A 56-year-old right-handed man was admitted to the hospital with a 7-day history of gradual-onset holocephalic headache. Two days after headache onset, he had developed dysarthria, musical hallucinations and progressive confusion. He had become non-verbal on the day of admission.
He had a 10-year history of type 2 diabetes mellitus and bilateral sensorineural hearing impairment, requiring hearing aids. Close family members had noted further hearing deterioration two weeks before admission, which was later confirmed by audiometry; this affected both sides symmetrically particularly at higher frequencies. His maternal grandmother also had hearing impairment. He did not smoke or drink alcohol and had not used illicit drugs.
His vital signs were stable but detailed physical examination was precluded by extreme agitation and aggressive behaviour. His attention was drawn only by standing directly in front of him, suggesting a bilateral peripheral vision loss. He moved all his limbs symmetrically without obvious ataxia and…