0:01

In looking at

0:04

masses in the neck,

0:07

we mentioned that thyroid lesions and lymph

0:10

nodes were the most common in adults.

0:13

I want to talk about the most common cystic lesion

0:17

in the neck. It actually is not the branchial cleft cyst.

0:21

The most common cystic lesion in the neck

0:23

of an adult is the thyroglossal duct cyst.

0:27

Let's look at thyroglossal duct cysts

0:29

and where we expect to see them.

0:31

Remember that the thyroglossal duct cysts arise from the foramen

0:35

cecum at the tongue base and the duct will extend through

0:42

the tongue base, around the hyoid bone and then down,

0:45

leading to the normal thyroid location.

0:48

And this is the root upon which the thyroid enlarged will

0:53

descend from the foramen cecum to the normal

0:57

position of the thyroid gland in the lower neck.

1:00

Well, most of the thyroglossal duct cysts that we see

1:05

are in the infrahyoid portion of the neck,

1:08

and then the remainder are either in the tongue and tongue

1:11

base or immediately associated with the hyoid bone itself.

1:16

So when you look for the thyroglossal duct cyst,

1:21

or if you're seeing a lesion in this location,

1:25

you want to look in the midline,

1:26

because 75% of thyroglossal duct cysts are in the

1:30

midline and only 25% are off midline.

1:33

And most of those that are off midline are also

1:37

in the infrahyoid portion where 65% arise.

1:41

So looking through this patient's neck,

1:44

they were complaining about a mass

1:47

in the midline near the hyoid bone.

1:50

So here we are coming down through the mandible.

1:52

We reach the hyoid bone,

1:54

and we see that there's nothing in the tongue base

1:56

or at the hyoid bone itself, but immediately

2:00

below the hyoid bone, we come into this cystic mass,

2:05

which is intimately associated with the strap muscles that are

2:10

located between the hyoid bone and the thyroid cartilage.

2:15

So the thyrohyoid musculature of the strap muscles.

2:19

You notice that it's in the midline,

2:21

embedded in the strap muscle.

2:23

This is pathognomonic for a thyroglossal duct cyst.

2:27

This doesn't occur in any other region to be embedded

2:30

in the strap muscles in the midline.

2:33

So we say this is clearly a thyroglossal duct cyst.

2:37

When you see the thyroglossal duct cyst,

2:39

you want to look for any enhancing or hyperdense

2:42

tissue associated with the cyst,

2:45

which may represent residual thyroid tissue within the cyst.

2:51

The reason why this is important is because just like you

2:54

can have incidental cancers in the thyroid gland,

2:58

you can have incidental

3:00

cancers in a thyroglossal cyst thyroid tissue that is present.

3:05

So in this case, no enhancing tissue to be concerned about.

3:11

The patient has normal thyroid gland down here and the cyst

3:16

terminates at the junction of the thyroid notch, frankly.

3:21

So it's really located between the hyoid

3:24

bone and the thyroid notch.

3:27

This is nicely demonstrated on the sagittal scan where you see

3:31

a heart shaped appearance of this thyroglossal duct cyst.

3:36

And it is often on either side of the hyoid bone,

3:42

both the anterior and posterior margin of the hyoid bone,

3:46

which is another characteristic feature

3:48

of a thyroglossal duct cyst.

3:51

This is treated surgically because of that potential for

3:54

having thyroid tissue within it and the potential for having

3:58

a cancer develop within a thyroglossal duct cyst.

4:02

And so, they do what's called a sistrunk procedure.

4:05

The sistrunk procedure takes out a portion of the tongue base

4:10

in the midline where there may be tracking thyroglossal

4:14

duct tissue and then takes out the cyst,

4:17

leaving the thyroid gland intact.

Case 22 - Thyroglossal Duct Cyst

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