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

Abstract

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.

Mylohyoid muscle defects: comparison of CT findings and dissected specimens

“…The classification is as follows: grade 0, normal anatomical structures; grade I, circumscribed thinning of the mylohyoid muscle, vertical reduction in muscle thickness during swallowing, and no signs of glandular penetration; grade II, herniation of the gland during swallowing and normal anatomical structures during rest; and grade III, constant hiatus in the mylohyoid muscle with permanent herniation of the sublingual gland. In that study, almost 20% of the cases were classified as grade II or grade III, whereas 40% showed at least unilateral thinning of the muscle classified as grade I. Keberle et al [9] reported two cases in which functional MRI [true fast imaging with steady state precession (FISP) sequence during the modified Valsalva maneuver] revealed submandibular herniation by the sublingual tissue through a gap in the mylohyoid muscle. The results of these two previous studies suggest that some mylohyoid defects and potential sublingual herniations through mylohyoid defects would be missed on normal static CT, MR, and ultrasound images, and this would be a pitfall.…”

Dynamic sonography and CT findings of unilateral submandibular gland agenesis associated with herniated hypertrophic sublingual gland

“…However, ipsilateral or contralateral compensatory sublingual hypertrophy to compensate for any salivary hypofunction can rarely occur in the absence of one submandibular gland. The hypertrophic sublingual gland may herniate through the mylohyoid gap and causes swelling and pseudomass in the submandibular region …”

“…The salivary gland tissue, mass lesions, and the fat tissue may protrude through the gap . It is reported that MRI with fast sequences can provide direct visualization of the mylohyoid gap level and the herniated sublingual tissue during the modified Valsalva maneuver . Although the sublingual gland shows a hyperintense signal on T1‐weighted images, it is often difficult to differentiate the sublingual gland from the fat located in the sublingual space.…”

Pitfalls in Diagnostic Radiology

“…It separates the sublingual space superiorly from the submandibular space inferiorly. Swallowing and/or a modifi ed Valsalva maneuver can cause herniation of the sublingual tissue that is confi ned within the mylohyoid muscle in the normal state or can aggravate the severity of the tissue herniation (Keberle et al 2005 ). Additional defects can be frequently observed along the lateral margin of the anterior two-thirds of the mylohyoid muscle (White et al.…”