Long-term Outcomes of Parent Artery Occlusion for Giant and Large Intracranial Carotid Artery Aneurysms: Coexistent Aneurysm Enlargement and De Novo Aneurysm Formation

Background: Parent artery occlusion (PAO) is used to treat giant or large unruptured intracranial carotid artery aneurysms. Although PAO effectively cures aneurysms, long-term follow-up studies have demonstrated subsequent coexistent aneurysm enlargement and de novo aneurysm formation. This retrospective study examined the long-term outcomes of coexistent aneurysm enlargement and de novo aneurysm formation in patients treated with PAO using endovascular internal trapping.Methods: We included patients with giant or large unruptured intracranial carotid artery aneurysms treated with PAO using endovascular internal trapping between January 2002 and March 2015 who were followed up for more than 12 months using magnetic resonance angiography or digital subtraction angiography.Results: Thirty patients were included (median age, 64 years [interquartile range [IQR], 57–70 years], 93% women). The median time to diagnosis was 130 months (IQR, 94–163 months). The median maximum diameter of the aneurysms treated with PAO was 25 mm (IQR, 20–32 mm). Seven patients had nine coexistent aneurysms, including two with enlargement. Additionally, two de novo aneurysms were identified. Enlarged coexistent aneurysms were detected in the posterior communicating and cavernous segments of the contralateral internal carotid artery at 14 and 110 months post-PAO, respectively. Two de novo aneurysms were detected at the paraclinoid segment of the contralateral internal carotid artery and ipsilateral posterior cerebral artery at 50 and 91 months post-PAO, respectively. Four patients with enlarged coexistent or de novo aneurysms were significantly younger at the time of PAO (44 vs. 66 years, p=0.01).Conclusions: Younger age is a risk factor for coexistent aneurysm enlargement or de novo aneurysm formation post-PAO. Therefore, careful follow-up is necessary, especially in younger patients.