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 18 F-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 123 I-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.