Acta Neurochir (Wien)(1997) 139:1026-1032 Acta Neurochirurgica 9 Springer-Verlag1997 Printed in Austria Open Surgery of Giant Paraclinoid Aneurysms Improved by Intraoperative Angiography and Endovascular Retrograde Suction Decompression R. Fahlbusch, Ch. Nimsky, and W. Huk Department of Neurosurgery, University of Erlangen-Ntirnberg, Erlangen, Federal Republic of Germany Summary In three consecutive cases of giant left sided paraclinoid aneurysms we employed an endovascular retrograde suction decompression technique in combination with intra-operative angiography. A double-lumen balloon catheter was placed in the left internal carotid artery by the transfemoral route. After balloon inflation and placement of a temporary clip distal to the aneurysm blood was aspirated and the aneurysm collapsed. Thus further dis- section of the aneurysm could easily be achieved and clips could be placed. Afterwards real-time digital subtraction angiography was performed. Intra-operative angiography led to clip repositioning in all cases either due to a clip induced stenosis of the parent vessel, or because of incomplete aneurysm obliteration. Afterwards success- ful clipping could be confirmed in all cases. Outcome was excellent in one case, good in the other. The third case, extremely complicat- ed by an accompanying craniopharyngioma, showed a satisfactory outcome, but presented new neurological deficits. Keywords: Giant aneurysm; paraclinoid aneurysm; intraopera- tive angiography; endovascular retrograde suction decompression. Introduction Giant aneurysm surgery is accompanied by higher morbidity especially in cases of proximal intracranial carotid artery (paraclinoid) aneurysms which offer no endovascular alternative. These aneurysms, originat- ing at the ophthalmic segment of the carotid artery, defined as the segment between the origins of the ophthalmic and the posterior communicating artery, are given different anatomical terms according to their origin and projection (ophthalmic, para-oph- thalmic, carotid-ophthalmic, ventral paraclinoid, superior-hypophyseal, carotid-cave) [7, 9]. Within the scope of the following contribution we will refer to these aneurysms as paraclinoid aneurysms as done by others [1, 5, 6, 21]. Subarachnoid haemorrhage, ophthalmological impairment, and micro embolism with transient or permanent neurological deficits indicate surgery. Not only the size of the aneurysm and often their very broad neck cause difficulties in the surgical treatment, but especially their location at the extra-/intradural transition of the carotid artery [9, 10] result in addi- tional surgical challenges, because it is difficult to gain proximal control and there is a strong retrograde flow through the ophthalmic artery and cavernous carotid branches [6]. Furthermore visualisation and dissection of the neck of the aneurysm may be very complicated due to the mere size of the aneurysm and due to a sac which often projects directly into the sur- gical approach. Also the closeness to the optic nerve and the oculomotor nerve have to be taken into account. Additionally there is the problem of incom- plete clipping and clip induced stenosis of the parent vessel. In recent years therefore different therapeutic approaches were developed, all of them designed to solve certain aspects of the complex problem. There are the direct attempt to clip or entrap the aneurysm without further additional measures [15, 16, 30] and the traditional carotid occlusion, the so called Hunter- ian occlusion [29], which was later complemented by additional extra-/intracraniat bypass [3, 5, 11, 15, 26, 35]. Interventional techniques such as balloon- and coil-placement [14, 31] can only be useful in certain cases with a narrow neck. Surgery under hypothermia with cardiac arrest presents a very complicated and risky method to achieve collapse of the aneurysm to facilitate clip application [8, 27]. Other methods which also try to reduce aneurysm size by collapse