see also:

• Parkinson's disease
• neurology
• bulbar palsy and pseudobulbar palsy

• a rare tauopathy neurologic degenerative disease which is often initially misdiagnosed as Parkinson's disease
• the second most common tauopathy behind Alzheimer's disease
• first described by Richardson, Steele, and Olszewski in 1963 as a form of progressive parkinsonism
• there are 7 main PSP subtypes but they eventually exhibit the clinical characteristics of the main subtype, PSP-Richardson's syndrome (PSP-RS) which accounts for 24-54% of cases (while PSP-P subtype has slower progression and accounts for 13-45% of cases)

• PSP of all phenotypes has a prevalence of 18 per 100,000, whereas PSP-RS affects approximately 5 to 7 per 100,000 individuals

• a 2026 study¹⁾ suggests the following as risk factors:
  • depression (often predates PSP by 10yrs)
  • delirium
  • irritable bowel syndrome (IBS)
  • heavy alcohol intake
  • obesity
• <1% have a FH of PSP
• mitochondrial dysfunction seems to be a factor involved in PSP

• symptoms typically appear in the 60s, causing rapid decline with frequent falls, stiffness, and swallowing difficulties
• progresses faster than Parkinson's, with significant mobility and swallowing issues typically leading to complications within 2 to 7 years of symptom onset
• long pre-clinical diagnostic phase of ~8 years (time to diagnosis 7.8 ± 2.8 years) where subtle changes in motor and cognitive function occur
• lunging forward when mobilizing
• fast walking
• unexplained backward falls
• difficulty moving eyes, particularly looking down, or keeping them open causing difficulty reading due to the inability to look downwards combined with diplopia when focusing at shot distances
  • inability to make vertical saccades, which is often worse with downward saccades
  • involuntary or passive eye movements may be normal
  • slower “square-wave jerks” may be visible when the patient fixes gaze at distance
• rigid, stiff movements, particularly in the neck and trunk
• bradykinesia
• apathy, a lack of inhibition, profound state of unease or dissatisfaction, irritability, impulsivity, and mild dementia symptoms
• contracture of the facial muscles
  • procerus sign - with a wide-eye stare, furrowing of forehead with a frowning expression, and deepening of other facial creases
• a backward tilt of the head with stiffening of the neck muscles, sleep disruption, urinary incontinence, and constipation
• MRI may show atrophy in the midbrain with preservation of the pons giving a “hummingbird” sign