Plunging Ranulas and Prevalence of the "Tail Sign" in 126 Consecutive Cases.

OBJECTIVES: Plunging (or diving) ranulas are extravasation pseudocysts arising from the sublingual gland that present as soft submandibular swelling. The "tail sign" has been widely reported as pathognomonic for their diagnosis. It is described as a smooth tapering comet-shaped unilocular fluid mass with its "tail" in the collapsed sublingual space (SLS) and its "head" in the posterior submandibular space. This sign is based on the premise that extravasated saliva from the sublingual gland in the SLS escapes and plunges, over the posterior edge of the mylohyoid muscle into the submandibular space. Therefore, some fluid must be present in the posterior SLS in almost all patients with plunging ranulas. This study aimed to determine the frequency of fluid seen with ultrasound (US) in the posterior SLS to corroborate the tail sign. METHODS: A total of 126 consecutive cases of surgically proven plunging ranulas were investigated with US over 13 years. The findings were reviewed retrospectively for the prevalence of fluid in the posterior SLS. RESULTS: Thirteen patients (10.3%) showed SLS fluid on US images. Most showed fluid extension through a mylohyoid dehiscence. Only 2 patients (1.6%) showed fluid within the posterior SLS, and 1 patient alone in this entire study showed all of the components of the classically described tail sign. CONCLUSIONS: This largest ever radiologic study showed low prevalence of the tail sign in 2 of 126 patients. A mylohyoid dehiscence was the more common route for extravasation. Absence of the tail sign does not exclude the diagnosis of a plunging ranula.

Types of sublingual gland herniation observed during sonography of plunging ranulas.

OBJECTIVES: Plunging ranulas have been shown to have a common trio of mylohyoid defects, sublingual gland herniation, and submandibular space fluid collections. The herniated sublingual gland may be susceptible to subclinical trauma. The purpose of this study was to investigate the frequency of occurrence of various types of active sublingual gland herniation observed during diagnostic sonographic studies. METHODS: Sonographic findings of sublingual gland herniation from 76 patients with a total of 80 plunging ranulas are presented. All sublingual gland herniations, including those on the contralateral side, were documented at the time of the examinations and reviewed later. The sonographic appearances of active sublingual gland herniation were given the names "slide," "wobble," "mushroom," and "retrusion" to reflect the observed movement. RESULTS: Mylohyoid defects were found in 98% of plunging ranulas. The different types of sublingual gland herniation observed were as follows: slide in 77.8%, wobble in 11.1%, mushroom in 9.7%, and retrusion in 1.4%. The unaffected contralateral side showed a wobble in 44.8% of cases and slide in 8.9%. CONCLUSIONS: Sublingual gland herniation through mylohyoid defects is easily missed if one is unaware. Prior knowledge of the various types of sublingual gland herniation and their frequencies of occurrence are very helpful during diagnostic sonographic examinations.