: A Potential Brain Tumor Mimic

O-(2-F-18-fluoroethyl)-L-tyrosine (F-18-FET) PET is a well-established method increasingly used for diagnosis, treatment planning, and monitoring in gliomas. Epileptic activity, frequently occurring in glioma patients, can influence MRI findings. Whether seizures also affect F-18-FET PET imaging is currently unknown. The aim of this retrospective analysis was to investigate the brain amino acid metabolism during epileptic seizures by F-18-FET PET and to elucidate the pathophysiologic background. Methods: Ten patients with 11 episodes of serial seizures or status epilepticus, who underwent MRI and F-18-FET PET, were studied. The main diagnosis was glioma World Health Organization grade II-1V (n = 8); 2 patients suffered from nonneoplastic diseases. Immunohistochemical assessment of LAT1/ LAT2/CD98 amino acid transporters was performed in seizure-affected cortex (n = 2) and compared with glioma tissues (n = 3). Results: All patients exhibited increased seizure-associated strict gyral F-18-FET uptake, which was reversible in follow-up studies or negative shortly before and without any histologic or clinical signs of tumor recurrence. F-18-FET uptake corresponded to structural MRI changes, compatible with cortical vasogenic and cytotoxic edema, partial contrast enhancement, and hyperperfusion. Patients with prolonged postictal symptoms lasting up to 8 wk displayed intensive and widespread 1 lobe) cortical F-18-FET uptake. LAT1/LAT2/CD98 was strongly expressed in neurons and endothelium of seizure-affected brains and less in reactive astrocytosis. Conclusion: Seizure activity, in particular status epilepticus, increases cerebral amino acid transport with a strict gyral F-18-FET uptake pattern. Such periictal pseudoprogression represents a potential pitfall of F-18-FET PET and may mimic brain tumor. Our data also indicate a seizure-induced upregulation of neuronal, endothelial, and less astroglial LAT1/LAT2/CD98 amino acid transporter expression