Progressive supranuclear palsy (PSP) is one of those neurodegenerative diagnoses that shows up on exams as a “pattern recognition” vignette: an older adult with early falls, vertical gaze palsy, and a stiff, axial, upright posture that doesn’t fit classic Parkinson disease (PD). If you can spot that triad fast, you’ll snag easy points.
PSP in one line (memorize this)
Progressive supranuclear palsy = a tauopathy causing early postural instability with falls + vertical (especially downward) gaze palsy + axial rigidity with poor levodopa response.
Visual / mnemonic device (quick-hit)
“PSP = Penguin Staring Problem”
Picture a tall, stiff penguin standing upright, falling backward, and staring straight ahead because it can’t look down.
- Penguin posture → axial rigidity, extended neck, upright stance
- Falling backward → early postural instability, early falls
- Staring / can’t look down → vertical gaze palsy (classically downward)
The high-yield core: how PSP presents
Key clinical features
- Early falls (often backward) due to postural instability
- Vertical supranuclear gaze palsy
- Impaired voluntary vertical eye movements (often downgaze first)
- Reflex eye movements may be relatively preserved early (think “supranuclear”)
- Axial rigidity > limb rigidity
- Pseudobulbar features: dysarthria, dysphagia, emotional lability
- Cognitive/behavioral changes (frontal executive dysfunction)
What makes it not typical Parkinson disease
- Poor or minimal response to levodopa
- Early gait/postural instability rather than late
- Prominent eye movement abnormalities (vertical gaze palsy is a giant clue)
- Tremor is usually less prominent than in PD
“Supranuclear” eye findings (exam-friendly)
Supranuclear palsy means the problem is above the ocular motor nuclei, so:
- Voluntary vertical gaze is impaired early
- Vestibulo-ocular reflex (VOR) can be relatively preserved early (you can sometimes elicit eye movement with head rotation when the patient can’t do it on command)
USMLE-style phrasing:
- “Difficulty looking down to read or descend stairs”
- “Frequent falls when walking, especially backward”
- “Staring, reduced blinking, masked facies”
Pathology: what PSP is made of
Etiology / pathology
- Sporadic neurodegenerative disorder
- Tauopathy: abnormal hyperphosphorylated tau accumulation in neurons and glia
- Classically involves:
- Midbrain (key for vertical gaze control)
- Basal ganglia and brainstem circuits for posture/gait
Gross imaging clue (Step 2-level pattern recognition)
- MRI may show midbrain atrophy with preserved pons → “hummingbird sign” (aka “penguin sign” in some descriptions)
Quick comparison table: PSP vs Parkinson disease vs MSA
| Feature | PSP | Parkinson disease | MSA (Multiple system atrophy) |
|---|---|---|---|
| Falls | Early, often backward | Later | Early-ish possible |
| Eye movements | Vertical gaze palsy (downgaze) | Usually normal early | No classic vertical palsy |
| Rigidity | Axial > limbs | Limbs often prominent | Variable |
| Autonomic failure | Not the main feature | Can occur later | Prominent early (orthostasis, urinary) |
| Levodopa response | Poor | Good (esp early) | Poor/limited |
| Pathology | Tau | -synuclein (Lewy bodies) | -synuclein (glial cytoplasmic inclusions) |
| MRI clue | Midbrain atrophy (“hummingbird”) | Often nonspecific | “Hot cross bun” (pons) can be seen |
Classic vignette (what the question stem will look like)
An older adult with:
- Frequent falls within the first year or two of symptoms
- Stiff, upright posture and gait instability
- Difficulty looking down (trouble reading, going down stairs)
- Parkinsonism that does not improve with levodopa
Diagnosis: Progressive supranuclear palsy
Management (what USMLE expects you to know)
- No disease-modifying therapy
- Symptomatic and supportive:
- Trial of levodopa may be attempted but usually minimal benefit
- PT/OT, gait training, fall prevention
- Speech/swallow evaluation (aspiration risk)
- Address mood/cognition and caregiver support
High-yield prognosis note: progressive course with increasing falls, dysphagia, aspiration risk.
Rapid-fire “don’t miss” facts
- PSP is a tauopathy, not a synucleinopathy.
- Vertical gaze palsy (especially downward) is the single most testable distinguishing feature.
- Think PSP when you see early falls + axial rigidity + poor levodopa response.
- MRI clue: midbrain atrophy → “hummingbird sign.”