Q.CINGULATE ISLAND SIGN on FDG -PET SCAN of brain is noted in
a.Alzheimer disease
b.DLB
c.both \
d.none
ANS---b ( DLB)
----The typical pattern of hypometabolic activity in Alzheimer disease on 18F-FDG PET images involves the parietotemporal region, precuneus, and posterior cingulate gyrus, with sparing of the sensorimotor strips and occipital region, which usually corresponds to the atrophic changes depicted on structural images.
----In patients with DLB, 18F-FDG PET images show asymmetric decreased activity in the frontotemporal lobes similar to that depicted in Alzheimer disease. However, there is preserved metabolism of the posterior cingulate cortex, resulting in the so-called cingulate island sign. Alzheimer disease almost invariably involves the posterior cingulate gyrus, and this is a useful differentiating factor. There is hypometabolism of the occipital lobes, which is helpful to differentiate DLB from typical Alzheimer disease.
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