[Aneurysm growth and enlargement of pre-aneurysmal lesions].

Three patients with cerebral aneurysms newly growing and enlarging for 2 to 10 years are reported. Case 1, a 54-year-old woman, had subarachnoid hemorrhage due to rupture of an intracranial aneurysm, growing from a small residual aneurysmal neck on the left internal carotid artery 10 years after the repair of the aneurysm. Case 2, a 63-year-old man, had a junctional dilatation on the left internal carotid-posterior communicating artery, developing into ruptured aneurysm about 10 years after the first hemorrhage. Case 3, a 52-year-old man, had multiple aneurysms on the bilateral bifurcations of middle cerebral arteries and left anterior cerebral artery-frontopolar artery junction. Angiography 2 years after the repair of the aneurysms revealed the new growth of a small aneurysm on the anterior cerebral artery at the junction of the fronto-orbital artery, developing from a localized vascular dilatation which had been recognized by the preoperative angiography. The existence of pre-aneurysmal lesions in arterial wall and the addition of hemodynamic impingement were thought to be one of the precipitating factors of aneurysmal formation. The pre-aneurysmal lesions in our study are as follows; a small part of thin wall of residual aneurysmal neck, a junctional dilatation, and a small evagination of arterial wall. It is necessary to discriminate a junctional dilatation and a small evagination of arterial wall from a small aneurysm with observation from multiple directions by the preoperative angiographic study. Our observations suggest that preaneurysmal lesions of the cerebral artery may develop into aneurysm and rupture, and hence the follow-up angiography is recommended for the cases with a preaneurysmal lesion or a small aneurysm for many years.