Patient History
16-year-old female with floor of mouth swelling.
Findings
Contrast-enhanced CT was performed from the skull base to the thoracic inlet. The study demonstrates bilateral low-attenuation lesions which are paramidline and located in the floor of the mouth. The left-sided lesion measures approximately 4.2 cm x 1.5 cm in largest axial dimensions. The lesion on the right measures approximately 2.7 cm x 8 mm. Both of these lesions are located medial to the mylohyoid muscle and lateral to the hyoglossus muscle and are consistent with ranulas.
The coronal reconstructions demonstrate the right-sided ranula to be superior to the mylohyoid muscle and therefore would be classified as a simple ranula. However, the left-sided ranula extends inferiorly below the mylohyoid muscle, likely through a boutonniere defect, in the anterior aspect of the mylohyoid muscle, into the left submandibular space. Thus, this would be considered a “diving”, "plunging" or "complex" ranula.
There is a surgical clip which may be due to prior attempted resection of this ranula. This study also demonstrates multiple fluid collections extending along the floor of the mouth located in the midline raphe and extending posteriorly into the tongue base in the region of the circumvallate papillae. The sagittal reconstructions also demonstrate a small fluid collection deep to the hyoid bone. It is unclear whether this fluid collection located in the region of the circumvallate papillae and extending deep to the hyoid bone is due to extension of the ranula or a coincidental thyroglossal duct cyst.
Visualized portion of the brain demonstrates a prominent enhancing pituitary gland which could be due to hormonal variation. The remainder of the brain is within normal limits, however, dedicated brain imaging is necessary for complete diagnostic evaluation.
Visualized portion of the lungs is grossly within normal limits. However, dedicated chest CT is necessary for complete diagnostic evaluation.
Conclusions
1. Bilateral ranulas (left greater than right) with the right being a simple ranula and the left extending below the mylohyoid muscle (“complex, plunging or diving”).
2. Loculated fluid collections involving the floor of the mouth which could represent rupture of the ranula from incomplete resection.
3. Cystic lesion involving the tongue base extending posterior to the hyoid bone which could either be due to posterior extension of the ranula or incidental thyroglossal duct cyst.
