Treatment of Large and Giant Intracranial Aneurysms with Onyx. Preliminary Findings

Abstract

Large and giant aneurysms account for three to seven per cent of intracranial aneurysms. They are mainly located in the carotid siphon or vertebrobasilar junction and usually give rise to mass effect, headache, haemorrhage or ischaemia. Treatment consists of surgical clipping or endovascular embolization and aims to exclude the aneurysm from the cerebral circulation to prevent haemorrhage. We describe our preliminary clinical and angiographic findings after endovascular embolization of large and giant intracranial aneurysms using Onyx and the remodelling technique. Six patients with large or giant intracranial aneurysms were treated. The maximum diameter of the aneurysmal sac varied from 15 to 33 mm, the neck measured from 5 to 10 mm and the sac-neck ratio varied from 2.14 a 4.7. Treatment (planned sessions in five patients and one in emergency) was performed in the angiography suite after detailed angiographic diagnosis including 3D formatting of the area of interest. Informed consent was obtained from the patients and their relatives. Intracranial compensation was tested angiographically and clinically before treatment. The polymer (Onyx HD 500 – 20% EVOH; 80% DMSO) was selectively injected into the lumen of the aneurysmal sac during balloon catheter occlusion of the aneurysm neck and parent vessel. Clinical and angiographic follow-up varied from three to 12 months and all patients were assessed angiographically 12 months after treatment. Complete occlusion was achieved after treatment in two aneurysms, both treated by Onyx alone. Occlusion was between 95 and 100% in two patients (one treated with Onyx alone, the other with GDCs + Onyx). Occlusion was more than 90% and less than 95% in one patient (GDCs + Onyx). Occlusion was less than 90% in the remaining patient treated with GDC + Onyx. In the four aneurysms not completely occluded, the residual part involved the neck region. Only one complication arose during treatment consisting of controlateral hemiparesis at the site of the aneurysm due to thrombus occlusion of the middle cerebral artery trifurcation, with full recovery of neurological deficit a month after treatment. Angiographic follow-up disclosed findings the same as those at the end of treatment in three patients whereas the residual aneurysm had increased by 5% in one patient. Two giant aneurysms showed a major recanalization of the aneurysmal sac. At clinical follow-up three patients reported a progressive reduction of ocular symptoms caused by compression: symptoms had slightly improved in one patient after treatment and in the remaining two with aneurysm recanalization diplopia and palpebral ptosis remained unchanged. All patients treated reported a mild progressive reduction of headache except for the patient presenting recanalization at follow-up after ten months. No major complications were found at follow-up. We plan to reserve this procedure for selected cases of large aneurysms not amenable to other treatments. Embolization should always be undertaken by physicians skilled in the remodelling technique and complete embolization of the aneurysm is crucial. The availability of new materials, easier to handle and more viscous and adhesive than Onyx, will simplify the procedure and prevent aneurysm recanalization.