De novo aneurysm formation and aneurysm growth following therapeutic carotid occlusion for intracranial internal carotid artery (ICA) aneurysms.

We herein report the long term results of 27 intracranial internal carotid artery (ICA) aneurysms treated by indirect surgery such as a trapping of the aneurysm or carotid ligation either with or without EC-IC bypass. These patients were then followed for a mean period of 10 years. Seventy-four percent of the aneurysms were categorized as either being giant or large. Late complications were observed in 7 patients. A rupture of newly formed aneurysms at the anterior communicating artery occurred in 2 cases 8 or 9 years after either trapping or performing a ICA ligation, respectively. In these patients, previous angiography could not reveal any abnormalities at the anterior communicating artery. A rupture of a contralateral ICA aneurysm was seen in a patient whose ipsilateral ICA was ligated for a ICA aneurysm 22 years previously. An enlargement of the contralateral giant cavernous ICA aneurysm became symptomatic 6 years after a partial ligation of the ICA combined with an EC-IC bypass for a giant cavernous carotid artery aneurysm on the other side. Two cases of sudden death occurred in a young patient and an elderly patient with a small anterior communicating artery aneurysm, 9 and 19 years respectively, after trapping of the ICA aneurysms, although the cause could not be definitely ascertained. Rebleeding occurred in one patient who died 8 years after a carotid ligation and a partial clipping of the ICA aneurysm. Haemodynamic stress may therefore play a major role in inducing new aneurysms or growing aneurysms.(ABSTRACT TRUNCATED AT 250 WORDS)