0:01

This is a diagram of the various

0:04

spaces of the suprahyoid neck.

0:06

What you see on this diagram are the masticator space

0:12

seen here enclosing the muscles of mastication,

0:16

the parotid space, the PS,

0:19

the parapharyngeal space.

0:20

And when we say parapharyngeal space,

0:22

we're talking about the prestyloid parapharyngeal space,

0:26

the retropharyngeal space, which is the RPS here,

0:30

the pharyngeal mucosal space,

0:33

and the perivertebral space.

0:36

And all these spaces are defined by layers

0:39

of the deep cervical fascia.

0:41

You notice here is our area of interest,

0:43

which is the carotid space.

0:45

It has all three layers of the deep cervical fascia.

0:49

It has the superficial portion,

0:51

which is the investing fascia.

0:53

It has the pretracheal middle portion of the deep

0:58

cervical fascia, the pretracheal fascia,

1:01

and it has the prevertebral fascia,

1:04

which is the deep layer of the deep cervical fascia.

1:07

And these fascial linings contain pathology

1:12

within the various spaces.

1:16

As we have discussed previously in

1:18

the Suprahyoid Space lectures,

1:21

the displacement of the prestyloid parapharyngeal fat

1:26

will help define in what space a lesion is in.

1:31

In the carotid space,

1:34

we have displacement of the prestyloid

1:36

parapharyngeal fat anteriorly.

1:39

Here you see the carotid space lesion and we notice

1:43

that this dark tissue, the fatty tissue,

1:45

is the prestyloid parapharyngeal space and we see that it

1:49

is displaced anteriorly by the lesion compared to the

1:55

normal positioning of the prestyloid

1:59

parapharyngeal space.

2:01

Now when we use this term styloid,

2:04

prestyloid or post-styloid parapharyngeal space,

2:06

what are we referring to?

2:08

On CT, the best thing that we can see is the styloid process

2:11

and therefore, a lesion that is behind the styloid

2:15

process is usually in the post-styloid parapharyngeal

2:19

space or the carotid space,

2:21

whereas those lesions that are in front of that styloid

2:26

process are in the prestyloid parapharyngeal space,

2:30

which is mostly fat.

2:31

So this lesion is displacing this styloid

2:35

process slightly anteriorly.

2:37

In MR, we often do not see the styloid process

2:40

because it's a piece of bone and therefore dark on the MR signal.

2:45

What we see and what we use in MR

2:48

are the styloid musculature,

2:51

which sit superficial to the carotid space or

2:55

the posterior belly of the digastric muscle,

2:58

which is the intermediate density tissue

3:01

that you're seeing on the CT scan.