0:01

In general, anterior circulation aneurysms are more

0:05

common than posterior circulation aneurysms, and we

0:08

usually look for those aneurysms most commonly in

0:11

the posterior communicating artery in the internal

0:15

carotid artery distal segment, as well as in the anterior

0:19

communicating artery. Middle cerebral artery aneurysms

0:23

uh, also occur and they usually

0:25

bleed into the Sylvian fissure.

0:27

Let's look at this case, however. This was a

0:29

patient again who presented with thunderclap

0:32

headache with severe pain in the back of the head.

0:36

On this non-contrast CT scan, what we

0:40

see is hyperdensity in the subarachnoid

0:43

space of the interpeduncular cistern.

0:46

This is the midbrain.

0:47

This is the interpeduncular cistern.

0:49

It looks like it's relatively well-localized

0:53

to the interpeduncular cistern.

0:56

No intraventricular hemorrhage.

0:57

No hemorrhage extending along the Sylvian fissures.

1:01

And in this location, what sits in the interpeduncular

1:04

cistern just adjacent to it, is the basilar artery.

1:08

So we would be concerned about

1:09

a basilar artery aneurysm.

1:11

This patient has had previous

1:13

enucleation for trauma to that eye, so—

1:17

It is uncommon to have the non-contrast

1:20

CT scan followed immediately by CTA.

1:25

So at this juncture in imaging, most patients

1:29

who have concern for subarachnoid hemorrhage

1:32

are going to get a non-contrast CT and a

1:35

CTA if that non-contrast CT is positive.

1:40

Conventional arteriography for diagnosing

1:43

aneurysm is much less common nowadays.

1:46

Due to the high quality of CTA, we

1:49

have with modern thin-section imaging.

1:52

So a CTA was indeed performed, and as you can

1:55

see, not too subtly, as we come up from below and

2:00

come to the basilar artery, we see the contrast

2:04

enhancing stain of this aneurysm, which is deviating

2:08

to the right side and posteriorly.

2:11

The evaluation of aneurysm with CTA is similar to

2:15

the evaluation with conventional arteriography,

2:17

in that we want to characterize the size of the

2:20

aneurysm, the width of the neck, whether or not

2:23

it's involving adjacent blood vessels, and whether

2:27

or not there's coil associated with it, and if we

2:30

can identify the site of where it has ruptured,

2:35

particularly if you're dealing with multiple aneurysms.

2:38

You wanna know which one of the aneurysms

2:40

bled because that's the one we're obviously

2:41

going to treat, because the incidence of re-

2:44

hemorrhage in the immediate 24 to 48 hours is

2:47

relatively high with an aneurysm which has bled.

2:50

So let's take a look at my favorite,

2:52

which is our coronal MIP imaging.

2:55

Here we see our anterior cerebral arteries anteriorly.

2:58

Here we see the distal internal carotid artery

3:02

with the A1 segments and the M1 segments.

3:05

And the middle cerebral artery.

3:06

You can see whether or not there's an aneurysm

3:09

of the MCA bifurcation in this location.

3:12

And as we go further posteriorly, we identify

3:15

the vertebrobasilar artery circulation.

3:18

Let's magnify this so that way

3:19

we get our best quality imaging.

3:23

Okay, so this is the left vertebral artery.

3:26

This is probably the right vertebral artery.

3:29

Let's make sure—no, the right vertebral artery

3:32

is here.

3:33

So this is our vertebrobasilar junction.

3:36

This little blood vessel here is our

3:38

anterior inferior cerebellar artery.

3:41

As we come up superiorly, we come to the

3:44

superior cerebellar artery and the posterior

3:48

cerebral artery branches of the basilar artery.

3:51

This aneurysm is sitting in between the posterior

3:55

cerebral and superior cerebellar arteries,

4:00

with likely involvement of the origin

4:02

of that superior cerebellar artery.

4:04

You could sort of see that coming right

4:05

here, and we would measure the width here.

4:09

Pretty easy to measure the width of that

4:12

aneurysm, which measures six millimeters

4:15

at the base, and then the overall dimension

4:20

around 5.5 millimeters of the aneurysm.

4:23

Posterior circulation

4:25

aneurysms nowadays are pretty much exclusively treated

4:30

with neurointerventional procedures, with coiling

4:34

and/or stenting or pipeline intervention procedures.

4:39

Surgery in the posterior fossa aneurysm is

4:43

very complicated and runs the risk of injuring

4:46

those vital brainstem or cerebellar structures.

4:50

So here we have the aneurysm.

4:51

Obviously, you're going to continue to evaluate

4:54

this patient for the potential for multiple

4:56

aneurysms because multiple aneurysms occur in

4:59

25% of patients who have a single aneurysm.

5:04

So we're gonna characterize this.

5:06

You can look at it in multiple planes to give

5:08

better definition of the size of the aneurysm.

5:12

You can see that this is projecting posteriorly,

5:15

as I mentioned, in intimate association with the

5:18

superior cerebellar artery.

5:21

It has an irregular contour to it, so

5:24

it likely has bled, and as we saw,

5:27

it bled into the interpeduncular cistern.

5:30

When you do a CTA for the intracranial

5:33

circulation for aneurysm, quite frequently,

5:35

we're also combining that with

5:38

the neck vessels.

5:39

Why? This is used for guidance for the

5:42

neurointerventionalists. They wanna know, in

5:44

order to get to that basilar artery aneurysm,

5:47

which vertebral artery should I catheterize?

5:50

We wanna catheterize, obviously, the larger

5:52

of the two vertebral arteries.

5:55

Here's your right side.

5:57

Your left side over here is the larger one.

6:02

And that will be helpful, again, if there are

6:04

kinks to that vessel or stenosis of that vessel

6:07

or dissections of that blood vessel.

6:10

It should be known in advance of planning the

6:15

intervention to address the basilar artery aneurysm.