Familial intracranial aneurysms.

The authors report seven individuals from two families, all of whom had aneurysmal subarachnoid hemorrhage. These cases and all reported cases of familial aneurysms (243 aneurysms in 177 patients from 74 families) were submitted to computer-aided multivariate analysis to determine if the aneurysms or the patients who harbor them differ from sporadic aneurysm cases. Familial aneurysms rupture at a smaller size (mean diameter 10.5 mm), and when the patient is younger (mean age 42.3 years and decennial age at peak incidence 40 to 49 years). There is a similar sex distribution (male to female ratio 48:52), a similar incidence of multiple aneurysms (21.5%), and a similar predominance of females over males with multiple aneurysms (2.2:1). Anterior communicating artery aneurysms occur less often in familial cases (19%) than in sporadic cases. In sibling pairs the aneurysms occur at the same or at mirror sites, and rupture within the same decade twice as frequently as randomly selected nonfamilial aneurysm patient pairs. The occurrence of aneurysms at identical and mirror sites is more frequent in familial cases and appears to be a function of the degree of kinship between affected individuals. These observations suggest a genetic basis for the pathogenesis of familial intracranial aneurysms.