MRI studies on DLB are rather rare, probably because they do not show peculiar signal changes or localized atrophy that may support the diagnosis. Except for a report by Hashimoto et al. (63), most MRI studies have been published by the group of Barber et al. in Newcastle upon Tyne (64-67). The few studies we performed in our patients with DLB concur with the published data.
The essential findings of a series of volumetric studies indicate that patients with dementia, either vascular or owing to Alzheimer's disease (AD) or DLB, present brain atrophy compared with control subjects. Atrophy in DLB is less marked than in patients with AD, with particular preservation of mesial temporal structures including amigdala, hippocampus, subiculum, and parahippocampal and dentate gyri. Preservation of these structures may, therefore, help to differentiate DLB from AD (63,65). Total brain volume is not significantly different in patients with DLB and vascular dementia (66), but white matter and basal ganglia hyperintensities in T2-weighted images are more frequent and extensive in patients with vascular dementia than in patients with AD and DLB (64).
Occipital hypoperfusion has been demonstrated in DLB (68,69). Because the visual hallucinations of DLB might also be related to structural changes in the occipital lobes, volumetric MRI measurements have been performed (70,71). The results are conflicting: in one series, occipital lobe volumes in DLB were not significantly different from those of AD and control groups (70); in the other series (71), occipital lobe atrophy was found in DLB but also in AD patients. Therefore, on the basis of these volumetric studies, discrimination of these two types of dementia was not possible.
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