Last Week's Medical Mystery

      You are rotating on the medical wards and asked by the admitting physician to make a diagnosis in a 71-year-old man who was brought to the hospital by his wife because she thought he has alzheimer's dementia. She noted that he was moody and had difficulty remembering recent events.
      On your neurological examination he was somnolent and scored poorly on the minimental test. The strength of his proximal leg muscles was diminished (2/4). His chest x-ray is shown below.
DIAGNOSIS: paraneoplastic encephalomyelitis (PEM) in a patient with squamous cell  lung cancer (SCLC).  PEM occurs in ∼3-4% of patients with SCLC and most commonly presents as the Lambert-Eaton myasthenia syndrome with limb weakness most evident in the proximal leg muscles. Other symptoms in PEM include impaired cognition, somnolence, and a Broca-like aphasia. Diagnosis is confirmed by serological testing (e.g., ANNA-1, anti-Hu autoantibodies).  
      

Chest x-ray shows a mass in the right parahilar region. Biopsy of the mass revealed squamous cell lung cancer. 

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