What is the role of imaging studies in the diagnosis of progressive supranuclear palsy (PSP)?

Updated: Sep 24, 2018
  • Author: Stephen M Bloomfield, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

MRI can help exclude NPH and multi-infarction syndromes. MRI can also be helpful in distinguishing PSP from MSA and CBD. Atrophy in the midbrain or cerebellum, whether general or focal, is the most common. Due to disproportionate atrophy of the dorsal midbrain relative to the pons, sagittal views on MRI can give the appearance of a "hummingbird". Still, up to a quarter of patients with PSP have no abnormality on computed tomography (CT) or MRI imaging of the brain. [26] Midbrain diameter of less than 17 mm, hyperintensity in the midbrain, atrophy or hyperintensity of the red nucleus, and hyperintensity in the globus pallidus are especially useful findings. PET and single-photon emission CT (SPECT) demonstrate prefrontal hypometabolism. Specialized PET scans can depict severe involvement of the dopaminergic system.

The most characteristic feature of PSP is the supranuclear downgaze palsy. Some patients who never develop this finding are found to have PSP at autopsy. There is an average delay in making a proper diagnosis of 3.6 years after symptom onset. The measurement of midbrain atrophy ratio on MRI is a useful tool in distinguishing early PSP from PD and age-matched controls. [27, 28]


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