Incidence of Convexal Subarachnoid Hemorrhage in the Elderly: The Mayo Clinic Study of Aging

Objectives Nontraumatic convexal subarachnoid hemorrhages in the elderly can be a manifestation of cerebral amyloid angiopathy associated with a high risk of future intracerebral hemorrhage. The incidence in the elderly population is unknown. Our objectives were to: 1) determine the incidence of convexal subarachnoid hemorrhage in a population-based study, and, 2) to compare apopolipoprotein-E genotype and amyloid positron emission tomographic (PET) imaging for those with versus without hemorrhage. Methods Between 11/29/2004 and 3/11/2017, 4462 individuals without hemorrhage at baseline participated in the population-based Mayo Clinic Study of Aging. We used the Rochester Epidemiology Project medical records-linkage system to identify intracerebral hemorrhages. Records and images were reviewed to identify convexal subarachnoid hemorrhage. Neuroimaging characteristics, demographics, medications, and apopolipoprotein-E genotype were recorded. Results Four cases were identified. The incidence of convexal subarachnoid hemorrhage was 14.1 per 100,000 person years. Three occurred in women, median age, 79 (range: 71-84). One patient had coexisting cerebral microbleeds. Two participants developed a subsequent lobar intracerebral hemorrhage at a median of 4.75 years after convexal subarachnoid hemorrhage. The apopolipoprotein-E -allele combinations of the 4 were: 3/3, 3/3, 2/2, and 2/3. On Pittsburgh Compound B-PET imaging, median standardized uptake value ratio with convexal subarachnoid hemorrhage was 1.86 (range: 1.38-2.34). Conclusions Convexal subarachnoid hemorrhage is rare in the older population, occurring with an incidence of about 14 per 100,000 person years. Yet, when present, it may be associated with a high risk of future intracerebral hemorrhage.