A 65-year-old man complains of difficulty in walking. He has a history of chronic subdural hematomas. Neurologic examination reveals psychomotor slowing, sphincter incontinence, and enlarged ventricles without convolutional atrophy. The most likely diagnosis is:

Normal-pressure hydrocephalus is characterized by the triad of gait apraxia (frontal lobe ataxia), incontinence, and dementia. The ventricles are moderately dilated. Huntington disease is a neurodegenerative disorder characterized by choreoathetosis, tremor, and dementia. Parkinson disease is characterized by a pill-rolling resting tremor, cogwheel rigidity, and bradykinesia (slowness in movement). Progressive supranuclear palsy is a movement disorder characterized by paresis of downward gaze.