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).

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.

Anatomic Landmarks

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.