Paraclinoid Carotid Aneurysms: Surgical Management, Complications, and Outcome Based on a New Classification Scheme

Abstract

The site of origin, projection, and relationship of aneurysms arising from the ophthalmic segment of the internal carotid artery (ICA) to adjacent structures are heterogeneous. Based on a retrospective analysis of 61 patients with aneurysms in this location, we developed a simple numerical classification system to guide surgical planning. We used angiographic findings to categorize the aneurysms. We followed the nomenclature of the carotid segments by Bouthillier et al (Neurosurgery 1996;38:425-432), C4 being the intracavernous ICA, C5 the clinoidal segment, and C6 the ophthalmic segment of the ICA. The aneurysms were divided into four major types: Types Ia and Ib projected superiorly and arose from the dorsal surface of C6. Type Ia was related to the ophthalmic artery. Type Ib aneurysms were sessile and had no branch relations. Type II aneurysms were related to the ventral wall of the C6 segment without any branch relation. Type IIIa variant arose from medial wall of the C6 segment and was related to the superior hypophyseal artery. Type IIIb arose from the medial wall of the C5 segment below the dural reflection without any branch relation. Large type IV aneurysms arose from the C5 and C6 segments, widening the distal dural ring. Patients' postoperative status and visual and overall outcomes were analyzed. Ultimately, this classification helped us to plan operative approaches and clip selection.

Figures

Figure 1

Types Ia and Ib variants arise from the dorsal surface of the C6 segment of the carotid artery seen here on a lateral projection. Type Ia aneurysms are closely related to the ophthalmic artery (OA) origin. Type Ib aneurysms have no branch relation and are often sessile. Type II variants arise from the ventral surface of the C6 segment without any branch relation. Type III aneurysms project medially.

Figure 2

Anteroposterior view of the carotid arteries. Types IIIa and IIIb aneurysms (supra– and infradiaphragmatic types) are closely related to the superior hypophyseal artery (SHA) origin. They arise on the medial surface of C5 and C6 segments. DS, diaphragma sella.

Figure 3

Type IV aneurysms are large broad–based aneurysms extending from the distal C4 segment to the proximal C6 segment. They widen the distal dural ring.

Figure 4

Typical angiographic pictures of each type of aneurysm. Types I (A), II (B), and IV (D) are best visualized on lateral angiographic projections and type III (C) on anteroposterior projections.

Figure 5

Diagrams illustrating the type of clip used to treat each type of aneurysm.