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Today I'd like to focus on the upper

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and lower alveolar ridge mucosa.

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And I have an example case which involves the

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right, uh, mandibular alveolar mucosa,

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which I'll use to help demonstrate some general points.

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So the first thing to say is, uh, that, uh,

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these lesions often present

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at an advanced stage early because the attached

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gingiva of the alveolar mucosa covers the

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alveolus and allows early marrow infiltration.

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In this case, I have a pre contrast T1 weighted image

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without fat suppression and a post contrast T1 weighted

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image with fat suppression in the coronal projection.

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The lesion is here.

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We know that it's originating from the alveolar mucosa

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because it's centered right at the level of

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the alveolar mucosa, which is lining the lateral

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border of the mandibular teeth on the right hand side.

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So I'd like to draw the margins of the lesion for you.

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So we can see here, the first thing that

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strikes attention is that it is invading the

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mandibular cortex on the right hand side.

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That can also be demonstrated

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well on the coronal projection.

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So these tumors tend to be T1 hypo

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intense, sometimes iso intense to muscle.

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They tend to be T2 hyper intense, and they also

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demonstrate, uh, moderate heterogeneous enhancement.

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Similar to other oral squamous cell malignancies.

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They have a tendency to spread in multiple directions.

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The mandibular ones often spread laterally

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into the buccal mucosa and the buccal space.

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So, in this case, you can see from the

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opposite side there are clean planes.

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I'll just draw some structures for you.

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On the abnormal side, all the buccal

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mucosa and the overlying buccinator muscle is

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obliterated by this T1 hypo intense lesion.

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On the normal side, we have the alveolar mucosa,

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we have a thin fat plane, which is called the

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buccal fat, and then we have the buccinator muscle.

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Whereas on the abnormal side,

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it's really taken over by tumor.

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So we can't really distinguish those planes anymore.

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If the tumour becomes more advanced, these can

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spread posteriorly into the masticator space.

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So the masticator space is best identified by the masseter

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muscle laterally and the pterygoid muscles medially.

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So that's mandibular alveolar tumours.

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Maxillary alveolar tumours, they behave slightly

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differently because of their proximity to the nasal cavity.

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So, alveolar mucosa of the maxillary teeth lies here.

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They tend to invade superiorly and may involve

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the maxillary sinus, or the hard palate, or

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alternatively go all the way into the nasal cavity.

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So they behave slightly differently

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because of their anatomy.

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One important thing that you always need to

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look for with alveolar mucosal tumors is the

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presence or absence of perineural infiltration.

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In this case, We are dealing with the inferior alveolar

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branch of the mandibular nerve, or the third division

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of the trigeminal nerve, for mandibular tumors.

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Whereas for maxillary tumors, it is branches of the

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maxillary nerve, or second division of trigeminal nerve.

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such as palatine nerves.

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And ways to look for that are using a combination of

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pre contrast and post contrast T1 weighted imaging.

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So I'm going to draw some structures for you.

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This here is the inferior alveolar nerve on the abnormal

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side within the mandibular canal of the mandible.

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On the post contrast imaging, We can see it enhancing.

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There are two features which I use to help diagnose

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the presence or absence of perineural invasion.

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The first one is abnormal thickening

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on pre contrast T1 weighted imaging.

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Asymmetric abnormal thickening.

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The right inferior alveolar nerve on this

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study does not demonstrate abnormal thickening.

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And, remember, is somewhat constrained by the confines

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of the bony mandibular canal in which it resides.

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The second feature that's important is

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asymmetric enhancement of the nerve.

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And it's important to mention it should be the

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nerve itself and not vessels around the nerve.

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Now, in this case, it is a subtle finding, but there

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is high suspicion of perineural invasion of the right

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inferior alveolar nerve, which lies in close proximity

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to the tumour and is demonstrating an infection.

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some enhancement, which we do not appreciate

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anywhere near as readily on the left hand side.

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This is a difficult finding to confirm

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sometimes, and in some cases the pathologist

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is required to make the final diagnosis.

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But if you see abnormal thickening on T1 weighted

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imaging, or abnormal intraneural enhancement

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on post contrast T1 weighted imaging,

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you should raise suspicion of perineural invasion.

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The last thing to say about these tumors is you

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need to keep in mind differentials, which include

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osteomyelitis, secondary to dental infection,

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or osteonecrosis, which may be due to previous

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radiation therapy, or the use of bisphosphonates.

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Much less common, the mandible may also be

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the site of metastasis or primary sarcoma.

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In our next vignettes, we will go

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on to formally stage this alveolar

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mucosal tumor.