0:01

Another entity that is important to understand

0:05

as a resident reading emergency department

0:09

neuroradiology studies is non-aneurysmal

0:12

perimesencephalic subarachnoid hemorrhage.

0:16

This is an entity which is thought to be due

0:19

to bleeding from small veins, as opposed to

0:24

arteries. However, it presents in a similar fashion

0:28

to a basilar artery tip subarachnoid hemorrhage.

0:32

That is, you have hemorrhage that is in the

0:36

perimesencephalic or interpeduncular cistern on CT that

0:41

looks, for all the world, like a clot that may

0:43

be associated with a basilar artery aneurysm.

0:48

So, subarachnoid hemorrhage

0:50

in the perimesencephalic cistern usually doesn't

0:53

extend very far into interhemispheric or sylvian

0:56

fissures, if at all, and there shouldn't be any

1:00

layering of intraventricular hemorrhage, and

1:03

there should be no intraparenchymal hemorrhage.

1:05

Now, these patients will likely get a

1:08

CTA, despite the fact that they may have a

1:11

characteristic appearance on the non-contrast CT.

1:14

The CTA will not show an aneurysm,

1:17

and it won't show the bleeding vein.

1:19

Yes.

1:20

The question then is, in the face of this subarachnoid

1:23

hemorrhage, are you still going to need to go to

1:27

the gold standard of conventional arteriography?

1:32

Most people would say no.

1:34

If it has this characteristic criteria, you can

1:38

simply do a follow-up CTA rather than having

1:41

to do a more invasive conventional arteriogram.

1:44

So, in patients with perimesencephalic

1:47

subarachnoid hemorrhage...

1:49

There were found two aneurysms out of the 71

1:54

patients and one case of vasculitis, but the

1:57

source of the hemorrhage was not identified.

2:01

No source of hemorrhage in

2:02

68 of the 71 patients, or 96%.

2:07

So, this is from an 11-year

2:10

experience in looking at CT-negative

2:14

subarachnoid hemorrhage.

2:16

So again, depending upon the comfort level of

2:20

the clinicians or the patient's history, you may

2:24

be able to stop with a CTA and just recommend

2:27

a follow-up to ensure that you're not missing a

2:30

basilar artery aneurysm, or in some people's hands,

2:33

they will still do a conventional arteriogram.

2:37

These are three different patients, all of

2:39

whom had negative arteriograms and yet positive

2:44

subarachnoid hemorrhage as evidenced by CT.

2:48

Here, we have hemorrhage just behind the dorsum

2:51

sella, in front of the pons, with a little bit of

2:55

extension into the wings of the sylvian region.

2:58

Here, we have a more dramatic area of hemorrhage at the

3:03

pons-midbrain junction, and here, we

3:05

have hemorrhage in the interpeduncular

3:07

cistern—less dense, but still hemorrhage.

3:12

All of these patients had negative arteriograms,

3:14

and the diagnosis was non-aneurysmal

3:18

subarachnoid hemorrhage due to weeping

3:21

veins, if you will, as most people believe.

3:23

In this case, these patients have a very good prognosis.

3:27

They don't have an arterial bleed,

3:28

they don't get into issues with vasospasm, and they

3:32

don't have the usual complications of hydrocephalus

3:36

or otherwise associated with subarachnoid hemorrhage.

3:40

This pattern on a CT is one that you

3:43

should recognize as a resident and suggest

3:46

that the differential diagnosis not only

3:50

includes a basilar tip aneurysm, but also

3:53

non-aneurysmal subarachnoid

3:55

hemorrhage from non-arterial sources.