Saccular intracranial aneurysm disease: distribution of site, size, and age suggests different etiologies for aneurysm formation and rupture in 316 familial and 1454 sporadic eastern Finnish patients.

OBJECTIVE: Finnish saccular intracranial aneurysm (sIA) disease associates to 2q33, 8q11, and 9p21 loci and links to 19q13, Xp22, and kallikrein cluster in sIA families. Detailed pheno t yping of familial and sporadic slA disease is required for fine mapping of the Finnish slA disease. METHODS: Eastern Finland, which is particularly isolated genetically, is served by Kuopio University Hospital's Department of Neurosurgery. We studied the site and size distribution of unruptured and ruptured slAs in correlation to age and sex in 316 familial and 1454 sporadic slA patients on first admission from 1993 to 2007. RESULTS: The familial and sporadic aneurysmic subarachnoid hemorrhage patients had slightly different median ages (46 vs 51 years in men; 50 vs 57 years in women), different proportion of males (50% vs 42%), equal median diameter of ruptured slAs (7 mm vs 7 mm) with no correlation to age, and equally unruptured sIAs (30% vs 28%). The unruptured sIAs were most frequent at the middle cerebral artery (MCA) bifurcation (44% vs 39%) and the anterior communicating artery (12% vs 13%), in contrast to the ruptured slAs at the anterior communicating artery (37% vs 29%) and MCA bifurcation (29% vs 29%). The size of unruptured slAs increased by age in the sporadic group. CONCLUSION: The MCA bifurcation was most prone to develop unruptured slAs, *suggesting that MCA branching during the embryonic period might be involved. The different site distribution of ruptured and unruptured slAs suggests different etiologies for sIA formation and rupture.The lack of correlation of size and age at rupture (exposure to risk factors) suggests that the size at rupture is more dependent on hemodynamic stress.