Clinical reasoning: an unusual case of subacute encephalopathy.

SECTION 1 A 52-year-old previously healthy man presented with 8 months of progressive cognitive decline. He complained of months of confusion, fatigue, depression, hypersomnolence, headaches, and, subsequently, urinary incontinence and unsteady gait. His family reported that he spoke of his deceased mother as if she were alive. His executive deficits progressed, leading to termination of his employment and a motor vehicle accident. He was evaluated and treated in Morocco before presenting to our institution for further care. Mental status examination was notable for slowed mentation and dyscalculia but was otherwise normal. Motor, sensory, and deep tendon reflex examination results were normal. Cerebellar and gait examination revealed wide-based gait and lower extremity dysmetria. Relevant laboratory evaluation revealed only a C-reactive protein of 1.79 (normal 0–0.99). Brain MRI obtained in Morocco 2 months prior to presentation had demonstrated bilateral thalamic T2 hyperintensities and patchy enhancement in the right medial temporal lobe, midbrain, and basal ganglia. A right thalamic biopsy obtained in Morocco had revealed “inflammatory cells” without evidence of malignancy.