What is the role of imaging studies in the management of Parkinson-plus syndromes?

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

Patients with parkinsonian syndromes unresponsive to dopamine agonists or levodopa should have an imaging study of the brain. MRI of the brain is preferred to CT, as it provides better visualization of midbrain and brainstem structures. PET imaging with fluorine-18-fluorodeoxyglucose (FDG) has been used to identify characteristic patterns of regional glucose metabolism in patients with idiopathic PD or variants of parkinsonism, such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD).

In a longitudinal study, Eckert et al compared PET diagnosis with a clinical diagnosis by a movement disorders specialist with 2-year follow-up. Diagnoses based on blinded computerized assessment of PET scans agreed with clinical diagnosis in 92.4% of all subjects (97.7% with early PD, 91.6% with late PD, 96% with MSA, 85% with PSP, 90.1% with CBGD) and in 86.5% of healthy control subjects. [49] At present, PET and SPECT scans remain research tools and are not routinely used for diagnosis.

Transcranial sonography (TCS) has been used as a tool for the differential diagnosis of these syndromes. Characteristic findings include hyperechogenicity in the substantia nigra in Parkinson disease, while hyperechogenicity in the lentiform nucleus is seen in MSA and PSP. Walter et al observed that lenticular nuclei hvperechogenicity is observed in 72-82% of patients with MSA and PSP but in only 10-25% of patients with Parkinson disease. Further studies are required to validate these findings. [50]

Magnetic resonance diffusion-weighted imaging regional apparent diffusion coefficients (rADCs) may also be helpful. Middle cerebellar peduncle and rostral pons rADCs in MSA are significantly greater than in PSP and Parkinson disease. Pavior et al reported that middle cerebellar peduncle rADC distinguishes MSA from PSP with a sensitivity of 91% and a specificity of 84%. [51]


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