Cerebrovascular reactivity in cerebral amyloid angiopathy, Alzheimer disease, and mild cognitive impairment.

Objective: To assess cerebrovascular reactivity in response to a visual task in participants with cerebral amyloid angiopathy (CAA), Alzheimer’s disease (AD), and mild cognitive impairment (MCI) using functional magnetic resonance imaging (fMRI). Methods: Prospective cohort study including 40 CAA, 22 AD, 27 MCI, and 25 healthy controls. Each participant underwent a visual fMRI task using a contrast-reversing checkerboard stimulus. Visual evoked potentials (VEP) were used to compare visual cortex neuronal activity in 83 subjects. General linear models using least-squares means, adjusting for multiple comparisons using Tukey’s test, were used to estimate: a) mean BOLD signal change during the task, and b) VEP differences between groups. Results: After adjusting for age and hypertension, estimated mean BOLD response amplitude was: CAA 1.88% (95% CI 1.60-2.15%), AD 2.26% (1.91%-2.61%), MCI 2.15% (1.84%-2.46%), and control 2.65% (2.29%-3.00%). Only CAA subjects differed from controls (p=0.01). In the subset with VEPs, group was not associated with prolonged latencies or lower amplitudes. Lower BOLD amplitude response was associated with higher WMH volumes in CAA (for each 0.1% lower BOLD response amplitude the WMH volume was 9.2% higher, 95% CI 6.0%-12.4%) but not other groups (p=0.002 for interaction) when controlling for age and hypertension. Conclusions: Mean visual BOLD response amplitude was lowest in CAA compared to controls, without differences in VEP latencies and amplitudes. This suggests that the impaired visual BOLD response is due to reduced vascular reactivity in CAA. In contrast to CAA, the visual BOLD response amplitude did not differ between AD or MCI and controls.