Functional MR imaging of submandibular herniation of sublingual tissues through a gap of the mylohyoid muscle in two cases of submandibular "masses".

Except for neoplasms, in symptomatic patients with submandibular swellings, gaps of the mylohyoid muscle may be the cause of herniations of sublingual tissues, such as fat and/or the sublingual gland. In two patients with a submandibular swelling, MRI with standard sequences including contrast enhancement was performed to exclude a neoplastic lesion. In addition, we performed a trueFISP sequence during modified Valsalva's maneuver. In both patients, a neoplasm was excluded. Instead, the trueFISP sequence during the modified Valsalva's maneuver showed submandibular herniation of sublingual tissues. If MRI of the floor of the mouth does not show a neoplasm, an additional functional MR investigation should be performed. Gaps of the mylohyoid muscle can be the cause of herniating sublingual tissues (similar to plunging ranulas). During the modified Valsalva's maneuver, sublingual fat and/or gland can herniate and cause a symptomatic submandibular swelling. A coronal trueFISP sequence is particularly suited to demonstrate this.