Regional cerebral blood flow differences in patients with mild cognitive impairment between those who did and did not develop Alzheimer's disease.

Mild cognitive impairment (MCI) is a heterogeneous condition associated with increased risk of Alzheimer's disease (AD) and other dementias. This study aimed to identify areas of initial hypoperfusion in MCI conversion to AD using technetium (Tc-99m) hexamethylpropyleneamine oxime (TC-99m HMPAO) single photon emission computed tomography (SPECT) to compare baseline cerebral hypoperfusion in converted MCI and non-converted MCI patients and normal controls. Forty-nine MCI patients were recruited for brain magnetic resonance imaging (MRI), detailed neuropsychological testing, Tc-99m HMPAO SPECT, and 1- to 2-year periodic follow-up to monitor progression to dementia status. We processed SPECT images with Statistical Parametric Mapping 8 (SPM8) software and performed voxel-based statistical parametric mapping analysis. Thirty-nine of 49 MCI patients were included in our analysis. Nine patients were diagnosed with conversion to AD, on average 19.0±6.6 months after initial assessment. Compared with normal controls, converted MCI patients demonstrated perfusion deficits in both parahippocampal gyri and right precuneus, and non-converted MCI patients demonstrated hypoperfusion in the left parahippocampal gyrus. Compared with non-converted MCI patients, converted MCI patients demonstrated significant hypoperfusion in both cingulate gyri and right precuneus. Our study suggests that using brain SPECT to identify initial hypoperfusion in patients with MCI may be helpful for predicting MCI patients likely to develop AD.