0:00

This is a case that is pretty easy if you scroll from

0:05

below and work your way up.

0:06

But let's do the opposite

0:08

and scroll from superiorly downward.

0:11

So as we look at this lesion in the cy nasal cavity, we see

0:15

that there is a lesion in the ethmoid science that has, uh,

0:20

distinct matrix within it.

0:21

There's thickening of the bone

0:24

and it looks as if it's still confined by the walls

0:28

of the ethmoid science and the nasal septum.

0:31

Looking at the soft tissues

0:33

and coming from above,

0:34

we would have a pretty broad differential diagnosis.

0:37

However, if we look at this lesion from the bone windows

0:41

below, we see the middle terminate showing a

0:46

ground glass appearance homogeneously

0:50

on the left side,

0:52

and there is that ground glass appearance to portions

0:56

of the rest of the lesion seen here on the posterior wall

1:00

of the left ethmoid sinus.

1:02

This ground glass appearance,

1:05

if we were just looking at the terminate,

1:07

we would say this is fibrous dysplasia.

1:08

And in point of fact, this is histologically proven

1:11

fibrous dysplasia.

1:13

It makes the point that

1:15

although we think of fibrous dysplasia

1:17

as being a bony lesion when it's filling the ethmoid sinus,

1:21

it may have soft tissue density

1:24

rather than just the ground glass bone density

1:27

on MRI scan fibrous dysplasia is very confusing

1:30

because it can have bright signal or dark signal.

1:33

On T one and T two A scan.

1:36

We're also gonna have the superimposition

1:38

of obstructed secretions.

1:40

So this is a diagnosis

1:41

that is actually much easier made on the CT than on the mr.

1:47

And fibrous dysplasia often involves the maxilla

1:50

and may involve the walls of the maxillary sinus,

1:54

and it may involve the skull base as well.

1:57

And in that situation, again, it may appear

2:01

as a cy nasal lesion.

2:03

For example, here's our clus

2:05

and the posterior wall of our sphenoid sinus,

2:07

that is showing additional features that are typical for

2:12

fibrous dysplasia, a bony developmental lesion

2:16

that can fill the perinasal sinuses.