Anatomy of the Retromolar Trigone
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Hello, everyone.
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Sidney Levy here, continuing our discussion of the anatomy
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of the oral cavity and its subsites as a prelude to
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the diagnosis and staging of squamous cell malignancy.
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Previously, we've discussed the,
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uh, buccal and alveolar mucosa.
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Now I'd like to discuss the retromolar trigone,
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where they both meet posteriorly.
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It's a very important region as it's really
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an intersection of, uh, different deep
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spaces and subsites of the oral cavity.
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So what is the retromolar trigone?
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I think it's easiest to draw these things, uh,
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but you can consider it the attached mucosa
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overlying the ascending ramus of the mandible
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inferiorly and the maxillary tuberosity superiorly.
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But let me draw it for you.
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Once again, I have our pre-contrast fat
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suppressed T1-weighted imaging in three planes.
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Before I go any further, I will quickly point out that
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this particular patient has an oral tongue malignancy,
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which we're not going to discuss any further.
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But in case you are wondering why there is some
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distortion of the appearance of the tongue on
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the coronal projection, that is the reason.
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So, firstly on the axial projection, uh, you can think of
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it as a, a triangular shaped region where the buccal mucosa
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laterally meets the alveolar mucosa medially and posteriorly
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at the posterior border of the upper and lower third molars.
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And there is a region of mucosa here
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which covers the ascending ramus of the
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mandible and the maxillary tuberosity.
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depending on whether you are inferior or superior.
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So think of it as a region here on the axial projection,
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bit more difficult to see on the coronal projection, but
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if you cross-reference with the axial or alternatively
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keep scrolling backwards along the molars until you reach
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the last one, it is once again a triangular region here.
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Okay.
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And just to give you a bit more orientation,
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this is the maxillary tuberosity.
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And that's the beginning of the
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ascending ramus of the mandible.
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The sagittal projections often I find, uh, the most
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helpful in completely showing the retromolar trigone.
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So here I have the posterior borders
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of the upper and lower third molars.
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And if I just draw a line here, which heads back as
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far as the anterior tonsillar pillar and then head
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upwards towards the, uh, maxillary tuberosity and
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then back to the posterior border of the third molar.
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You have an approximately trapezoidal or triangular
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region of mucosa, which is the retromolar trigone.
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There's the maxillary tuberosity.
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There's the beginning of the
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ascending ramus of the mandible.
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The anterior tonsillar pillar is a line at that
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level, and these are the posterior third molars.
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So in summary, the retromolar trigone is very important
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and one should be familiar with its detailed anatomy.
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You could consider it to be the attached mucosa
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overlying the ascending ramus of the mandible
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inferiorly and the maxillary tuberosity superiorly.
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65 00:03:52,210 --> 00:03:53,170
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It begins anteriorly at the posterior border
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of the upper and lower third molars.
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And posteriorly, it extends as far as the
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anterior tonsillar pillar, which happens to
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be the anterior boundary of the oropharynx.
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I often find it helpful to look for it
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on the axial and sagittal projections.
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Thank you.
Sidney Levy, PhD, MBBS
Radiologist and Nuclear Medicine Specialist
I-MED
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