0:00

Let's review conal lesions of the orbit.

0:03

These are the lesions that will affect

0:05

the muscle cone themselves.

0:08

As I mentioned,

0:09

the most common of these is thyroid eye disease,

0:12

also known as thyroid orbitopathy

0:15

or Graves ophthalmopathy.

0:17

The reason why I do not personally use the term Graves

0:20

ophthalmopathy is that Graves' disease implies that the

0:24

patient has thyrotoxicosis or hyperthyroidism.

0:28

In point of fact,

0:29

you can have thyroid eye disease with extraocular

0:31

muscle enlargement and proptosis.

0:34

Whether you are euthyroid or even having been treated.

0:38

The Graves' disease, the patient may be hypothyroid.

0:42

So the association of thyroid eye disease is not

0:44

dependent on the thyroid hormone state of the patient.

0:48

It can occur in euthyroidism, hyperthyroidism, or hypothyroidism

0:53

and that's why my preferred term is thyroid eye disease.

0:58

These slides are showing one.

1:00

Of the other manifestations of Thyroid Eye Disease and

1:02

that is that one can see fatty infiltration of the

1:07

extraocular muscles themselves with thyroid eye disease

1:11

as well as the proliferation of the intraconal and

1:15

extraconal orbital fat as well as the

1:18

extraocular muscles enlargement.

1:21

So remember our mnemonic I'm slow for the involvement of

1:25

the inferior rectus muscle and the medial rectus muscle

1:28

and the superior rectus muscle while relatively sparing

1:31

lateral rectus and superior oblique

1:34

or inferior oblique muscles.

1:36

The importance here is to remember to look at the

1:39

orbital apex and identify whether or not there

1:42

is sufficient fat around the optic nerve,

1:45

which implies that it is not compressed and therefore

1:47

not at risk for ischemic compressive optic neuropathy.

1:53

Remember also that the characteristic feature of

1:56

Thyroid Eye Disease is that it spares the

2:00

muscle tendon insertion on the globe.

2:03

This is a patient who had unilateral exophthalmos

2:07

from thyroid eye disease.

2:09

Here is another case where we have isolated unilateral

2:12

inferior rectus muscle involvement

2:16

with thyroid eye disease.

2:19

We contrast that with the patients who have pseudotumor.

2:22

Pseudotumor of the extraocular muscles will affect not

2:27

only the muscle but also the tendon

2:29

insertion on the globe.

2:32

In this case, the superior rectus muscle, which is even

2:36

getting fatter as it comes forward to the globe.

2:39

And at its muscular insertion, there is edema that's

2:43

characteristic of pseudotumor or idiopathic orbital

2:46

inflammation which is different from thyroid

2:52

we again see the relative sparing of

2:55

the tendon insertions at the

3:00

globe with thyroid eye disease.

3:03

What other conditions might cause enlargement

3:06

of the extraocular muscles?

3:08

You can see edema of the extraocular muscles

3:11

in patients who have, for example,

3:14

a carotid cavernous fistula secondary

3:16

to venous engorgement.

3:18

You can also see enlargement of the extraocular muscles

3:23

in glycogen storage disease that may infiltrate the

3:27

muscle with the deposition of the glycogen material.

3:31

These would be in the differential diagnosis

3:34

of extraocular muscle enlargement.

3:36

I want to make the point that rhabdomyosarcomas of

3:41

the orbit do not affect the extraocular muscles.

3:45

They are extra-muscular in their origin, and they are one

3:50

of the orbital neoplasms that can affect the child.