Paraneoplastic Cerebellar Atrophy

40-year-old male with progressive ataxia, dysarthria, and confusion over the past 2 years. The anatomic T1-and fluid sensitive T2-weighted images demonstrate volume loss within the cerebellar hemispheres and vermis with ex vacuo enlargement of the fourth ventricle and dilitation of the vermian and cerebellar sulci. The differential includes: alcohol induced cerebellar degeneration, iatrogenic causes such as phenytoin, multisystem atrophy, ataxia telangiectasia, Freidreich ataxia, paraneoplastic cerebellar degeneration, olivopontocerebellar atrophy and cerebellar hypoplasia. The patient was eventually diagnosed with lung adenocarcinoma, and the neurologic symptoms and cerebellar abnormalities were secondary to an associated paraneoplastic syndrome. Paraneoplastic cerebellar degeneration is considered to be an autoimmune disorder. Symptoms may include dizziness, blurred or double vision, oscillopsia and gait abnormalities. The symptoms are not related to direct tumor invasion, chemotherapy, malnutrition or infection.