Lecture 7: CNS Pathologies - Stroke

Question 1

Describe blood supply to brain

Answer 1

see circle of willis (slide 4)

• arterial supply occurs via carotid and the vertebral arteries that originate from the aortic arch

Question 2

What % of cardiac output does the brain demand?

Answer 2

15-20%

Question 3

blood-brain barrier
* what is it
* what forms it

Answer 3

membrane that regulates the movement of molecules from the blood into the CNS

Formed by:
- capillary endothelial cells in the brain are connected by tight junctions to form a physical barrier

• astrocytes, pericytes & neurons also contribute to formation of the barrier

Question 4

General definition of stroke

Answer 4

acute loss of perfusion to vascular territories of the brain. Leads to ischemia and loss of neurologic function in the affected areas

Question 5

List and define the 3 types of stroke

Answer 5

1. Thrombotic closure of a blood vessel by atherosclerotic buildup (occlusive)
2. Embolic blood supply blocked by movement of an obstructive object (ischaemia, infarction)
3. Hemorrhagic bleeding from a vessel (e.g., a ruptured aneurysm)

Question 6

Describe the perfusion borders in the brain

Answer 6

see slide 9 + homunculus

ACA: medial portions of hemispheres. supply the frontal lobes, the parts of the brain that control logical thought, personality and voluntary movement. If both anterior cerebral territories are affected, profound mental symptoms may result (akinetic mutism)

MCA: lateral portions of hemispheres. specifically portion of frontal lobe, lateral surfaces of temporal and parietal lobe. includes the primary motor and sensory areas of the face, throat, hand and arm. in the dominant hemisphere, supplies areas for speech.

PCA: posterior portion of hemispheres. supply the temporal and occipital lobes of the left and right cerebral hemispheres and thalami. occipital lobe infarction causes opposite visual field defect

Question 7

The MCA, ACA, and PCA originate from?

Answer 7

MCA and ACA: internal carotid

PCA: stem in most individuals from the basilar arteries, but sometimes originate from the ipsilateral internal carotid arteries

Question 8

What cerebral arteries are most likely occluded?

Answer 8

MCA

Question 9

What are some clinical presentations in those with a PCA occlusion?

Answer 9

• thalamic syndrome (hypersensitivity to pain)
• Weber’s syndrome (ipsilateral oculomotor nerve paralysis & contralateral hemiplegia, due to midbrain lesion)
• hemianopsia and other symptoms including color blindness, failure to see to-&-fro movements, verbal dyslexia, and hallucinations.

Question 10

Describe some clinical presentations if you had a right MCA thrombo-embolic lesion

Answer 10

eye deviation toward lesion

conjugated eye deviation

left side hemiplegia (paralysis of lower face, arm, leg, on one side of body)

unconsciousness

Question 11

How to recognize and assess a stroke?

Answer 11

Recognize:

Spot a stroke: FAST
Face drooping
Arm weakness
Speech difficulty
Time to call 911

Assess:
First 3 letters of stroke
Smile
Talk
Raise both arms

Question 12

Describe TIA

Answer 12

transient ischemic attack: A “mini stroke” that occurs when a blood clot blocks an artery for a short time.

TIA symptoms occur rapidly and last a relatively short time.

Unlike a stroke, when a TIA is over, there’s no permanent injury to the brain.

There is no way to tell if symptoms of a stroke will lead to a TIA or a major stroke.

Rupture of atherosclerotic plaque, pieces travel downstream, can get lodged in smaller vessels

Question 13

How can strokes be assessed?

Answer 13

Noncontrast computed tomography (CT scan) is the first line imaging modality. Differentiates between ischemic from hemorrhagic
Clots will be hyperdense (remember CT anagram)

Magnetic resonance imaging (MRI) allows for earlier detection of brain injury than CT. MRI may also be used to recognize blood, localize the hemorrhage, and also date the age of the hemorrhage.

Question 14

How can hemorrhagic strokes appear on T1 vs T2 MRIs?

Answer 14

In an acute bleed (< 24 hours), blood appears differently depending on the MR protocols used. On T1 imaging blood appears as isointense, while on T2 imaging blood appears as hyperintense

Question 15

• How do hemorrhagic stroke patients differ from ischemic stroke patients
• how do hemorrhages present on MRI
• what are some common etiologies for hemorrhagic stroke

Answer 15

Hemmorrhage patients present similarly to those with ischemic stroke, except that they tend to appear more ill, with signs of increased intracranial pressure.

Signs and symptoms can include a sudden,
extremely severe headache, nausea, vomiting,
stiff neck, sudden weakness in an area of the
body, sudden difficulty speaking, and even loss
of consciousness, coma, or death.

Hemorrhage appears as a readily identifiable hyperintense (bright) area within the brain.

The most common etiologies are trauma, leakage from small intracerebral arteries secondary to chronic hypertension, aneurysmal rupture, iatrogenic anticoagulation, cocaine abuse, or cerebral amyloidosis (a neurological condition in which amyloid proteins build up on the walls of the arteries in the brain).

Question 16

Describe: angiography
* how is it performed
* what is it used for?

Answer 16

A catheter is threaded for direct visualization of blood vessels under X-ray during injection of radiopaque substance or contrast medium.

used to detect abnormalities of blood vessels, such as narrowing (stenosis) or blockage (occlusions) throughout the circulatory system.

commonly used to diagnose atherosclerosis, to detect an aneurysm, tumor, blood clot, or arteriovenous malformations (abnormal tangles of arteries and veins) in the brain; and to diagnose problems with the retina of the eye.

Question 17

What is magnetic resonance angiography

Answer 17

MRI modality that uses gadolinium-based contrast to better visualize the blood vessels. The vascular anatomy can be reconstructed 3-dimensionally to look at the entire vascular tree to identify vascular lesions at an earlier stage.

Question 18

Define: penumbra

Answer 18

the reversibly injured brain tissue around the ischemic core which is the target for the treatment of acute stroke

Question 19

Describe the rate of cerebral blood flow

Answer 19

60 and 100 ml/100 g/min.

Question 20

When a cerebral artery is occluded, ischemic brain tissue can be divided into 3 functional components. Describe them

Answer 20

• Infarct core tissue with severe perfusion deficit dies rapidly.
• Surrounding ischemic penumbra tissue with moderately reduced blood flow may be salvageable with reperfusion. Otherwise, the tissue will progress to infarction.
• The oligemic region has mildly reduced blood flow and is more likely to survive.

Question 21

Describe the modified rankin scale

Answer 21

Way to chart the level of severity following a stroke. 0 = no symptoms

6 is deceased

Question 22

What is an immediate treatment for thrombolytic stroke? What are the cautions around the use of this treatment?

Answer 22

inject thrombolytic substance called tissue Plasminogen Activator (tPA)

must be sure its a thrombolytic stroke. if hemorrhagic, tPA will cause death

Question 23

Define: mechanical Thrombectomy

Answer 23

Catheter-based therapies to disrupt or extract the clot

can also use suction jets, laser energy, ultrasonography, and corkscrew extractors.

• catheter aspiration thrombectomy

Question 24

What is the rationale for using angioplasty and stent for coronary vascular occlusion and stroke treatment?

What are the associated risks?

Answer 24

Push out the walls with stent to increase the lumen and increase circulation

Can be risky as it can break up plaque resulting in it being lodged downstream –> stroke

Question 25

Is the benefit of endovascular stroke therapy in the extended time window (6 to 16 hours) universal or limited to subgroups?

Answer 25

Endovascular therapy resulted in better functional outcome among a broad patient population

Question 26

Define: aneurysm

Answer 26

abnormal bulge of an artery that can rupture, leading to hemorrhage. They are sometimes called berry aneurysms because they are often the size of a small berry

Question 27

Symptoms of a ruptured cerebral aneurysm

Answer 27

sudden, extremely severe headache, nausea, vomiting, stiff neck, sudden weakness in an area of the body, sudden difficulty speaking, and even loss of consciousness, coma, or death.

Question 28

Aneurysm treatment

Answer 28

clipping to stop bleeding (when ruptured)

coil procedure for cerebral aneurysm (before rupture)

Once the aneurysm is full of coils, blood cannot enter it. This means the aneurysm is sealed off from the main artery, which prevents it growing or rupturing.

Question 29

Define: subarachnoid hemorrhage (SaH)

Answer 29

When blood is released into the subarachnoid space, it irritates the lining of the brain, increases pressure on the brain, and damages brain cells.

At the same time, the area of brain that previously received oxygen-rich blood from the affected artery is now deprived of blood, resulting in an ischemic stroke. SaH is frequently a sign of a ruptured aneurysm.

Question 30

What is a devastating complication of Subarachnoid Hemorrhage (SaH)

Answer 30

Vasospasm which is associated with delayed cerebral ischemia (DCI)

Autonomic mechanisms senses blood outside the blood vessel and signals for vasospasm (constriction of smooth muscle)

Over a 2-week period after aneurysm rupture, gradual arterial narrowing occurs in 70% of cases. About 30% will develop persistent neurological deficits caused by DCI.

Question 31

Describe a treatment to prevent vasospasm and delayed cerebral ischemia

Answer 31

Blocking the stellate ganglion (autonomic ganglion @ C6-C7) - blocks the inappropriate autonomic response that causes vasospasm and delayed cerebral ischemia

only experts can do. many risks. not available everywhere

more widely performed after the invention of fluoroscopy

Question 32

What are the risks of Stellate Ganglion Block treatment after SaH

Answer 32

needle in wrong place
- hematoma
- carotid / internal jugular vein trauma
- damage to vagus nerve or brachial plexus
- pneumothorax
- hemothorax
- thoracic duct injury (leak of lymph)
- esophageal performation (chance of infection is high)
- infection: neuraxial meningitis, abscess, osteitis (bone)

Question 33

What happened to Bob Saget

Answer 33

• died in hotel room
• fell in shower and hit back of head
• brain bounced off the front of the cranium

Contrecoup injury: brain bruise opposite side of impact. Can also tear delicate vessels on brain surface resulting in subarachnoid hemorrhage

Person can regain consciousness temporarily but the accumulation of blood will squeeze soft tissues until the victim dies of trauma while sleeping it off