The Clinical Significance and Characteristic Shape of Ruptured 'Very Small'Cerebral Aneurysms

ABSTRACT

The size of unruptured intracranial aneurysms is an important factor that determines their rupture potential; however, the critical threshold size remains to be established. Some useful informations for determining the threshold size have been provided by the reports on the long-term follow-up of previously diagnosed unruptured aneurysms and clinical or autopsy studies on the size of ruptured aneurysms. Among the ninety-eight patients with ruptured cerebral aneurysms the authors managed during the last 4 years and the size of which were identified neuroradiologically and/or intraoperatively, eight cases(8.2%) had very small (maximum diameter less than 5mm) aneurysms. Their clinical features were not remarkably different from the usual aneurysmal SAH. As for the morphology, all of the eight had thin wall and narrow neck; in five cases the aneurysmsal sac had elongated shape. Several clinical reports on the ultimate rupture of previously diagnosed very small unruptured aneurysms and the formidable incidence of very small ruptured aneurysms in such clinical studies as this suggest that very small aneurysms also have a definite risk of rupture. The clinical significance of the narrow neck and elongated sac of the very small ruptured aneurysms observed in the authors' cases seems to be characteristic enough to deserve further investigation.