Presentation
Cognitive decline and reduction in executive function
Patient Data
There is moderate reduction in uptake in bilateral parietal lobes, especially the precuneus and lateral parietal cortex. Mild-moderate reduction of uptake in the occipital lobes and mild reduction in the superior frontal cortex. Normal uptake is present in the posterior cingulate gyrus.
A "cingulate island sign" (arrow) is produced when the posterior cingulate gyrus has normal metabolism and there is abnormal reduced uptake in the adjacent parietal and occipital lobes. This gives the appearance of a discrete 'island' of comparatively more intense uptake in the region of the posterior cingulate gyrus.
Case Discussion
Lewy body disease (or dementia with Lewy bodies) is a neurodegenerative disease, which is the second most common cause of dementia behind Alzheimer disease. On FDG PET/CT, there is most commonly bilateral abnormal reduction in parieto-occipital metabolism/tracer uptake with relative preservation of uptake in the posterior cingulate gyrus ("cingulate island sign").
While there can be overlap in the FDG PET imaging features of Lewy body disease and Alzheimer disease, patients imaged with Alzheimer disease usually have reduction of uptake in the posterior cingulate gyrus and relative preservation of uptake in the occipital cortices.
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