Progressive supranuclear palsy

Progressive supranuclear palsy (PSP), also known as the Steele-Richardson-Olszewski syndrome, is a neurodegenerative disease with no efficacious treatment. 

Epidemiology

Progressive supranuclear palsy typically becomes clinically apparent in the 6^th decade of life, and progresses to death usually within a decade (2 - 17 years from diagnosis)

Clinical presentation

Progressive supranuclear palsy is characterised by decreased cognition, abnormal eye movements (supranuclear vertical gaze palsy), postural instability and falls, as well as parkinsonian features and speech disturbances ^1-3. 

Radiographic features

MRI

Although certain features help in favouring PSP over alternative clinical diagnoses (Parkinson disease and muliple system atrophy for example) it should be noted that except in classical cases, feature can usually at most be suggestive of the diagnosis (rather than pathognomonic), as there is overlap with other conditions. Features include ^1-4:

• midbrain atrophy
  • reduction of anteroposterior midbrain diameter, at the level of the superior colliculi on axial imaging (< 12mm [reference needed]) : which can give a mickey mouse appearance ⁶
  • reduced area of the midbrain on midline sagittal
  • reduced midbrain to pons ratio: ~ 0.12  (normal ~ 0.24) on midline sagittal
  • hummingbird sign also known as the penguin sign ⁵
• T2 : diffuse high-signal lesions in :
  • pontine tegmentum
  • tectum of the midbrain
  • inferior olivary nucleus

Differential diagnosis

Clinically it can be challenging to distinguish PSP from other entities especially when features are not typical ^1,3: 

• Parkinson disease
  • spares the midbrain and superior cerebellar peduncles
• multiple system atrophy (MSA)
  • predominantly affects middle cerebellar peduncles and pons (hot cross bun sign)
• corticobasal degeneration (CBD)
  • cortical atrophy prominent