p>David P. Singer, MD
Patrick K. Sullivan, MD
Division of Plastic Surgery
Brown University School of Medicine
Rhode Island Hospital
Providence, Rhode Island
Published in the Plastic and Reconstructive Surgery Journal 1112 :1150-1154, September 15, 2003. Presented in part at the American Society for Aesthetic Plastic Surgery Annual Meeting, May 2002 and VIII Congress of Italian and American Plastic Surgeons, June 2002
Submandibular gland resection for aesthetic reasons has been hotly debated. Detractors maintain that the procedure is dangerous as it puts too many important structures at risk, notably motor nerves. The present study was undertaken to elucidate the neurovascular and soft tissue anatomy of the digastric triangle via cadaver dissections so that a surgical approach to achieve safe aesthetic submandibular resection could be performed. Fifteen digastric triangles dissections were performed in fixed and fresh cadaver specimens. The dissection focus was to understand the submandibular neurovascular relationships, capsule as well as fascial layers, and measurements to known structures. The marginal mandibular nerve was located external to the submandibular capsule, approximately 3.7 centimeters cephalad to the inferior margin of the gland. The hypoglossal nerve is posterior to the digastric sling in a position that is protected deep within the visceral layer of the neck. The lingual nerve is located underneath the mandibular border, crossing anterior to the submandibular duct. The vascular supply is variant, but with an average of 1.5 vessels entering medially to the superficial lobe of the gland, 1 intermediate vessel entering medially to supply the superficial and deep lobes, and 1 deep perforator which runs from the central portion of the deep lobe to the superficial lobe. Appreciation of this anatomy is critical in the submental approach for partial resection. Although it can be technically challenging, we believe the anatomy is straight forward and we have found partial submandibular gland resection can be executed via a consistent, safe approach to optimize facial rejuvenation in the select patient.
The delineation of the mandibular and cervicomandibular angles plays a very important role in the appearance of facial youth and harmony1,2. The evolution of techniques to address this area surgically underscores the importance of the neck in facial rejuvenation. In particular, submandibular fullness can be appreciable in a variety of patients. This submandibular fullness is represented by increased gland volume and laxity of the neck fascial layers with gland ptosis. SMAS suspension techniques during rhytidectomies and platysma plication procedures can indirectly address submandibular fullness via increasing fascial support of the gland. Nonetheless, there are patients which develop more noticeable submandibular fullness after rhytidectomy which compromises the aesthetic contour of their neck. Further, there are select patients with definitive submandibular fullness who would be excellent candidates for primary partial submandibular gland resection to achieve an optimal aesthetic result.
Submandibular contouring for aesthetic indications is encircled in controversy, belied predominately by the risk for nerve injury. SMAS rhytidectomy techniques with risks to injure the facial nerve were born through similar criticism, substantiated through anatomic evaluation, and accepted into plastic surgery practice. Hence, the goal is to understand the neurovascular anatomy and soft tissue anatomy of the digastric triangle through cadaver dissections. This anatomy along with variations can be learned and taught to skilled plastic surgeons. Through this anatomic appreciation, a logical surgical approach to partial submandibular gland resection can be justified. This enables the plastic surgeon to expand his armamentarium to enhance facial rejuvenation.
METHODS & ANATOMIC OBSERVATIONS
Fifteen digastric triangle dissections in fixed and fresh cadavers were performed upon seven females and eight males. The dissection focus was to define (1) vascular supply and relationships to the submandibular gland (2) nerves including the marginal mandibular nerve, lingual nerve, hypoglossal nerve, and mylohoid nerve (3) submandibular gland capsule and fascial layers (4) measurements of the submandibular gland position to known anatomic structures including the mentum, thyroid notch, hyoid, and marginal mandibular nerve.
Vasculature: There are usually one to two vessels entering the medial aspect of the superficial lobe as well as an intermediate vessel entering the medial aspect of the capsule to supply both the superficial and deep lobes. Hence, there are usually one to three vessels (average was two) entering the medial aspect of the submandibular gland, which are in the territory of the superior thyroid artery. There is a deep perforator which courses through the central aspect of the deep lobe to pierce the posterior aspect of the superficial lobe (see Table 1). The arterial distribution of this perforator is the facial or lingual artery. The facial artery passes behind the posterior digastric muscle and ascends vertically to lie posterior to the submandibular gland or interposed between the deep and superficial lobes. The facial vein is found between the deep and superficial lobes at the lateral extent of the capsule. A variant course of the facial vein was identified superficial or lateral to the superficial lobe of the gland in two cadavers.
Nerves: With the exception of the autonomic plexus to the submandibular gland, all the nerves were found external to the submandibular capsule which encircles the gland. The hypoglossal nerve is found posterior to the tendonous juncture of the anterior and posterior digastric muscle deep within the visceral layer of the neck. The lingual nerve is located cephalad-medial to deep lobe; the submandibular duct crosses behind the lingual nerve near the mylohyoid border. While these structures course posterior to the mylohyoid muscle to continue medially toward the base of the tongue, they are essentially protected underneath the mandible border when visualized laterally. The marginal mandibular nerve is identified approximately 3.7 cm (range 3-4.2 cm) cephalad to the inferior limit of the submandibular gland (see Table 1). The marginal mandibular nerve is found on the posterior surface of the platysma while crossing superficial to the facial vein. The marginal mandibular nerve was identified below the inferior border of the mandible in three cadavers (20% of the cadavers). The mylohoid nerve(v3) is found cephalad-medial to the submandibular gland coursing medial to innervate the mylohyoid muscle. The secremotor innervation to the gland originates in the superior salivary nucleus, where the parasympathetic preganglionic fibers transverse through the chorda tympani of the seventh cranial nerve to join the lingual nerve. The submandibular ganglion abuts the lingual nerve, where the postganglionic fibers originate and directly pierce the capsule along with facial artery perforators to enter the deep lobe and cephalad aspect of the gland.
Lobe Structure/Fascial Layers: The superficial lobe is inferior medial to the deep lobe structures which can extend around the mylohyoid muscle. The capsule of the submandibular gland is derived form the superficial layer of the deep cervical fascia.
Clinical Measurements: All distances were measured from the midline point to the medial aspect of the submandibular gland (see Table 2). The average distance from the mentum to the submandibular gland was 5.2 cm (range 4.8-6.0 cm); thyroid notch to submandibular gland was 3.4 cm (range 2.4-4.0 cm); and hyoid to submandibular gland was 2.5 cm (range 1.9-3 cm). The average submandibular gland diameter was 3.6 cm (range 3-4.2 cm).
The surgical technique conforms to facial aesthetic incisions with a respect for pertinent soft tissue structures. Pre-operative marking of the submandibular gland ptosis is done with the patient in the standing position. The surgery is performed through the standard submental incision. The subplatysmal space in entered and dissection is performed to the lateral extent of the gland. A strong headlight, one inch malleable ribbon retractors, a variety of insulated instruments, and a cautery are utilized throughout the procedure to ensure excellent visualization and control of bleeding. Vessel clips are held in reserve. The submandibular gland capsule is incised obliquely at the most inferior/caudal extent of the gland. The remainder of the procedure is within the limits of the capsule which provides a reasonably safe area of dissection as the key nerves are external to the capsule. The superficial lobe of the gland is visualized, then bluntly and carefully mobilized inferiorly. Importantly, there are one to three vessels entering the medial aspect of the superficial lobe as well as a central perforator from the deep lobe. Careful dissection of these vascular structures avoids avulsion and allows cauterization prior to resection. The superficial lobe is then partially resected with bovie cautery in an oblique fashion parallel to the mandibular border to address the degree of submandibular gland ptosis. Alternatively, Bipolar Scissors or the Harmonic Scalpel (Ethicon Endo-Surgery, Cincinnati, OH) could be utilized to accomplish the partial resection of the gland5,6. The base of the residual submandibular gland is cauterized, to provide hemostasis and minimize the potential for a salivary fistula. Finally, the submandibular capsule is frequently closed with 3.0 mersilene to buttress the remainder of the gland in order to avoid the potential for future gland ptosis and optimize the neck contour.
Submandibular surgery for otolaryngology and oncologic issues is the basis for our comfort level in this area due to earlier extensive experience with neck dissections and submandibular gland excision prior to entering plastic surgery. It is also a resource of information regarding the anatomic complexity and surgical techniques used for submandibular gland alteration. We believe the anatomy is straight forward and we have found the risks of surgical excision of the submandibular gland to be very low. Review of literature corroborates this philosophy objectively by revealing low complication rates for neurovascular injury in complete gland resection.
As attention to neck rejuvenation procedures has increased, different techniques to surgically manage submandibular fullness have developed. Certain patients with a lesser degree of submandibular fullness can occasionally have effective contouring by non-resection methods including SMAS and platysma plication techniques. More definitive submandibular fullness mandates a more direct, i.e. resection technique, to address this area. Pompeo de Pina et Al. reported their clinical technique and experience in eight patients where they partly excised twelve glands. The surgery was performed through a direct approach overlying the gland at the lower edge of the mandible or through a standard rhytidectomy incision with access through a platysmal myotomy. The disadvantage of the direct approach is aesthetic compromise secondary to incision placement in a more visual area of the neck. Further, recurrence of submandibular gland fullness/ptosis may be a concern due to the lack of buttressing the submandibular capsule in their technique. In either approach, rhytidectomy or direct approach, the marginal mandibular nerve can be relatively close to the field of dissection due to the lateral to medial technique. Nonetheless, the study was remarkable for no complications or salivary fistulas in the eight patients. Another approach to submandibular fullness is to directly imbricate the platysma overlying the gland. This is potentially more hazardous as the marginal mandibular nerve is never visualized and could easily be strangulated by the suture imbrication.
The surgical technique presented herein recognizes the pertinent anatomy while addressing the concerns of other approaches. The marginal mandibular nerve motor innervation to the depressor anguli oris, depressor labii inferioris, orbicularis oris, mentalis, and risorius commands respect in reference to submandibular contouring. The medial approach is ideal in that it maximally avoids the nerve (1) as demonstrated by the average distance of the gland to the nerve is 3.7 cm (2) the course of the nerve laterally can potentially be lower whereas medially its course is more cephalad towards the lower lip (3) there is no dissection pathway for crossing the nerve (4) a caudal approach to the gland within the confines of the capsule. Other nerves including the lingual nerve, hypoglossal nerve, and mylohyoid nerve are adequately protected by distance and soft tissue structures. Further, the vascular supply to salivary glands is plentiful such that a preemptive knowledge is beneficial to minimize difficult bleeding. The dissections identified the medial perforators which are important in mobilizing and resecting the submandibular gland with hemostatic control. The clinical measurements demonstrate that five centimeters from the submental incision to the gland is a reasonable working distance. Nonetheless, the submental incision is relatively limited access to the submandibular gland requiring precision of dissection as there is significant and variant vascular supply. In sum, these anatomic concepts justify the surgical approach for partial submandibular resection.
Submandibular gland contouring is a safe and effective way to manage enlarged or ptotic submandibular glands while performing facial rejuvenation surgery. However, submandibular gland contouring is technically challenging and time consuming when done through a limited submental incision as the surgeon is working in a hole. This can be moderated by a thorough understanding of the anatomy along with a well planned surgical approach. Extensive experience in oncologic head and neck dissections is helpful as the indirect approach via the submental incision significantly changes exposure to the gland, critical blood vessels and nerves. Fortunately the key nerves have been demonstrated to be a significant distance from the dissection through this submental approach. The variable blood vessels described in this study remain the challenge. To this end, cautery, vessel clips and additional surgical instrumentation assists with the limited exposure and treatment of the potentially problematic vasculature.
The authors wish to thank Rod Rohrich, M.D., William Adams, M.D. Steve Byrd, M.D., and the University of Texas Southwestern Anatomy Lab Personnel for their generous contributions. Further, the authors are grateful to Ted Goslow, Ph.D, and the Brown University Medical School Anatomy Lab for their eager support of the anatomic pursuits of the study. Dr. Bruce Connell, Dr. Tim Marten, and Dr. Joel Feldman are recognized for their prior work and intellectual curiosity in submandibular contouring in the facial rejuvenation patient.
Patrick K. Sullivan, MD
Brown School of Medicine
Rhode Island Hospital
Suite 235 Plain St., Suite 502
Providence, Rhode Island 02905
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- Submandibular gland is encircled prior to the dissection which is done entirely through the limited submental incision.
- Submandibular gland capsule with platysma retracted superficially and laterally with extensive incision for anatomic demonstration in the cadaver.
- Superficial and intermediate vessels to superficial lobe of submandibular gland with capsule retracted laterally.
- Marginal mandibular nerve (MMN) identified after window removed from platysma; submandibular gland partially visualized at medial aspect of platysma demonstrating distance from MMN.
- Hypoglossal nerve deep in the neck posterior to the submandibular gland coursing underneath the posterior digastric muscle.
- Lingual nerve crossing anterior to the submandibular duct underneath the border of the mandible.