The Cingulate Island Sign on FDG‐PET vs. IMP‐SPECT to Assess Mild Cognitive Impairment in Alzheimer's Disease vs. Dementia with Lewy Bodies

BACKGROUND AND PURPOSE The cingulate island sign (CIS) on 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET); ie, the relative preservation of mid‐posterior cingulate cortex metabolism, is a supportive biomarker in the diagnostic criteria for dementia with Lewy bodies (DLB). However, limited information is currently available on the diagnostic value of the CIS on FDG‐PET or 123I‐iodoamphetamine single‐photon emission computed tomography (IMP‐SPECT) for differentiating between mild cognitive impairment (MCI) due to Alzheimer's disease (AD) (MCI‐AD) and MCI due to DLB (MCI‐DLB). METHODS We examined the CIS ratio in 9 AD patients, 9 DLB patients, 8 patients with MCI‐AD, and 9 patients with MCI‐DLB using FDG‐PET and IMP‐SPECT. The CIS ratio was calculated using NEUROSTAT software. RESULTS In the dementia groups, a receiver operating characteristic analysis of the CIS ratio showed significant accuracy for differentiating between AD and DLB on FDG‐PET and IMP‐SPECT. In the MCI groups, only the FDG‐PET derived CIS ratio displayed significant accuracy for differentiating between AD and DLB. CONCLUSIONS The FDG‐PET and IMP‐SPECT derived CIS ratios are both useful for differentiating between AD and DLB. The FDG‐PET derived CIS ratio is more valuable than the IMP‐SPECT derived CIS ratio for differential diagnosis in patients with MCI. A larger study is needed to confirm these results.