Background: Cerebral amyloid angiopathy (CAA), characterized by accumulation of β-amyloid in cortical vessels, is an established cause of hemorrhagic and ischemic brain damage. Although Boston criteria can accurately diagnose CAA in patients who had lobar intracerebral hemorrhage (ICH), its value in asymptomatic older adults is unknown.
Objective: We aimed to compare the amyloid load, structural MRI measures and risk factors between asymptomatic subjects who would qualify for a diagnosis of probable CAA based on lobar microbleeds (LMB) and superficial siderosis (SS) to subjects without these MRI findings.
Methods: Healthy older adults (n=181) prospectively enrolled in Harvard Aging Brain study had research MRIs and Pittsburgh Compound B (PiB) PET scans. Probable CAA was diagnosed based on presence of 2 or more LMBs or a combination of LMB/SS. Distribution volume ratio (DVR) of PiB-retention, white matter hyperintensity (WMH) and hippocampal volume (HV) were calculated. Demographics, APOE status, risk factors, and imaging markers were compared between subjects with and without probable CAA diagnosed based on LMB/SS.
Results: Participants had mean age 74.5±5.8 and 56% were female. Forty-six (25%) subjects had lobar MBs, 11(6%) had deep and 4(2%) cerebellar MBs. The 22 subjects diagnosed with probable CAA had higher occipital DVR (1.35 vs 1.28, p=0.004) and higher WMH (0.51 vs 0.16, p=0.005) when compared to persons without MB. These associations remained significant after adjustment for age and gender. Age, HV, ApoE status and vascular risk factors were similar between probable CAA and no MB/SS subjects (all p>0.2).
Conclusions: Probable CAA diagnosis based on presence of lobar MBs and/or SS on MRI of healthy elderly volunteers is associated with other radiologic markers of CAA (posterior amyloid load, WMH) but not with vascular risk factors or markers of Alzheimer’s Disease (HV, ApoE 4). Boston criteria and amyloid imaging thus may allow early diagnosis of CAA even in asymptomatic subjects without ICH or dementia.