0:01

This is an MR of the brain in an eight-year-old

0:04

with seizures and there are some abnormalities

0:09

in the left temporal pole with some abnormal

0:12

enhancement that we'll evaluate in a moment.

0:16

But I want to point out this enhancement

0:19

in the left internal auditory canal.

0:21

It's fairly subtle.

0:22

We don't see anything in the

0:23

right internal auditory canal.

0:25

The patient had yearly surveillance for

0:27

her epilepsy and approximately three years

0:29

later, the left-sided lesion had enlarged

0:32

to nearly fill the internal auditory canal.

0:35

but not extend through or

0:36

expand the porus acousticus.

0:38

And there's some abnormal enhancement

0:40

in the right internal auditory canal.

0:42

So this patient has neurofibromatosis type

0:46

2, although it was not initially known.

0:50

If we fast forward a few years, we

0:53

now have a more classic appearance

0:55

of lesions filling bilaterally,

1:00

extending through the porus acousticus.

1:02

And having a rounded component in the cerebral

1:08

pontine angle cistern, people have sometimes

1:11

referred to this morphology as looking like

1:14

an ice cream cone, where you have the cone,

1:18

being the enhancing portion, conforming to

1:21

the boundaries of the internal auditory canal.

1:23

Then the ice cream on top, where it can sort

1:25

of balloon out less constrained by the bony

1:28

confines of the internal auditory canal.

1:32

So this lesion, if we fast forward

1:36

a few more years, gets much larger.

1:39

We see the component in the cerebro

1:43

pontine angle cistern has grown significantly,

1:47

causes marked mass effect upon the pons.

1:51

the middle cerebellar peduncle and the

1:54

cerebellar hemispheres bilaterally, and it's

1:57

starting to distort the fourth ventricle.

1:58

You can see another year

2:01

later, it grows even further.

2:03

So there's significant mass

2:07

effect upon the brainstem.

2:10

Now, This patient has a number of other

2:13

manifestations of neurofibromatosis

2:15

type 2 that, due to the complexity, I'm

2:17

going to discuss in a separate case.

2:20

But right now, in this case, we're going

2:22

to focus on the cerebral pontineangle

2:24

cisterns and the vestibular schwannomas.

2:28

So how do you treat these?

2:30

This patient was developing bilateral

2:32

sensorineural hearing loss, not to

2:34

mention the mass effect upon the brainstem.

2:36

Well, on an audiogram, a vestibular

2:40

schwannoma has a very characteristic

2:42

description of a retrocochlear disorder.

2:45

Sensorineural hearing loss.

2:46

That means it's deep to the cochlea.

2:49

So because the hearing loss is related to mass

2:53

effect upon the cochlear nerve, a cochlear

2:56

implant device will not help this patient

2:58

because the cochlea is not the problem.

3:00

The problem is the transmission

3:02

from the cochlea to the brainstem.

3:05

So how do they do that?

3:07

Well, the hearing can possibly

3:09

be addressed by decompressing the

3:12

cerebral pontine angle cistern lesion.

3:15

and this patient underwent a left-sided

3:21

translabyrinthine approach to the cerebral

3:25

pontineal cistern for a section of that

3:28

the left side of the vestibular schwannoma.

3:31

So, because of the translabyrinthine

3:33

approach, the cochlea and the cochlear

3:36

nerve themselves were no longer going

3:38

to be able to function for hearing.

3:40

That doesn't eliminate the chances of

3:43

this patient having some degree of hearing

3:46

restoration attempted on the left side.

3:50

Why is that?

3:51

Well, it is possible for them to have, and

3:54

we can see this hypointense line right here.

3:58

This is a brainstem implant.

4:00

And there's a set of patch electrodes

4:03

that go on the surface of the brainstem,

4:06

approximately the lateral surface of the

4:08

medulla oblongata in the region of the olivary

4:10

nuclei, instead of a cochlear implant which

4:13

stimulates the cochlear nerve in the cochlea.

4:15

This attempts to stimulate

4:17

the nerves in the brainstem.

4:19

So if we remember the auditory pathway

4:22

going, once it goes into the brainstem,

4:24

going to the superior olivary nucleus, the

4:26

lateral lemniscus, the inferior colliculi,

4:30

and the medial geniculate nucleus.

4:33

This attempts to stimulate that pathway.

4:37

So while there has been destruction of the inner

4:41

ear structures and the cochlear nerve in order

4:44

to relieve the brainstem mass effect, there

4:48

is still an attempt at hearing preservation.

4:51

And these devices can be MRI compatible

4:54

with appropriate MRI scanning parameters.

4:58

Now the right sided lesion still remains.

5:01

still very large.

5:02

If we look, it's almost four centimeters.

5:07

So, the right sided lesion may need to

5:10

get addressed at some point also, and

5:13

as we see in this case, in this image,

5:17

the right sided lesion, the cerebral

5:20

pontine angle component was resected.

5:22

Now, the internal auditory

5:22

canal component was not.

5:24

This resection relieved the mass effect

5:26

upon the brainstem, but did not resect

5:29

the component in the internal auditory

5:31

canal, which is very difficult to access.

5:33

Now, the left side, they were able to access

5:35

it because of the translabyrinthine approach.

5:37

Okay.

5:38

In this case, they performed

5:41

a retrosigmoid approach.

5:49

reconstruction material overlying their

5:52

approach, and they go between the skull base and

5:58

the cerebellum to resect the lesion, whereas on

6:03

the left side, they performed a mastoidectomy

6:06

and went through the vestibule and semicircular

6:08

canals, which are no longer present.

6:11

The cochlea is present now

6:13

traversing this resection cavity

6:15

where we see fat packing material.

6:17

We see the lead for the brainstem implant

6:20

as an attempt at hearing preservation.

6:23

So we can see the very profound evolution

6:28

from a subtle enhancing lesion that was

6:31

not initially identified to these very

6:36

large bilateral vestibular schwannomas.

6:39

Now, I will say an incidental finding

6:42

of neurofibromatosis type 2 and subtle

6:44

enhancement in the intralabyrinthine canal,

6:46

it's not unexpected sometimes for

6:48

that to not be initially identified.

6:51

This is not a place that's

6:52

normally in our search pattern.

6:53

And since this patient was receiving imaging

6:56

surveillance for her epilepsy, this did not

7:00

result in any alteration in care because Once

7:03

this was identified and once it was known

7:05

she had neurofibromatosis type two, the

7:09

patient would just get imaging surveillance and

7:11

audiograms until there was need for surgical

7:14

intervention, which It was almost a decade

7:18

after the neurofibromatosis type two diagnosis

7:21

was confirmed before she did go to surgery.

7:23

So while it's ideal to find this the first

7:27

time, fortunately in this case, it did

7:29

not have a negative impact in delaying the

7:33

diagnosis because it was still almost a

7:35

decade before any intervention was performed.

7:38

So this shows the evolution.

7:40

of vestibular schwannomas from a

7:44

very subtle incidental finding to

7:46

very large findings that eventually

7:49

require bilateral surgical procedures.