Altered cerebrovascular reactivity velocity in mild cognitive impairment and Alzheimer's disease

Inter-individual variation in neurovascular reserve and its relationship with cognitive performance is not well understood in imaging in neurodegeneration. We assessed the neurovascular reserve in amnestic mild cognitive impairment (aMCI) and Alzheimer's dementia (AD). 28 healthy controls (HC), 15 aMCI and 20 AD patients underwent blood-oxygen level dependent (BOLD) imaging for 9 minutes, breathing alternatively air and 7% CO2 mixture. The data was parcellated into 88 anatomical regions, and CO2 regressors accounting for different wash-in and wash-out velocities were fitted to regional average BOLD signals. Velocity of cerebrovascular reactivity (CVR) was analyzed and correlated with cognitive scores. aMCI and AD patients had significantly slower response than HC (mean time to reach 90% of peak: HC 33 seconds, aMCI and AD 59 seconds). CVR velocity correlated with mini mental state examination (MMSE) in 35 out of 88 brain regions (p=0.019, corrected for multiple comparisons), including several regions of the default-mode network, an effect modulated by age. This easily applicable protocol yielded a practical assessment of CVR in cognitive decline