Dementia With Lewy Bodies

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Metabolic Studies

DLB has not been examined as extensively with PET and SPECT as other atypical parkinsonian disorders. Albin and colleagues have reported the 18FDG PET findings of six demented individuals with pathologically verified diffuse Lewy body disease (71), three of whom had had pure DLB and three combined DLB and Alzheimer's disease (DLB-AD) pathology. These patients showed hypome-tabolism in association cortices with relative sparing of subcortical structures and primary somatomotor cortex, a pattern reported previously in AD. The main difference in comparison to patients with AD was the more pronounced hypometabolism in the occipital association cortex and primary visual cortex, indicating the presence of diffuse cortical abnormalities in DLB and suggesting that FDG-PET may possibly be useful in discriminating DLB from AD antemortem (Fig. 4).

This finding has been confirmed in larger series of 13 patients with DLB and 53 patients with AD (72). Similar differences in brain perfusion patterns between DLB and AD have been found using 99mTechnetium labeled perfusion markers and SPECT (73).

A direct metabolic comparison of patients with PD and DLB has not been performed to date to our knowledge; since occipital decreases in occipital metabolic activity has been described in PD (74) as well, it would be very interesting to determine whether occipital hypometabolism discriminates not only between DLB and AD but also between DLB and PD.

Dopaminergic System

The presynaptic system has been characterized in DLB using both PET and SPECT. Using [18F]dopa PET, Hu and colleagues (75) described a reduction of striatal dopamine uptake in 6 patients with DLB whereas the values in the 10 AD patients were not significantly different from normal.

Table 2

Synopsis of the Characteristic PET and SPECT Findings in Different Parkinsonian Disorders

Table 2

Synopsis of the Characteristic PET and SPECT Findings in Different Parkinsonian Disorders

Imaging Modality and Measured Parameter

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