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Progressive Supranuclear Palsy (PSP)

Summary

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  • Progressive neurodegenerative disorder characterised by postural instability, supranuclear gaze palsy, and cognitive decline
  • Pathologically defined by accumulation of tau protein in neurons and glial cells
  • Imaging shows midbrain atrophy with the 'hummingbird' sign in the sagittal plane1

Pathophysiology

  • Accumulation of hyperphosphorylated tau protein in neurons and glial cells
  • Neuronal loss and gliosis in affected areas
  • Familial cases associated with MAPT gene mutations

Demographics

  • Typically affects individuals over 60 years of age
  • Estimated prevalence of 5-6 per 100,000
  • No clear ethnic or geographical predisposition

Diagnosis

  • Clinical diagnosis based on:
    • Progressive balance and gait disturbances
    • Supranuclear gaze palsy, particularly affecting vertical eye movements
    • Cognitive decline and behavioural changes
  • Supportive features:
    • Axial rigidity
    • Dysphagia and dysarthria
    • Frontal lobe signs
  • Imaging shows excessive midbrain volume loss
  • Definitive diagnosis requires neuropathological confirmation

Imaging

  • Midbrain atrophy is the hallmark:
    • Sagittal: flattening/concavity of the superior midbrain ("hummingbird" or "penguin silhouette" sign) and a reduced midbrain-to-pons ratio
    • Axial: concave lateral midbrain margins ("morning glory" sign)
  • Superior cerebellar peduncle atrophy; third ventricle/interpeduncular cistern widening
  • The MR parkinsonism index combines these measurements to support the diagnosis

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  • 75-year-old patient with postural instability and supranuclear palsy.
  • The midbrain tegmentum is atrophic causing a flattened superior border.
  • The DaTscan shows reduced tracer uptake in the putamina (particularly on the right).

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  • 65-year-old patient presented with instability, free falls, and a vertical gaze palsy.
  • MRI showed marked atrophy of the pons.
  • DaTscan showed loss of normal tracer uptake in both corpora striata.

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  • 60-year-old patient presented with poor balance, multiple falls, and rigidity. Initially diagnosed with Parkinson's disease, there was a poor response to levodopa.
  • MRI showed marked midbrain atrophy (as well as a moderate burden of small vessel disease).

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  • 70-year-old patient presented with parkinsonism.
  • MRI showed marked atrophy of the midbrain over a three year period.
  • DaTscan showed high background uptake and with loss of the normal uptake in the striatum.

Treatment

  • No disease-modifying therapy; levodopa is usually poorly responsive

Differential diagnosis (midbrain/atrophy patterns)

Imaging differential Differentiating feature
Parkinson's disease Preserved midbrain volume; nigrosome-1 loss on SWI
MSA — parkinsonian type Putaminal atrophy with a lateral rim; "hot cross bun" pons rather than midbrain atrophy
Corticobasal degeneration Asymmetric perirolandic cortical atrophy
Normal pressure hydrocephalus Ventriculomegaly with DESH; preserved midbrain

  1. Boxer et al. Advances in progressive supranuclear palsy: new diagnostic criteria, biomarkers, and therapeutic approaches. 2017. The Lancet. Neurology - Open in new tab. ↩