Familial aneurysmal subarachnoid hemorrhage: a community-based study

Area of Science:

• Neurology
• Epidemiology
• Genetics

Background:

• Familial occurrence of intracranial aneurysms is documented but often involves few affected individuals.
• The aggregation of intracranial aneurysms within families may be coincidental due to their prevalence.
• Previous studies have not definitively established a significant familial risk for aneurysmal subarachnoid hemorrhage (SAH).

Purpose of the Study:

• To investigate the familial occurrence of aneurysmal subarachnoid hemorrhage (SAH) within a defined community.
• To determine if family members of patients with ruptured aneurysms have an elevated risk of developing SAH.
• To assess whether the observed familial aggregation of aneurysmal SAH is statistically significant or due to chance.

Main Methods:

• Retrospective cohort study identifying all patients with aneurysmal SAH in Rochester, Minnesota (1970-1989).
• Family histories were obtained from index patients or their relatives to identify affected first- and second-degree relatives.
• Observed SAH incidence in first-degree relatives was compared to expected rates based on community-specific age- and sex-adjusted incidence data.

Main Results:

• Fifteen percent of index patients reported a first- or second-degree relative with aneurysmal SAH.
• Eleven cases of aneurysmal SAH were observed among first-degree relatives, compared to an expected 2.66 cases.
• A significantly increased relative risk of 4.14 (95% CI 2.06-7.40, p < 0.001) for aneurysmal SAH was found in first-degree relatives.

Conclusions:

• Aneurysmal subarachnoid hemorrhage (SAH) demonstrates significant familial aggregation, occurring in approximately one in five patients in this community.
• The familial clustering of aneurysmal SAH is not fortuitous and represents a genuine increased risk.
• First-degree relatives of individuals with aneurysmal SAH exhibit approximately a fourfold higher risk of developing the condition.