F-18 Fluorodeoxyglucose PET/CT Findings in a Case of Anti-NMDA Receptor Encephalitis

Abstract

A 23-year-old woman with a history of rapid-cycling bipolar disorder was brought in by her family after 4 days of increasing psychological disturbance characterized by declining mental status, hallucinations, orofacial dyskinesias, and bizarre behavior. A paraneoplastic encephalopathy was suspected clinically, prompting whole-body and dedicated brain 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) positron emission tomography and computed tomography (PET/CT) imaging that showed relative hypometabolism of the bilateral occipital lobes and cerebellum, and relative hypermetabolism of the bilateral frontal, temporal, and parietal lobes. Subsequent cerebrospinal fluid analysis demonstrated strongly positive anti-N-methyl-D-aspartate receptor (anti-NMDAR) autoantibody titers that, in conjunction with the patient's clinical presentation, were diagnostic of anti-NMDAR encephalitis. The FDG PET/CT appearance of anti-NMDAR encephalitis has not been previously characterized in the literature, and FDG PET/CT brain imaging findings from this patient with clinically confirmed anti-NMDAR encephalitis are presented here.