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July 2015Background
A ranula is a mucocele arising in the floor of the mouth, secondary to the obstruction of the salivary ducts of the sublingual glands. “Plunging” ranulas present as masses involving the submandibular triangle or other neck spaces, secondary to herniation of a portion of the sublingual gland through dehiscences in the mylohyoid muscle. The cervical component of a ranula is a pseudocyst lined by granulation or connective tissue that is without a true epithelial lining. Another hallmark feature of plunging ranulas is the lack of respect for tissue planes, often following the previous elevation of neck flaps or extending deeply into the soft tissues and fascial planes of the neck. Ranulas may result from any type of traumatic or iatrogenic injury to the sublingual gland or its ducts.
Ranulas uniformly arise from the sublingual gland, which constitutively secretes saliva with high protein content. A ranula will increase in size when lymphatic drainage and clearance by macrophages recruited in the inflammatory response are insufficient to keep pace with the extravasation of mucous. Spontaneous regression has been reported, and some authors suggest deferring surgery until the lesion has been present for six months, particularly in recurrent cases where the diagnosis is clear.
Fine needle aspiration (FNA) is routinely used by some authors for diagnosis of ranulas based on aspiration of mucous, presence of amylase in the fluid, and/or cytology consistent with inflammation. However, FNA under local anesthesia may not be well tolerated by children. Imaging is not uniformly necessary, but it may be useful to confirm diagnosis. With ultrasound, ranulas appear as hypoechoic cystic masses with internal echoes. For plunging ranulas, a dehiscence in the mylohyoid muscle is characteristically observed. For recurrent lesions or plunging ranulas, computed tomography or magnetic resonance imaging may be helpful to localize the lesion and exclude other etiologies. However, imaging may not always give a definitive diagnosis. For example, lesions such as dermoid cysts may also appear as well-circumscribed, low attenuation masses.
Intraoral treatment options for ranulas include simple incision and drainage, marsupialization, excision of the ranula with or without excision of the sublingual gland, or excision of the sublingual gland with “evacuation” of a plunging ranula. External cervical approaches include needle aspiration of the cervical component, excision of the submandibular gland, excision of the pseudocyst, or external incision and drain placement, all of which may be combined with intraoral approaches. Use of OK-432, various lasers, and robotic surgery have also been reported. Many case series are small; and many reports combine pediatric and adult cases, intraoral and plunging ranulas, primary and recurrent cases, and a variety of surgical approaches, contributing to a lack of clarity in the literature.
Best Practice
Intraoral excision of the ipsilateral sublingual gland is recommended for most ranulas. Plunging ranulas may be amenable to the evacuation of contents through the intraoral incision, but in revision cases or large pseudocysts a cervical incision is advised to confirm diagnosis, and to allow placement of a drain through the neck with application of a neck pressure dressing. Complete excision of the pseudocyst wall is not necessary (Laryngoscope. 2013;123:1826-1827).