Incidence and Prognosis of Acute Convexity Subarachnoid Hemorrhage in Sporadic Cerebral Amyloid Angiopathy: A Population-Based Study

BACKGROUND: Cerebral amyloid angiopathy (CAA) is a common cause of acute convexity subarachnoid hemorrhage (cSAH). We aimed to report the incidence and prognosis of cSAH secondary to CAA in a population-based cohort. METHODS: The Normandy Stroke Study prospectively identified people with SAH in Caen Normandy Metropole (France). This analysis included participants with a first-ever cSAH that met the Boston 2.0 criteria for probable CAA and occurred between May 15, 2017, and December 31, 2023. The incidence of cSAH secondary to CAA was determined in individuals aged ≥50 years after standardization to the 2013 European population. The cumulative risk of subsequent intracerebral hemorrhage was calculated with death as a competing event. RESULTS: Among 193 participants with a first-ever SAH, 27 (14.0%) had a cSAH, and 18 (9.3%) met the Boston 2.0 criteria for probable CAA (mean age 79 years, 66.7% women). Among these, 17 (94.4%) were aged ≥70 years, and 16 (88.9%) presented with transient neurological symptoms. The standardized incidence of cSAH secondary to CAA was 1.7 per 100 000 person-years (95% CI, 1.0–2.7) at ages ≥50 years. Three-year cumulative risks were 30.0% (95% CI, 10.2–53.0) for intracerebral hemorrhage and 21.8% (95% CI, 0.0–41.2) for death. CONCLUSIONS: Acute cSAH secondary to CAA remains a rare event at the population level. The high risk of intracerebral hemorrhage during follow-up underscores the importance of accurately identifying cSAH, particularly in people aged ≥70 years presenting with transient neurological symptoms.