Microsurgical management of large and giant paraclinoid aneurysms

Abstract

Background

Because of the complex topographic anatomical relationship between vascular, dural and bone structures, paraclinoid aneurysms, especially those of larger size, remain a great challenge for vascular neurosurgeons. We present our microneurosurgical experience of 51 consecutive patients with large and giant paraclinoid aneurysms to scrutinize our personal strategies related to surgical treatment.

Methods

Fifty-one patients with large or giant paraclinoid underwent micorneurosurgical aneurysm treatment. Operative strategies were planned according to preoperative state-of-the-art imaging studies, and a pterional-transsylvian approach was routinely used. Proximal control of the internal carotid artery (ICA) was achieved by exposure of the cervical portion of the vessel. Intraoperative electroencephalogram and somatosensory evoked potential monitoring, indocyanine green (ICG) videoangiography and/or microvascular Doppler ultrasonography (MDU) were regularly used. A postoperative digital subtraction angiography or computed tomography angiography was performed to verify the efficacy of treatment.

Results

Forty-three large and giant paraclinoid aneurysm necks (84%) were directly clipped, seven unclippable aneurysms (14%) were trapped with extra-intracranial high-flow revascularization, and one aneurysm (2%) was treated with only ICA proximal Hunterian ligation. Two patients (4%) died in the early postoperative period. In 84% of the patients, the Glasgow Outcome Scale score was 4 or 5 at discharge. At the 6-month follow-up examination, the Rankin Outcome Scale score was 0-2 in 90% of patients.

Conclusions

Temporary parent vessel occlusion, retrograde suction decompression, endoaneurysmectomy, parent vessel clip reconstruction, and bypass vascular anastomosis are essential techniques to treat complex paraclinoid aneurysms. The combined use of electrophysiological monitoring, MDU, intraoperative ICG videoangiography, and endoscopy can substantially improve microsurgical outcome.

Introduction

Paraclinoid aneurysms originate from the segment of internal carotid artery (ICA) between the proximal dural ring and the origin of the posterior communicating artery (PcomA) [16], [17], [19]. They are classified into the following five subtypes according to Sundt: transitional segment aneurysm, carotid cave aneurysm, ophthalmic-carotid segment aneurysm, superior hypophyseal-carotid segment aneurysm, and posterior carotid wall aneurysm [1], [10], [23]. Morbidity and mortality rates related to the treatment of these lesions have improved dramatically because of increased knowledge of the surgical anatomy of this region and refined skull base techniques.

Several surgical landmarks of the paraclinoid aneurysms may define the distal dural ring of the ICA. Many authors have studied the anatomical location of the ophthalmic artery of the proximal and distal dural ring. Punt [27] advocated that the anatomical location of the origin of the ophthalmic artery in digital subtraction angiography (DSA) be regarded as a surgical landmark of the dural ring. Taptas [33], in turn, suggested that the anterior clinoid process (ACP) could be the surgical landmark of the dural ring. However, because there are some variants in ACP and ophthalmic artery origin and also because the volume of the ACP is large, neither is a reliable surgical landmark. Murayama [21] believed that the distal dural ring has an impression in the ICA, which was demonstrated in computed tomography angiography (CTA) [3], [14], but when atherosclerosis and calcification of the ICA are severe, there is some interference. However, Hashimoto [11] and Gonzalez [9] indicated that the optic strut, which could be viewed in CTA, is a reliable surgical landmark because of its small volume and its relative constant anatomical location near the proximal dural ring.

Paraclinoid aneurysms arise at the clinoid and ophthalmic segment of the ICA [6], [16]. Because of the complex topographical anatomical relationship between neurovascular dural structures and bone structures, the treatment of paraclinoid aneurysms remains a great challenge for vascular neurosurgeons [7], [10], [31]. The base of these aneurysms is partially or even totally buried in the skull base, and without special tricks, treating these aneurysms, especially those of large or giant size, is formidable. Although endovascular techniques have improved, large and giant aneurysms at this site are often incompletely treated (because of the broad neck) or can recur (recanalization, aneurysm regrowth), even after the best endovascular treatment [35]. Consequently, open microsurgery remains the best definitive treatment for large and giant paraclinoid aneurysms when appropriate microsurgical techniques/equipment and experience are available. If direct microsurgery is unfeasible, trapping with or without a bypass procedure, depending on the collateral blood flow, should be considered [4], [20], [32]. We present our consecutive microsurgical series of 51 large and giant paraclinoid aneurysms treated in the same institution by the same neurosurgical group over a 10-year period, from May 1998 to August 2007.