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Table 1.  

Differential Imaging Findings in Parkinsonian Syndromes

Table 2.  

Differential Imaging Findings in Dementias

Technology Insight: Imaging Neurodegeneration in Parkinson's Disease: Imaging Approaches


Imaging Approaches

Imaging the changes associated with the pathology of PD involves either detecting alterations in brain structure or examining functional changes in brain metabolism and receptor availability. MRI scans can reveal brain structural changes such as reductions in volume, alterations in water proton T2 relaxation signals or in water diffusion, and changes in magnetic susceptibility or in magnetization transfer. MRI also enables the exclusion of structural lesions such as basal ganglia tumors and calcification, multiinfarct disease, and hydrocephalus as causes of parkinsonism. Transcranial sonography (TCS) can detect structural midbrain and striatal changes, which manifest as hyper echogenicity, in parkinsonian disorders.

Functional imaging (PET, single-photon emission CT [SPECT], functional MRI, and proton magnetic resonance spectroscopy) provides a means of detecting and characterizing the regional changes in brain blood flow, meta bolism, and receptor binding that are associated with parkinsonian disorders. Radiotracerbased PET and SPECT potentially provide a sensitive means of detecting subclinical disease in patients who are at risk for subcortical degenerations, and these techniques might also provide biomarkers for objective assessment of disease progression.

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