0:01

So this session will be on normal anatomy

0:03

of the oral cavity imaging, and the first

0:08

area that we'll talk about is the region

0:09

of the buccal space and the buccal region.

0:12

So the buccal area is this region

0:14

between your cheek and your gum.

0:16

And if you actually have ever dipped snuff

0:18

before, I hope none of you have, but if you have,

0:20

the area that you put the little snuff

0:22

in is between your cheek and your gum.

0:24

So this little schematic illustration of

0:26

a cancer right here between your cheek and

0:28

your gum identifies the normal buccal area.

0:31

And on the right-hand side, on this non-contrast

0:34

T1 weighted image, we have this tumor right here.

0:36

In this case, it was lymphoma

0:38

involving the right buccal area.

0:41

The next area of the oral cavity is

0:43

the oral tongue, and the other name for

0:45

the oral tongue is the mobile tongue.

0:47

So here's a schematic illustration

0:49

of a tumor involving the oral tongue.

0:51

The applied anatomy that you should remember is

0:54

that there is a chevron-shaped papilla right here,

0:56

which is referred to as a circumvallate papilla.

0:59

And right at the apex of the chevron is the foramen

1:02

cecum. Posterior to the circumvallate papilla,

1:06

we can see the region of the tongue

1:08

base, and anterior to the circumvallate

1:11

papilla is the oral or the mobile tongue.

1:14

And on the right-hand side, here's a

1:16

tumor involving the oral tongue that,

1:19

in this case, stopped short of the midline.

1:22

The next area that we'll talk about is the floor

1:24

of mouth, and if we were talking about the concept

1:27

of the spaces of the head and neck, then we

1:29

would refer to this area as a sublingual space.

1:31

So just realize that the floor of mouth and

1:34

the sublingual space are the exact same areas.

1:37

In the construct of this session, we' will be

1:39

talking about the oral cavity, and the proper

1:41

terminology is the floor of the mouth.

1:44

So the floor of the mouth is essentially all

1:46

of that area that's located below the tongue.

1:49

So basically sublingual, meaning lingua

1:52

is Latin for tongue, and that area

1:54

below the tongue is a sublingual space.

1:56

So when you look on the schematic illustration,

1:58

here is the tongue right here, and everything

2:00

below the tongue is in the floor of the mouth.

2:04

When we look at the coronal images,

2:06

here, we can see this muscle right here.

2:08

This is the mylohyoid muscle, and this

2:10

attaches to the mylohyoid line of the mandible.

2:13

And here we can see the lingual cortex of the mandible,

2:16

and the mylohyoid muscle attaches to the hyoid bone.

2:20

So this area, it almost looks

2:22

like a hammock, if you will,

2:23

that goes from the mandible down to the hyoid bone

2:25

forms the inferior and lateral

2:28

margin of the floor of the mouth.

2:30

So when we look in this coronal image here, here's our

2:33

mandible here on the right-hand side, the mylohyoid

2:35

muscle comes down, attaches to the hyoid bone.

2:38

Here is the other half of the mylohyoid muscle.

2:41

It attaches to the mylohyoid line.

2:43

So everything above this U-shaped structure

2:46

here is located within the sublingual space.

2:49

So the way that I think of it,

2:50

I almost think of it as a teacup.

2:52

So the way that I look at the teacup is that

2:54

the rim of the teacup is formed by the mandible,

2:57

the border, and the inferior area of the

2:59

teacup is formed by the mylohyoid muscle,

3:02

that basically forms a margin of that teacup.

3:05

And then the floor of the sublingual space

3:08

is formed by this area right

3:10

here, which would be the hyoid bone.

3:11

So basically that T comes and forms

3:14

in this cup, and everything within that

3:16

teacup is in the sublingual space.

3:19

So here's a schematic illustration

3:21

of a floor of mouth carcinoma.

3:23

Just the applied anatomy again, is that

3:25

notice this muscle that extends from the

3:27

genial tubercle back to the transverse fibers

3:30

here are called the genioglossus muscles.

3:33

So these genioglossus muscles

3:35

run from anterior to posterior.

3:37

These transverse fibers are in the

3:39

tongue base, so we can apply this when

3:41

we start looking at normal structures.

3:44

So this is an example of a floor of mouth carcinoma.

3:47

I just want to point out the normal anatomy here.

3:49

Here is the normal anatomy of the

3:51

muscle going from the genial

3:53

tubercle back to the tongue base.

3:54

That's the geniohyoid muscle. Very subtly here,

3:58

these are the normal enhancing structures of the

4:01

sublingual, of the lingual artery. And this area,

4:04

just anterior, is a subtle tumor involving

4:07

the anterior aspect of the floor of the mouth.

4:10

More posteriorly,

4:11

this is the hyoglossus muscle,

4:13

and laterally is the mylohyoid muscle.

4:15

The sublingual gland is located

4:17

right here at the tip of the arrow.

4:19

The sublingual gland contains fat,

4:21

and that's the sublingual gland

4:22

located right at the tip of the arrow.

4:25

This image on the right.

4:26

This is why we perform imaging.

4:28

In this particular case, the CT scan.

4:30

We know the patient has a cancer,

4:32

but notice how the lingual cortex is intact.

4:35

So that's important information to discuss when

4:37

you're looking at floor of mouth carcinomas.

4:40

Now contrast that case with this case.

4:43

This is the patient that has a cancer

4:44

involving the floor of the mouth.

4:45

When we look at the bone algorithms,

4:47

we can see that that bone is eroded.

4:49

Very important information

4:51

from an oncologic perspective.

4:53

The next area that we'll talk

4:54

about is the retromolar trigone.

4:56

So when we look at the retromolar trigone,

4:58

it's important to count the teeth.

5:00

So when we look at the teeth, we can see the

5:02

central incisor, the lateral incisor,

5:04

the canine, the first premolar, second premolar,

5:07

first molar, second molar, third molar.

5:09

That area that's posterior to the third molar

5:13

is referred to as the retromolar trigone.

5:16

This is a triangular space that's located

5:18

just posterior to that third molar.

5:21

There is a retromolar trigone along the

5:23

alveolar ridge and also the maxillary ridge.

5:25

So basically it has a floor and a roof.

5:28

In this particular case, we're looking in the maxilla,

5:30

and right at my arrow here is the retromolar trigone.

5:34

So here's a normal anatomy on your left-hand

5:36

side, and on the right-hand side, here's a cancer

5:39

that's located right in the retromolar trigone.

5:43

So this is what it looks like clinically.

5:45

This was a patient that had a

5:46

retromolar trigone carcinoma.

5:48

This is what we would expect to see schematically,

5:51

and this is what we see radiologically.

5:53

So the normal anatomy is the following.

5:55

If you look at the uninvolved on the patient's

5:58

left-hand side, we can see this fat right here,

6:00

posterior, in this case, to the maxillary tuberosity.

6:04

And on the right-hand side, we can see this cancer

6:06

that's located posterior to the maxillary tuberosity,

6:09

in the retromolar trigone.

6:11

Notice the cancer is extending anteriorly along

6:14

this muscle here, which is the buccinator muscle.

6:17

We can see that tumor growing anteriorly,

6:20

and we can see the tumor growing posteriorly

6:22

along the superior constrictor muscle.

6:24

The last component of the oral

6:26

cavity is the hard palate.

6:28

So when we look at the hard palate, here's

6:30

a schematic illustration of the hard palate.

6:33

This is a contrast-enhanced T1-weighted imaging

6:36

study demonstrating cancer involving the hard

6:38

palate, and this is it on the coronal image.

6:42

So when we look at the normal anatomy, again, here's

6:44

a schematic illustration of a hard palate carcinoma.

6:48

When we look at the coronal imaging,

6:49

the mucosa overlying the hard palate just

6:52

should be about three or four millimeters.

6:54

It should be very, very thin.

6:56

In this particular case, we can see there's way

6:58

too much soft tissue overlying the hard palate.

7:01

You can see this is about

7:02

eight millimeters to a centimeter.

7:04

So clinically, the referring physicians can see

7:07

this cancer, but what they cannot do is see

7:09

deep to this cancer, looking at that hard palate.

7:13

So radiologically, it's always important

7:15

to understand where that hard palate is and

7:17

comment on the integrity of the hard palate.

7:20

In this particular case, another

7:21

hard palate carcinoma.

7:23

But notice the bone right here.

7:25

In this case, this bone is completely

7:27

eroded.

7:28

So this type of cancer would require maxillectomy,

7:31

whereas the one that I showed before would be a

7:33

wide local excision. Posterior to the hard palate,

7:37

there's a space right here

7:38

called the pterygopalatine fossa.

7:40

The actual anatomy is a sphenopalatine foramen,

7:43

the pterygopalatine fossa, and the pterygomaxillary fissure.

7:46

This, if you will, is a very high-rent

7:48

district because hard palate tumors can extend

7:51

into this area once in, as in this case,

7:54

it extends into the pterygopalatine fossa.

7:57

We have to realize that there are

7:58

a lot of important structures.

8:00

So the second division of the fifth cranial nerve

8:02

runs in the roof of the pterygopalatine fossa.

8:05

It runs posteriorly to this round foramen,

8:08

which is foramen rotundum, and eventually

8:10

back into the trigeminal ganglion.

8:13

So in this particular case, we can see that

8:15

this case is an adenoid cystic carcinoma

8:18

growing back into the pterygopalatine fossa.

8:20

Look at the normal appearance on the opposite side.

8:23

We can see way too much enhancement.

8:25

Now when we have this tumor involving this area,

8:28

we now see this linear enhancement extending

8:30

posteriorly, and this linear enhancement is

8:33

tumor that's extending along the second

8:36

division of the fifth cranial nerve.

8:39

When we look at the coronal images, we can

8:40

see this abnormal asymmetrical enhancement

8:43

of V2 compared to the left-hand side.

8:46

And this tumor is growing all the way

8:47

back into the skull base, specifically

8:50

involving the trigeminal ganglion.

8:53

So in summary, what we've done is

8:55

that we've gone over the five components of

8:57

the oral cavity, and this will serve as our

9:00

baseline when we start discussing different

9:02

pathologies involving the oral cavity.