Hemorrhagic Stroke Flashcards
As we have already discussed, hemorrhagic stroke comprises only 20% of all strokes and these are roughly equally divided between hemorrhage into the brain, i.e., intracerebral or parenchymal hemorrhage and hemorrhage into the subarachnoid space. Once again this slide presents CT scans of patients with hemorrhagic stroke on the left.
The CT scan at the top demonstrates hemorrhage into the basal ganglia and the two scan below present hemorrhage into the subarachnoid space.
Label these cerebral hemorrhages from left to right?
Left to right (top to bottom)
Note the small black arrows pointing to blood filling the sulci overlying the left neocortex (recall you are looking at the brain slice from the bottom up).
The next CT scan presents an example of blood in the basal ganglia, i.e., intracerebral hemorrhage (ICH).
The third scan presents an epidural hemorrhage, i.e. blood between the inner plate of skull bone and the dura. Note the convex or lens shape of the hemorrhage that is characteristic of an epidural bleed.
The last scan presents an example of subdural hemorrhage over the left cerebral hemisphere. This patient has actually suffered at least two subdural hemorrhages separated by several weeks or more in occurrence. Note the layer of bright white blood as the outer most layer and beneath it a second less dense layer that contains two distinct densities. The upper most portion of this inner layer is less dense (darker) than the lower layer.
Recognizing that red blood cells will lyse and release their contents over time can you figure out why this inner layer contains these two distinct density patterns. Also can you determine which of the two layers, the outer or inner layer, represents the most recent hemorrhage.
We have already covered the point that the incidence of cerebral hemorrhage is roughly equally divided between bleeding around the brain, subarachnoid hemorrhage and bleeding into the brain, parenchymal or intracerebral hemorrhage.
What are some common causes of hemorrhagic stroke?
- Berry aneurysm
- Vascular malformation
- Traumatic
- Mycotic aneurysm
- Hypertension
- Tumor
- Bleeding diatheses
- Anticoagulant complication
- Congophilic Angiopathy
- Vasculitis
- Illicit drug use
Subarachnoid hemorrhage is most commonly caused by what?
rupture of a saccular (berry) aneurysm.
Describe berry aneurysms
These aneurysms reflect developmental defects in the blood vessel wall that tend to enlarge with time. Detectable defects in the brain blood vessel walls are common with 20% of the population having an aneurysm measuring 2 mm or less in diameter. Such aneurysms rarely if ever rupture. Approximately 5% of the population has a cerebral aneurysm measuring 2 – 5 mm in diameter and will occasionally bleed. Aneurysms larger than 5 mm in diameter rupture and bleed at a rate of 1-3% per year. Fortunately aneurysms of this diameter are less common and cause approximately 30,000 subarachnoid hemorrhages in the U.S. each year.
This is a Netter slide showing the most common locations for berry aneurysms. They include: 85% anterior circulation (30% ACA, 30% ICA, and 25% MCA), and 15% posterior circulation (2% PCA,, 10% Basilar, 3% Vertebral)
Note that while patients may have multiple (one, two, three, or more) aneurysms, this drawing showing many aneurysms is simply intended to show their most likely locations and not a patient with numerous aneurysms. The lower two figures present an AP (anterior-posterior) view of a cerebral arteriogram with an aneurysm (yellow arrow) of presumably the anterior communicating artery (left figure) and a large posterior communicating aneurysm (right figure)
What are the main risk factors for having a subarachnoid hemorrhage?
- Tobacco use
- Ethanol abuse
- Hypertension
- Oral contraceptives
- Stimulant drugs (cocaine, etc.)
- Low cholesterol
- Genetics (polycystic kidneys, Marfan’s syndrome)
What is the prognsosis of a subarachnoid hemorrhage?
The clinical consequences of subarachnoid hemorrhage from a ruptured berry aneurysm are dire. 10-15% of such patients die before they reach the emergency room. An additional 25% die during the next three months raising the overall mortality to approximately 40%. Those patients that survive the initial bleed have a 40% chance of having neurologic sequelae.
How might a subarachnoid hemorrhage present?
Patients with rupture of a berry aneurysm typically present to the emergency department with complaints of the “worst headache of my life”.
Some but not all patients may rapidly lose consciousness secondary to the large pulse pressure change delivered to the brainstem as a result of arterial blood entering the subarachnoid space.
Neck stiffness and pain, photo- and phonophobia follow the rupture of a berry aneurysm within hours. These later symptoms reflect irritation and inflammation of the meninges secondary to the breakdown products of red blood cell lysis.
Focal neurologic signs are more commonly minor or absent and this helps distinguish this type of stroke from ischemic stroke.
What are the signs of a SAH?
Blood pressure may be elevated and the patient may manifest cardiac arrhythmias. The latter cardiac symptoms are related to red blood cell breakdown products that irritate brainstem centers regulating heart rate.
Retinal hemorrhages may be present
While focal neurologic signs are infrequent, some when present help to localize the arterial site of the aneurysm. For example, third CN paresis resulting in a dilated pupil and ophthalmoparesis is consistent with an aneurysm at the junction of the internal carotid and PCOM arteries; paraparesis (bilateral leg weakness) suggests an aneurysm of the anterior cerebral artery; hemiparesis is consistent with a middle cerebral artery aneurysm.
Irritation of the meninges with the signs described earlier is usually delayed for several hours after rupture of the aneurysm and the onset of headache.
What is the most helpful noninvasive diagnostic test to identify a subarachnoid hemorrhage?
non-contrast CT scan
The amount of blood and its location help determine the site of the berry aneurysm and also the likelihood of a delayed complication called “vasospasm”. Recognize that the CT scan may be negative in a patient with a ruptured berry aneurysm, especially if the bleeding is slight or if the scan is delayed for a day or more after the rupture.
Importantly, if you suspect a subarachnoid hemorrhage you must perform a lumbar puncture to look for subarachnoid blood. A lumbar puncture is the only method to 100% rule out a subarachnoid bleed.
Rules for an LP with a SAH
It is important to delay the lumbar puncture for 3 to 4 hours after onset of a headache that you believe to be caused by a subarachnoid hemorrhage.
The reason for this is to allow time for some of the red blood cells in the subarachnoid space to lyse and release hemoglobin into the spinal fluid. The presence of hemoglobin or its breakdown products in spinal fluid will help significantly in your being able to distinguish between the appearance of blood in the spinal fluid that occurred from nicking a vein while performing the spinal tap and blood that resulted from the rupture of a berry aneurysm hours earlier.
To distinguish the two conditions you must have the blood tinged spinal fluid centrifuged IMMEDIATELY. Red blood cells derived from a nicked vein during the tap will remain intact and be ‘spun down’ during centrifugation leaving the supernatant crystal clear. In contrast, a red tinge or discoloration of the supernatant after centrifugation indicates that hemoglobin is dissolved in the spinal fluid from red blood cells that have been in the spinal fluid for several hours, i.e. from a ruptured aneurysm.
This is a Netter slide summarizing some of the points we have just reviewed in regards to SAH.
The man presents with a severe headache, he may lose consciousness, and he may demonstrate a positive Kerning’s or Brudzinski sign (both signs of meningeal irritation).
The lower figures demonstrate bloody spinal fluid that does not clear after collecting several tubes indicating a ruptured berry aneurysm and spinal fluid that tends to clear after collecting three tubes suggesting the blood came from a traumatic spinal tap, i.e. a nicked vein.
The three yellow tubes reflect discoloration of the spinal fluid, called xanthochromia, that results from the break down of hemoglobin. Such yellow discoloration takes a day or more after rupture of the an aneurysm to develop.
Once the diagnosis of a SAH is confirmed with either a CT scan or lumber puncture, the next task is to to what?
identify the site of the ruptured blood vessel. The MRI is an excellent noninvasive method to identify aneurysm that are larger than 5 mm but the gold standard diagnostic procedure is the 4-vessel digital subtraction arteriogram
I just want to make a few additional comments about diagnosing cerebral aneurysms. Firstly, there is no need to perform a lumbar puncture if imaging shows blood in the subarachnoid space. In fact, an LP is contraindicated because removal of CSF could suddenly lower the CSF pressure and remove a tamponade effect by the clot on the dome of the aneurysm and trigger a second bleed.
Previously, CT was superior to MRI in detecting acute intracerebral blood but MRI software has evolved to the point that MRI performs just as well as CT in this regard.
Thirdly, CT angiography now provides resolution that almost matches digital subtraction angiography and therefore, CTA has replaced DSA for most routine screening purposes.
Finally, catheter angiography and DSA are used for the endovascular removal of clot in acute stroke, for stent placement in stenotic arteries, for the repair of aneurysms with coils and stents and for other endovascular procedures.
The definitive therapy for a berry aneurysm is:
either the placement of small coils within the aneurysm through an intra-arterial catheter to cause the aneurysm to clot and seal itself, the surgical placement of a metal clip at the neck of the aneurysm, or a combination of the two procedures.
This is a Netter slide showing the surgical approach prior to clipping a basilar artery aneurysm.
This slide shows a variety of clips that have been developed to seal of berry aneurysms.
This slide presents a DSA of a basilar tip aneurysm (yellow arrow) before placement of coils in the lumen of the aneurysm (left) and after placement of the coils (right). Note after coil placement the aneurysm has clotted off and the arteriographic dye cannot enter the aneurysm.
In addition to coiling aneurysms, interventionalists can divert arterial blood flow away from an aneurysm using flexible stents. This reduce pressure and movement of blood into the aneurysm, and blood that is not continuously moving tends to clot. Clotting off the aneurysm prevents it from rupturing, essentially obliterating it. This is shown in the upper panel. In the lower panel is shown how a top of the basilar artery aneurysm can be managed with stents and coiling, thereby avoiding what once was considered the Mount Everest of all neurosurgical procedures, the clipping of a basilar tip aneurysm.
Hemorrhage into the substance of the brain may be caused by a variety of conditions with ____ ______ being the most frequent.
head trauma
After head trauma, hypertension is the next most common cause of parenchymal hemorrhage. Why?
Chronic elevation of the blood pressure causes injury to small cerebral blood vessels and the production of microaneurysm called Charcot Bouchard aneurysms. These aneurysms develop in small, penetrating microvessels located in the basal ganglia, thalamus, pons, and cerebellum. Consequently, these brain regions are the most common sites for intraparenchymal hemorrhages caused by hypertension.
•Hypertensive bleeds occur most frequently where?
in the basal ganglia (30%), thalamus (20%), pons (5%), and the cerebellum (10%)
