APA Dictionary of Psychology

a progressive neurological disorder usually starting in the 6th decade of life and characterized by oculomotor palsy, with downward gaze particularly affected. The condition may be accompanied by parkinsonism, postural instability, speech and swallowing difficulties, dystonia, personality changes, and typically mild cognitive impairment. Pathology often shows loss of neurons and gliosis in various regions of the brainstem, basal ganglia, and midbrain. Also called Steele–Richardson–Olszewski syndrome; supranuclear palsy.