00:01
So let's talk a little bit more
about subarachnoid hemorrhage
and understand how we evaluate
and manage those patients.
00:07
Subarachnoid hemorrhage
is a type of stroke.
00:10
It's a type of
cerebrovascular accident.
00:13
And it results from intracranial
hemorrhage into the subarachnoid space
between the arachnoid and the pia mater
layers that are surrounding the brain.
00:22
As we look at that schematically,
where is the blood and what is happening.
00:26
Again, here we see the
bones out on the surface
and we move down into
the parenchyma inferiorly
and the subarachnoid blood is
developing in the subarachnoid space.
00:36
This is right out on
the surface of the brain
and we can see problems with
increased intracranial pressure
as a result of decreased CSF
reabsorption and other problems
as a result of
location of the blood.
00:50
In terms of epidemiology, subarachnoid
hemorrhage is a type of hemorrhagic stroke.
00:55
Hemorrhagic strokes account for 15-20%
of the cerebrovascular accidents.
01:00
The majority of
strokes are ischemic,
but this small portion up to
15-20% of strokes are hemorrhagic.
01:08
50% of hemorrhagic strokes are
due to subarachnoid hemorrhage.
01:11
The other 50% of hemorrhagic strokes
are intraparenchymal hemorrhages.
01:17
When we think about
subarachnoid hemorrhage,
we want to think about
trauma and aneurysms.
01:22
Saccular aneurysms or
outpouching of the blood vessel
increased the risk of
subarachnoid hemorrhage.
01:28
Rupture of a saccular aneurysm
is one of the most common causes
of subarachnoid hemorrhage.
01:33
And you can see that
depicted on the schema here.
01:35
We have a normal blood
vessel at the bifurcation
or just distal to
the bifurcation.
01:40
We have this circular
outpouching of the blood vessel
and then extrusion of blood out
of the surface of that aneurysm
contributing to
subarachnoid hemorrhage.
01:49
And this bifurcation area is
often where we see aneurysms
as a result of the flow and abnormal
flow of blood that can occur
and the intensity of the blood pressure
around those bifurcation areas.
02:03
3-5% of the population may have
radiographic evidence of an unruptured
saccular aneurysm but the vast
majority will not rupture.
02:12
So just because you have an aneurysm
doesn't mean it will rupture.
02:15
And we use the size and the appearance
and the location to guide us
in terms of whether patients should
undergo preventative intervention
to prevent a rupture or
they should be monitored.
02:26
Trauma is a trigger for
potential rupture of an aneurysm
in addition to being a cause
of subarachnoid hemorrhage,
even in patients
without an aneurysm.
02:35
And 15-20% of subarachnoid
hemorrhages are non-aneurysmal.
02:39
So a patient presents with
a subarachnoid hemorrhage,
we look for an aneurysm
and don't find it.
02:43
Then we need to think about trauma
or other vascular abnormalities.
02:49
What's the clinical presentation
for subarachnoid hemorrhage?
Well, one I want you to think
about thunderclap headache.
02:55
That is the severe,
sudden worst headache of my life
that began rapidly and
the rapidity of onset
of that severe worst
headache of my life
is what makes it a
thunderclap headache.
03:06
This is sudden in onset,
it begins in seconds,
and patients typically describe that
the worst headache of their life
really began in seconds.
03:14
And that's indicative of
a thunderclap headache
and should prompt evaluation
for subarachnoid hemorrhage.
03:20
We can see other symptoms,
neck stiffness and pain
as a result of
meningeal irritation.
03:25
This correlates with spreading of blood
into the CSF causing meningeal irritation.
03:30
Often presents hours after
the onset of headache.
03:32
We can see altered loss of
consciousness from increased ICP.
03:36
Seizures as a result of blood
being right on the cortical surface
and nausea/vomiting from
increased ICP as well.
03:44
How about the diagnosis?
We diagnose subarachnoid hemorrhage
the same as we do every other
type of intracranial hemorrhage
with a non-contrast head CT.
03:52
And this is really the
cornerstone of how we evaluate
hemorrhages and
subarachnoid hemorrhage.
03:57
CT has a sensitivity
of up to 100%
if performed within the first
6 hours of presentation.
04:04
And so patients who present suddenly
and we see a non-contrast head CT,
if it shows subarachnoid
hemorrhage, that's what it is.
04:10
If it doesn't,
it's very unlikely to be that.
04:14
And that is if reviewed by a
qualified neuroradiologist.
04:17
But sometimes CT can miss a
subtle subarachnoid hemorrhage
or a sentinel bleed, a small bleed
from an aneurysm that then stops.
04:25
And in those cases,
additional evaluation may be needed
and we'll talk about
that in just a minute.
04:31
CT scan should include cuts
through the base of the brain.
04:34
We want to look at the base of
the brain around the blood vessels
where we can see aneurysms
and subarachnoid develop.
04:40
Locations of blood in subarachnoid
hemorrhages include the Basal cistern
which is the most
common, Sylvian fissure,
the interhemispheric fissure
and interpeduncular fossa
and here we're looking at an
image of subarachnoid blood
in addition to intra
ventricular blood
resulting in significant
increase in intracranial pressure
and ventriculomegaly unlikely
in a patient who is comatose.
05:04
In addition to CT, evaluation of
subarachnoid hemorrhage can include
a lumbar puncture and historically
this was very important
in the evaluation of
subarachnoid hemorrhage.
05:13
As the sensitivity and
specificity of CT hadn't improved,
we see less spinal taps needed
for evaluation of these patients.
05:21
This should be performed
if there's a high
index of clinical suspicion
for subarachnoid hemorrhage.
05:27
And typically we see
elevation and opening pressure
and an elevation in the
red blood cell count.
05:33
Importantly, sometimes we can see
an elevated red blood cell count
in the first tube as we insert
the needle that clears over time.
05:41
And that's a traumatic tap,
where we hit a blood vessel on the way in,
we see that blood in the first tube
and we see that it goes down over time.
05:49
When we see blood in the first tube
and the same blood in the second
and third and fourth tube as
we collect the spinal fluid
that suggests some intrinsic production
of blood in the spinal fluid.
05:58
And that's the signature for what
we see with subarachnoid hemorrhage.
06:01
Occasionally, amount of blood
in the subarachnoid space
and CSF is small and we may just see
a xanthochromic cerebrospinal fluid
which would also support concern for
a sentinel bleed or subarachnoid.