Aneurysms of the Ophthalmic (C6) Segment of the Internal Carotid Artery

Abstract

Aneurysms arising from the intradural ophthalmic (C6) segment of the internal carotid artery (ICA) constitute 5% to 11% of all intracranial aneurysms; 25% of these aneurysms are giant, and 50% are multiple. Critical to the successful treatment of these aneurysms is an understanding of the embryologic development, regional anatomy, and radiographic techniques. In part 1 of this review, we discuss theories of Dorcas Hager Padget (neuroembryologist and neurosurgical illustrator) and Pierre Lasjaunias to clarify the complex embryology of this cerebral vasculature and to identify the vascular anomalies of the C6 segment. Next, we provide comprehensive detail of the bone, connective tissue, and vascular structures that are intimately related in the confining space surrounding the distal dural ring (DDR) and anterior clinoid process. The anatomic complexity of the region surrounding the C6 segment of the ICA partly explains the surgical challenge in treating aneurysms of this segment and the relatively high incidence of postoperative complications. We review the radiologic techniques to assess these aneurysms when planning treatment, such as the role of cerebral angiography in providing details about the hemodynamic function of the vessels (eg, collateral circulation pattern, potential recipient vessels for bypass) and the role of the DDR in distinguishing aneurysms of the extradural or intradural segment of the ICA. Although these aneurysms remain challenging, the information reviewed in part 1 helps to understand these aneurysms more clearly in terms of embryology, anatomy, and radiology for successful treatment strategies. Applications of this information are discussed in part 2, in which we review clinical experience and treatment strategies.A neurysms arising from the intradural ophthalmic (C6) segment 1 of the internal carotid artery (ICA) constitute approximately 5% to 11% of all intracranial aneurysms. A significant 25% of these aneurysms are giant, and approximately 50% are multiple. 2-4 These aneurysms are traditionally regarded as challenging lesions because of the anatomical complexity of the region. Aneurysms of the C6 segment arise from the ICA between the distal dural ring (DDR) and the origin of the posterior communicating artery. The term ophthalmic refers to the main branch, the ophthalmic artery, which arises from this segment. Understanding the complex embryology of cerebral vasculature is critical to explain the anatomical variations commonly associated with these vessels. After early embryologic studies, the seminal treatise of Dorcas Hager Padget on ''The development of the cranial arteries in the human embryo'' contributed significantly to the understanding of this embryology 5 but did not address vascular anomalies. Subsequently, Pierre Lasjaunias and his colleagues explained a number of the vascular anomalies in this region (eg, theories of extradural origin of the ophthalmic artery). 6-10 We draw from the theories of Padget and Lasjaunias to clarify the most frequently occurring vascular anoma...

A comparative propensity-adjusted analysis of microsurgical versus endovascular treatment of unruptured ophthalmic artery aneurysms

“…In this study, the risk of new or worse visual deficits was lower than that previously reported in the neurosurgery literature, with less than 7% risk of occurrence in patients who received microsurgical treatment and only 1% risk in patients who received endovascular treatment; in comparison, earlier studies reported a risk of visual complications at long-term follow-up as high as 30% in patients who underwent microsurgical procedures and 6% in patients who underwent endovascular procedures. 4,[13][14][15][16][17][18] Interestingly, the rates of immediately postoperative new or worse visual deficits were similar between the two cohorts in our study, but the visual deficits in endovascularly treated patients appeared to be more transient than the visual deficits in microsurgically treated patients. A potential confounder was that the endovascular cohort had a mean follow-up period of more than 2 years compared with less than 6 months for the microsurgical cohort.…”

“…12 In addition, visual complications are observed in only 3% to 6% of patients who undergo endovascular treatment of OA aneurysms. [13][14][15][16][17][18] In comparison, the visual complication rate after microsurgical treatment is approximately 5%, with rates ranging from as low as 3% to as high as 30% in contemporary studies. 2,4,14,16,[19][20][21][22][23][24][25][26] Thus, controversy remains regarding the optimal treatment modality for OA aneurysms.…”