Middlemore Hospital, Counties Maukau, Auckland, New Zealand.
J Ultrasound Med. 2020 Feb;39(2):273-278. doi: 10.1002/jum.15100. Epub 2019 Jul 23.
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.
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.
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.
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.
潜水性舌下腺囊肿是舌下腺外渗性假性囊肿，表现为下颌下区软组织肿胀。“尾巴征”已被广泛报道为其诊断的特征性表现。它被描述为一种光滑的渐细彗星形单房液性肿块，其“尾巴”位于舌下间隙（SLS）的塌陷处，其“头部”位于下颌下间隙的后部。这个征象的前提是，SLS 中的舌下腺外渗唾液逸出并“潜水”，越过下颌舌骨肌的后缘进入下颌下间隙。因此，几乎所有潜水性舌下腺囊肿患者的 SLS 后区都必须存在一定量的液体。本研究旨在通过超声（US）确定 SLS 后部可见液体的频率，以佐证“尾巴征”。
回顾性分析了 13 年来 126 例经手术证实的潜水性舌下腺囊肿患者的 US 检查结果，以评估 SLS 后部液体的发生率。
13 例（10.3%）US 图像显示 SLS 有液体。大多数患者表现为黏液肌裂处液体延伸。只有 2 例（1.6%）患者的 SLS 内有液体，而在整个研究中仅 1 例患者出现了经典描述的尾巴征的所有成分。
这是迄今为止最大的放射学研究，在 126 例患者中仅有 2 例（1.6%）出现“尾巴征”。黏液肌裂是外渗的更常见途径。缺乏尾巴征并不能排除潜水性舌下腺囊肿的诊断。
