Spontaneous occlusion of supraclinoid aneurysms after the creation of extra-intracranial bypasses using long grafts: Report of two cases

OBJECTIVE: We describe two cases of giant supraclinoid aneurysms, treated b y means of saphenous vein grafting between the external carotid artery and the middle cerebral artery, which unexpectedly spontaneously occluded. CLINICAL PRESENTATION: Two patients presented with subarachnoid hemorrhage and headache, respectively. In the first case, angiography showed an aneury sm of the right internal carotid artery (ICA), which had been treated by cl ipping. Repeat angiography showed a giant aneurysm of the right ICA, the fo rmation of which was probably caused by sliding of the clip that had been a pplied during the previous operation. The patient was operated on again, bu t it was impossible to exclude the aneurysm because no clear neck could be identified. In the second case, magnetic resonance imaging and cerebral ang iography showed a large, partially thrombosed aneurysm of the supraclinoid segment of the left ICA. TECHNIQUE: In view of the patients' ages and the statuses of compensatory c irculation, each patient underwent cerebral revascularization with a long s aphenous vein graft placed between one branch of the middle cerebral artery and the external carotid artery, in anticipation of subsequent endovascula r treatment of the aneurysm and/or closure of the ICA in the neck. Postoper ative angiography demonstrated spontaneous occlusion of the aneurysms. CONCLUSION: Thrombosis of an aneurysm may occur spontaneously or after expl orative surgery. However, it should be remembered that spontaneous occlusio n of an aneurysm may be induced or favored by hemodynamic vascular alterati ons that take place inside the aneurysm after a high-flow extra-intracrania l bypass has been created.