A Rare Adult Cause of Dizziness

A 55-year-old man was seen with progressively worsening dizziness over 10 months. The initial assessment with unremarkable laboratory and imaging studies suggested a peripheral vestibular disorder. He was then lost to follow-up but later was seen with worsening ataxia. Additional imaging studies showed subtle parenchymal lesions in the posterior fossa. The differential diagnoses included nutritional deficiencies, autoimmune disorders, systemic malignancies, and intracranial tumors. The final diagnosis was confirmed by a biopsy.