Key points

Introduction

The sublingual gland is the smallest of the 3 major salivary glands. It is located in the floor of the mouth beneath the tongue, anterior and above the submandibular gland. It extends in the submucosa of the floor of the mouth from the canine/first premolar area posteriorly to the second molar region. It is a mucus-secreting gland, which produces approximately 5% of the mouth’s volume of salivary supply. The main duct of the sublingual gland is Bartholin duct, which opens with or near the submandibular duct. There are several smaller ducts, called the ducts of Rivinus, which open independently along the sublingual fold ( Fig. 1 ).

Anatomy of sublingual gland.

( From LaPorte SJ, Juttla JK, Lingam RK. Imaging of the floor of the mouth and the sublingual space. RadioGraphics 2011;31:1215–30; with permission.)

Pathology

The primary reason for excision of the sublingual gland is the presence of an associated mucous cyst in the floor of the mouth below the tongue, called a ranula. It is the most common disorder associated with the sublingual glands. Ranulas generally are caused by trauma to the ducts of the sublingual gland, causing them to rupture, which results in mucin collection within the connective tissues to form a mucous pseudocyst.

There are 2 types of ranulas: oral ranulas and plunging (cervical) ranulas. Oral ranulas are due to extravasation of mucus from a ruptured duct, which pools above the mylohyoid muscle in the floor of the mouth below the tongue. Clinically, it appears as a translucent, bluish, dome-shaped, fluctuant swelling in the floor of the mouth ( Fig. 2 ). The cervical or plunging ranula, on the other hand, results from mucus from the sublingual gland that dissects between the fascial planes and muscle of the base of the tongue to accumulate below the mylohyoid muscle in the submandibular space, forming a collection in the upper neck ( Fig. 3 ). The cervical ranula presents as a mass in the upper neck just below the inferior border of the mandible.

Oral ranula.

Plunging ranula.

( A ) Intraoral view of ranula. ( B ) Extraoral view of cervical ranula in submandibular area.

The first attempt at management of an oral ranula should be marsupialization of the ranula. For small ranulas, placement of circumferential sutures and deroofing of the lesion usually is curative. For larger ranulas, the tongue and tissues within the floor of the mouth compress the wound edges, allowing them to heal before re-epithelialization and fibrosis occur. This leads to a rapid recurrence of the mucous cyst. In such cases, after marsupialization of the ranula, the entire pseudocyst should be packed with gauze packing a strip for 7 days. The packing material should be placed firmly into the cavity to fill the entire cystic area. One end is left out of the cavity and the mucosa is closed loosely over the packing with 1 or 2 sutures to keep it in place. This allows for epithelialization of the cyst cavity while simultaneously sealing the duct that is causing the mucinous leak. The gauze packing also causes a foreign body inflammatory reaction, which results in fibrosis and atrophy of the involved acini. The gauze packing should be removed slowly in segments over a 3-day or 4-day period. If the ranula recurs, then the ranula and the sublingual gland should be removed.

The management of the cervical ranula involves surgical excision of the oral portion of the ranula along with the associated sublingual salivary gland. The plunging ranula resolves by simply excising the sublingual salivary gland and aspirating the fluid in the submandibular space followed by a pressure dressing. There are surgeons, however, who believe that an extraoral approach to address the mucinous pseudocyst in the submandibular area is necessary.

Surgical anatomy

The sublingual salivary gland is a superficial structure in the floor of the mouth, covered only by mucosa. The average size of the normal sublingual gland is 32 mm × 12 mm. The anatomic boundaries are the mucosa of the floor of mouth superiorly, the mylohyoid muscle inferiorly, the medial surface of the mandible laterally, and the muscles along the base of the tongue medially ( Fig. 4 ). Within the confines of this anatomic space, significant structures are the submandibular duct, lingual nerve, and sublingual artery ( Fig. 5 ). Unlike the other major salivary glands, the sublingual gland is not encapsulated but is dispersed throughout the surrounding tissues of the floor of the mouth in an irregular globular form. In the anterior portion of the sublingual space, the gland follows the curvature of the inner surface of the mandible and remains in close contact with the bone until around the first/second molar area, where the origins of the mylohyoid muscle displace the posterior portion of the gland away from the bone. The anterior portion of the gland is wider than the posterior third.

( A ) Anatomical view showing relationship of sublingual gland with lingual nerve. ( B ) Anatomy of structures in the floor of the mouth

The submandibular duct courses anteromedially superior to the mylohyoid muscle. #, crossing location of the submandibular duct and lingual nerve.

( Modified from Sittitavornwong S, Babston M, Denson D, et al. Clinical anatomy of the lingual nerve: a review. J Oral Maxillofac Surg. 2017;75(5):926.e7; with permission.)