Parkinson's disease commonly presents with resting tremor, bradykinesia, and rigidity, but it does not typically cause vertical gaze palsy or prominent postural instability early in its course.

Progressive supranuclear palsy is a rare neurodegenerative disease that represents with extrapyramidal signs, frequent falls, and difficulty speaking, all of which the patient presents. It also often presents with problems of eye movement, especially the inability to aim the eyes properly, a symptom the patient is likely experiencing as light sensitivity.

This would typically present with more autonomic symptoms, such as orthostatic hypotension, than this patient has.

Huntington's disease typically presents earlier in life (ages 30-50) and includes hyperkinetic movements (chorea) and cognitive decline, which this patient does not have.