A 68-year-old woman presents with a 2-month history of rapidly progressive cognitive decline, unsteadiness, and visual disturbances. Her family reports she has become increasingly confused, getting lost in her own home, and is unable to use utensils due to shaking. She reports seeing “distorted shapes” and colors. Her medical history includes hypertension and hypothyroidism. She has no history of neurosurgery, corneal transplantation, or receipt of human growth hormone. She has no family history of dementia. She does not consume alcohol or recreational drugs.

The patient is disoriented to time and place, with erratic attention. Vital signs are normal.