Atlas of General Surgical Techniques (Courtney M. Townsend Jr., B. Mark Evers)

The SAN is identified in the posterior triangle as it enters the trapezius muscle. A spreading technique using a fine hemostat or Metzenbaum scissors is used to dissect the soft tissue and fascia overlying the nerve. The nerve is traced as it passes from the trapezius muscle to the SCM muscle (Figure 2-10).

The SAN exits the SCM muscle and dissection continues anteriorly and superiorly to the skull base, transecting the overlying muscle with the nerve constantly in view. This divides the SCM muscle in two (Figure 2-11). The posterior belly of the digastric muscle is retracted superiorly for exposure of the nerve and the IJV at the skull base. The relationship of the SAN to the IJV is noted during this dissection.

The nerve is sharply dissected from the underlying tissue. The branch to the SCM muscle must be divided to mobilize the nerve. A nerve hook or vein retractor can be used to retract the nerve as it is being skeletonized to minimize trauma.

Accessory nerve

FIGURE 2–10

Accessory nerve

Trapezius muscle

FIGURE 2–11

The IJV at the skull base is isolated circumferentially from the surrounding tissue so that it can be ligated at a later time.

The sternal and clavicular heads of the SCM muscle are transected one fingerbreadth above the clavicle (Figure 2-12). Upward traction is placed on the muscle with a sponge, and the layers of the muscle are carefully transected so as not to injure the contents of the carotid sheath that lie immediately deep to the muscle.

Once the SCM muscle is divided inferiorly, the posterior belly of the omohyoid muscle is visualized. The tissue overlying the muscle posteriorly is incised (Figure 2-13).

Sternocleidomastoid muscle (clavicular head)

FIGURE 2–12

Sternocleidomastoid

muscle

Carotid sheath

Fascia covering

Omohyoid muscle

Omohyoid muscle (posterior belly)

FIGURE 2–13

The muscle belly itself is transected near its origin at the scapula (Figure 2-14) and elevated anteriorly to its attachment at the hyoid bone. The anterior jugular veins will be encountered at this point and should be ligated. This defines the anterior limit of the neck dissection.

The fascia underlying the posterior belly of the omohyoid muscle is incised horizontally. The supraclavicular fat pad is then opened using blunt dissection exposing the brachial plexus

and phrenic nerve, which lies on the surface of the anterior scalene muscle (Figure 2-15). The dissection should not continue until the brachial plexus and phrenic nerve are identified, because injury to these structures can be catastrophic. The transverse cervical vessels will also be seen in this area. It is not always necessary to divide these vessels.

Sternocleidomastoid

muscle

Omohyoid muscle

FIGURE 2–14

The fibro-fatty tissue between the brachial plexus and the anterior border of the trapezius muscle (supraclavicular fat pad) is clamped and ligated. The brachial plexus must be directly visualized while the clamps are being placed. This tissue can be bluntly dissected using a finger. This area is known as the “bloody gulch,” and bleeding will occur if the tissue is not ligated (Figure 2-16).

Dissection is then carried superiorly along the anterior border of the trapezius muscle until the SAN is encountered. The SAN is retracted anteriorly to avoid injury during this dissection. The SCM muscle is transected just inferior to the mastoid tip, and the fascia is incised at its posterior aspect (Figure 2-17). This allows the specimen to be retracted medially.

Accessory nerve

Phrenic nerve

Brachial plexus

FIGURE 2–16

Incise through fascia

Accessory nerve

Transverse cervical vessels

FIGURE 2–17

The specimen, including the fibro-fatty and lymphatic tissue in level V, as well as the superior aspect of the SCM muscle, is dissected in a posterior to anterior direction. The specimen is passed underneath the SAN, gently retracting the SAN laterally (Figure 2-18).

The deep limit of dissection is the fascia of the deep cervical muscles; the dissection proceeds along the medial aspect of the levator scapulae and the scalene muscles. The rootlets of the cervical plexus are exposed. The cutaneous branches are transected and removed with the specimen. Care must be taken to preserve the nerve supply to the posterior compartment musculature and the contributions to the phrenic nerve. This is done by transecting the cervical rootlets approximately 1 cm anterior to the takeoff of the phrenic nerve, that is, “high” in the specimen. Vessels typically accompany the rootlets and should be controlled using bipolar cautery or suture ligation. In addition, care must be taken to avoid direct injury to the phrenic nerve by lifting it off the anterior scalene muscle with the specimen (Figure 2-19).

Fibro-fatty tissue

Accessory nerve

Phrenic nerve

FIGURE 2–18

Cervical rootlets

Phrenic nerve

FIGURE 2–19

The dissection now proceeds in a cephalad direction in a plane between the IJV and the carotid sheath. The dissection also proceeds medially and superiorly along the anterior belly of the omohyoid muscle. The hypoglossal nerve (located approximately 2 cm superior to the carotid bifurcation) and the descendens hypoglossi branch are visible in the course of dissection. Following the descendens hypoglossi branch superiorly will help in identification of the hypoglossal nerve. Retraction of the posterior belly of the digastric muscle is needed for visualization (Figure 2-22).

The ranine veins lie lateral to the hypoglossal nerve and require ligation to avoid meddlesome bleeding. Ligation of these vessels is done with the hypoglossal nerve under direct visualization to avoid inadvertent injury to and/or transection of the nerve.

The surgical specimen is now pedicled on the upper end of the IJV. The specimen is flipped into its anatomic position, and the IJV is doubly clamped, transected, and ligated using a 2-0 silk tie (Figure 2-23).

Cut ansa hypoglossi

Hypoglossal nerve

FIGURE 2–22

FIGURE 2–23

As seen here, the SCM muscle, IJV, omohyoid muscle, and nodal levels 1-5 have been removed, preserving the SAN (Figure 2-24).

The surgical specimen is removed from the surgical field, and each level of nodal dissection is labeled for the pathologists.

Internal jugular vein

External jugular vein

Lymphatic pedicle

FIGURE 2–24