Dissection Of The Submandibular Fossa

Removal of the submental and submandibular lymph nodes (area I) comes next. From a technical standpoint, this maneuver may be accomplished without removing the submandibular gland. In fact, preservation of the submandibular gland was originally described by Osvaldo Suarez as one of the advantages of the functional approach to the neck. However, the surgical treatment of most primary tumors that require the inclusion of level I as part of the dissection also requires the removal of the submandibular gland. On the other hand, those tumors in which the submandib-ular gland may be preserved without compromising the oncological safety of the operation, such as cancer of the larynx, hypopharynx, or thyroid gland, usually do not require the dissection of level I. Thus, to avoid centering the controversy where it is less necessary, the following description will present the surgical details of submandibular and submental lymph node removal (area I) including the resection of the submandibular gland (for technical details concerning submandib-ular gland preservation see Chapter 5).

Dissection of the submandibular and submental triangle starts with a fascial incision along the upper boundary of the surgical field, from the midline to the tail of the parotid gland (Fig. 4-17). Before reaching the deep plane, the anterior jugular vein must be ligated and divided. The fascia is then incised at the submental area and the tissue in the submental region is dissected inferiorly. The incision is continued posteriorly 1 cm below and parallel to the lower border of the mandible to avoid injuring the marginal mandibular branch of the facial nerve.

The marginal nerve runs superficially in the submandibular gland fascia (Fig. 4-18). Most of the times its identification is tedious and unnecessary. Safe preservation of this branch of the facial nerve may be accomplished by using the facial vein as a landmark. This maneuver begins with the identification of the facial vein at the lower border of the submandibular gland (Fig. 4-19A). The vein is then ligated and divided (Fig. 4-19B). The distal ligature is left long, with a hemostat attached, so that it can be reflected superiorly over the body of the mandible (Fig. 4-19C). As the

Figure 4-17 The fascia has been incised along the upper boundary of the surgical field and retracted inferiorly (right side). sf, superior skin flap; ml, midline of the neck; F, Fascia retracted inferiorly; SC, sternocleidomastoid muscle; SG, submandibular gland; fv, facial vein.
Figure 4-18 Marginal mandibular branch of the facial nerve on the right side of the neck. mn, marginal nerve; fv, facial vein; fa, facial artery.

fascia and the distal stump of the anterior facial vein are retracted superiorly, the marginal mandibular branch of the facial nerve is taken away from the dissection that follows.

The dissection is then continued over the anterior border of the submandibular gland. The posterior border of the mylohyoid muscle is dissected free from the submandibular gland and retracted anteriorly. The dissection continues along the superior border of the submandibular gland to identify the facial artery which may go superficial to, trough, or even posterior to the submandibular gland. The artery is ligated and divided, thus freeing the superior border of the gland. When the facial artery goes superficial to the submandibular gland it may be dissected from the submandibular gland and preserved (Fig. 4-20). At the anterosuperior border of the gland, the lingual nerve must be identified. This is accomplished by retracting the mylohyoid muscle medially and the submandibular gland in a posteroinferior direction. In so doing, the subman-

Figure 4-19 Surgical maneuver to preserve the marginal nerve on the right side of the neck. (A) The facial vein is identified immediately below the submandibular gland. (B) The vein is ligated and divided. (C) The distal ligature is left long and reflected superiorly. SG, submandibular gland; fv, facial vein; SC, sternocleidomastoid muscle; dl, distal ligature reflected superiorly.

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Figure 4-19 Surgical maneuver to preserve the marginal nerve on the right side of the neck. (A) The facial vein is identified immediately below the submandibular gland. (B) The vein is ligated and divided. (C) The distal ligature is left long and reflected superiorly. SG, submandibular gland; fv, facial vein; SC, sternocleidomastoid muscle; dl, distal ligature reflected superiorly.

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Figure 4-19 (continued)

dibular ganglion and its accompanying vein will bring the lingual nerve into the field (Fig. 4-21). The submandibular duct is identified inferior to the lingual nerve. A hemostat is placed across the submandibular ganglion and vein, and both structures are ligated and divided. This frees the lingual nerve, which retracts superiorly, out of the field. After it has been ligated and divided, the gland is retracted inferiorly to identify the genioglossus and hyoglossal muscles. The dissection is continued inferiorly on the medial side of the submandibular gland to identify the digastric muscle and the proximal end of the facial artery. If it was not previously preserved, the artery is ligated again immediately above the digastric muscle. The hypoglossal nerve is identified coursing in an

Figure 4-20 Facial artery running superficial to the right submandibular gland. SG, submandibular gland; FA, facial artery.
Figure 4-21 Lingual nerve in the submandibular fossa (right side). LN, lingual nerve; SG, submandibular gland; wd, Whartons's duct; gv, submandibular ganglion and accompanying vein.
Figure 4-22 Right submandibular fossa after removal of the submandibular gland. DM, digastric muscle; fa, facial artery; ln, lingual nerve; hn, hypoglossal nerve; S, specimen including the submandibular gland and the lymphatic tissue from the submandibular region.

anterosuperior direction just above and medial to the anterior belly of the digastric muscle. This completely frees the submandibular gland (Fig. 4-22), which is included in the specimen along with the fibrofatty tissue containing the lymph nodes from the submandibular and submental regions (area I).

Figure 4-23 The posterior belly of the digastric muscle leads the forthcoming dissection (right side). it, intermediate tendon of the digastric muscle; dl, distal ligature of the facial vein.

Figure 4-24 Section of the stylomandibular ligament on the right side of the neck. it, intermediate tendon of the digastric muscle; pb, posterior belly of the digastric muscle; sh, stylohyoid muscle; dl, distal ligature of the facial vein; SM, stylomandibular ligament; hn, hypoglossal nerve; lv, lingual vein.

Figure 4-24 Section of the stylomandibular ligament on the right side of the neck. it, intermediate tendon of the digastric muscle; pb, posterior belly of the digastric muscle; sh, stylohyoid muscle; dl, distal ligature of the facial vein; SM, stylomandibular ligament; hn, hypoglossal nerve; lv, lingual vein.

The specimen is reflected inferiorly, and the fascia over the digastric and stylohyoid muscles is incised from the midline to the tail of the parotid gland (Fig. 4-23). Following the posterior belly of the digastric muscle the stylomandibular ligament is transected (Fig. 4-24). At this level, the retromandibular vein, the posterior auricular vein, and the external jugular vein are identified.

Figure 4-25 Hypoglossal nerve in the right submandibular fossa. (A) The hypoglossal nerve is identified underneath the intermediate tendon of the digastric muscle. A lingual vein can be seen crossing superficial to the nerve. (B) The lingual vein has been ligated and the nerve is separated from the lymphatic tissue in the submandibular triangle. hn, hypoglossal nerve; it, intermediate tendon of the digastric muscle; lv, lingual vein crossing the hypoglossal nerve.

Figure 4-25 Hypoglossal nerve in the right submandibular fossa. (A) The hypoglossal nerve is identified underneath the intermediate tendon of the digastric muscle. A lingual vein can be seen crossing superficial to the nerve. (B) The lingual vein has been ligated and the nerve is separated from the lymphatic tissue in the submandibular triangle. hn, hypoglossal nerve; it, intermediate tendon of the digastric muscle; lv, lingual vein crossing the hypoglossal nerve.

They should be ligated and divided according to their anatomical distribution. Depending on the lower extension of the tail of the parotid gland, part of the gland may also be included in the resection. This will facilitate the visualization of the upper jugular nodes (upper part of area II) as well as include in the specimen the infraparotid lymph nodes.

The digastric and stylohyoid muscles are retracted superiorly, exposing the hypoglossal nerve as well as the lingual veins that follow and cross the nerve in this area (Fig. 4-25). The lingual veins should be carefully ligated because they may be a source of troublesome bleeding. When bleeding occurs in this area, bipolar coagulation may be used instead of clamps and ligatures to avoid injury to the hypoglossal nerve.

The dissected tissue is finally pulled inferiorly and dissected free from the subdigastric and upper jugular spaces. At this moment, the specimen includes the submandibular and submental lymph nodes (area I), the uppermost jugular nodes (upper part of area II), and (optionally) the submandibular gland.

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