SPECIAL FEATURES OF FAMILIAL INTRACRANIAL ANEURYSMS - REPORT OF 215 FAMILIAL ANEURYSMS

FAMILIAL INTRACRANIAL ANEURYSMS (FIAs) were compared with nonfamilial aneurysms (non-FIAs); the study group from east Finland included 167 f amily members from 85 families with FIAs. In every family, there has b een two or more proven cases of subarachnoid hemorrhages among first-d egree family members. Two-hundred and fifteen FIAs were found. The pat ients with FIAs were younger, and their aneurysms were smaller. Half o f the FIAs were on the middle cerebral artery (n = 106 of 215), prefer entially on the right side. Nearly one-third of the ruptured FIAs were smaller than 6 mm, and more than 80% of the aneurysms were under 14 m m in diameter. There were no significant differences between the frequ ency of aneurysms at mirror sites in FIA and non-FIA groups. Among sib lings with FIAs, the frequency of pairs with age at onset within 10 ye ars of each other was more than twice that expected from randomly sele cted pairs in the non-FIA group.