Development of New Aneurysm and Enlargement of Small Aneurysm

Abstract

The authors reported 7 cases that showed development of new aneurysms or enlargement of small aneurysms originally less than 3 mm in diameter. New aneurysms of the anterior communicating artery and the right pericallosal artery were found in one case. In this patient with a 5 year history of hypertension, cerebral angiography performed 8 years before following a head trauma had revealed marked arteriosclerosis and a hypoplasia of A1, but no aneurysm. Development of an aneurysm from a dilatation at the origin of the right embryonal posterior cerebral artery was found 3 years after the clipping of an aneurysm of the left internal carotid artery in the other case. In 3 cases, a small unruptured aneurysm all originally less than 3 mm in diameter previously noted in conjunction with a ruptured aneurysm were found to have enlarged 3 to 13 years after the clipping of the ruptured aneurysm. In these 3 cases, anomalies of the circle of Willis, such as hypoplasia of unilateral A1, infundibular dilatation at the origin of the posterior communicating artery and the embryonal posterior cerebral artery were revealed. Arteriosclerosis and hypertension were noted in 2 cases. In 2 cases, a small ruptured aneurysm, which had not been recognized at the first subarachnoid hemorrhage, was noted to have enlarged 5 and 10 years after the first bleeding. Changes of the arterial wall due to hypertension, arteriosclerosis, etc., and hemodynamic stress caused by anomalies of the circle of Willis seemed to be responsible for the new development of aneurysm and the enlargement of aneurysm. A small aneurysm less than 3 mm in diameter, including an unruptured aneurysm that is found in association with the ruptured aneurysm, have a high incidence of progressive enlargement and rupture. Therefore, even a small aneurysm should be diagnosed and treated precisely.