Exposure of the Carotid Bifurcation

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Chapter 32

Exposure of the Carotid Bifurcation

Jerry Goldstone

Introduction

Carotid endarterectomy is one of the most frequently performed vascular operations. The vast majority of these procedures are for atherosclerosis at the bifurcation of the common carotid artery, which lies within the anterior triangle of the neck, usually at the upper border of the thyroid cartilage (Fig. 32-1, A). The key anatomic boundaries are the sternocleidomastoid muscle, the midline, and the mandible (Fig. 32-1, B).

FIGURE 32–1 Carotid stenosis, incision lines for endarterectomy, and platysma.

Carotid Endarterectomy

The procedure begins with proper positioning of the patient, with the neck extended and turned toward the opposite side. The incision can be made along the anterior border of the sternocleidomastoid muscle (SCM) or transversely (obliquely) in a skin crease overlying the carotid bifurcation (Fig. 32-1, B). The bifurcation can easily be located with duplex ultrasound. The platysma muscle is then divided, exposing the deep cervical fascia (Fig. 32-1, C).

Surgical Principles

The external jugular vein and greater auricular nerve lie in this plane; the vein can be ligated, but the nerve must be preserved to avoid numbness of the ear lobe (Fig. 32-2, A).

FIGURE 32–2 Nerves and fascial layers of neck.

Next, two key steps are necessary to expose the carotid bifurcation. The first is mobilization of the anterior border of the SCM, which is invested within two layers of the deep cervical fascia (Fig. 32-2, B). If a transversely oriented incision is used, this requires creation of subplatysmal flaps, both cephalad and caudad, on the plane of the anterior SCM fascial layer.

The second step, after the SCM is retracted laterally, is mobilization of the internal jugular vein, which lies lateral and anterior to the common carotid artery within the carotid sheath. This sheath is loose, fibroareolar tissue rather than a single, well-defined layer. Mobilization of the internal jugular vein exposes the common carotid artery as well as the vagus nerve, which usually is posterior to the artery but may be anterior, where it is more susceptible to injury.

The ansa cervicalis nerve (also known as ansa hypoglossi) is often seen running along the anterior surface of the common carotid artery (Fig. 32-2, A). This nerve can be divided with impunity, and the cranial end followed to its junction with the hypoglossal nerve. The hypoglossal nerve runs between the internal jugular vein and internal carotid artery and is usually found about 2 cm above the carotid bifurcation. However, its position can vary. Often, small jugular venous tributaries drain the SCM at this level, along with accompanying arteries that must be divided. Extreme care must be taken to avoid bleeding in this location; attempts to control bleeding are a common cause of injury to the hypoglossal nerve.

The largest tributary of the internal jugular vein is the common facial vein, an important landmark that almost always overlays the location of the carotid bifurcation. The facial vein should be carefully mobilized, divided, and suture-ligated. The jugular vein can then be retracted laterally and its position maintained with a self-retaining retractor. Rarely, the hypoglossal nerve is low lying and closely attached to the underside of the facial vein, making it vulnerable to injury when the vein is divided.