0:01

One might ask, what is the role of MRI scanning

0:06

in the patient with subarachnoid hemorrhage?

0:10

Well, as I mentioned, there is a small percentage

0:13

of patients, around 5% of patients with modern CT

0:16

technology, who have subarachnoid hemorrhage, which

0:20

is not obvious or not present on the CT scanning.

0:24

These are usually patients who have this.

0:27

Headache that's been going on for two, three

0:30

days and then present to the emergency room.

0:33

Even though it was the worst headache

0:34

of their life, they self-medicate, and

0:37

they present, uh, in a later fashion.

0:40

After two or three days, that subarachnoid

0:42

hemorrhage that occurred may become isodense

0:47

to normal cerebrospinal fluid on the CT scan.

0:51

However,

0:52

FLAIR imaging, which is seen here, is

0:56

sensitive to subarachnoid hemorrhage for up

1:00

to a week after it occurs in FLAIR imaging.

1:03

Remember, the CSF should be dark, like in this ventricle.

1:08

In this case, what we're seeing is high signal intensity

1:12

in the Sylvian fissures bilaterally in a patient who had

1:15

delayed presentation for subarachnoid hemorrhage.

1:19

So, in that instance,

1:21

you may see evidence of subarachnoid hemorrhage on the

1:24

FLAIR scan in patients who have a negative CT scan.

1:29

In my personal opinion, if there is that

1:32

suspicion of subarachnoid hemorrhage, it's

1:36

better for the clinicians to do a lumbar

1:38

puncture and look for xanthochromia, evidence

1:41

of prior hemorrhage, rather than proceeding to

1:44

the next imaging study, which is the MRI scan.

1:48

On this FLAIR scan, I can't tell you whether

1:51

what's making this bright in the Sylvian fissure

1:55

is subarachnoid hemorrhage or meningitis.

2:00

That is the role of lumbar puncture because the

2:02

severe headache could be from either of the two.

2:04

So, even if I see this bright signal,

2:06

I might say, oh, there's, there's high

2:08

signal intensity in the subarachnoid space.

2:09

It could be blood, or it could be meningitis or pus.

2:14

You need a lumbar puncture.

2:15

So, why perform the MRI scan,

2:18

right?

2:19

So, let's move on.

2:21

As I mentioned, the site of the

2:23

aneurysm can be implied from the CT scan.

2:27

In this case, we have a

2:28

hemorrhage in the basal cisterns.

2:30

We have hemorrhage in the interhemispheric

2:32

fissure, but more importantly, we have parenchymal

2:35

hemorrhage in the medial left frontal lobe.

2:38

This would indicate an anterior communicating

2:41

artery or anterior cerebral artery

2:43

distribution aneurysm in this patient.

2:47

Some of the risk factors for aneurysm occurrence,

2:49

rupture, and growth are important to note

2:53

as part of your review of the electronic medical record.

2:56

Aneurysms have a rate of bleeding of 2 to 3% per

3:01

year when they are discovered incidentally. However,

3:07

an aneurysm that has bled in the emergency

3:11

situation has a relatively high rate—a 10

3:14

to 20% rate of re-bleeding within the first

3:18

24 to 48 hours. And for that reason, I love—

3:22

uh, surgeons will treat the patient

3:24

immediately upon discovery of the aneurysm.

3:28

Some of the risk factors for recurrent hemorrhage

3:31

include smoking, hypertension, a family

3:34

history of multiple aneurysms, a coagulopathy,

3:37

and, in general, rebleeding in aneurysms

3:41

occurs more frequently in women than in men.

3:45

The larger the size of the aneurysm, the

3:48

higher the rate of rupture and rebleed.

3:51

If that aneurysm shows growth over time,

3:54

sometimes we will do serial imaging of

3:57

patients who have asymptomatic aneurysms.

4:00

This is because, for example, if you find an

4:03

aneurysm, a new aneurysm, in a 75-year-old,

4:06

given the life expectancy to 82 and potential

4:11

comorbidities, the incidence of rupture of that

4:15

aneurysm, if it's asymptomatic, is 2 to 3%.

4:18

Let's say they have 10 more years of life

4:20

expectancy, then it's a 20% risk that they

4:23

would bleed if they have congestive heart

4:26

failure, cancer, and other comorbidities.

4:29

It may be that you just sort of follow

4:31

that aneurysm and see whether it grows.

4:34

If it does grow, then you intervene.

4:36

If it doesn't grow, then you take

4:38

that risk of bleeding at 2 to 3%.

4:41

A patient who has had a prior hemorrhage

4:43

is more likely to have the potential for

4:45

re-bleeding. The morphology, if it's an irregular

4:49

aneurysm, or has the term that the interventionalist

4:53

uses—Murphy's teat—in that there's a little

4:56

point to the aneurysm that shows that it

5:00

may be one that has a propensity for

5:03

hemorrhage, also is another risk factor for

5:07

aneurysm rupture. And if you have multiple

5:09

aneurysms, the likelihood that one will rupture

5:12

is sort of a multiple of this—2 to 3% per year.

5:15

CTA, MRA, and conventional arteriography are kind

5:19

of boring as far as their ability to detect aneurysms.

5:23

We would still say that conventional arteriography

5:26

is the gold standard, but with modern CTA and MRA,

5:31

the detection rate of aneurysms

5:34

is in the mid to high 90% range.

5:38

It's pretty uncommon to miss an aneurysm on CTA and

5:42

MRA currently. And when you do miss them, they're very

5:46

small aneurysms that have a low likelihood of bleeding.

5:51

With digital subtraction angiography, we now

5:54

have the capability of doing all kinds of three-

5:56

dimensional and crazy reconstructions that allow the

6:01

planning of the coiling and/or stenting or pipeline

6:05

treatment of aneurysms. And these are three-

6:09

dimensional data sets at the time of conventional

6:13

arteriography and quite beautiful in their evaluation.

6:17

Something to be emphasized is that those

6:21

patients who have aneurysms of the anterior

6:25

cerebral artery or anterior communicating artery.

6:29

And/or the vertebrobasilar artery circulation.

6:32

These are almost exclusively treated

6:34

with interventional procedures.

6:36

Now, neurosurgical clipping of aneurysms is

6:40

usually when there has been an unsuccessful

6:43

attempt at endovascular treatment or,

6:47

in middle cerebral artery aneurysms. Middle cerebral

6:50

artery aneurysms are easier to get to neurosurgically.

6:54

They just go down the Sylvian fissure, and these are

6:57

harder to get to via endovascular methodologies.

7:01

And they may be more irregular and friable.

7:04

Therefore, this is still an indication

7:07

for primary neurosurgical treatment for

7:10

middle cerebral artery distribution aneurysms.

7:14

And this was all pointed out in one of the classic

7:18

multi-institutional studies known as the ISAT trial,

7:22

the International Subarachnoid Aneurysm Trial.

7:25

They had a huge number of aneurysms that were

7:28

randomized to clipping versus coiling, and what

7:33

they found was that there was overwhelming evidence.

7:37

In fact, they had to stop the study early

7:39

because of the benefit of doing coiling versus surgery

7:43

with regard to the risk of death and disability.

7:47

There was much more risk reduction with coiling

7:50

as opposed to surgery, so this trial was

7:53

stopped early in support of endovascular

7:57

treatment of anterior circulation aneurysms.

8:00

However, they did not include posterior circulation

8:03

aneurysms in this trial because those are treated,

8:07

by default, via endovascular treatment because of

8:11

the high risk of surgery in the posterior fossa.

8:14

At the same time, middle cerebral artery

8:16

aneurysms were not randomized in this trial because

8:20

it was said that they were preferentially treated

8:23

with clipping due to easier surgical

8:27

access and more difficult endovascular access.