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

Abstract

O-(2-18 F-fluoroethyl)-L-tyrosine ( 18 F-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 18 F-FET PET imaging is currently unknown. The aim of this retrospective analysis was to investigate the brain amino acid metabolism during epileptic seizures by 18 F-FET PET and to elucidate the pathophysiologic background. Methods: Ten patients with 11 episodes of serial seizures or status epilepticus, who underwent MRI and 18 F-FET PET, were studied. The main diagnosis was glioma World Health Organization grade II-IV (n 5 8); 2 patients suffered from nonneoplastic diseases. Immunohistochemical assessment of LAT1/ LAT2/CD98 amino acid transporters was performed in seizure-affected cortex (n 5 2) and compared with glioma tissues (n 5 3). Results: All patients exhibited increased seizure-associated strict gyral 18 F-FET uptake, which was reversible in follow-up studies or negative shortly before and without any histologic or clinical signs of tumor recurrence. 18 F-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 18 F-FET uptake. LAT1/ LAT2/CD98 was strongly expressed in neurons and endothelium of seizure-affected brains and less in reactive astrocytosis.