fMRI Surrogate of Cerebral Vascular Reactivity is Impaired in Cerebral Amyloid Angiopathy but Not Alzheimer’s Disease (P1.190)

Objective: To assess cerebral vascular reactivity in response to a visual task in patients with cerebral amyloid angiopathy (CAA), Alzheimer’s disease (AD), and mild cognitive impairment (MCI) using functional magnetic resonance imaging (fMRI). Background: CAA is characterized by beta-amyloid deposition in cerebral small vessels, while beta-amyloid accumulates in the brain parenchyma in AD. Previous fMRI studies have shown decreased blood oxygen level dependent (BOLD) signal in response to a visual stimulus in CAA compared to similarly-aged controls. Design/Methods: Study participants consisted of 40 CAA, 22 AD, 27 MCI, and 25 healthy controls. Each subject 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 of 114 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: Mean age was 71.3±8.1 years; 45.6% were women. After adjusting for age and hypertension, estimated mean BOLD percent signal change was: CAA 1.87% (95% CI 1.60–2.14%), AD 2.21% (1.87%–2.56%), MCI 2.15% (1.84%–2.46%), and control 2.65% (2.31%–3.00%). Only CAA subjects differed from controls (p=0.008). When white matter hyperintensity (WMH) volume was added to the model, only WMH volume (p=0.002) and not group (p=0.12) was associated with mean BOLD percent signal change. In the subset with VEPs, only higher age, but not group, was associated with prolonged latencies (p=0.001) and lower amplitudes (p=0.001). Conclusions: Mean visual BOLD percent signal change was lowest in CAA compared with controls, without differences in VEP latencies and amplitudes. This suggests that vascular reactivity is impaired in CAA. WMH volume was strongly associated with mean BOLD changes. Decreased visual BOLD amplitudes appear to be a phenomenon relatively specific to CAA, not AD. Disclosure: Dr. Switzer has nothing to disclose. Dr. Cheema has nothing to disclose. Dr. McCreary has nothing to disclose. Dr. Batool has nothing to disclose. Dr. Zwiers has nothing to disclose. Dr. Charlton has nothing to disclose. Dr. Zerna has nothing to disclose. Dr. Stafford has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Software Ru0026D Engineer at Circle Cardiovascular Imaging Inc. Dr. Frayne has nothing to disclose. Dr. Goodyear has nothing to disclose. Dr. Smith has nothing to disclose.