Common Cervical and Cerebral Vascular Variants

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Key points

  • Successful open and endovascular carotid artery intervention depends on a thorough foundational knowledge of cervical and intracranial vascular anatomy.

  • Variant vascular anatomy is frequently observed during preprocedural evaluation and endovascular intervention.

  • Alterations in the normal patterns of blood supply to the cerebral vascular territories often occur as a consequence of variant vascular anatomy.

  • Recognition of cervical and intracranial vascular variants, and the corresponding changes in

Normal Anatomy

In approximately 70% of individuals, the innominate artery, left common carotid artery (CCA), and left subclavian arteries arise in sequence from a left-sided arch of the aorta. The innominate artery then branches into the right subclavian artery and the right CCA. The bilateral vertebral arteries arise as proximal branches of their respective subclavian artery.1 A frequently used classification system for the normal aortic arch is based on the relationships of the origins of the great vessels

Anomalies of the common carotid artery

The normal and common variant branching patterns of the paired CCA origins are described in an earlier section. The CCA does not typically have any major branches, except in the presence of common carotid bifurcation variants. In 62% of individuals, the bifurcation of the CCA is near the upper margin of the thyroid cartilage at C3-C4.11 The typical anatomic landmark used during carotid catheterization is the angle of the mandible. However, variation exists, and the bifurcation can be found as

Normal Anatomy

The proximal ECA arises from either the third aortic arch or aortic pouch, with contributions of the distal branches from the first aortic arch. Eight to 9 major branches from the ECA are typically described, and these are named according to their respective territories, without consideration of the site of origin from the ECA.5 Extensive anastomoses for collateral flow exist between ECA branch territories. For this reason, an understanding of the naming system according to vascular territory

Normal Anatomy

The ICA provides the majority of the blood supply to the cerebral hemispheres. The Bouthillier classification is the system most widely used to describe the anatomy of the ICA. This system divides the ICA into 7 segments according to the direction of blood flow and various anatomic boundaries (Fig. 1).19 The cervical segment is formed from the fetal third aortic arch, and the remaining segments are from the cranial extensions of the embryonic dorsal aortas.20

The cervical segment (C1) has 2

Persistent carotid-vertebrobasilar anastomoses

Persistent carotid-basilar and carotid-vertebral anastomoses are relatively rare but potentially clinically relevant anomalies of the cervical and intracranial vasculature (Fig. 3).25 When performing a carotid angiogram, the presence of carotid-vertebrobasilar anastomoses may be suggested by simultaneous filling of the basilar artery, alone or together with the vertebral artery. In a series of 4400 cerebral angiograms studied by Yilmaz and colleagues,26 the incidence of persistent primitive

Normal Anatomy

The normal vertebral artery (VA) can be divided into 4 segments. The V1, or extraosseous, segment arises as the first branch of the subclavian artery and enters into the C6 transverse foramen. The V2, or foraminal, segment ascends through the C6 to C3 transverse foramina, then turns sharply superolaterally through the C2 transverse foramen and ascends through the more laterally positioned C1 transverse foramen. The V3, or extraspinal, segment extends from the top of the C1 transverse foramen to

Normal Anatomy

As described earlier, the ICA ascends through the skull base and is classically divided into 7 segments (see Fig. 1). The C7 communicating segment then divides at the ICA terminus into the M1 segment of the middle cerebral artery (MCA) and A1 segment of the anterior cerebral artery (ACA). The bilateral A1 segments course toward the midline, where the anterior communicating artery (AComm) connects the ACAs and marks the division between the A1 and A2 segments of the ACA.

The intradural V4 segment

Summary

Variant vascular anatomy can have profound implications for cervical and intracranial endovascular intervention. The potential exists for significant morbidity and mortality if there is a failure to recognize these vascular variants. This article provides a foundational knowledge of the common and critical variants that may be encountered, and briefly outlines the implications of these variants for approaches to endovascular therapy.

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  • Cited by (2)

    The authors have nothing to disclose.

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