Higher risk of intracranial aneurysms and subarachnoid haemorrhage in siblings of families with intracranial aneurysms.

We studied 154 families with 1,105 first-degree relatives of whom 146 had aneurysmalsubarachnoid hemorrhage. Unruptured intracranial aneurysms were identified in 63 (19%) of the 326 screened relatives. Siblings had a higher risk of aneurysmal subarachnoid hemorrhage (RR:1.62, 95% CI:1.12-2.38) and parents a lower risk (RR:0.44, 95% CI:0.24-0.81) than children. Siblings also had a higher risk of unruptured intracranial aneurysms (RR:2.28, 95% CI:1.23-4.07, age-adjusted RR:2.04, 95% CI:1.07-3.92) than children.Conclusion: Siblings of patients with aneurysmal subarachnoid hemorrhage have a significanthigher risk of both unruptured intracranial aneurysms and aneurysmal subarachnoid hemorrhage and parents have a lower risk of aneurysmal subarachnoid hemorrhage than children. Discussion: Type of kinship is a relevant factor to consider in risk prediction and screening advice in families with familial aneurysmal subarachnoid hemorrhage.