0:01

Incomplete partition type three is very uncommon,

0:05

much less so in frequency than incomplete

0:09

partitions type one or two,

0:11

with two probably being the most common.

0:14

These are examples from the literature,

0:16

from the descriptions of incomplete

0:19

partition type three,

0:20

from the Neuroradiology article in December 2019 and

0:24

recent American Journal of Neuroradiology

0:27

article in June 2020.

0:30

Both of them show the same finding,

0:31

and that is this appearance of this corkscrew-like

0:35

cochlea, almost to me looks like a snowman cochlea,

0:40

where you have the dilated cochlea with

0:42

abnormal development of the modiolus.

0:45

You may also see abnormal enlargement of portions of

0:50

the semicircular canals as well as potentially an

0:55

abnormal development of the endolymphatic sac.

0:59

But it's this corkscrew cochlea that is typical

1:02

of the incomplete partition type three.

1:06

Here we have in the article by Hung,

1:09

the normal cochlea with the basal turn,

1:11

the modiolus, the middle turn.

1:13

We're just getting to the apical turn versus the

1:17

abnormal turns and the corkscrew-like appearance of

1:20

the cochlea in incomplete partition type three.

1:24

On these diagrams on C and D, as you can see,

1:27

the patients have abnormal enlargement of the

1:31

canal to the superior vestibular nerve.

1:35

And there's a spiral structure, as they say,

1:38

going from the internal auditory canal into the

1:41

cochlea, which is connected to the cochlear nerve,

1:44

as you see here.

1:45

And this is also abnormal development.

1:48

So here's our curvilinear structure connected

1:51

to the cochlear nerve. Here's the facial nerve,

1:53

cochlear nerve,

1:55

vestibular superior and inferior vestibular nerves.

1:57

And we have this kind of strange appearance of this

2:01

curvilinear structure within the internal auditory

2:03

canal for the cochlear nerve secondary to the

2:06

maldevelopment that's associated with incomplete

2:09

partition type three. To remind you,

2:13

these are the different appearances of the cochlea

2:17

in type one, type two, and type three.

2:19

Type one, absence of the modiolus and cystic cochlea.

2:23

Type two, not enough turns.

2:25

We have the basal turn,

2:27

but the middle and apical turns are not

2:30

developed the way they are normally.

2:32

And then we have this type three corkscrew

2:35

appearance to the cochlea.

2:36

This is another example of incomplete

2:39

partition type three on the CT scan

2:43

spiral appearance to the cochlea,

2:45

or as I look at it,

2:47

sort of the snowman appearance to the cochlea.

2:52

And you often will have maldevelopment of the

2:57

vestibular aqueduct in. This case on this MRI scan.

3:01

So this is a CIS MRI scan.

3:04

This is the internal auditory canal.

3:07

And as you can see there's at the arrowhead,

3:09

a dilated vestibular aqueduct in this example,

3:12

but also the enlarged superior vestibular nerve,

3:17

the long white nerve,

3:18

and the abnormally enlarged facial nerve

3:22

canal in the labyrinthine portion.

3:24

So the fallopian canal is the other term for the

3:27

labyrinthine portion of the facial nerve canal,

3:29

and that's dilated as well.

3:32

So some of the dysplasias that you can see

3:36

with incomplete partition type three.