A 76-yo male presents to the ED with a 7-month history of increasing ataxia and flailing movements of his extremities, especially his lower extremities, as well as intermittent, uncontrollable “spasms” of his face. His doting wife notes that he has been losing weight, estimated to be about 20 lbs over the last 6 months. He also complains of a mild, nonproductive cough.

His past medical history is notable for HTN, diet-controlled DM, and tobacco use. He denies illicit drugs or excessive alcohol use. On physical exam you note a frail, elderly-looking male in no acute distress.  Vital signs are unremarkable. You note that he has rapid, intermittent, involuntary abduction and adduction of both thighs and sometimes his arms. There is no discernable pattern to these movements. His mentation is intact. He has nystagmus on upward and horizontal gaze. Reflexes, strength and sensation are intact; Romberg is negative but full examination, including gait, is impaired due to his odd movements. Lung exam demonstrates mild rhonchi throughout. The rest of his physical examination is negative.

ROS: No fevers, chills, night sweats. + intermittent tingling/numbness in the extremities, though he cannot articulate this further. No headache, visual changes, or vomiting/nausea. + anorexia.

CXR reveals a L parahilar mass, 2cm x 5cm, and patchy atelectasis. CT head (contrast/noncontrast) and brain MRI show age-related changes, but are otherwise unremarkable. Routine lab studies are unrevealing and notable only for a sodium of 133, normal WBC, and mild anemia (Hgb 10.4). Lumbar puncture is unremarkable. Sputum and blood cultures are negative. AFB x 1 is negative.  

Histopathology after fine-needle biopsy of the lung mass is shown below: