Decreased perfusion of the posterior cingulate gyri shown by a cingulate island score is a possible marker of vulnerability to behavioural and psychological symptoms of Alzheimer's disease: a pilot study.

BACKGROUND: The cingulate island score (CIScore), which indicates the Z-score ratio of the posterior cingulate gyri to the medial occipital area, has been shown to be useful for differentiating dementia with Lewy bodies from Alzheimer's disease (AD). Our aim was to investigate associations between the clinical symptoms of AD and the CIScore as an index of the relative decrease in perfusion of the posterior cingulate gyri that occurs in the early stages of AD.

METHODS: Seventeen patients with early-stage AD and 13 patients with amnesic mild cognitive impairment were examined. Z-score maps of technetium-99m ethyl cysteinate dimer single-photon emission computed tomography images acquired from the patients were converted, and the CIScore was determined by using the easy Z-score imaging system. The relationships between the CIScore and clinical symptom scores were tested.

RESULTS: A significant correlation was identified between the CIScore and the Neuropsychiatric Inventory Questionnaire score. No significant correlations were identified between the CIScore and other measures of cognitive function. Based on a CIScore of 0.39, we correctly differentiated patients with and without behavioural and psychological symptoms of dementia (BPSD), with a sensitivity of 72.2% and specificity of 75.0%.

DISCUSSION: Using technetium-99m ethyl cysteinate dimer single-photon emission computed tomography, we observed that decreased posterior cingulate gyri perfusion, relative to the medial occipital area, in prodromal and early AD was closely associated with behavioural and psychological symptoms of dementia. Therefore, our findings suggest that CIScore is not only useful for discriminating dementia with Lewy bodies from AD, but it can also be clinically used as a specific indicator of the vulnerability to behavioural and psychological symptoms of dementia in the early stages of AD.