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Structural and functional imaging

MIBG

Cardiac scintigraphy with [123I]-MIBG enables the quantification of post-ganglionic cardiac sympathetic innervation, and several studies have demonstrated reduced cardiac uptake compared with mediastinal uptake in DLB and PD, as opposed to AD [73]. In one meta-analysis MIBG distinguished two diagnostic clusters: one including PD, individuals with RBD, and DLB, the second including AD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), VaD, and frontotemporal dementia [74]. Patients with PD-D or DLB have lower cardiac [123I]- MIBG uptake than those with PD, in parallel with reduced cardiovascular autonomic function [75]. Direct comparative studies of DLB and PD-D are needed to complete the picture, with better

Table 18.2 Psychotic symptoms in dementia with Lewy bodies (DLB), Parkinson's disease with dementia (PD-D), and Alzheimer's disease (AD)

Symptom

DLB (n = 98)

PD-D (n = 48)

AD (n = 40)

visual

71 (72%)

24 (50%)

10 (25%)

Auditory

37 (38%)

10 (21%)

4 (10%)

Delusions

56 (57%)

14 (29%)

12 (30%)

Data from Ballard et al. (1999) [62] and Aarsland et al. (2001) [59].

information needed to enable the interpretation of results in patients with concurrent cardiovascular disease.

Magnetic resonance imaging (MRI)

Using structural MRI, the typical finding in DLB is relative preservation of hippocampal and medial temporal lobe volumes in comparison with AD. Other cortical and subcortical changes have also been reported in DLB, including in the substantia innominata, hypothalamus, and dorsal midbrain [76]. Similar changes have been reported in PD-D. However, the two studies comparing grey matter in PD-D and DLB by MRI have conflicted, one reporting no differences [77] whereas the other found more pronounced cortical atrophy in DLB than in PD-D [78]. A further study focusing on voxel-based morphometry of grey and white matter densities between DLB and PD-D showed decreased grey matter density in PD-D in bilateral dorsolateral prefrontal, temporal, occipital, posterior cingular, and right parietal cortical areas compared with controls [79]. DLB showed similar changes but more pronounced atrophy, with significantly decreased grey matter density in left occipital, parietal, and striatal areas compared with PD-D. White matter analyses showed decreased density in PD-D and DLB compared with controls, with a greater decrease in DLB compared with PD-D. Additionally, the relative decrease of white matter relative to grey matter was more pronounced in DLB.

MRI diffusion tensor tractography shows significantly lower fractional anisotropy in the anterior cingulate fasciculi in PD-D and PD compared with controls, and this value correlated with the MMSE score [80]. A recent study showed that among patients with VH, DLB patients had more atrophy in pre-motor bilateral regions than PD-D patients, and the severity of hallucinations correlated with the intensity of grey matter volume reduction in the right inferior frontal gyrus and left precuneus only in DLB patients [81].

 
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