Cingulate island sign

The cingulate island sign is a highly specific radiological sign described in dementia with Lewy bodies.

It refers to the pattern of metabolism seen on FDG-PET in patients with dementia with Lewy bodies . On FDG-PET, there is occipital hypometabolism with relative sparing of the posterior cingulate cortex, thus creating the appearance of an 'island' of normal metabolism in the posterior cingulate region . The same pattern can also be appreciated in SPECT, whereby the posterior cingulate region has relatively normal perfusion while there is surrounding occipital hypoperfusion .

The cingulate island sign has been described as a useful radiological differentiator between dementia with Lewy bodies, which has the sign, and Alzheimer disease, in which the sign is not present . However, it has been found that as dementia with Lewy bodies progresses over time, the sign disappears, likely due to concomitant Alzheimer disease .