ACR Codes: 2.-1
A ranula is a benign cystic mass resulting from obstruction of a sublingual or minor salivary gland. A simple ranula remains within the sublingual space. This is as opposed to a diving or plunging ranula which extends from the sublingual space to involve the submandibular and/or parapharyngeal spaces. The sublingual spaces are defined as the paired spaces within the floor of the mouth on either side of the midline genioglossus muscles. Within the sublingual spaces lie the sublingual glands, the lingual arteries, small superior portions of the submandibular glands, and the submandibular gland ducts. Inferolateral to the mylohyoid muscle is the submandibular space, a large anatomic space that is continuous across the midline and contains the submandibular nodes and the bulk of the submandibular glands. There are no posterior fasciasl borders limiting the sublingual and submandibular spaces, allowing free communication between these spaces at the posterior margin of the mylohyoid muscle.
Differential considerations of cystic lesions in the sublingual and/or the submandibular spaces include, other than ranulas, congenital abnormalities, inflammatory lesions, and neoplasia.
Congenital lesions that may be encountered in the floor of mouth or submandibular space region include cystic hygromas, cysts of the second branchial cleft, and cysts of the suprahyoid thyroglossal duct. Differentiation of cystic hygromas fromranulas can be accomplished on the basis of their typical lack of association with sublingual space and by multilocularity, when present.
Cysts of the second branchial cleft are presumed to arise from incomplete obliteration of the embryonic branchail apparatus. The characteristic location and lack of an association with the sublingual space usually allow easy distinction between second branchial cleft cysts and ranulas.
Thyroglossal duct cysts are the result of incomplete obliteration of the embryonic thyroglossal duct. In most instances, the finding of a cystic lesion in the anterior midline at the level of the hyoid bone easily establishes the diagnosis of a thyroglossal duct cyst. When they occur in the submandibular space, they can be distinguished from ranulas because thyroglossal duct cyst are in a midline location.
Inflammatory lesions which present as cystic lesions in the floor of the mouth include acute abscesses and chronic low grade infectious processes. The characteristic signatures of skin involvement and gas with the lesion, in addition to less specific findings like wall thickening and disregard for fascial planes help exclude ranulas.
When dermoids, epidermoids and ranulas are located within the sublingual space, their radiographic distinction must be based on the internal architecture of the lesions. Epidermoids which occur in the sublingual space cannot be distinguished from a simple ranula by radiographic criteria. With dermoids, special attention must be directed to detecting focal collections of fat or subtle inhomogeneities within the central fluid-filled cyst. Lipomas can be diagnosed easily with CT density measurements. Adenopathy that occurs with malignancy aids in distinguishing it from ranulas.
Reference(s): REFERENCES:
1. Coit, W.E., Harnsberger, H.R., Osborn, A.G, et al. Ranulas and Their Mimics: CT Evaluaton. Radiology 1987; 163: 211-216.
2. Charnoff, S.K. and Carter, B.L. Plunging Ranula: CT Diagnosis. Radiology 1986; 158: 467-468.
Use this for Comments and SuggestionsMedPix® is sponsored by the Department of Radiology and Radiological Sciences, USUHS, Bethesda, MD We do not accept paid advertisements.
Disease Topic 3975 
Click Here for MedPix®-2
for Comments and Suggestions
