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Address reprint requests and correspondence: Adam Zanation, MD, University of North Carolina, 170 Manning Drive, Campus Box #7070, Chapel Hill, NC 27599.
A variety of pathology commonly affects the salivary glands including both benign and malignant tumors as well as infectious and inflammatory disease. Although newer techniques including sialo-endoscopy are emerging for the treatment of inflammatory and obstructive disorders, excision of the submandibular gland remains the treatment of choice for tumors of the submandibular gland and remains an important option for the treatment of refractory inflammatory disease. Relevant surgical anatomy, perioperative management, surgical technique, and possible complications are discussed.
The submandibular glands along with the parotid glands comprise the 4 paired major salivary glands. Although the submandibular glands are smaller in size than the parotid glands, they actually account for the majority of basal salivary volume production.
The impact of adequate saliva production quality of life should not be underestimated. A vast array of pathology can affect the salivary glands. In accordance with importance, diseases of the salivary glands are common reasons for referral to the otolaryngologist.
Our primary goal herein is to describe the surgical technique of submandibular gland (SMG) removal as would be performed for non-neoplastic disease or small intraglandular benign neoplasms, with the understanding that the extent of surgery may frequently needs to be adjusted based on the presenting pathology. Relevant surgical anatomy, indications, preoperative considerations, postoperative care, and possible complications are also briefly reviewed.
Surgical anatomy
The SMG resides within the submandibular triangle of the neck that is bounded by the inferior border of the mandibular body, as well as, the anterior and posterior bellies of the digastric muscle. The deep aspect of the SMG rests on the hyoglossus muscle. The lingual and hypoglossal nerves also course along the surface of the hyoglossus. The lingual nerve provides parasympathetic innervation to the submandibular gland via the submandibular ganglion. The anterior aspect of the SMG is both deep and superficial to the mylohyoid muscle. These relationships are illustrated in Fig. 1. The superficial layer of the deep cervical fascia invests the SMG creating the fibrous capsule of the gland. The marginal mandibular branch of the facial nerve courses in the superficial layer of the deep cervical fascia, over the surface of the gland and innervates the depressors of the lower lip. The (anterior) facial vein courses over posterior belly of the digastric and the superficial surface of the gland. The facial vein is deep to the superficial layer of the deep cervical fascia and the marginal mandibular nerve. The facial artery is also intimately associated with the submandibular gland. The facial artery enters the submandibular triangle posteriorly from deep to the digastric where it enters the gland (or a trough in its surface) coursing around the gland and exiting near the antegonial notch of the mandible joining the facial vein in its course over the inferior border of the mandible. Overlying the fascia of the gland, from deep to superficial, are the platysma muscle, subcutaneous fat and skin.
Figure 1This illustration demonstrates critical anatomy of the submandibular gland and surrounding structures. Note that the submandibular gland is both superficial and deep to the mylohyoid muscle anteriorly. The hyoglossus muscle represents the floor of the dissection when removing the submandibular gland. The hypoglossal and lingual nerves run on the superficial aspect of the hyoglossus muscle.
Non-neoplastic disease of the submandibular glands generally present with recurrent pain and swelling of the involved gland(s) which is often aggravated by oral intake. Evaluation for Sjögren's and other inflammatory salivary disorders including IgG4, SSA, SSB, and minor salivary gland biopsy should be considered.
Jackson N, Mitchell J, Walvekar R. Inflammatory disorders of the salivary glands. In: Cummings Otolaryngology. Vol 2. 6th ed. 85. Saunders, an imprint of Elsvier Inc.:1223-1237.
A host of infectious processes can affect the salivary glands. Considerations include but are not limited to acute suppurative bacterial sialadenitis, viral infections (human immunodeficiency virus, mumps, and hepatitis), and granulomatous infections (mycobacterial infection and actinomycosis).
Jackson N, Mitchell J, Walvekar R. Inflammatory disorders of the salivary glands. In: Cummings Otolaryngology. Vol 2. 6th ed. 85. Saunders, an imprint of Elsvier Inc.:1223-1237.
Culture, serology, and use of empirical antibiotics should be tailored to the presentation. History of exposure to radiation or radioactive iodine should be elicited. Imaging with ultrasound and or contrasted computed tomography scan is indicated prior to gland excision, to both identify sialoliths and rule out neoplastic processes.
Jackson N, Mitchell J, Walvekar R. Inflammatory disorders of the salivary glands. In: Cummings Otolaryngology. Vol 2. 6th ed. 85. Saunders, an imprint of Elsvier Inc.:1223-1237.
Ductal pathology such as strictures can be visualized with contrast injection sialograms or magnetic resonance sialography. Sialography, however, is becoming less practical as sialoendoscopy is generally both diagnostic and therapeutic for ductal pathology.
For patients with non-neoplastic disease, the impact of a surgical decrease in saliva production with gland removal must be weighed against the symptoms endured managing the gland conservatively. Special caution is warranted in patients with polyglandular conditions such as Sjögren's disease or radioactive iodine sialadenitis as they will not compensate well for a surgical loss of salivary tissue. When significant symptoms persist despite trial of conservative treatment (gland massage, antibiotics, sialogogues, and warm compresses), medical optimization of rheumatologic disorders and gland sparing surgical procedures (sialoendoscopy or transoral stone removal) it is appropriate to consider removal of a diseased submandibular gland.
Neoplastic disease
Tumors of the submandibular gland generally present as a slowly enlarging painless mass. Pain, paresthesia, or weakness of marginal mandibular or hypoglossal nerves are highly suggestive of malignancy. Complete discussion of the evaluation and management of salivary gland tumors and malignancy is out of the scope of this article. An excellent review of the preoperative evaluation of SMG tumors has been recently presented by Atula et al.
Caution should be taken interpreting fine needle aspiration results suggesting benign salivary neoplasm as sensitivity for malignancy can range from 75% to 90% even at experienced centers.
Extraglandular structures involved by malignancy should be removed en bloc with the gland. If malignancy is associated with cervical lymphadenopathy, lymphadenectomy of all involved nodal basins as well as at least levels 1-3 nodes should be performed.
If malignancy is identified, postoperative radiation should be discussed in the context of multidisciplinary tumor board, but is generally indicated for high grade histology, adenoid cystic carcinoma, advanced stage, close or positive margins, perineural invasion, and recurrent disease or lymphatic metastasis.
The patient should be made aware of this possibility preoperatively.
Surgical technique
Positioning and incision planning
The procedure is performed under general anesthesia. We prefer to avoid paralytics to allow monitoring of the marginal mandibular nerve. The patient is positioned supine with a small shoulder roll to extend the neck. The head is turned to the side opposite of the lesion. We typically drape in such a way that the ipsilateral lower lip can be visualized. An adhesive drape can be used to exclude the mouth from the field and maintain visualization. Some surgeons choose to use a facial nerve monitoring system, with a monitoring probe in the ipsilateral lower lip. This is not required, but can be useful especially in conjunction with a nerve stimulator.
The incision is planned to avoid injury to the marginal mandibular nerve and for optimal cosmetic outcome. The incision should at least 2 cm below the inferior border of the mandible and at the expected lower limit of the submandibular gland in a naturally occurring horizontal skin rhytid. Usually 3-4 cm in length is generally adequate. The incision is marked and injected with 1% lidocaine with epinephrine. The incision is incised sharply. The subcuticular fat and platysma are divided as well.
Preserving the marginal mandibular nerve
There are several methods for exposing the SMG while protecting the marginal mandibular nerve. All have different advantages and disadvantages. Typically, a subplatysmal flap is raised superiorly to the inferior border of the mandible using electrocautery or scalpel. It is key to follow the platysma closely as the marginal mandibular nerve is directly subjacent to the platysma muscle. Once this is accomplished, self-retaining retractors can be placed.
The most direct approach is to identify the marginal mandibular nerve in its course through the superficial layer of deep cervical fascia over the SMG. This can be aided by the use of a nerve stimulator and loupe magnification as the nerve can be quite fine in caliber. The nerve is then mobilized superiorly over the mandible after dissecting it from the surrounding connective tissue. An easily identifiable portion of the nerve is usually found crossing the facial vein near inferior border of the mandible. More anteriorly, the nerve (or minor branches of it) can be found anywhere on the surface of the gland, but never below it. The disadvantage of this approach is the risk of damaging the nerve while dissecting along it. In addition, failure to identify the most inferior branch of the nerve may lead to inadvertent partial nerve sacrifice.
Another approach is to after raise a superiorly based deep cervical fascial flap. After the platysma flap is elevated, the digastric muscle is exposed along its course by dividing the overlying fascia. At this time, the facial vein running over the posterior belly of the digastric is ligated at the level of the digastric muscle. The marginal mandibular nerve is always superficial to the facial vein. Next the superficial layer of deep cervical fascia investing the gland (containing the nerve and the facial vein) is mobilized off of the parenchyma of the gland with blunt dissection using Tenotomy scissors. This plane is avascular. This flap is very thin and easy to disrupt. Although at times the nerve is easily seen in the fascial flap, this method is still useful to avoid trauma to the nerve that may occur when dissecting it directly. The fascial flap can then be secured over the mandible with a stay suture to protect the nerve during the remainder of the gland removal. This technique is illustrated in Fig. 2.
Figure 2Elevation of the superficial layer of deep cervical fascia and facial vein off of the superficial surface of the submandibular gland to protect the marginal mandibular nerve. The marginal mandibular nerve is contained in the superficial layer of the deep cervical fascia and will not be found inferior to the submandibular gland. The marginal mandibular nerve is reliably superficial to the facial vein.
A third approach keeps the deep cervical fascia and nerve on the undersurface of the platysma. Using this method the digastric is identified directly after the platysma is divided. The facial vein is ligated at the level of the digastric. Then similar to the fascial flap approach, the gland parenchyma is exposed bluntly on its inferior aspect. Then in the superiorly based skin/fat/platysma/deep cervical fascia composite flap is elevated directly off the parenchyma of the gland. This anatomically based approach avoids all dissection of the nerve but precludes any identification of it. This is our preferred method for non-neoplastic disease where limited exposure is acceptable and close dissection of the gland is not problematic.
Mobilization of the submandibular gland and identification of the hypoglossal nerve
With the superficial surface of the gland now exposed and the marginal mandibular nerve protected, the gland is then freed with blunt dissection from the inferior border of the mandible dividing binding fascial attachments. The distal facial artery is identified in this process and is divided as it exits its course within the gland to cross over the mandible at the antegonial notch. Remaining fascial attachments to the digastric muscle are also identified with blunt dissection and divided sharply. Keeping this dissection directly over the digastric muscle is key to prevent the inadvertent injury of the hypoglossal nerve which runs deep to digastric muscle. The anterior most aspect of the gland is retracted posteriorly with an Alice clamp and separated with cautery from the underlying mylohyoid muscle. At this time, multiple branches of the submental arteriovenous system are encountered at this time and should be controlled with hemeo-clips or bipolar cautery to maintain hemostatic technique and optimal visualization. When the posterior border of the mylohyoid is reached, no further structures are divided or cauterized until the hypoglossal nerve is identified. To expose the hypoglossal, the deep aspect of the mylohyoid is mobilized gently with an Army Navy retractor. The retractor is then placed under the mylohyoid to retract it forward, exposing the hyogolossus muscle. The gland is then retracted superiorly out of the wound to identify the hypoglossal emerging from under the digastric. It is found covered in fascia on the surface of the hyoglossus muscle, accompanied by its characteristic vena comitans (ranine vein). This maneuver is demonstrated in Fig. 3. If the identification is in any question, application of a nerve stimulator should result in a contraction of the underlying deep tongue musculature that is easily seen through the neck wound.
Figure 3Identification of the hypoglossal nerve. This is performed by retracting the posterior border of mylohyoid muscle anteriorly and the submandibular gland superiorly to expose the course of the hypoglossal. The nerve is covered by fascia on the surface of the hyoglossus muscle and usually accompanied by a characteristic vena comitans (ranine vein). Arrow indicates direction of retraction on the submandibular gland.
Dividing the submandibular ganglion, submandibular duct, proximal facial artery and removing the gland
With the hypoglossal identified and protected, one can focus on identifying the final key attachments of the gland. First the gland is grasped and pulled inferior. This will draw the lingual nerve into view by tenting it downward at the submandibular ganglion, see Fig. 4. The ganglion is tied off with 2.0 silk inferior to the course of the lingual nerve and divided at its connection with the gland. Next the gland is pulled posterior and lateral which will expose the anteriorly oriented duct. The duct is usually enveloped in salivary gland tissue from the sublingual gland. Some blunt dissection along the expected course of the duct in this glandular tissue should easily identify it. It is wise to palpate the duct to ensure no stones are retained in the distal end of the duct, which might be unintentionally retained in the patient. The duct is tied off to prevent communication to the oral cavity and divided, see Fig. 5. The final attachment of the gland is the proximal facial artery. This is identified as it emerges from deep to the posterior belly of the digastric, into the posterior aspect of the submandibular triangle, see Fig. 6. The artery is cross clamped, ligated with 2.0 Silk, and divided freeing the specimen from the patient.
Figure 4Identification of the lingual nerve and submandibular ganglion. This is performed by anterior retraction of the mylohyoid and inferior traction on the gland which draws the lingual nerve inferiorly into the field of dissection. The ganglion shown diagrammatically here is rather amorphous in surgical dissection. It is surgically identified as the attachment point of the gland to the lingual nerve. Arrow indicates direction of retraction on the submandibular gland.
Figure 5Identification of submandibular duct in preparation for ligation. Posterior retraction on the submandibular gland will place the duct on tension and facilitate its identification. The duct will be enveloped in sublingual gland tissue as it exits the anterior aspect of the submandibular gland. The duct should be dissected from this tissue for identification, suture ligated and then divided. Arrow indicates direction of retraction on the submandibular gland.
Figure 6Identification and division of the proximal facial artery. The proximal facial artery emerges from deep to the posterior belly of the digastric muscle and enters the submandibular gland (surface) on its deep posterior aspect. Retracting the gland out of the wound bed aids in identification. The artery is suture ligated and divided, releasing the submandibular gland. Arrow indicates direction of retraction on the submandibular gland.
It is possible when clinically appropriate to preserve the facial artery entirely. To perform this, the artery is identified at the mandible or posterior digastric and dissected bluntly along its course which is partially buried in the glandular tissue. Three or more small arterial branches from the artery to the gland will need to be divided to free the gland. Although small in caliber these can bleed quite with surprising vigor and therefore should be securely controlled with small hemeo-clips to prevent postoperative hemorrhage.
Wound closure
The wound should be irrigated with copious normal saline. Meticulous hemostasis is obtained with bipolar cautery protecting the preserved nerves. Often it is appropriate to close the wound without a drain provided there was minimal dissection outside of the capsule of the gland. A small suction drain is reasonable if more extensive dissection is performed. The platysma is reapproximated with absorbable sutures. The skin is closed for optimal cosmetic outcome. We prefer a running subcuticular absorbable monofilament suture. We also generally place a light pressure dressing or “jaw braw” for 24 hours if no drain is used. Postoperative antibiotics are not indicated if there was no clinical evidence of acute infection. It is prudent to examine the floor of mouth mucosa prior to emergence from anesthesia if there was significant fibrosis or difficult dissection. If a mucosal injury is identified this should be repaired primarily with absorbable sutures.
Postoperative care
The patient can typically resume oral diet immediately. We do not routinely use postoperative antibiotics. However, antibiotics may be reasonable if the gland appeared to be actively infected or mucosal injury was encountered. We caution patients against vigorous activity or heavy lifting for 5 days to reduce the risk of hematoma formation. Patients typically are discharged on the day of surgery unless they need to stay for the management of a suction drain. Pain is usually minimal. Significant pain for greater than 48 hours may represent a developing wound complication and is indication for early clinical examination.
Complications
The complications of submandibular gland surgery are related to the surrounding nerves and the potential for salivary contamination of the wound. Preuss et al have reviewed their experience with 258 submandibular gland excision for a diverse range of pathology.
Preoperative discussion of these complications, however unlikely, is key for setting patient expectations and facilitating informed decision making.
Summary and conclusions
Excision of the submandibular gland can be safe and is indicated in appropriately selected patients for the treatment of a diverse set of pathologies. Every effort should be made to salvage glands affected by non-neoplastic disease prior to excision. Salivary gland malignancy is associated with significant mortality. The management thereof is complex and should be undertaken by an experienced multidisciplinary team. A deep understanding of complex anatomical relationships of the submandibular gland to surrounding structures is the key for safe and effective submandibular gland surgery.
Jackson N, Mitchell J, Walvekar R. Inflammatory disorders of the salivary glands. In: Cummings Otolaryngology. Vol 2. 6th ed. 85. Saunders, an imprint of Elsvier Inc.:1223-1237.
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