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Surgical approaches to the submandibular gland: A review of literature
International Journal of Surgery 7 (2009) 503–509
Contents lists available at ScienceDirect
International Journal of Surgery journal homepage: www.theijs.com
Review
Surgical approaches to the submandibular gland: A review of literatureq David D. Beahm a, Laura Peleaz a, Daniel W. Nuss a, b, c, Barry Schaitkin b, Jayc C. Sedlmayr c, Carlos Mario Rivera-Serrano b, Adam M. Zanation d, Rohan R. Walvekar a, * a
Department of Otolaryngology Head and Neck Surgery, LSU Health Science Center, 533 Bolivar Street, Suite 566 New Orleans, LA 70112, United States Department of Otolaryngology Head and Neck Surgery, University of Pittsburgh, Pittsburgh, PA, United States c Department of Cell Biology and Anatomy, LSU Health Sciences Center, New Orleans, LA, United States d Department of Otolaryngology Head Neck Surgery, UNC School of Medicine, Chapel Hill, NC b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 July 2009 Received in revised form 4 September 2009 Accepted 12 September 2009 Available online 24 September 2009
Objectives: Surgical excision of the submandibular gland (SMG) is commonly indicated in patients with neoplasms, and non-neoplastic conditions such as chronic sialadenitis, sialolithiasis, ranula and drooling. Traditional SMG surgery involves a direct transcervical approach. In the recent past, alternative approaches to SMG excision have been described in effort to offer minimally invasive options or better cosmetic results. The purpose of this article is to describe the surgical approaches to the SMG and present relevant surgical anatomy via cadaveric dissection and a systematic review of literature to compare and contrast each technique. Study design: Cadaveric dissection with fresh human cadaver heads followed by a review of the literature. Methods: Cadaver heads were dissected via both the transcervical and transoral approaches to the submandibular gland with the use of endoscopic assistance when indicated. Key landmarks and anatomic relationships were recorded via photo documentation. A review of the literature was conducted using a Medline search for approaches to SMG excision, including indications, results and complications. Results: While the traditional SMG excision remains a direct transcervical approach, many other methods of excision are described that include open, endoscopic, and robot assisted resections. The approaches vary from being transcervical, submental, transoral or retroauricular. Conclusions: Alternative approaches to the SMG are feasible but should be tailored to the individual patient based on factors such as pathology, patient preferences, availability of technology, and the experience and skill of the surgeon. Ó 2009 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
Keywords: Submandibular gland Cadaveric dissection Surgical approaches Salivary glands
1. Introduction Surgical incisions to access to head neck lesions have rapidly evolved from traditional incisions along natural skin creases or aesthetic units to more cosmetically acceptable incisions in the local region or from remote locations that permit comprehensive surgery. These access incisions are often smaller and complemented by endoscopy, robotic instrumentation, and laparoscopic techniques that allow the surgeon to achieve and maintain an excellent operative exposure and view. The impetus to move to more minimally invasive techniques has been that these procedures are associated with better cosmesis, less scarring, diminished blood loss, shorter hospital stay, and lower morbidity.
q Grant support: None. * Corresponding author. Assistant Professor, Department of Otolaryngology Head Neck Surgery, LSU Health Sciences Center, 533 Bolivar Street, Suite 566, New Orleans, LA 70112. Tel.: þ1 504 568 4785; fax: þ1 504 568 4460. E-mail address: [email protected] (R.R. Walvekar).
In the recent past, there have been several articles discussing novel approaches to excise the submandibular gland (SMG). Surgical excision of the SMG is commonly indicated in patients with neoplasms, chronic sialadenitis, sialolithiasis, and to manage chronic drooling (sialorrhea) not responsive to conservative treatment. While the classic SMG surgery has involved a transcervical approach, several other approaches have recently been described that can be classified as ‘open’ or ‘endoscopic’ approaches (see Table 1). The purpose of this article is to review the surgical approaches to the SMG in order to provide a comprehensive review of the various surgical approaches to the SMG. The various approaches will be compared and contrasted in order to highlight the advantages and disadvantages of each technique. 2. Relevant anatomy The submandibular triangle is delineated by the anterior and posterior bellies of the digastric muscle and the mandible. Anteriorly, the floor of the triangle is the mylohyoid muscle; posteriorly it is the
1743-9191/$ – see front matter Ó 2009 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijsu.2009.09.006
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Table 1 Classification of approaches to the submandibular gland. Open Transoral approach External approach Lateral transcervical Retroauricular Submental
Endoscopic Endoscopy assisted Transoral Submental Lateral transcervical Completely endoscopic Robot-assisted approach
hyoglossus muscle.1 The SMG occupies most of this triangle, below the mylohyoid muscle.2 A part of the gland extends around the free edge of the mylohyoid muscle that divides the gland into a smaller anterior and larger posterior part. The mylohyoid muscle must be retracted in order to gain access to the both parts of the gland.3 The submandibular duct, or ’’Wharton’s duct’’, is approximately 5 cm in length and arises from the anterior portion of the gland. It traverses the floor of mouth between the mylohyoid and genioglossus muscles alongside the tongue. Its opening is found at the base of the frenulum of the tongue just posterior to the inferior incisors on the submandibular caruncle via one to three orifaces.1,2 The sublingual space is an important anatomical region that lies between the tongue and the mandibular ramus containing the deep portion of the sublingual gland, the anterior portion of the Wharton’s duct, and the lingual nerve which carries parasympathetic nerve fibers to the gland. During its course, the lingual nerve loops under the duct running a lateral to medial course and travels deep and superior to the SMG (Fig. 1); it is most easily identified by reflecting the posterior portion of the mylohyoid muscle.2 Also relevant is the hypoglossal nerve, which lies inferior and medial to the lower third of the gland under the posterior belly of the digastric muscle.3 The SMG is enclosed within a sheath formed by the investing fascia of the neck that is attached superiorly to the mandible. The marginal mandibular nerve forms an important external landmark as it passes just superficial to the fascia of the SMG and deep to the plane
Fig. 2. Arterial Supply to the Submandibular gland. (SMG: Submandibular gland; FA: Facial artery with branches to the submandibular gland; DG: Anterior belly of digastric muscle).
of the platysma.4 Consequently, surgical dissection within the fascia of the SMG poses the least risk to the marginal mandibular nerve. The vascular pole of the gland is formed by the facial artery and vein (Fig. 2). Identification and ligation of these vessels permits complete liberation of the gland in any approach. The facial vessels traverse vertically through the submandibular triangle across the mandible.2 3. Methods A review of the literature was conducted using a Medline search for approaches, indications, results, and complications of SMG excision. Relevant anatomy was further illustrated through cadaveric dissection and photo documentation. A synopsis of the various surgical approaches to the SMG is provided. Fig. 3 (A, B, and C) illustrate the postauricular, lateral transcervical, and submental surgical incisions used to access the SMG in frontal, lateral, and submental views. 4. Results Twenty seven articles were identified for review. Each article was assigned a rating of the level of evidence as outlined by the US Preventive Task Force.5 Overall, 3 level II-2 studies were identified and 22 level III studies were identified. There were no articles identified that exhibited level I, II-1, or II-3 evidence. The articles were stratified according to operative technique categorized by us as either ‘‘open’’ or ‘‘endoscopic.’’ The ‘‘endoscopic’’ category was further subdivided into ‘‘endoscopy assisted’’ and ‘‘completely endoscopic’’ (Table 1). The open technique approaches include: the lateral transcervical, submental, retroauricular, and transoral approaches. The endoscopic assisted approaches include the lateral transcervical, submental, and transoral endoscopy assisted approaches. The completely endoscopic approach includes the robot assisted techniques. Advantages and disadvantages of each technique are summarized in Table 2. 5. Discussion 5.1. Open techniques
Fig. 1. Lateral Transcervical approach. The lingual nerve loops under the duct running a lateral to medial course and the travels deep and superior to the submandibular gland. The hypoglossal nerve lies inferior and medial to the lower third of the gland under the posterior belly of the digastric muscle.
5.1.1. Lateral transcervical approach The lateral transcervical approach is the standard and timetested means of surgical access to the SMG. Indications for excision via this approach include neoplasm of the SMG, chronic
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Fig. 3. A–CCervical incisions (postauricular, lateral transcervical, and submental) for approaches to the submandibular gland (A:Frontal view; B:Lateral view; C:Submental view).
sialadenitis, sialolithiasis, radioactive iodine-induced sialdenitis,6 chronic drooling, Kuttner tumor and Kimura disease.7–9 Some authors have advocated a partial or total submandibular resection via a transcervical approach for facial rejuvenation.10 Lateral transcervical submandibular resection is most commonly performed under general anesthesia. However, some authors advocate SMG resection under local anesthesia in a select patient population. Criteria for gland excision under local anesthesia include a clinically mobile mass without features of malignancy based on fine needle aspiration biopsy (FNAB) in patients who prefer local anesthesia or are at high risk with general
Table 2 Advantages and Disadvantages of Reviewed Surgical Approaches to the SMG.
anesthesia. In addition, there was no size limitation to the removal of the mass provided it was deemed to be resectable with a 6 cm incision. In their study, Chow et al. had no procedures that required conversion to general anesthesia. They conclude that SMG excision under local anesthesia is feasible in appropriately selected patients and ultimately can shorten hospital stay and facilitate day surgery.11 The standard lateral transcervical approach is described in Table 37,8 for comparison with other newer approaches that will be subsequently discussed. Complications of traditional SMG excision include hematoma (2–10%), wound infection (2–9%), fistula
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Table 3 Traditional approach to the submandibular gland: lateral transcervical approach. A 4–6 centimeter incision in placed in lateral neck crease approximately 2 to 3 centimeters below the lower edge of the mandible. Subplatysmal skin flap is developed and the marginal mandibular nerve is identified and protected. The facial vein is identified and ligated at the inferior border of the gland and reflected superiorly with the fascia over the submandibular gland. This maneuver exposes the submandibular gland and ensures protection of the marginal mandibular nerve. The facial artery is ligated or may be preserved by ligating only the branches of the facial artery to the gland. Blunt dissection then continues towards the superiomedial gland at which point the mylohyoid muscle must be retracted anteriorly to complete the dissection. Posterior and inferior traction on the gland facilitates identification and differentiating Wharton’s duct, the lingual nerve with its attachment to the submandibular ganglion, and the hypoglossal nerve. The submandibular duct is then ligated and divided close to its opening in the floor of the mouth. The gland is liberated from the submandibular ganglion and removed preserving the lingual and hypoglossal nerves.
formation (1–3%), and neurological complications. Neurological complications include damage to marginal mandibular (7.7–36%), hypoglossal (0–7%) and lingual (0–22.5%) nerves.6–9,12,13 5.1.2. Submental approach The submental approach provides access to the submandibular triangle via a midline horizontal incision just superior to the submental-cervical crease at the level of the hyoid bone, (4.5 1.9 cm). The location is patient dependent determined by pre-existing neck creases, amount of submental fat and skin texture. The site of the incision is marked pre-operatively along the least prominent line of the submental area in the frontal and lateral views of the face and the neck. The submental approach allows quick access to the gland. The SMG is bluntly dissected free of surrounding fascia in a subplatysmal plane. The dissection differs from the traditional approach in that the anterior free edge of the gland is first encountered (Fig. 4A and B). Following this, the facial vein and artery are ligated and the gland is separated from the edge of the mylohyoid muscle. The submandibular ganglion is identified and separated from the gland. Finally the submandibular duct is ligated and the gland is delivered through the incision. A drain is placed within the incision and is removed on the second or third postoperative day.14 Roh compared the submental approach to the traditional lateral transcervical approach in a prospective randomized fashion. There were a total of 20 patients, with 10 patients in each arm of the study. There were no statistically significant differences in the two approaches with respect to incision length, operative time, nerve injuries, and number of days of hospitalization. However, the average visual analog scales measurements showed a higher patient satisfaction due to cosmetic concerns in the submental approach group (p ¼ 0.01; 8.8 1.9 vs. 5.4 3.2).14 5.1.3. Retroauricular approach Roh also described a retroauricular approach to the SMG.15 Since the initial report in 2005, Roh and other authors have continued to report on the utility of this approach.16 The main advantage is the improved cosmesis of the resultant scar. The incision is designed in the lower portion of the postauricular sulcus arching toward the middle to upper 1/3rd of the sulcus before transitioning across and downward into the hairline; the portion of the incision in the hairline is set ½ to 1 cm into the hair bearing area (Fig. 3B). The main disadvantage of the retroauricular approach is the extent of the skin flap that must be raised to access the Wharton’s duct proximally which can be 10 cm from the postauricular incision. The
Fig. 4. Submental approach.
incision is carried downward through the subcutaneous tissues and onto the sternocleidomastoid muscle at which point the flap is elevated anterior to the SMG. Special attention must be paid to avoid damage to the hair follicles and great auricular nerve and its branches during flap elevation in order to prevent postoperative complications. Once the gland is exposed, extirpation proceeds as in any open approach.15 Due to the depth of the operative field (Fig. 3), endoscopy can enhance the view of the operative field (Fig. 5). In his study, comparing this approach to the standard transcervical approach, Roh found no significant differences in operative time, scar hypertrophy and length of hospital stay between the two procedures. In his series, there were no iatrogenic palsies of the marginal mandibular nerve with the retroauricular approach, while
Fig. 5. Retroauricular approach. View of skin flap elevated prior to full exposure of the submandibular triangle.
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there were two such reported complications with the standard approach. The study concluded that the retroauricular approach is safe and comparable to the standard approach. As would be expected, the overall patient satisfaction with the resultant scar on a visual analog scale was significantly higher with patients from the retroauricular cohort (p < 0.001; 8.9 þ/ 0.9 points vs. 4.2 þ/ 2.9 points).16 5.1.4. Transoral approach While first described in modern medical literature in 1960,17 the transoral approach to the SMG had not gained popularity until recently described by Hong et al18,19 (see Table 4). Advantages of the transoral approach include: less risk of iatrogenic injury to the marginal mandibular nerve, avoidance of an external scar, minimal risk of postoperative mucocele formation, or inflammation of Wharton’s duct.18,19 In his series, Hong reported on 31 patients who underwent a transoral resection of the SMG and later followed this with a retrospective chart review of 77 patients undergoing the same surgery showing similar results. Abnormal tongue sensation was noted in 74% of patients and temporary limitation of tongue movement was noted in 70% of patients.20 Restriction of tongue movement due to scar contraction was noted in 10% of patients in the first paper but this was lowered to 2% in the most recent article with these patients being asymptomatic.18,20 Hong later followed the initial report with a review of 12 patients with pleomorphic adenoma of the SMG excised with this approach. They noted 50% of patients had anesthesia of the tongue and 40% had limitation of tongue movement, all of which resolved within two weeks of surgery.21 Weber et al. have published their experience with seven patients reporting 43% abnormal tongue sensation, no change in tongue movement or restriction due to scar contracture. They attributed their lower complication rates to several critical maneuvers such as planning to leave a cuff of gingival mucosa to allow a tension free closure and prevent tongue tethering. The authors limited the amount of lingual nerve dissection consequently limiting stretch injury to the nerve which is responsible for abnormal tongue sensation. The authors pointed out that the only patient in their experience where a transoral approach was inadequate to allow excision of the gland had previous surgery and a small oral cavity. These can be considered as relative contraindications to this approach.19 Kauffman recently reported a case series of nine patients with only 25% of patients having temporary change in tongue sensation and no patients having lasting complications. This series further validates the safety of transoral excision in selected patients.22
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applied to the excision of the SMG. Endoscopic approaches to the SMG can be further classified as ’’endoscopy assisted’’ and ‘‘completely endoscopic’’ approaches. 5.2.1. Endoscopic-assisted transoral approach Endoscopically-assisted transoral excision of the SMG again is similar to its open counterpart. The main advantage of the endoscopic assistance in addition to those that are natural to the transoral approach i.e. lack of a cervical scar and lower incidence of facial nerve palsy again, are good visualization, magnification and illumination of the anatomical landmarks, and consequently a wider surgical field as compared to the conventional intraoral approach (Figs 6 and 7). Guerrissi and Taborda describe two cases with this technique which were successfully performed for sialadenitis secondary to sialolithiasis.3 However, Weber et al did not perceive any difficulties with exposure via the conventional transoral incision. In their series, a single patient required conversion to a transcervical approach which in their opinion would not have been preventable even with endoscopic guidance.19 It must be recognized that the endoscopy assisted transoral approach has several disadvantages which are common to all endoscopic procedures and include: the cost of the endoscopic equipment, the learning curve associated with the surgeon becoming familiar with the technique, and increased operative and setup time.23 5.2.2. Endoscopic-assisted submental approach Chen et al., describe a minimally invasive endoscopic invasive resection of the SMG. The incision placement for this approach is in a submental area similar to the submental approach described by Roh et al.24 This procedure differs from the conventional submental approach in that a smaller incision (20–25 mm) is placed over the skin crease in the hyoid midline. Dissection is performed in a subplatysmal plane. The first assistant maintains an operative view using an endoscope and the second assistant maintains the working space with two retractors which lift up away from the skin. Vessels are ligated using Endoclips (Ethicon Endosurgery) and excision is performed standard fashion using an ultrasound-activated scalpel (Harmonic Scalpel, Ethicon Endosurgery). A drain is placed for drainage.25
5.2. Endoscopic approaches As technology advances and the boundaries of the endoscope are ever challenged, it logically follows that this technology be Table 4 Transoralapproach to the submandibular gland. An incision is made in the floor of mouth from the submandibular papilla to the retromolar trigone. A cuff of mucosa on the gingival side is preserved to allow for tension free closure and to prevent limitation of tongue mobility due to scar contracture. The lingual nerve is identified and dissected free of its attachments to the submandibular duct and gland. The submandibular gland is bluntly dissected and delivered into the surgical wound by applying external pressure on the neck. The hypoglossal nerve is identified and preserved. Branches of the facial artery and vein are ligated with care not to disrupt the marginal mandibular branch of the facial nerve. The gland is removed and the wound bed irrigated and closed in a tension free manor.
Fig. 6. Transoral approach. Endoscopic view of transoral approach showing submandibular duct (D), lingual nerve (L), and sublingual gland (SLG).
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inflammatory adherences to surrounding structures that resulted in a bloody surgical field.30
Fig. 7. Transoral approach. Endoscopic view of the operative field.
The advantages of this approach include a smaller incision as compared to the standard submental approach and the previously discussed advantage of endoscopic visualization. In addition, the use of an ultrasound-activated scalpel which does not transmit an electric current reduces the risk of thermal injury to the marginal mandibular nerve as compared to monopolar and bipolar electrocautery.26 However, the disadvantages include those that are common to all endoscopic procedures as well as a significant increase in operative time as compared to the conventional submental approach [70 min, (50–120 min) vs. 41 min, (32–56 min)].25 The application of endoscopic approaches in soft tissue surgery has been thwarted by the challenges fundamental to endoscopic neck surgery including the lack of a well-defined sac and the risk of emphysematous dissection.23 The risk of CO2 insufflation to create a working space in the neck includes massive subcutaneous emphysema, hypercarbia, gas embolization, and some types of arrhythmias.25 Terris et al, developed hybridized techniques to enable an endoscopic approach for the resection of the SMG in a porcine model.27 However, the era for endoscopic neck surgery began with the first description of a parathyroidectomy using CO2 insufflation.28,29 Since then there have been number of reports that have used CO2 insufflation for the purpose of endoscopic neck surgery. These developments will certainly define the approaches to the SMG in the future. 5.2.3. Endoscopic transcervical approach Guyot et al (2005) described an endoscopic approach for the SMG that does not rely on CO2 insufflation to create an operative pocket. In a cadaveric study carried out on 6 non-embalmed cadavers, 12 endoscopic submandibular resections were performed. Access to the subplatysmal plane of dissection was achieved via two 15 mm incisions (one anterior and the other posterior), 10 mm below the submandibular area. A 4 mm diameter, 30-degree endoscope provided the surgical view when placed in the posterior incision. The operative pocket was created and maintained using trans-cutaneous sutures. The dissection was otherwise conducted in a usual fashion. Extirpation of the gland was done through one of the incisions. In all cases gland excision was successful. The operative time decreased with experience from 120 min for the first case to 35 min for the last case. The limitations for an endoscopic approach were defined as presence of
5.2.4. Endoscopic submandibular gland excision using CO2 insufflation Monfared et al (2002) described an endoscopic approach to the SMG in a porcine model using balloon dissection to create an operative pocket which was constantly maintained with low pressure (no more than 4 mm Hg) CO2 insufflation. Three incisions were made. The central 14 mm incision accepts the 12 mm trocar which houses the endoscope while the two lateral incisions (6–7 mm) were used to place the 5 mm operative trocars. Twelve SMGs were successfully excised endoscopically in seven pigs with no conversion to open surgery. The median operative time was 59 min (range, 42– 165 min).27 Terris recently expanded this approach with the addition of the daVinci robotic system to resect the SMG with a mean operative time of 48 min and with no conversions to open surgery.27,31 The main advantage of the robotic-enhanced endoscopic surgery includes a virtual three dimensional vision projection system with an endoscopic arm and two operative arms that can be controlled by the surgeon from a remote console. In addition, the robotic arm permits use of a full range of articulated instruments which can reproduce surgical maneuvers in difficult to access locations. The disadvantages of robotic surgery such as high cost and lengthy setup time are great, and further customization of surgical instrumentation for otolaryngology practice remain to be challenges for the future.23,32 6. Conclusions Newer approaches to the SMG have distinct advantages in terms of cosmesis over the traditional lateral transcervical approach. Although most approaches are feasible and have been successfully performed in humans, they are not widely practiced or accepted as standard of care in most academic institutions and also in community settings. In cases where SMG resection is deemed necessary, we recommend careful selection of the approach based on individual patient characteristics and needs, skill and experience of the surgeon, familiarity with endoscopic technique, and availability of necessary instrumentation. Conflicts of interest None Funding None Ethical approval Not applicable Acknowledgement The authors would like to thank Dr. Richard Whitworth and Dr. William Swartz, Mr. Antony Wells and Mr. Reginauld Delmore, Department of Anatomy; Jeffrey LaCour MD, Department of Otolaryngology Head and Neck Surgery, Louisiana State University School Health Sciences Center, New Orleans, LA; Eugene New, New Orleans, LA (for illustrations), and Trey Joseph, Stryker, New Orleans, LA for their contributions. References 1. Cummings C. Otolaryngology & head neck surgery. In: Cummings C, editor. Salivary gland. New York: Mosby; 1998. p. 1201–9. 2. Lalwani A. Current Diagnosis and Treatment in Otolaryngology–Head and Neck Surgery: Second Edition. New York: McGraw-Hill Medical, 200:5. 3. Guerrissi JO, Taborda G. Endoscopic excision of the submandibular gland by an intraoral approach. J Craniofac Surg 2001;12:299–303. 4. Moore KL, Dalley AF. Clinically Oriented Anatomy, Fourth Edition. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. 1012–1015.
D.D. Beahm et al. / International Journal of Surgery 7 (2009) 503–509 5. Harris RP, Helfand M, Woolf SH, Lohr KN, Mulrow CD, et al. Current methods of the US preventive services task force: a review of the process. Am J Prev Med 2001;20:21–35. 6. Smith AD, Elahi MM, Kawamoto Jr HK, Lorenz HP, Hedrick MH. Excision of the submandibular gland by an intraoral approach. Plast Reconstr Surg 2000;105:2092–5. 7. Preuss SF, Klussmann JP, Wittekindt C, Drebber U, Beutner D, GuntinasLichius O. Submandibular gland excision: 15 years of experience. J Oral Maxillofac Surg 2007;65:953–7. 8. Torroni AA, Mustazza MC, Bartoli DD, Iannetti GG. Transcervical submandibular sialoadenectomy. J Craniofac Surg 2007;18:613–21. 9. Milton CM, Thomas BM, Bickerton RC. Morbidity study of submandibular gland excision. Ann R Coll Surg Engl 1986;68:148–50. 10. Singer DP, Sullivan PK. Submandibular gland I: an anatomic evaluation and surgical approach to submandibular gland resection for facial rejuvenation. Plast Reconstr Surg 2003;112:1150–4. discussion 1155–1156. 11. Chow TL, Chan TT, Choi CY, Lam SH. Submandibular sialoadenectomy with local anesthesia in the era of minimally invasive surgery. Otolaryngol Head Neck Surg 2008;138:752–5. 12. Berini-Aytes L, Gay-Escoda C. Morbidity associated with removal of the submandibular gland. J Craniomaxillofac Surg 1992;20:216–9. 13. Smith WP, Peters WJ, Markus AF. Submandibular gland surgery: an audit of clinical findings, pathology and postoperative morbidity. Ann R Coll Surg Engl 1993;75:164–7. 14. Roh JL. Removal of the submandibular gland by a submental approach: a prospective, randomized, controlled study. Oral Oncol 2008;44:295–300. 15. Roh JL. Retroauricular hairline incision for removal of upper neck masses. Laryngoscope 2005;115:2161–6. 16. Roh JL. Removal of the submandibular gland by a retroauricular approach. Arch Otolaryngol Head Neck Surg 2006;132:783–7. 17. Downton D, Qvist G. Intra-oral excision of the submandibular gland. Proc R Soc Med 1960;53:543–4. 18. Hong KH, Kim YK. Intraoral removal of the submandibular gland: a new surgical approach. Otolaryngol Head Neck Surg 2000;122:798–802.
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19. Weber SM, Wax MK, Kim JH. Transoral excision of the submandibular gland. Otolaryngol Head Neck Surg 2007;137:343–5. 20. Hong KH, Yang YS. Surgical results of the intraoral removal of the submandibular gland. Otolaryngol Head Neck Surg 2008;139:530–4. 21. Hong KH, Yang YS. Intraoral approach for the treatment of submandibular salivary gland mixed tumors. Oral Oncol 2008;44:491–5. 22. Kauffman RM, Netterville JL, Burkey BB. Transoral excision of the submandibular gland: techniques and results of nine cases. Laryngoscope 2009;119: 502–7. 23. Terris DJ, Amin SH. Robotic and endoscopic surgery in the neck. Operative Techniques in Otolaryngol; 2008::36–41. 24. Roh JL, Yoon YH, Park CI. Removal of nonthyroidal neck masses with improved cosmetic outcomes in skin-lifting surgery. Otolaryngol Head Neck Surg 2006;135: 463–8. 25. Chen MK, Su CC, Tsai YL, Chang CC. Minimally invasive endoscopic resection of the submandibular gland: a new approach. Head Neck 2006;28:1014–7. 26. Jackson LL, Gourin CG, Thomas DS, Porubsky ES, Klippert FN, Terris DJ. Use of the harmonic scalpel in superficial and total parotidectomy for benign and malignant disease. Laryngoscope 2005;115:1070–3. 27. Monfared A, Saenz Y, Terris DJ. Endoscopic resection of the submandibular gland in a porcine model. Laryngoscope 2002;112:1089–93. 28. Gagner M. Endoscopic subtotal parathyroidectomy in patients with primary hyperparathyroidism. Br J Surg 1996;83:875. 29. Naitoh T, Gagner M, Garcia-Ruiz A, Heniford BT. Endoscopic endocrine surgery in the neck. An initial report of endoscopic subtotal parathyroidectomy. Surg Endosc 1998;12:202–5. discussion 206. 30. Guyot L, Duroure F, Richard O, Lebeau J, Passagia JG, Raphael B. Submandibular gland endoscopic resection: a cadaveric study. Int J Oral Maxillofac Surg 2005;34:407–10. 31. Terris DJ, Haus BM, Gourin CG, Lilagan PE. Endo-robotic resection of the submandibular gland in a cadaver model. Head Neck 2005;27:946–51. 32. Haus BM, Kambham N, Le D, Moll FM, Gourin C, Terris DJ. Surgical robotic applications in otolaryngology. Laryngoscope 2003;113:1139–44.
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Review
Surgical approaches to the submandibular gland: A review of literatureq David D. Beahm a, Laura Peleaz a, Daniel W. Nuss a, b, c, Barry Schaitkin b, Jayc C. Sedlmayr c, Carlos Mario Rivera-Serrano b, Adam M. Zanation d, Rohan R. Walvekar a, * a
Department of Otolaryngology Head and Neck Surgery, LSU Health Science Center, 533 Bolivar Street, Suite 566 New Orleans, LA 70112, United States Department of Otolaryngology Head and Neck Surgery, University of Pittsburgh, Pittsburgh, PA, United States c Department of Cell Biology and Anatomy, LSU Health Sciences Center, New Orleans, LA, United States d Department of Otolaryngology Head Neck Surgery, UNC School of Medicine, Chapel Hill, NC b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 July 2009 Received in revised form 4 September 2009 Accepted 12 September 2009 Available online 24 September 2009
Objectives: Surgical excision of the submandibular gland (SMG) is commonly indicated in patients with neoplasms, and non-neoplastic conditions such as chronic sialadenitis, sialolithiasis, ranula and drooling. Traditional SMG surgery involves a direct transcervical approach. In the recent past, alternative approaches to SMG excision have been described in effort to offer minimally invasive options or better cosmetic results. The purpose of this article is to describe the surgical approaches to the SMG and present relevant surgical anatomy via cadaveric dissection and a systematic review of literature to compare and contrast each technique. Study design: Cadaveric dissection with fresh human cadaver heads followed by a review of the literature. Methods: Cadaver heads were dissected via both the transcervical and transoral approaches to the submandibular gland with the use of endoscopic assistance when indicated. Key landmarks and anatomic relationships were recorded via photo documentation. A review of the literature was conducted using a Medline search for approaches to SMG excision, including indications, results and complications. Results: While the traditional SMG excision remains a direct transcervical approach, many other methods of excision are described that include open, endoscopic, and robot assisted resections. The approaches vary from being transcervical, submental, transoral or retroauricular. Conclusions: Alternative approaches to the SMG are feasible but should be tailored to the individual patient based on factors such as pathology, patient preferences, availability of technology, and the experience and skill of the surgeon. Ó 2009 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
Keywords: Submandibular gland Cadaveric dissection Surgical approaches Salivary glands
1. Introduction Surgical incisions to access to head neck lesions have rapidly evolved from traditional incisions along natural skin creases or aesthetic units to more cosmetically acceptable incisions in the local region or from remote locations that permit comprehensive surgery. These access incisions are often smaller and complemented by endoscopy, robotic instrumentation, and laparoscopic techniques that allow the surgeon to achieve and maintain an excellent operative exposure and view. The impetus to move to more minimally invasive techniques has been that these procedures are associated with better cosmesis, less scarring, diminished blood loss, shorter hospital stay, and lower morbidity.
q Grant support: None. * Corresponding author. Assistant Professor, Department of Otolaryngology Head Neck Surgery, LSU Health Sciences Center, 533 Bolivar Street, Suite 566, New Orleans, LA 70112. Tel.: þ1 504 568 4785; fax: þ1 504 568 4460. E-mail address: [email protected] (R.R. Walvekar).
In the recent past, there have been several articles discussing novel approaches to excise the submandibular gland (SMG). Surgical excision of the SMG is commonly indicated in patients with neoplasms, chronic sialadenitis, sialolithiasis, and to manage chronic drooling (sialorrhea) not responsive to conservative treatment. While the classic SMG surgery has involved a transcervical approach, several other approaches have recently been described that can be classified as ‘open’ or ‘endoscopic’ approaches (see Table 1). The purpose of this article is to review the surgical approaches to the SMG in order to provide a comprehensive review of the various surgical approaches to the SMG. The various approaches will be compared and contrasted in order to highlight the advantages and disadvantages of each technique. 2. Relevant anatomy The submandibular triangle is delineated by the anterior and posterior bellies of the digastric muscle and the mandible. Anteriorly, the floor of the triangle is the mylohyoid muscle; posteriorly it is the
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Table 1 Classification of approaches to the submandibular gland. Open Transoral approach External approach Lateral transcervical Retroauricular Submental
Endoscopic Endoscopy assisted Transoral Submental Lateral transcervical Completely endoscopic Robot-assisted approach
hyoglossus muscle.1 The SMG occupies most of this triangle, below the mylohyoid muscle.2 A part of the gland extends around the free edge of the mylohyoid muscle that divides the gland into a smaller anterior and larger posterior part. The mylohyoid muscle must be retracted in order to gain access to the both parts of the gland.3 The submandibular duct, or ’’Wharton’s duct’’, is approximately 5 cm in length and arises from the anterior portion of the gland. It traverses the floor of mouth between the mylohyoid and genioglossus muscles alongside the tongue. Its opening is found at the base of the frenulum of the tongue just posterior to the inferior incisors on the submandibular caruncle via one to three orifaces.1,2 The sublingual space is an important anatomical region that lies between the tongue and the mandibular ramus containing the deep portion of the sublingual gland, the anterior portion of the Wharton’s duct, and the lingual nerve which carries parasympathetic nerve fibers to the gland. During its course, the lingual nerve loops under the duct running a lateral to medial course and travels deep and superior to the SMG (Fig. 1); it is most easily identified by reflecting the posterior portion of the mylohyoid muscle.2 Also relevant is the hypoglossal nerve, which lies inferior and medial to the lower third of the gland under the posterior belly of the digastric muscle.3 The SMG is enclosed within a sheath formed by the investing fascia of the neck that is attached superiorly to the mandible. The marginal mandibular nerve forms an important external landmark as it passes just superficial to the fascia of the SMG and deep to the plane
Fig. 2. Arterial Supply to the Submandibular gland. (SMG: Submandibular gland; FA: Facial artery with branches to the submandibular gland; DG: Anterior belly of digastric muscle).
of the platysma.4 Consequently, surgical dissection within the fascia of the SMG poses the least risk to the marginal mandibular nerve. The vascular pole of the gland is formed by the facial artery and vein (Fig. 2). Identification and ligation of these vessels permits complete liberation of the gland in any approach. The facial vessels traverse vertically through the submandibular triangle across the mandible.2 3. Methods A review of the literature was conducted using a Medline search for approaches, indications, results, and complications of SMG excision. Relevant anatomy was further illustrated through cadaveric dissection and photo documentation. A synopsis of the various surgical approaches to the SMG is provided. Fig. 3 (A, B, and C) illustrate the postauricular, lateral transcervical, and submental surgical incisions used to access the SMG in frontal, lateral, and submental views. 4. Results Twenty seven articles were identified for review. Each article was assigned a rating of the level of evidence as outlined by the US Preventive Task Force.5 Overall, 3 level II-2 studies were identified and 22 level III studies were identified. There were no articles identified that exhibited level I, II-1, or II-3 evidence. The articles were stratified according to operative technique categorized by us as either ‘‘open’’ or ‘‘endoscopic.’’ The ‘‘endoscopic’’ category was further subdivided into ‘‘endoscopy assisted’’ and ‘‘completely endoscopic’’ (Table 1). The open technique approaches include: the lateral transcervical, submental, retroauricular, and transoral approaches. The endoscopic assisted approaches include the lateral transcervical, submental, and transoral endoscopy assisted approaches. The completely endoscopic approach includes the robot assisted techniques. Advantages and disadvantages of each technique are summarized in Table 2. 5. Discussion 5.1. Open techniques
Fig. 1. Lateral Transcervical approach. The lingual nerve loops under the duct running a lateral to medial course and the travels deep and superior to the submandibular gland. The hypoglossal nerve lies inferior and medial to the lower third of the gland under the posterior belly of the digastric muscle.
5.1.1. Lateral transcervical approach The lateral transcervical approach is the standard and timetested means of surgical access to the SMG. Indications for excision via this approach include neoplasm of the SMG, chronic
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Fig. 3. A–CCervical incisions (postauricular, lateral transcervical, and submental) for approaches to the submandibular gland (A:Frontal view; B:Lateral view; C:Submental view).
sialadenitis, sialolithiasis, radioactive iodine-induced sialdenitis,6 chronic drooling, Kuttner tumor and Kimura disease.7–9 Some authors have advocated a partial or total submandibular resection via a transcervical approach for facial rejuvenation.10 Lateral transcervical submandibular resection is most commonly performed under general anesthesia. However, some authors advocate SMG resection under local anesthesia in a select patient population. Criteria for gland excision under local anesthesia include a clinically mobile mass without features of malignancy based on fine needle aspiration biopsy (FNAB) in patients who prefer local anesthesia or are at high risk with general
Table 2 Advantages and Disadvantages of Reviewed Surgical Approaches to the SMG.
anesthesia. In addition, there was no size limitation to the removal of the mass provided it was deemed to be resectable with a 6 cm incision. In their study, Chow et al. had no procedures that required conversion to general anesthesia. They conclude that SMG excision under local anesthesia is feasible in appropriately selected patients and ultimately can shorten hospital stay and facilitate day surgery.11 The standard lateral transcervical approach is described in Table 37,8 for comparison with other newer approaches that will be subsequently discussed. Complications of traditional SMG excision include hematoma (2–10%), wound infection (2–9%), fistula
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Table 3 Traditional approach to the submandibular gland: lateral transcervical approach. A 4–6 centimeter incision in placed in lateral neck crease approximately 2 to 3 centimeters below the lower edge of the mandible. Subplatysmal skin flap is developed and the marginal mandibular nerve is identified and protected. The facial vein is identified and ligated at the inferior border of the gland and reflected superiorly with the fascia over the submandibular gland. This maneuver exposes the submandibular gland and ensures protection of the marginal mandibular nerve. The facial artery is ligated or may be preserved by ligating only the branches of the facial artery to the gland. Blunt dissection then continues towards the superiomedial gland at which point the mylohyoid muscle must be retracted anteriorly to complete the dissection. Posterior and inferior traction on the gland facilitates identification and differentiating Wharton’s duct, the lingual nerve with its attachment to the submandibular ganglion, and the hypoglossal nerve. The submandibular duct is then ligated and divided close to its opening in the floor of the mouth. The gland is liberated from the submandibular ganglion and removed preserving the lingual and hypoglossal nerves.
formation (1–3%), and neurological complications. Neurological complications include damage to marginal mandibular (7.7–36%), hypoglossal (0–7%) and lingual (0–22.5%) nerves.6–9,12,13 5.1.2. Submental approach The submental approach provides access to the submandibular triangle via a midline horizontal incision just superior to the submental-cervical crease at the level of the hyoid bone, (4.5 1.9 cm). The location is patient dependent determined by pre-existing neck creases, amount of submental fat and skin texture. The site of the incision is marked pre-operatively along the least prominent line of the submental area in the frontal and lateral views of the face and the neck. The submental approach allows quick access to the gland. The SMG is bluntly dissected free of surrounding fascia in a subplatysmal plane. The dissection differs from the traditional approach in that the anterior free edge of the gland is first encountered (Fig. 4A and B). Following this, the facial vein and artery are ligated and the gland is separated from the edge of the mylohyoid muscle. The submandibular ganglion is identified and separated from the gland. Finally the submandibular duct is ligated and the gland is delivered through the incision. A drain is placed within the incision and is removed on the second or third postoperative day.14 Roh compared the submental approach to the traditional lateral transcervical approach in a prospective randomized fashion. There were a total of 20 patients, with 10 patients in each arm of the study. There were no statistically significant differences in the two approaches with respect to incision length, operative time, nerve injuries, and number of days of hospitalization. However, the average visual analog scales measurements showed a higher patient satisfaction due to cosmetic concerns in the submental approach group (p ¼ 0.01; 8.8 1.9 vs. 5.4 3.2).14 5.1.3. Retroauricular approach Roh also described a retroauricular approach to the SMG.15 Since the initial report in 2005, Roh and other authors have continued to report on the utility of this approach.16 The main advantage is the improved cosmesis of the resultant scar. The incision is designed in the lower portion of the postauricular sulcus arching toward the middle to upper 1/3rd of the sulcus before transitioning across and downward into the hairline; the portion of the incision in the hairline is set ½ to 1 cm into the hair bearing area (Fig. 3B). The main disadvantage of the retroauricular approach is the extent of the skin flap that must be raised to access the Wharton’s duct proximally which can be 10 cm from the postauricular incision. The
Fig. 4. Submental approach.
incision is carried downward through the subcutaneous tissues and onto the sternocleidomastoid muscle at which point the flap is elevated anterior to the SMG. Special attention must be paid to avoid damage to the hair follicles and great auricular nerve and its branches during flap elevation in order to prevent postoperative complications. Once the gland is exposed, extirpation proceeds as in any open approach.15 Due to the depth of the operative field (Fig. 3), endoscopy can enhance the view of the operative field (Fig. 5). In his study, comparing this approach to the standard transcervical approach, Roh found no significant differences in operative time, scar hypertrophy and length of hospital stay between the two procedures. In his series, there were no iatrogenic palsies of the marginal mandibular nerve with the retroauricular approach, while
Fig. 5. Retroauricular approach. View of skin flap elevated prior to full exposure of the submandibular triangle.
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there were two such reported complications with the standard approach. The study concluded that the retroauricular approach is safe and comparable to the standard approach. As would be expected, the overall patient satisfaction with the resultant scar on a visual analog scale was significantly higher with patients from the retroauricular cohort (p < 0.001; 8.9 þ/ 0.9 points vs. 4.2 þ/ 2.9 points).16 5.1.4. Transoral approach While first described in modern medical literature in 1960,17 the transoral approach to the SMG had not gained popularity until recently described by Hong et al18,19 (see Table 4). Advantages of the transoral approach include: less risk of iatrogenic injury to the marginal mandibular nerve, avoidance of an external scar, minimal risk of postoperative mucocele formation, or inflammation of Wharton’s duct.18,19 In his series, Hong reported on 31 patients who underwent a transoral resection of the SMG and later followed this with a retrospective chart review of 77 patients undergoing the same surgery showing similar results. Abnormal tongue sensation was noted in 74% of patients and temporary limitation of tongue movement was noted in 70% of patients.20 Restriction of tongue movement due to scar contraction was noted in 10% of patients in the first paper but this was lowered to 2% in the most recent article with these patients being asymptomatic.18,20 Hong later followed the initial report with a review of 12 patients with pleomorphic adenoma of the SMG excised with this approach. They noted 50% of patients had anesthesia of the tongue and 40% had limitation of tongue movement, all of which resolved within two weeks of surgery.21 Weber et al. have published their experience with seven patients reporting 43% abnormal tongue sensation, no change in tongue movement or restriction due to scar contracture. They attributed their lower complication rates to several critical maneuvers such as planning to leave a cuff of gingival mucosa to allow a tension free closure and prevent tongue tethering. The authors limited the amount of lingual nerve dissection consequently limiting stretch injury to the nerve which is responsible for abnormal tongue sensation. The authors pointed out that the only patient in their experience where a transoral approach was inadequate to allow excision of the gland had previous surgery and a small oral cavity. These can be considered as relative contraindications to this approach.19 Kauffman recently reported a case series of nine patients with only 25% of patients having temporary change in tongue sensation and no patients having lasting complications. This series further validates the safety of transoral excision in selected patients.22
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applied to the excision of the SMG. Endoscopic approaches to the SMG can be further classified as ’’endoscopy assisted’’ and ‘‘completely endoscopic’’ approaches. 5.2.1. Endoscopic-assisted transoral approach Endoscopically-assisted transoral excision of the SMG again is similar to its open counterpart. The main advantage of the endoscopic assistance in addition to those that are natural to the transoral approach i.e. lack of a cervical scar and lower incidence of facial nerve palsy again, are good visualization, magnification and illumination of the anatomical landmarks, and consequently a wider surgical field as compared to the conventional intraoral approach (Figs 6 and 7). Guerrissi and Taborda describe two cases with this technique which were successfully performed for sialadenitis secondary to sialolithiasis.3 However, Weber et al did not perceive any difficulties with exposure via the conventional transoral incision. In their series, a single patient required conversion to a transcervical approach which in their opinion would not have been preventable even with endoscopic guidance.19 It must be recognized that the endoscopy assisted transoral approach has several disadvantages which are common to all endoscopic procedures and include: the cost of the endoscopic equipment, the learning curve associated with the surgeon becoming familiar with the technique, and increased operative and setup time.23 5.2.2. Endoscopic-assisted submental approach Chen et al., describe a minimally invasive endoscopic invasive resection of the SMG. The incision placement for this approach is in a submental area similar to the submental approach described by Roh et al.24 This procedure differs from the conventional submental approach in that a smaller incision (20–25 mm) is placed over the skin crease in the hyoid midline. Dissection is performed in a subplatysmal plane. The first assistant maintains an operative view using an endoscope and the second assistant maintains the working space with two retractors which lift up away from the skin. Vessels are ligated using Endoclips (Ethicon Endosurgery) and excision is performed standard fashion using an ultrasound-activated scalpel (Harmonic Scalpel, Ethicon Endosurgery). A drain is placed for drainage.25
5.2. Endoscopic approaches As technology advances and the boundaries of the endoscope are ever challenged, it logically follows that this technology be Table 4 Transoralapproach to the submandibular gland. An incision is made in the floor of mouth from the submandibular papilla to the retromolar trigone. A cuff of mucosa on the gingival side is preserved to allow for tension free closure and to prevent limitation of tongue mobility due to scar contracture. The lingual nerve is identified and dissected free of its attachments to the submandibular duct and gland. The submandibular gland is bluntly dissected and delivered into the surgical wound by applying external pressure on the neck. The hypoglossal nerve is identified and preserved. Branches of the facial artery and vein are ligated with care not to disrupt the marginal mandibular branch of the facial nerve. The gland is removed and the wound bed irrigated and closed in a tension free manor.
Fig. 6. Transoral approach. Endoscopic view of transoral approach showing submandibular duct (D), lingual nerve (L), and sublingual gland (SLG).
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inflammatory adherences to surrounding structures that resulted in a bloody surgical field.30
Fig. 7. Transoral approach. Endoscopic view of the operative field.
The advantages of this approach include a smaller incision as compared to the standard submental approach and the previously discussed advantage of endoscopic visualization. In addition, the use of an ultrasound-activated scalpel which does not transmit an electric current reduces the risk of thermal injury to the marginal mandibular nerve as compared to monopolar and bipolar electrocautery.26 However, the disadvantages include those that are common to all endoscopic procedures as well as a significant increase in operative time as compared to the conventional submental approach [70 min, (50–120 min) vs. 41 min, (32–56 min)].25 The application of endoscopic approaches in soft tissue surgery has been thwarted by the challenges fundamental to endoscopic neck surgery including the lack of a well-defined sac and the risk of emphysematous dissection.23 The risk of CO2 insufflation to create a working space in the neck includes massive subcutaneous emphysema, hypercarbia, gas embolization, and some types of arrhythmias.25 Terris et al, developed hybridized techniques to enable an endoscopic approach for the resection of the SMG in a porcine model.27 However, the era for endoscopic neck surgery began with the first description of a parathyroidectomy using CO2 insufflation.28,29 Since then there have been number of reports that have used CO2 insufflation for the purpose of endoscopic neck surgery. These developments will certainly define the approaches to the SMG in the future. 5.2.3. Endoscopic transcervical approach Guyot et al (2005) described an endoscopic approach for the SMG that does not rely on CO2 insufflation to create an operative pocket. In a cadaveric study carried out on 6 non-embalmed cadavers, 12 endoscopic submandibular resections were performed. Access to the subplatysmal plane of dissection was achieved via two 15 mm incisions (one anterior and the other posterior), 10 mm below the submandibular area. A 4 mm diameter, 30-degree endoscope provided the surgical view when placed in the posterior incision. The operative pocket was created and maintained using trans-cutaneous sutures. The dissection was otherwise conducted in a usual fashion. Extirpation of the gland was done through one of the incisions. In all cases gland excision was successful. The operative time decreased with experience from 120 min for the first case to 35 min for the last case. The limitations for an endoscopic approach were defined as presence of
5.2.4. Endoscopic submandibular gland excision using CO2 insufflation Monfared et al (2002) described an endoscopic approach to the SMG in a porcine model using balloon dissection to create an operative pocket which was constantly maintained with low pressure (no more than 4 mm Hg) CO2 insufflation. Three incisions were made. The central 14 mm incision accepts the 12 mm trocar which houses the endoscope while the two lateral incisions (6–7 mm) were used to place the 5 mm operative trocars. Twelve SMGs were successfully excised endoscopically in seven pigs with no conversion to open surgery. The median operative time was 59 min (range, 42– 165 min).27 Terris recently expanded this approach with the addition of the daVinci robotic system to resect the SMG with a mean operative time of 48 min and with no conversions to open surgery.27,31 The main advantage of the robotic-enhanced endoscopic surgery includes a virtual three dimensional vision projection system with an endoscopic arm and two operative arms that can be controlled by the surgeon from a remote console. In addition, the robotic arm permits use of a full range of articulated instruments which can reproduce surgical maneuvers in difficult to access locations. The disadvantages of robotic surgery such as high cost and lengthy setup time are great, and further customization of surgical instrumentation for otolaryngology practice remain to be challenges for the future.23,32 6. Conclusions Newer approaches to the SMG have distinct advantages in terms of cosmesis over the traditional lateral transcervical approach. Although most approaches are feasible and have been successfully performed in humans, they are not widely practiced or accepted as standard of care in most academic institutions and also in community settings. In cases where SMG resection is deemed necessary, we recommend careful selection of the approach based on individual patient characteristics and needs, skill and experience of the surgeon, familiarity with endoscopic technique, and availability of necessary instrumentation. Conflicts of interest None Funding None Ethical approval Not applicable Acknowledgement The authors would like to thank Dr. Richard Whitworth and Dr. William Swartz, Mr. Antony Wells and Mr. Reginauld Delmore, Department of Anatomy; Jeffrey LaCour MD, Department of Otolaryngology Head and Neck Surgery, Louisiana State University School Health Sciences Center, New Orleans, LA; Eugene New, New Orleans, LA (for illustrations), and Trey Joseph, Stryker, New Orleans, LA for their contributions. References 1. Cummings C. Otolaryngology & head neck surgery. In: Cummings C, editor. Salivary gland. New York: Mosby; 1998. p. 1201–9. 2. Lalwani A. Current Diagnosis and Treatment in Otolaryngology–Head and Neck Surgery: Second Edition. New York: McGraw-Hill Medical, 200:5. 3. Guerrissi JO, Taborda G. Endoscopic excision of the submandibular gland by an intraoral approach. J Craniofac Surg 2001;12:299–303. 4. Moore KL, Dalley AF. Clinically Oriented Anatomy, Fourth Edition. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. 1012–1015.
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