0:00

I'd like to offer you the opportunity to look at the

0:04

next series of about ten slides through the anatomy

0:08

and stop the recording and quiz yourself on the

0:12

anatomy before I describe the anatomic structures.

0:15

So they will be labeled either with

0:17

the letters or with numbers.

0:19

And you can quiz yourself and see how well you

0:21

already know the anatomy and

0:24

then maybe even correct me.

0:27

So here's an initial axial scan.

0:31

And as we look at the anatomy of the external

0:34

auditory canal, we will start with that,

0:35

but we will continue into the anatomy overall

0:39

of the temporal bone. As I said,

0:41

I think it's always good to review this.

0:43

There's always important things that

0:45

we can each teach each other.

0:48

On this axial CT scan in bone window,

0:53

we identify A as the helix of the ear.

0:56

This is a portion of the external ear.

1:00

B as the cartilaginous portion of

1:03

the external auditory canal.

1:04

We're starting with the bony portion across here.

1:07

This is right at the junction between cartilaginous

1:09

and bony portion. C as the tympanic membrane.

1:15

And where actually the arrow is,

1:17

is in the middle ear cavity.

1:19

But you can faintly see the tympanic membrane.

1:21

If you're doing CT scans that are two

1:24

millimeters thick or less,

1:26

you should routinely be able to

1:28

see the tympanic membrane.

1:32

D. Here is the anterior epitympanic space.

1:35

This is a portion of the middle ear cavity

1:38

that is residing further anterior.

1:41

So the anterior epitympanic space and E represents

1:45

the bony portion of the external auditory canal.

1:56

We're flipping to look at the right side

1:58

of the temp. Bone and the skull base.

2:02

So again, these are numbered for you.

2:05

You can quiz yourself and put a stop to the

2:09

recording at this juncture and write down your

2:12

answers. Or you can follow along with me.

2:17

Number one represents the foramen ovale.

2:21

Foramen ovale is the egress of the third

2:25

division of the fifth cranial nerve.

2:27

The fifth cranial nerve is called

2:29

the trigeminal nerve.

2:30

And the third division of the fifth cranial

2:32

nerve is the mandibular nerve.

2:34

And it goes out through the foramen

2:36

ovale represented as number one.

2:40

Number two here is foramen spinosum.

2:43

It's just posterior lateral to foramen ovale and it

2:47

transmits the middle meningeal artery

2:49

as well as some nondescript nerves.

2:54

Number three you should identify as the

2:56

carotid canal. We are just at the

3:00

level of the foramen lacerum which is going to be

3:03

found here as the petrous portion of the internal

3:10

carotid artery runs over top of foramen

3:14

lacerum. Number four is the jugular foramen.

3:19

This is obviously where the jugular vein is

3:23

transmitted as well as the cranial nerves 9, 10, and

3:27

11 in pars nervosa and pars

3:29

vascularis of the jugular.

3:32

Foramen number five, we see the sigmoid sinus junction.

3:38

With the transverse sinus, and some people refer

3:41

to the bone overlying it as the sigmoid plate.

3:50

Again,

3:50

I'll give you a moment to determine whether

3:53

you want to identify the anatomy.

4:00

So here we go.

4:02

Number six is the 7th cranial nerve.

4:07

Actually,

4:08

the descending portion of the 7th cranial nerve is

4:11

a little bit more posterior to this arrowhead.

4:15

However,

4:16

you notice that there are these other little areas

4:18

of soft tissue that are just adjacent

4:22

to the 7th cranial nerve.

4:25

The one that the arrow is actually pointing

4:27

to is the corda tympani nerve.

4:29

This circles back after leaving the stylomastoid

4:34

foramen and comes back up the temporal bone for a

4:37

brief period of time as a soft tissue process

4:41

just adjacent to the 7th cranial nerve.

4:45

Number seven, on first blush,

4:48

might look like a small internal auditory canal.

4:52

This is not the internal auditory canal.

4:55

It's below the internal auditory canal,

4:57

and it represents the cochlea.

5:00

Aqueduct.

5:00

So the cochlear aqueduct is communicating with

5:04

the posterior phosphate subarachnoid space,

5:07

and it is a communication for the CSF space from the

5:12

intracranial compartment communicating

5:15

to the cochlea.

5:22

Next slide,

5:25

number eight is the basal turn of the cochlea.

5:30

And number nine represents that little bony hillock

5:37

that overlies the cochlea basal turn.

5:40

And that is the cochlear promontory.

5:44

So this little bony prominence on number

5:48

nine is the cochlear promontory.

5:51

On number ten,

5:52

we are pointing to the descending

5:54

portion of the facial nerve.

5:58

Let's look at a little bit more.

6:00

Anatomy on this same side that has not been labeled.

6:05

Here is the medial or I'm sorry,

6:08

the lateral aspect of what was seen on the

6:11

previous slide of the cochlear aqueduct.

6:14

So this is a portion of the cochlear aqueduct

6:17

coming towards the cochlea.

6:21

What you're seeing posteriorly and medial to the

6:25

cochlear promontory is the beginning

6:28

of the round window.

6:31

The round window is an area of air that leads

6:37

to the basal turn of the cochlea.

6:39

Its importance is that it is through the round

6:41

window that cochlear implants are inserted.

6:48

From the round window,

6:50

we can move posteriorly and we come to this

6:53

airspace, which is medial to the 7th nerve.

6:59

And this is the sinus tympani.

7:01

The sinus tympani and the bone

7:03

that overlies the 7th nerve,

7:06

which is the pyramidal eminence and then the facial

7:09

nerve recess represent anatomy of the hypotympanum.

7:16

This bony area that connects

7:21

the

7:23

round window to the sinus

7:25

tympani is the subiculum.

7:34

Let's continue to the next level above.

7:36

We started down low at the Cochlear aqueduct.

7:39

And now we're moving our way superiorly.

7:45

What we're seeing is a lot of the anatomy

7:47

of the middle ear cavity.

7:51

So number eleven represents that

7:54

anterior epitympanic space.

7:57

It's a little outpouching of the middle

8:00

cavity.

8:03

Number twelve represents

8:07

the neck of the malleus.

8:11

And you see a small soft tissue structure which is

8:15

leading to the neck of the malleus from the cochlear

8:20

form process, which is this area over here.

8:22

And this is the tensor tympani muscle.

8:28

Number 13 is the long process of the incus.

8:33

It's the second little bright dot

8:35

of the middle ear ossicles.

8:36

So we have the neck of the malleus and

8:40

the long process of the incus.

8:41

And this is going to communicate with

8:44

the stapes at the oval window.

8:49

Number 15, you should recognize as that

8:52

airspace I mentioned previously,

8:53

which is the sinus tympani, and then medial

8:57

to that is the pyramidal eminence, and

9:00

then, I'm sorry,

9:01

lateral to that is the Promontory, and then

9:03

lateral to that is the facial nerve recess with

9:06

the facial nerve residing just below here.

9:11

Here we see a little bit of the cochlear aqueduct

9:15

communicating with the turns of the cochlea.

9:19

And this is one of the semicircular canals.

9:22

And we're just getting into the cutting portion

9:25

of the Vestibular aqueduct.

9:31

Okay, continuing onward, number 16.

9:35

Again, the same anterior epitympanic recess.

9:39

Number 17 is that muscle,

9:42

the tensor tympani muscle, which leads from the

9:44

cochleariform process to the neck of the malleus.

9:48

Here we are seeing the stapes.

9:51

It's very faintly seen, mean,

9:52

even using 1 mm thick slices,

9:55

the stapes is such a small structure that

9:57

we can barely see the incus.

9:59

This is the

10:00

posterior crus of the stapes.

10:02

This is the anterior crus of the stapes.

10:07

And the long process of the incus is going to

10:10

communicate with the stapes at the incudostapedial joint.

10:13

The pedial joint.

10:16

Number 19 is a representation of the facial nerve.

10:20

Again,

10:20

sinus tympani, pyramidal eminence, facial nerve,

10:23

some of the structures of the hypotympanum.

10:27

And number 20 is the vestibular aqueduct.

10:34

That's the soft tissue that is associated

10:38

with the vestibular aqueduct,

10:40

which is that bony kind of canal.

10:50

Okay, so again, you can quiz yourself,

10:53

you can listen to me.

10:56

Number 20 is a portion of the cochlea,

10:59

what we're seeing.

11:00

Here is just cutting through the

11:02

apical turn of the cochlea.

11:05

This is the middle turn of the cochlea, and on a

11:09

previous slice when I was showing the round window,

11:12

we saw the basal turn of the cochlea.

11:15

So those are the three turns: basal turn,

11:17

middle turn, and apical turn of the cochlea.

11:20

We're actually showing very nicely this area which

11:24

leads from the internal auditory canal to

11:28

the cochlea. This is the cochlear aperture,

11:32

the cochlear aperture leading from the internal

11:35

auditory canal to the cochlea.

11:38

And this little amorphous hyperdensity within the

11:41

cochlea is going to be part of the modiolus, which

11:45

is effectively the skeleton of the cochlea.

11:49

Number 21 is pointing to the mastoid antrum,

11:53

some of the mastoid air cells.

11:56

22 is pointing to the internal auditory canal.

12:04

And 23,

12:05

I will give you triple credit if you're able

12:08

to identify this little structure.

12:11

This little structure is the semicircular canal.

12:14

It transmits the vestibular nerve,

12:16

which goes to the semicircular canals

12:19

from the internal auditory canal.

12:22

It's one of the branches of the vestibular nerves,

12:27

and it's a nicely demonstrated small canal.

12:33

That is one that they try to avoid when they

12:37

do vestibular schwannoma resections,

12:40

because if they hit that nerve postoperatively,

12:43

the patients often have vertigo

12:45

or persistent dizziness.

12:48

We're nicely seeing the vestibular

12:50

aqueduct again over here.

12:52

And you also have a nice view of the stapes

12:55

anterior crus, posterior crus, and that portion

13:00

of the superstructure of the stapes that we call

13:03

the capitulum, which is articulating with

13:07

the long process of the incus.

13:09

This is our neck of malleus, tensor tympani muscle,

13:14

long process of incus.

13:22

We are continuing further superiorly

13:26

on section 24.

13:28

We are seeing what is sometimes referred to

13:31

as the "ice cream" on the ice cream cone.

13:34

The ice cream on the ice cream cone.

13:37

This is the ice cream cone.

13:38

The ice cream is the head of the malleus.

13:41

And the ice cream cone

13:44

here is the short process of the incus.

13:50

That's number 24, the head of the malleus.

13:54

Number 25 is the vestibule.

13:56

And from the vestibule, we will identify

13:58

the semicircular canals.

14:02

Number 26 is pointing to the tympanic portion of the

14:06

facial nerve or the horizontal

14:07

portion of the facial nerve.

14:12

Excuse me. 27.

14:15

We are seeing the geniculate ganglion.

14:18

This is at the junction between the Fallopian canal

14:26

portion of the facial nerve or the labyrinthine

14:29

portion of the facial nerve.

14:31

Number 28,

14:32

with the tympanic portion of the facial nerve at

14:36

that junction, one has the geniculate ganglion.

14:40

So this is what's sometimes called the first genu,

14:43

the first turn when the labyrinthine portion

14:46

initially goes anteriorly to the geniculate

14:48

ganglion, the 7th nerve anglian,

14:50

and then moves horizontally across the

14:54

tympanic portion of the facial nerve.

14:56

So all these are portions of the facial nerve, the

15:00

circular portion is the part in

15:01

the internal auditory canal,

15:03

the labyrinthine portion in the Fallopian canal.

15:06

Pre-ganglionic, pre-geniculate ganglion.

15:10

And then the posterior, the post-geniculate portion

15:14

or tympanic or horizontal portion of

15:16

the facial nerve. Again, vestibule.

15:19

We're getting a little bit of the

15:19

lateral semicircular canal.

15:21

We're just hitting a portion of the

15:23

posterior semicircular canal.

15:29

We're moving further superiorly here.

15:32

We see the genu of the superior semicircular canal.

15:37

Remember, it's going to loop up and back down.

15:40

And so we're seeing the anterior and posterior genu

15:43

of the superior semicircular canal with a little

15:46

portion of the posterior semicircular canal.

15:49

Cut and cross-section here.

15:50

These are big mastoid air cells.

15:59

This

16:00

canal, which goes between the anterior and posterior

16:05

limbs of the superior semicircular canal,

16:09

transmits the arcuate artery. It is sometimes called the

16:11

arcuate canal or semiarcular canal, going between

16:14

the arches of the superior semicircular canal.