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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: Conclusions



Table 1 and Table 2 summarize the differential imaging findings in parkinsonian syndromes and dementias, respectively.

TCS and MRI can both be used to image structural changes in the substantia nigra of patients with PD. Although the altered signals that are observed do not correlate well with either clinical status or loss of dopamine terminal function in the striatum, they might prove to be valuable for revealing a susceptibility to PD. By contrast, PET and SPECT measurements of dopamine terminal function do correlate significantly with clinical disability. In patients who are suspected of having PD, a finding of normal presynaptic dopaminergic function on a PET or SPECT scan implies a good prognosis.

The severity of a parkinsonian tremor correlates better with loss of 5-HT1A receptor binding potential in the median raphe than with nigro striatal dysfunction, which indicates that midbrain tegmentum pathology is involved in the generation of the tremor. Surprisingly, depression in PD seems to reflect a loss of noradrenergic and limbic monoaminergic function, rather than a serotonergic etiology.

DLB can be reliably discriminated from AD by the detection of a loss of striatal DAT binding in the former. Amyloid pathology contributes notably to DLB in the majority of cases, whereas only 20% of patients who have PDD show a raised plaque load.

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