Dementia with Lewy bodies (DLB) is recognized as a distinct neurodegenerative disease with established clinical criteria. Lewy bodies, which are the characteristic features of Parkinson’s disease in the substantia nigra, are abundant in the neocortex. They are commonly found in people with other types of dementia and DLB by itself is less common than the mixed (AD and Lewy body) type. However, pathologic studies have revealed a consistent pattern of vulnerability to Lewy body formation across subcortical, paralimbic, and neocortical structures that was not related to the amount of AD changes, indicating that dementia with Lewy bodies is a distinct pathology rather than a variant of AD. Clinically, patients with DLB exhibit symptoms close to those of AD patients, but with relevant motor features of Parkinsonism. Generally, DLB is diagnosed when cognitive symptoms develop within a year or two of movement disorder/Parkinsonian symptoms.
Based on in vivo cerebral MRI studies, patients with DLB have various morphologic changes, including global brain volume loss, regional atrophy in the frontal and temporal lobes, hippocampus, and amygdala. Differences in the severity of atrophy between AD and DLB have been investigated, usually reporting similar losses in the total brain volume, but less severe atrophy in the hippocampus and temporoparietal cortex in DLB patients than in those with AD.

1H-MRS

There are few MRS studies on patients with DLB, and the technique is not generally used for diagnostic purposes in this disease. It is interesting to note, however, that in comparison with AD patients, those with DLB show less (or no) decrease in NAA/Cr levels in brain regions such as the posterior cingulate gyri. This may reflect the relative sparing of neurons in that region seen at autopsy, and again could be useful at early disease stages to distinguish patients with DLB from other dementia syndromes. Increases in the Cho/Cr ratio have been reported in DLB, which have been suggested to be due to increased membrane turnover in this disease.