Unexpectedly low prevalence of intracerebral hemorrhages in sporadic cerebral amyloid angiopathy

Abstract

In a retrospective study of a consecutive autopsy series of 2060 elderly subjects (mean age 78.5 +/- 6.8 SD years), sporadic cerebral amyloid angiopathy (CAA) of various degrees was detected in 73.2% and in 98.5% of autopsy-confirmed cases of typical (plaque and tangle) Alzheimer disease (AD). Spontaneous (non-traumatic) intracerebral hemorrhages (ICH) (excluding microbleeds) were seen in 5.6% of the total cohort and in 7.2% of definite AD cases; CAA was found in 49% of brains without and in 48.7% with ICH which was not significantly different. The latter groups showed a significantly higher frequency of severe degrees of CAA than those without ICH (80.4 vs 30.9%, p < 0.001). Patients with CAA were older than those without CAA, showing a higher frequency of clinical dementia and pathologically confirmed AD, but signs of hypertension (history and/or autopsy) were seen in 41 and 33.6% of these cases, respectively, compared to 70-75% in patients with non-CAA related ICHs. CAA-related ICH much more frequently involved cerebral lobes or hemispheres, while non-CAA related lesions were more often located in basal ganglia and brainstem. The data of a lower prevalence of CAA in cases without than with ICH, but a similar prevalence of ICH with and without CAA do not support the concept that CAA represents the most evident risk factor for ICH in the aged. While severe degrees of CAA were indeed associated with ICH, the general prevalence of large ICH in this autopsy cohort was much higher in cases without CAA, probably due to other risk factors including hypertension, which was documented in around 40% of cases with CAA-related ICH. APOE epsilon3/4 and epsilon4/4 were significantly more frequent in AD (n = 163) than in age-matched controls (n = 47) and were associated with more severe degrees of CAA, but no general genotyping in ICHs with and without CAA was performed. Hence, the role of APOE in the pathogenesis of ICH with and without CAA needs further elucidation.