Thread by @ASHNRSociety

We're kicking off #HNxHN on Submandibular and Sublingual Space from @ASHNRSociety & @ESHNRSociety . Follow below for a recap thread and then check out the full length talks online.
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First, we'll start with a discussion on anatomy of these spaces by Dr. Julie Bykowski.

“Finding the genioglossus (muscle) is key to getting your bearings when evaluating scans that may be degraded due to dental artifact or distortion due to tumors.”
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The hyoglossus muscle is an important landmark for the sublingual space. The lingual nerve and submandibular duct travel lateral to the hyoglossus, and the lingual artery and vein are deep/medial to it.
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The submandibular space is a triangular region superficial to the mylohyoid muscle between the mandible and hyoid. There is no fascial separation between the SMS and lateral pharynx, important when considering routes of spread.
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Which anatomic structure delineates the boundary between the submandibular and submittal spaces?
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FDG is taken up by salivary glands and excreted in saliva. This is usually a symmetric process and physiologic. However, in cases of asymmetric, correlating for prior surgery/radiation, gland atrophy, or mass on anatomic imaging is useful.
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Chorda tympani supplies parasympathetic innervation to promote glandular saliva production via submandibular ganglion. The lingual nerve fibers via chorda tympani supply taste to anterior 2/3 tongue, & hypoglossal n. supplies most of the motor innervation to the tongue.
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A few anatomic variants to be aware of:
Mylohyoid boutonniere – when SLG herniates into SMS.
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Another variant:
Stafne defect – depression on the lingual aspect of the mandible associated with ectopic SMG tissue. This is well-corticated and usually inferior to inferior alveolar nerve.
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And lastly:
SMG transfer – SMG mobilized anteriorly into submental triangle. Search clinical history to prevent mistaking this for a tumor recurrence.
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Incredible review of relevant anatomy and variants of the SLS/SMS by Dr. Bykowski 🌟

Now, Dr. Beale will take us through some important pathology of these regions. @DrTimBeale

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True primary SLS neoplasia is rare.

Most tumors in the SLS are related to invasion from a floor of mouth mucosal SCC. (left image)

When a primary masses does arise within the SLS, 90% are malignant, half of which are adenoid cystic carcinooma. (right image)
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There are 3 groups of lingual / sublingual lymph nodes, important to consider when you have a ventral tongue or FOM cancer: midline (US image), paraglandular (ax T1 MRI), and parahyoid.
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Remember that tumors can cause duct obstruction! Here, an ACC of the sublingual gland has obstructed the submandibular duct.
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Let’s move to inflammatory SLS conditions.

A ranula is a pseudocystic thick mucin collection. Simple types are confined to the SLS and superficial to the SLS (left). Diving/plunging ranulas extends into SMS thru mylohyoid defect or around the posterior free edge (right).
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Dermoid & epidermoid are rare, slow-growing, and are often midline. These can be difficult to diagnoses from a ranula when they are off midline. Ranula should connect to SLG while dermoid should not.
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Now into the SMS…
Salivary calculus can result in SMG duct and upstream inflammation and possible secondary infection. If calculi are palpable on bimanual exam they can often be removed intraorally.
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SMG neoplasms: ~60% benign, ~40% malignant (most commonly ACC). Cytology is difficult here, consider core biopsy. Inflammation and malignancy can look similar, have a low threshold for biopsy.
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IgG4 disease – non-neoplastic chronic sclerosing sialadenitis aka Kuttners “tumor”, which are often bilateral. A wide DDX includes sarcoid, lymphoma, and salivary neoplasia so biopsy is often required.
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Take-home points @DrTimeBeale:
-Exclude FOM SCC/sublingual tumor as cause SMS swelling
-Look for tail of fluid connecting ranula to SLG
-SMG inflammation & tumor can be tough to distinguish & often require tissue
-Dental/mandibular cause are also on ddx swelling
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That’s a wrap!
Thanks to Dr. Bykowski and Dr. Beale (@DrTimBeale) for their stellar reviews of the sublingual and submandibular spaces,
and to our moderators Dr. Hoxworth and Dr. Loney (@elizabethloney2).

We’ll see you back next month for more #HNRad fun.
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