0:00

As I mentioned, I interpret and give

0:04

a report on the sinus CT scans in

0:07

different ways depending upon the setting.

0:10

If it's a patient who's an inpatient and is pre bone

0:13

marrow transplant and they're looking for sinusitis,

0:16

my attention to the anatomic variants is not as

0:19

directed as when it is a patient who is being sent

0:23

ultimately for functional endoscopic sinus surgery.

0:26

Nonetheless, we'll go through a case and look at

0:29

some of the normal anatomy and point out some of the

0:32

normal variants that one can see in a typical case.

0:36

So I usually will start out with the patient

0:39

in the thin section axial and the thin

0:42

section coronal reconstructed images.

0:44

Sometimes I make my own coronal reconstructions

0:48

isn order to get the highest anatomic variant.

0:51

As you can see on this case, the thin section axials

0:55

are 0.6 millimeters, but the coronal images are

0:59

reconstructed at two millimeters by the techs.

1:02

Still pretty high resolution at two millimeters.

1:05

And for most people, they generally look at

1:08

the paranasal sinuses for the anterior sinonasal

1:12

cavity in the coronal plane, and maybe for the

1:15

posterior sinonasal cavity in the axial plane.

1:18

At least that's how I do it.

1:20

So here we are starting anteriorly and

1:22

obviously we have our nasal septum and nasal

1:24

bones, and we're coming into the orbits.

1:26

I'm looking at this in the bone algorithm

1:29

in order to look for sinusitis, as well as

1:32

the bony anatomy and normal variations.

1:36

So as you can see, there are some ethmoid

1:39

air cells that are anterior to the

1:42

insertion site of the middle turbinate.

1:44

So these would be termed your

1:46

agger nasi cells, a normal variant.

1:48

Here we have some nasal septal deviation,

1:51

which frankly is often more common than

1:54

having a straight nasal septum, and that may

1:57

narrow the sinonasal cavity on one side.

2:01

Here are our middle turbinates.

2:02

Here are our inferior turbinates, and we can

2:05

see that there is some aeration of the vertical

2:08

lamella of the middle turbinate, but it really

2:12

isn't so wide that it's causing narrowing.

2:15

We are about to see here the maxillary sinus

2:18

ostium, the infundibulum, the hiatus semilunaris, and

2:22

this area of the middle meatus on the left side.

2:26

On the right side.

2:27

Maxillary sinus ostium.

2:29

Infundibulum, hiatus semilunaris, and that middle meatus section.

2:34

As we go further anteriorly, we would

2:37

identify the drainage pathway of the

2:40

frontal sinus and the frontal recess.

2:42

In this case, there are some anterior

2:44

ethmoid air cells, which are narrowing.

2:46

Again, we are looking at the nasal septum.

2:49

It has a perpendicular plate.

2:51

It has a vomer, and it has a cartilaginous portion.

2:55

Here's our superior turbinate.

2:56

I haven't talked too often about that.

2:58

That too may be an aerated air cell.

3:02

It's unusual, but it's the smallest of the turbinates,

3:05

our superior, middle, and then our inferior turbinate.

3:09

I had mentioned that the middle

3:10

turbinate has an attachment

3:12

to the orbit, and you can see this, this is what

3:16

was referred to as the basal or ground lamella.

3:18

You can see this on the contralateral side as well.

3:21

And remember that that air cell, which is

3:24

between the ethmoidal bulla and the ground

3:27

lamella, is called the sinus lateralis.

3:30

This anatomic structure, the basal

3:33

lamella and the attachment of the

3:36

middle turbinate to the cribriform plate

3:40

was of great interest and concern early

3:44

in functional endoscopic sinus surgery.

3:46

Remember I said that they used to take down the

3:48

middle turbinate in order to widen the airway?

3:52

Nowadays, that's not done, and it's not done,

3:54

as I mentioned, in part because of the

3:56

patient sensation after middle

3:58

turbinates have been removed.

3:59

But when they used to take down the middle turbinate,

4:02

and, you know, they've got this big scope that's

4:06

crunching on the, uh, bulla of the middle turbinate—

4:09

what sometimes happened was they would crack the

4:13

cribriform plate, and that would lead to a CSF leak.

4:16

So as they were removing it, its vertical

4:18

attachment could pull on that cribriform plate

4:22

and cause a crack, leading to CSF leakage.

4:25

Similarly, when they were twisting

4:27

it off, that attachment that I had

4:30

demonstrated to the orbital medial wall,

4:33

that sometimes would pull,

4:35

and they could get an orbital hematoma.

4:38

So because of those complications that can

4:41

occur, it's important to understand that

4:43

anatomy of the attachments of the middle

4:45

turbinate to the lateral orbital wall, as well

4:49

as to the cribriform plate. Here we have

4:51

our sphenoid sinuses, our ethmoid sinuses.

4:55

On this example, we do not see the Onodi cell.

4:59

However, we do see the normal

5:02

neurovascular structures

5:03

I mentioned, those including the

5:05

maxillary nerve in the foramen rotundum,

5:08

the Vidian nerve in Vidian canal,

5:10

the optic nerve in the optic canal.

5:12

This is the

5:14

anterior clinoid process, and then along

5:17

the sides here where we're gonna have the

5:19

carotid artery and the cavernous sinus.

5:21

As I mentioned, on the axial scans to the left,

5:24

that's usually where I'm evaluating the sphenoid

5:27

sinus and the posterior ethmoid air cell complex,

5:30

mainly because they drain through this area

5:32

right here that you see best on the right side.

5:34

That's the sphenoethmoidal

5:36

recess, that common drainage.

5:38

And then from there, it's gonna

5:40

be draining into the middle meatus,

5:42

as you saw on the sagittal diagram. On the axial

5:46

scans, the other thing to be aware of are any

5:49

areas of dehiscence of the sphenoid sinus, which may

5:53

include along the wall of the carotid canal here.

5:56

It may include along the inferior orbital

5:58

fissure, and it may include along the wall of the

6:02

optic canal. So anterior clinoid process,

6:05

optic canal with optic nerve, sphenoid

6:07

sinus, in this case, posterior ethmoid

6:10

and superior ethmoid air cell complex.

6:13

Of course, after looking at the images in the bone

6:17

algorithm to look for sinus inflammation, and I think

6:19

you might have noticed there was a tiny bit of mucosal

6:22

thickening in the left and right maxillary sinus.

6:27

You would look at the soft tissue

6:28

windows, usually in the thin sections.

6:30

These are 0.75 here, and we look for

6:35

abnormalities in the upper neck structures.

6:38

Very important to look at the periantral fat here

6:40

to identify whether or not there's any extension

6:43

of inflammation outside the paranasal sinuses.

6:46

We look at the orbits to look particularly along

6:48

the medial wall to see whether any ethmoid sinus

6:51

disease has extended into the extraconal orbits.

6:55

And then, obviously, we're gonna be looking at the

6:56

sphenoid sinus region for cavernous sinus thrombosis.

6:59

And finally, the brain to look whether there's

7:02

any complications of sinusitis affecting the

7:05

brain, which could include subdural or epidural

7:08

empyemas or sinus thrombosis, or frank abscess.