Striking Bilateral Cerebellar Hypermetabolism on 18F FDG-PET in a Patient of Sudden Onset Gait Ataxia with Absence of Paraneoplastic Antibody and Other Localizing Imaging Indicator.

Abstract

A 69-year-old gentleman presented with complains of giddiness, gait ataxia, vomiting, and slurring of speech with clinical signs pointing to cerebellar etiology. The magnetic resonance imaging brain revealed no significant abnormality. ¹⁸F-fluorodeoxyglucose (¹⁸F FDG) positron emission tomography (PET)/computed tomography showed hyper-metabolism in bilateral cerebellar hemispheres, pons, mid-brain and bilateral medial temporal cortices. Further quantitative NeuroQ analysis of ¹⁸F FDG-PET showed similar findings. Paraneoplastic antibody panel (anti-Hu, anti-Yo, anti-Ri, NMDA, CASPR-2 etc.) was negative. Clinical suspicion and PET imaging correlation led the neurologist to suspicion of inflammatory/autoimmune etiology, and the patient was empirically started on four cycles of plasma exchange therapy and course of steroids, however, no significant clinical response was noted. At post-6 months of ¹⁸F FDG-PET, he expired out of respiratory illness (pneumonia).