Submandibular Gland Excision

Considerations

• Identifying and preserving the marginal mandibular nerve (MMN)

  • Most commonly injured in dissection of level Ib 

  • The Hayes-Martin maneuver involves ligation of the posterior facial vein and superior reflection of the investing fascia (superficial layer of the deep cervical fascia, which encloses the SMG) below the mandible to preserve the marginal mandibular nerve. The peri-facial nodes thus remain undissected. (article link, atlas link)

    • NOTE: The literature varies in quality and methodology (cadaveric vs living) and the results and conclusions vary accordingly.

    • The classic paper came in 1962 from Dingman and Grabb. Much of the literature since comes from outside the US. To my knowledge, there are no review articles on this topic. 

    • 2007: Clinical observations of the anatomy and function of the marginal mandibular nerve

      • When the neck was extended the nerve was displaced in an anterior and downward direction with the lowest point 1.25+/-0.7 cm below the mandible between the posterior and anterior facial veins

      • The nerve was >1 cm below the lower border of the mandible in 54% of dissections

      • When the intent was to preserve the nerve, dysfunction was 16%

      • The incidence of marginal mandibular nerve dysfunction following neck dissection is comparable to that observed following submandibular gland excision for benign disease

      • Placement of incisions 2 cm below the lower border of the mandible will put the nerve at risk in a significant number of patients.

    • 2007: Anatomical localisation of the marginal mandibular branch of the facial nerve

      • Comprised of one branch (32%), two branches (40%) and three branches (28%)

      • The relationship of the nerve to the lower border of the mandible was variable: it was either totally above the lower border of the mandible (28%), below the mandible (44%) or in 28% of cases lying above and below it

      • The branch which lay below the lower border of the mandible crossed it opposite the masseter muscle or opposite the facial artery or else anterior to the facial artery

      • The branches which lay above the lower border of the mandible were always deep into the superficial layer of the parotid fascia

      • However, below the mandible all the branches ran intrafascially

      • The termination of the nerve was always deep to the muscles of the lower lip

    • 2013: The course of the marginal mandibular branch of the facial nerve in adult cadavers. An anatomic study

      • One branch (36.4%), and two branches (63.6%)

      • The distance of the nerve from the inferior border of the mandible varied from 13.06-40.08 mm, with an average distance of 21.91 mm

      • There were communications with buccal branch only in 4.6%

      • All the branches of the marginal mandibular branch ran laterally to the facial artery in 97.7%

      • In one specimen, the 2 marginal mandibular branches ran between the facial artery and vein

    • 2014: The marginal mandibular nerve in relation to the inferior border of the mandible

      • • The MMN runs, on average: 

          • 0.75 mm below the gonion

          • 0.08 mm superior to the posterior border of the antegonial notch

          • 0.06 mm superior to the arc of the antegonial notch

          • 1.29 mm superior to the anterior border of the antegonial notch

          • 3.6 mm superior to the point at which the facial artery reaches the inferior border of the mandible

          • 10.9 mm superior to the vertical line that extends from the commissure of lip to the inferior border of the mandible

Preparation

• • Bedside ultrasound 

  • Facial nerve monitor 

    • Trace the path of the MMN

  • Shoulder roll

  • Head elevated and turned away slightly 

  • Bimanual SMG palpation and marking 

  • Mark the incision in a natural neck crease 2 fingerbreadths (> 2 cm) from the mandible's lower margin 

    • May incorporate into a selective neck dissection incision 

Procedure

• • Incise the skin and platysma 

    • Be aware of the MMN deep to the platysma as the superficial layer of the deep cervical fascia is encountered

• Dissect to the inferior margin of the SMG

• Incise the fascia of the SMG  

• Elevated the SMG fascia flap

• Optional: Locate and ligate the facial vein, elevate with the flap (Hayes-Martin maneuver)

  • Dissect to the superior margin of the SMG

  • Dissect to the anterior margin of the SMG at the level of the anterior digastric 

  • Reflect the SMG posteriorly 

  • Identify the mylohyoid 

  • Dissect to the posterior margin of the SMG

    • Cauterize perforating vessels 

  • Retract the mylohyoid anteriorly 

    • 90 degree retractor is helpful

  • Identify the sublingual gland and lingual nerve immediately deep the mylohyoid

  • Dissect the lingual nerve

  • Identify the SMG duct with its vein

  • Identify the hypoglossal nerve emerging deep from the posterior digastric 

• Dissect the SMG duct to the FOM and ligate here

• Reflect the SMG inferiorly 

• Identify the facial artery indenting the postero-superior SMG

• Dissect facial artery feeding vessels to the SMG

  • Ligate either the facial artery or its feeding vessels

  • Deliver the SMG

  • Irrigate 

  • Place the (passive) drain

  • Layered closure: Platysma, deep dermis 

    • Avoid sewing the MMN 

Post-op

• • Medications 

  • Follow-up 

    • Remove drain POD ***

    • RTC POD ***

High-Yield

Links

• • eMedicine: Salivary Gland Neoplasms 

• Vimeo: (5:20) Surgical Video Submandibular Gland Excision from Mass. Eye and Ear

  • YouTube: (28:55) Submandibular gland excision full hd - Dr. Sridhar Reddy - excellent video quality but lacking narration