A 21-year-old male with a history of ADHD and anxiety, presented with 6 weeks of progressive fatigue and cognitive deficit. He had a recent trip to Florida where he developed afebrile upper respiratory infection which improved after an amoxicillin course. He then gradually developed slowed cognition and drowsiness followed by left sided brief muscle twitches, imbalance, and diplopia. His neurological exam showed decreased concentration, bradykinesia, and left sided dyskinesia. 

Enhanced brain MRI showed bilateral extensive confluent T2/FLAIR signal hyperintensity in basal ganglia, inferior frontal, and medial temporal, central midbrain and dorsal pons with mild edema. There was a mild nodular enhancement of the right putamen and vascular enhancement through both basal ganglia. 

Repetitive CSF studies showed a WBC count (22-32 cell/????), protein (56-66 mg/dL), oligoclonal bands (6-10), increased IgG index and synthesis rate. Whole body PET scan, testis ultrasound and CSF flow cytometry were unremarkable for malignancy. Hypermanganesemia, rheumatologic disorders, and Wilson’s disease were ruled out. Extensive CSF evaluation for infections, paraneoplastic and autoimmune encephalitis panels was unremarkable except for anti-NMDAR antibody. Encephalitis associated with basal ganglia involvement and/or rhombencephalitis were ruled out by negative serum and CSF antibodies against KELCH-like 11 protein, Ma/Ta, and GABA-A. He received seven plasma exchanges followed by steroids with symptomatic, MRI and CSF improvement. As he improved, his clinical picture evolved into pure psychiatric symptoms with auditory and visual hallucinations and obsessive-compulsive behavior.