Continued Concern About Parent Vessel Steno-Occlusive Progression With Onyx HD-500 and the Utility of Quantitative Magnetic Resonance Imaging in Serial Assessment

BACKGROUND: Onyx HD-500 is a liquid embolic used to treat intracranial aneurysms. OBJECTIVE: To determine the incidence of parent vessel stenosis and the management strategy for these patients. METHODS: Medical records of patients treated with Onyx HD-500 between 2008 and 2011 were retrospectively reviewed. Clinical and radiographic evaluations were assessed. Quantitative magnetic resonance angiography and NOVA (VasSol, Chicago, Illinois) images were reviewed for patients in whom these examinations were acquired. RESULTS: Seventeen patients underwent treatment of unruptured internal carotid artery aneurysms. Three patients (17.6%) developed visual symptoms after the procedure: 2 permanent and 1 transient. Four patients (23.5%) developed delayed internal carotid artery stenosis at the 6- to 8-month follow-up angiography, despite a standard antiplatelet regimen with confirmed sensitivities to aspirin and clopidogrel. Quantitative magnetic resonance angiography was obtained in all patients with stenosis to guide treatment. One patient progressed to complete but asymptomatic internal carotid artery occlusion. The second and third patients had asymptomatic stenosis of 40% and 70%, respectively, both of which resolved on follow-up angiography. The fourth patient developed critical stenosis distal to the aneurysm neck. Quantitative magnetic resonance angiography demonstrated adequate flow in the first 3 patients and decreased flow in the fourth patient, necessitating angioplasty and stenting. Prolonged dual antiplatelet regimens were continued in 2 of the 4 patients, 1 with progression of stenosis and 1 with improvement of stenosis. CONCLUSION: We observed a higher rate of parent vessel steno-occlusive progression after aneurysm embolization with Onyx HD-500 than reported in the literature, despite overall low morbidity. Quantitative vessel flow imaging was useful in subsequent medical management and decision making to perform therapeutic angioplasty/stenting to preserve flow.