0:00

Just as we employ thin section imaging in CT scanning,

0:05

we have to employ thin section imaging on MRI as well.

0:10

And usually these are sequences

0:12

that are T2 weighted, that is, that have bright CSF signal.

0:16

The reason why we want bright CSF signal is so that

0:19

we can see the endolymph and the perilymph

0:22

within the cochlear and vestibular system.

0:25

The pulse sequences that are typically used are

0:28

referred to as FIESTA in the GE scanner,

0:31

3D-CISS in Siemens, and TFE or Turbo

0:36

Field Echo with Philips.

0:37

So you will hear these terms: Fast Imaging

0:40

Employing Steady-state Acquisition, FIESTA.

0:43

Constructive Interference Steady State,

0:46

CISS imaging with Siemens.

0:48

Some people call it KISS,

0:49

depending upon how romantic they are that day.

0:52

But I refer to it as CISS imaging.

0:54

And then we have the Turbo Field Echo

0:56

or TFE with Philips.

0:59

This is an example of a FIESTA GE pulse sequence.

1:03

As you see, the CSF is bright,

1:07

and if we look at the cochlear vestibule,

1:10

we are also seeing bright signal dominating.

1:14

Now, what's nice about this is that we can therefore see

1:18

the cranial nerves very nicely outlined

1:22

by the cerebrospinal fluid.

1:24

So we can see that this cranial nerve that I'm going

1:27

to mark as number one is anteriorly located.

1:31

And depending upon whether we're at the upper portion

1:34

of the internal auditory canal or the lower portion of

1:36

the internal auditory canal, we would say, all right,

1:39

well, if it's anterior and inferior,

1:41

it's going to be the cochlear nerve.

1:43

Whereas if it's anterior but superior,

1:46

it's going to be one of the superior vestibular nerves.

1:50

What's posterior here,

1:53

and I'll mark it as two,

1:55

in the internal auditory canal,

1:57

posterior and inferior is going to be a portion

2:01

of the inferior vestibular nerve.

2:05

So inferior and posterior inferior vestibular nerve,

2:11

superior and posterior is going to be the superior

2:14

vestibular nerve, anterior inferior cochlear nerve,

2:17

anterior superior 7th cranial nerve.

2:20

Alright. You also see on the right-hand side

2:23

a pretty nice example of the modiolus.

2:25

Remember, the skeleton of the cochlea is

2:28

referred to as the modiolus.

2:30

And we can see this separation into the...

2:32

this is actually the middle turn and the apical turn of the

2:37

cochlea with its internal anatomy being the skeleton,

2:41

being the modiolus.

2:43

We're also seeing a portion of the vestibular system.

2:48

And in this section,

2:49

we are also seeing a portion of the posterior

2:52

semicircular canal cut in cross-section.

2:55

As with CT, these FIESTA,

3:00

CISS, Turbo Field Echo scans can be reconstructed

3:04

in multiplanar view.

3:07

So, this is an example of use of 3D FIESTA to look for

3:12

superior semicircular canal dehiscence.

3:15

In this case,

3:17

we've taken our axial anatomy in the FIESTA sequence

3:20

and we've reconstructed it in an oblique

3:22

fashion to look at semicircular canals.

3:26

And what you have here is a reconstruction through the

3:29

beautifully demonstrated superior semicircular

3:32

canal coming to the vestibule.

3:34

And we note that there is bone above the superior

3:37

semicircular canal between it and the brain.

3:40

And therefore, there is no superior semicircular

3:43

canal dehiscence in this example.

3:46

And these sections can be taken,

3:48

not only in multiplanar view,

3:51

but we can even reconstruct in a 3D format and

3:55

make MIP images or 3D volumetric images.

3:58

And here you're nicely seeing that superior

4:00

semicircular canal, the lateral semicircular canal,

4:03

the posterior semicircular canal,

4:05

the turns of the cochlea even.

4:08

And this is again turns of the cochlea in

4:11

a three-dimensional reconstruction.

4:13

I want to just point out one other portion

4:16

of the anatomy that is important,

4:17

and that is the spiral lamina.

4:20

The spiral lamina divides the cochlea into the

4:23

scala vestibuli and the scala tympani.

4:26

And this is another portion of the anatomy that is

4:31

important with respect to congenital abnormalities

4:34

of the cochlea and vestibule,

4:35

but also may be part of the problem associated with

4:39

Meniere's disease. Frankly, with Meniere's disease,

4:42

we really don't have great anatomic correlation

4:45

with the patient's symptomatology.

4:46

But people are looking at this fine anatomy within the

4:50

turns of the cochlea known as the spiral lamina.

4:54

Here is an example of the use of CISS or FIESTA,

4:58

or Turbo Field Echo scanning to look for cochlear nerve

5:04

absence or aplasia in a patient who had congenital

5:08

sensorineural hearing loss. So, this is the example,

5:12

if you will, of the anatomy here,

5:15

the separation, superior to inferior,

5:19

being the crista falciformis that I mentioned,

5:21

and then the separation of the anatomy anterior

5:24

to posterior being Bill's bar.

5:26

So again,

5:27

anterior-superior, 7th cranial nerve.

5:31

People refer to that as seven-up.

5:33

Cochlear nerve, anterior and inferior.

5:35

So, cochlear down.

5:37

Posteriorly, separated into superior

5:40

vestibular and inferior vestibular nerves.

5:43

So, let's look at that anatomy doing cross sections

5:47

oblique to the internal auditory canal.

5:50

In this example, we can see this is the anterior,

5:54

the front of the face is here,

5:55

posteriorly with the cerebellum is here.

5:58

And we can see

6:00

anterior and superior, the 7th cranial nerve,

6:03

anterior and inferior, the cochlear nerve.

6:06

And these are the superior and

6:08

inferior vestibular nerves,

6:10

more posteriorly within the internal auditory canal.

6:14

Let's shift to this patient.

6:16

This patient, we don't see the same anatomy.

6:19

We're not exactly through the same slice.

6:22

And in point of fact,

6:24

we have these anterior superior 7th cranial nerve,

6:28

seven-up, but we are missing the cochlear nerve.

6:34

We have the superior vestibular nerve and the inferior

6:36

vestibular nerve, but we are missing this nerve,

6:38

which is the cochlear nerve.

6:40

This is a patient who has congenital sensorineural

6:42

hearing loss due to cochlear nerve aplasia.

6:45

Nicely demonstrated on this CISS, FIESTA, Turbo Field Echo,

6:50

three-dimensional pulse sequence with the

6:52

three-dimensional reconstruction

6:53

in an oblique coronal plane.