In this rare brain disease, trouble looking down causes the falls
Progressive supranuclear palsy often begins with unexplained falls in people in their sixties. One reason is striking: patients gradually lose the ability to move their eyes voluntarily up and down, so steps and kerbs slip out of view. It is often mistaken for Parkinson's, yet it is a distinct disease driven by tau protein.
Richardson, Steele and Olszewski described PSP in 1963 as a kind of progressive parkinsonism, although a French case from 1951 already matched it and was confirmed at autopsy. It is now known as the second most common tauopathy after Alzheimer's disease: clumps of a particular form of tau build up and parts of the brain degenerate. Its ultimate cause is still uncertain. Across all forms it affects about 18 people per 100,000, symptoms typically start between 60 and 70, men are slightly more often affected, and no link to race, place or job has been found.
For two thirds of patients the first sign is poor balance: lurching forward, walking fast, colliding with things and falling. About one in five show early dementia symptoms, and apathy, disinhibition and anxiety are common. Subtle changes, including slower reactions and weaker grip, can appear roughly eight years before diagnosis. Later come slurred speech, swallowing problems and a stiff, backward-tilted neck, though some people keep their thinking intact to the end.
The eyes are the diagnostic giveaway. Patients struggle to read because they cannot glance downward; upward gaze fails next. Yet when an examiner gently tips the head, the eyes move normally, showing that reflex pathways survive while voluntary control fades. Doctors also look for slow square-wave jerks, trouble converging on near objects, which causes double vision, and the procerus sign: a wide-eyed stare with a deeply furrowed, frowning forehead.
The commonest subtype, Richardson's syndrome, brings symmetrical stiffness and slowness with little tremor, responds poorly to the dopamine drugs used for Parkinson's, affects men about 1.8 times as often as women and lasts on average 5.9 years. A Parkinson-like subtype with tremor responds better to levodopa. Certainty requires examining the brain after death. A 2024 to 2025 clinic study found dystonia, involuntary muscle contraction, in 64.8 percent of 88 patients, with botulinum toxin helping some.
Source: Progressive supranuclear palsy
