What are the latest criteria for diagnosing Progressive Supranuclear Palsy (PSP)?

Latest Diagnostic Criteria for Progressive Supranuclear Palsy (PSP)

The 2017 Movement Disorder Society (MDS) criteria are the latest diagnostic standards for Progressive Supranuclear Palsy (PSP), recognizing eight distinct clinical phenotypes beyond the classic Richardson's syndrome presentation. 1

Core Clinical Features

The MDS criteria identify four key functional domains that predict PSP:

1. Ocular Motor Dysfunction

   • Vertical supranuclear gaze palsy (especially downward gaze initially)
   • Slowing of vertical saccades
   • Absence of optokinetic nystagmus vertically 2

2. Postural Instability

   • Early falls (within first year of symptom onset)
   • Prominent postural instability
   • Tendency to fall backward 2, 1

3. Akinesia/Rigidity

   • Axial rigidity more prominent than appendicular rigidity
   • Minimal tremor (distinguishing from Parkinson's disease)
   • Poor or transient response to levodopa 2, 3

4. Cognitive Dysfunction

   • Executive dysfunction
   • Behavioral/personality changes
   • Progressive cognitive impairment 2, 1

Diagnostic Categories

The MDS criteria stratify diagnosis into three levels of certainty:

1. Probable PSP

   • Requires vertical supranuclear gaze palsy
   • Prominent postural instability with falls in first year
   • Age of onset ≥40 years
   • Gradual progression of symptoms 4, 1

2. Possible PSP

   • Either vertical supranuclear gaze palsy OR both slowing of vertical saccades and prominent postural instability with falls in first year
   • Age of onset ≥40 years
   • Gradual progression of symptoms 4, 1

3. Suggestive of PSP

   • Presence of core clinical features but not meeting criteria for possible or probable PSP
   • May represent early disease stage 1

4. Definite PSP

   • Requires neuropathological confirmation
   • History of possible or probable PSP 4

PSP Phenotypes

The MDS criteria recognize eight distinct clinical phenotypes:

1. PSP-Richardson's syndrome (PSP-RS) - The classic presentation with early falls, vertical gaze palsy
2. PSP-Parkinsonism (PSP-P) - Asymmetric onset, tremor, initial response to levodopa
3. PSP with predominant frontal presentation (PSP-F)
4. PSP with progressive gait freezing (PSP-PGF)
5. PSP with predominant speech/language disorder (PSP-SL)
6. PSP with predominant ocular motor dysfunction (PSP-OM)
7. PSP with predominant postural instability (PSP-PI)
8. PSP with predominant corticobasal syndrome (PSP-CBS) 1

Supportive Diagnostic Features

Imaging Findings

• MRI: Regional volume loss patterns, particularly midbrain atrophy ("hummingbird sign")
• FDG-PET: Hypometabolism in medial frontal and anterior cingulate cortices, striatum, and midbrain
• DaTscan (Ioflupane SPECT): Decreased radiotracer uptake in the striatum (not specific to PSP) 5, 2

Clinical Course

• Mean age of onset: 63 years
• Mean survival from symptom onset: approximately 9 years
• Progressive dependence in activities of daily living typically after 4 years 2

Diagnostic Challenges

• The original NINDS-SPSP criteria (1996) had excellent specificity but limited sensitivity for variant PSP phenotypes 4, 1
• Studies show that only 43% of pathologically-confirmed PSP cases matched the original clinical criteria at time of death, and only 14% at symptom onset 6
• PSP-P (32% of cases) is frequently misdiagnosed as Parkinson's disease due to asymmetric onset, tremor, and initial levodopa response 3
• Clinical features may change dramatically as disease progresses, requiring reassessment of diagnosis 6

Key Differential Diagnoses

• Parkinson's disease
• Multiple system atrophy
• Corticobasal degeneration
• Dementia with Lewy bodies
• Vascular parkinsonism 5, 2

The MDS criteria significantly improve sensitivity for diagnosing PSP across its spectrum of clinical presentations while maintaining diagnostic specificity, making them the current gold standard for clinical diagnosis of PSP.