Overview Of The Submandibular Gland

What is the Submandibular Gland?

The submandibular gland is the second largest major salivary gland, paired, mixed seromucous but predominantly serous. It contributes ∼60-70% of unstimulated whole saliva. Weight ∼7-16g.

It lies in the submandibular triangle, with a superficial and deep lobe continuous around the posterior border of mylohyoid.

Anatomy:

Figure 1: Anatomical relations of the major salivary glands

Gross Anatomy:

Superficial lobe:

Larger, fills most of submandibular triangle. Lies between mandible above and digastric muscles below.
Deep lobe:

Smaller, lies above mylohyoid, in floor of mouth, between mylohyoid and hyoglossus.
Duct - Wharton's duct (submandibular duct):

5cm long, arises from deep lobe, runs forward between mylohyoid and hyoglossus, then between sublingual gland and genioglossus, opens at sublingual caruncle beside lingual frenulum. Crosses lingual nerve.

Relations:

Superficial: skin, platysma, cervical branch of facial nerve

Medial: mylohyoid, hyoglossus, lingual nerve, hypoglossal nerve, facial artery

Posterior: tail of parotid, facial artery grooves its posterior surface

Lateral: mandible, medial pterygoid, facial vein

Blood supply:

Facial artery (submental and submandibular branches), lingual artery. Venous: facial vein, submental vein.
Lymph:

Submandibular lymph nodes -> deep cervical.
Nerve supply:

Secretomotor parasympathetic from superior salivatory nucleus -> chorda tympani -> lingual nerve -> submandibular ganglion -> gland. Sympathetic from superior cervical ganglion via facial artery plexus.

Layers from Skin to Gland:

Skin
Superficial fascia with platysma
Deep cervical fascia (investing layer) forming capsule – splits to enclose gland.
Superficial layer of deep fascia + marginal mandibular nerve + facial vein + cervical branch of facial nerve
Glandular capsule (false capsule from investing fascia, true capsule from condensation)
Gland parenchyma

Marginal Mandibular Nerve:

Branch of facial nerve (VII)
Runs in plane deep to platysma, superficial to investing fascia, often just below angle of mandible
Relation:
Hayes Martin maneuver – nerve lies 1-2cm below mandible, but in 20% can be below. To preserve: incision 2 fingerbreadths (2-3cm) below mandible, elevate flap in subplatysmal plane, ligate facial vein – nerve lies deep to vein. Stay superficial to fascia until mandible identified, then incise fascia over gland.

Figure 1: Mylohyoid muscle dividing the submandibular gland

Histology

Mixed tubuloacinar gland. Serous acini predominant (more than mucous), with serous demilunes of Gianuzzi capping mucous acini. Myoepithelial cells, intercalated ducts, striated ducts. More serous than sublingual, less than parotid.

Pathologies

Tumours

Only ∼8-10% of salivary tumours, but ∼50% are malignant (vs parotid 20% malignant).

Benign (50%):

Facial nerve exits stylomastoid foramen, enters gland, divides into temporofacial and cervicofacial trunks, then into 5 terminal branches at anterior border: Temporal, Zygomatic, Buccal, Marginal Mandibular, Cervical – “Two Zebras Bit My Cheeks” – forming pes anserinus. Lies between superficial and deep lobes, more superficial inferiorly.

Malignant:

Adenoid cystic carcinoma – commonest malignant in submandibular
Mucoepidermoid carcinoma
Acinic cell carcinoma
Carcinoma ex pleomorphic adenoma
Adenocarcinoma NOS, squamous cell carcinoma

Sialolithiasis / Calculi

Commonest salivary disease. 80-90% of all salivary calculi occur in submandibular gland.

Why commoner in submandibular than parotid:

Wharton’s duct is longer, larger caliber, tortuous, upward course against gravity
Saliva is more alkaline, more mucinous, higher calcium and phosphate concentration – more viscous
Flow is slower, more stagnant
pH alkaline promotes precipitation
Presence of mylohyoid flexure

Other:

Cysts: ranula (plunging), mucus retention cyst, epidermoid
Abscess: acute suppurative
sialadenitis (ascending infection)
Neurofibroma, lipoma
Sialadenosis
IgG4-related disease / Kuttner tumour (chronic sclerosing sialadenitis)

Note: on Sjogren's Syndrome:

Autoimmune lymphocytic infiltration of exocrine glands. Triad: xerostomia, xerophthalmia, parotid enlargement. Submandibular involved in 50%. Histology: focal lymphocytic sialadenitis with epimyoepithelial islands. Associated with anti-Ro (SSA), anti-La (SSB), Rheumatoid factor. Risk of MALT lymphoma 44x.

Investigations

Plain X-ray:

Lateral oblique, AP mandible - 80% calculi radio-opaque in submandibular (vs 40% parotid) - Occlusal X-ray: For distal duct stones
Sialography:

Iodinated contrast into Wharton's duct - filling defects, strictures. Contraindicated in acute infection
Ultrasound:

First line, 90% sensitive for stones >2mm, distinguishes solid/cystic, vascularity on Doppler
Magnetic resonance imaging (MRI):

Gold standard for soft tissue, tumour extent, perineural spread, deep lobe, marrow invasion. MR sialography non-invasive
Others:

Fine needle aspiration cytology (FNAC), sialendoscopy, scintigraphy

Gold standard for tumours: MRI with gadolinium; for calculi: Ultrasound + non-contrast CT.

Management of Pathologies

Sialadenitis:

Hydration, sialogogues, massage, antibiotics (anti-staph), incision drainage if abscess
Sialolithiasis:

Conservative, sialendoscopy + basket retrieval, intracorporeal lithotripsy, transoral duct slitting, gland excision for proximal/hilar large stones with chronic sialadenitis
Benign tumours:

Excision of gland (with tumour) - extracapsular dissection not safe as in parotid
Malignant:

Gland excision + neck dissection (levels I-III) + adjuvant radiotherapy +/- chemotherapy

Step-By-Step Excision Of Submandibular Gland

Indications: Chronic sialadenitis with failed conservative, recurrent sialolithiasis (hilar/proximal), benign/malignant tumours, Kuttner tumour, ranula plunging.

Rule of 2s:

2 fingerbreadths below mandible
2 cm from angle
2 layers: platysma and investing fascia
2 arteries: facial and lingual (ligate)
2 nerves to preserve: marginal mandibular, hypoglossal; 1 nerve to see but preserve - lingual
2 veins: facial and submental
Drain for 2 days

Procedure:

1. Anaesthesia:

General anaesthesia with nasotracheal or orotracheal tube away from field. Supine, neck extended, head turned opposite, shoulder roll. Hypotensive anaesthesia helpful.
2. Skin incision:

5-6cm curvilinear submandibular (Risdon) incision, 2 fingerbreadths (2-3cm) below and parallel to inferior border of mandible, from angle to near hyoid. Mark.

3. Elevation of flap with preservation of marginal mandibular nerve:

Incise skin, subcutaneous tissue, platysma.
Elevate superior flap in subplatysmal plane up to mandible.
Identify and ligate anterior facial vein – nerve lies deep/superficial to vein. Hayes Martin: elevate vein with flap to protect nerve.
Incise investing fascia over gland after nerve identified.

4. Dissection of superficial lobe:

Retract gland inferiorly, identify facial artery at posterior border, ligate doubly – proximal and distal (artery grooves gland and may be encountered twice).
Dissect capsule off mylohyoid anteriorly and digastric inferiorly. Preserve submental vessels if possible.

5. Deep lobe dissection and identification of structures:

Retract mylohyoid anteriorly with Langenbeck. Deep lobe appears.
Identify:
1. Lingual nerve – crosses duct from lateral to medial, has 2-3 fibres from submandibular ganglion hanging below it.
2. Wharton’s duct – below lingual nerve.
3. Hypoglossal nerve – deeper, on hyoglossus muscle, with vena comitans.
Dissect duct anteriorly, ligate and divide. Free lingual nerve.
Identify hypoglossal, preserve.
Ligate small vessels to lingual and facial arteries.

6. Haemostasis:

Bipolar cautery, check lingual, facial, submental arteries. Saline wash.
7. Drain:

Insert 10-14F suction drain (Redivac) through separate stab, fix.
8. Closure:

In layers - mylohyoid/digastric area not closed tight, platysma with Vicryl 3-0, skin subcuticular.

Complications

Marginal mandibular nerve injury (most common 5-10%) – lip deviation
Lingual nerve injury – loss of taste anterior 2/3, tongue anesthesia
Hypoglossal nerve injury – tongue deviation to operated side
Bleeding / hematoma from facial artery
Infection, salivary fistula, sialocele
Scar hypertrophy, keloid
Residual stone in duct stump
Frey syndrome – rare in submandibular excision

Management: Most nerve praxias recover 3-6 months. Physiotherapy, eye care if facial weakness, exploration if hematoma.

Methods of Managing Calculi

Conservative: hydration, lemon drops, gland massage
Transoral sialolithotomy for distal duct stones
Sialendoscopy with Dormia basket for <5mm
Laser lithotripsy (Holmium:YAG), extracorporeal shock wave
Submandibular gland excision for hilar, intraparenchymal >10mm, recurrent infection

Note on HIV infection of Parotid

HIV-associated salivary gland disease – benign lymphoepithelial cysts, diffuse infiltrative lymphocytosis syndrome (DILS). Bilateral parotid > submandibular enlargement, CD8 infiltration, associated with cervical lymphadenopathy. Manage with HAART, aspiration, sclerotherapy, superficial parotidectomy if cosmetic.

In conclusion,

Submandibular gland though small, has complex anatomy and high propensity for calculi and malignancy compared to parotid. Understanding of fascial layers and nerve relations is key to safe excision.

Get in Touch

Read doctor-produced health and medical information written for you to make informed decisions about your health concerns.

Address

Adenta

Email

info@grovehealth.net

Working Hours

Mon - Friday @ 8am - 5 pm