De novo aneurysm formation after carotid artery occlusion for cerebral aneurysms.

Therapeutic parent artery occlusion has been routinely utilized for management of some intracranial aneurysms. One possible long-term complication of this procedure is "de novo" formation of aneurysms. The purpose of this paper is to estimate the incidence of de novo aneurysm formation, the time period between occlusion and formation, and the most common sites of formation. A PubMed search was performed for all articles between 1970 and 2008 reporting cases of both therapeutic carotid occlusion and de novo cerebral aneurysms. The 20 papers reviewed reported 187 patients having undergone therapeutic carotid occlusion. Of the 163 patients reported in complete-case series, seven developed new aneurysms (4.3%). Thirty-six total new aneurysms were reported, ranging from 1 to 5 per patient. The average time period between occlusion and detection of de novo aneurysm was 9.1 years (range: 2 to 20 years). These aneurysms occurred mostly in the anterior circulation, predominately the anterior communicating artery and posterior communicating artery, and frequently occurred contralateral to the site of occlusion. Therapeutic parent artery occlusion is a likely risk factor for de novo aneurysm formation. Noninvasive follow-up studies should be performed, especially between 2 and 10 years after occlusion.