0:01

So, this will be our first case.

0:02

And this is a lesion that's involving

0:05

the left cerebellar pontine angle.

0:07

So, let's take a look at why this patient

0:09

presented. So, in the last series about technique.

0:11

The point that I want to make is this.

0:13

Here's our cochlear, here's our vestibule,

0:15

here's our internal auditory canal.

0:18

And we can actually see the small little nerves

0:20

right here in the internal auditory canal.

0:22

So, we can see these lesions.

0:24

It's extending this little nerve,

0:26

extending laterally,

0:27

and all of a sudden it runs into this large

0:29

mass that's located in the left CP angle.

0:32

So, on the non-contrast T1-weighted images,

0:34

we can see that it's low T1 signal,

0:37

it's high signal on the T2,

0:39

demonstrating that it's cystic.

0:41

And on the FLAIR sequences, we can see there's

0:43

complete suppression of the signal.

0:45

Now, when we do give contrast,

0:47

which is not shown on this specific image,

0:49

there is no enhancement whatsoever.

0:52

So, our differential diagnosis on this is either

0:54

going to be an arachnoid cyst or an epidermoid.

0:58

And in this particular case,

0:59

this is a classic example of an arachnoid cyst.

1:03

On a non-contrast T1, T2,

1:06

and FLAIR sequences. In subsequent vignettes,

1:10

we will now demonstrate the importance of other

1:14

sequences and how we can separate this

1:16

arachnoid cyst from epidermoids.