Lecture 7: CNS Pathologies - Stroke Flashcards
Describe blood supply to brain
see circle of willis (slide 4)
- arterial supply occurs via carotid and the vertebral arteries that originate from the aortic arch
What % of cardiac output does the brain demand?
15-20%
blood-brain barrier
* what is it
* what forms it
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
General definition of stroke
acute loss of perfusion to vascular territories of the brain. Leads to ischemia and loss of neurologic function in the affected areas
List and define the 3 types of stroke
- Thrombotic closure of a blood vessel by atherosclerotic buildup (occlusive)
- Embolic blood supply blocked by movement of an obstructive object (ischaemia, infarction)
- Hemorrhagic bleeding from a vessel (e.g., a ruptured aneurysm)
Describe the perfusion borders in the brain
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
The MCA, ACA, and PCA originate from?
MCA and ACA: internal carotid
PCA: stem in most individuals from the basilar arteries, but sometimes originate from the ipsilateral internal carotid arteries
What cerebral arteries are most likely occluded?
MCA
What are some clinical presentations in those with a PCA occlusion?
- 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.
Describe some clinical presentations if you had a right MCA thrombo-embolic lesion
eye deviation toward lesion
conjugated eye deviation
left side hemiplegia (paralysis of lower face, arm, leg, on one side of body)
unconsciousness
How to recognize and assess a stroke?
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
Describe TIA
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
How can strokes be assessed?
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.
How can hemorrhagic strokes appear on T1 vs T2 MRIs?
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
- How do hemorrhagic stroke patients differ from ischemic stroke patients
- how do hemorrhages present on MRI
- what are some common etiologies for hemorrhagic stroke
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).
Describe: angiography
* how is it performed
* what is it used for?
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.
What is magnetic resonance angiography
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.
Define: penumbra
the reversibly injured brain tissue around the ischemic core which is the target for the treatment of acute stroke
Describe the rate of cerebral blood flow
60 and 100 ml/100 g/min.
When a cerebral artery is occluded, ischemic brain tissue can be divided into 3 functional components. Describe them
- 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.
Describe the modified rankin scale
Way to chart the level of severity following a stroke. 0 = no symptoms
6 is deceased
What is an immediate treatment for thrombolytic stroke? What are the cautions around the use of this treatment?
inject thrombolytic substance called tissue Plasminogen Activator (tPA)
must be sure its a thrombolytic stroke. if hemorrhagic, tPA will cause death
Define: mechanical Thrombectomy
Catheter-based therapies to disrupt or extract the clot
can also use suction jets, laser energy, ultrasonography, and corkscrew extractors.
- catheter aspiration thrombectomy
What is the rationale for using angioplasty and stent for coronary vascular occlusion and stroke treatment?
What are the associated risks?
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
Is the benefit of endovascular stroke therapy in the extended time window (6 to 16 hours) universal or limited to subgroups?
Endovascular therapy resulted in better functional outcome among a broad patient population
Define: aneurysm
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
Symptoms of a ruptured cerebral aneurysm
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.
Aneurysm treatment
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.
Define: subarachnoid hemorrhage (SaH)
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.
What is a devastating complication of Subarachnoid Hemorrhage (SaH)
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.
Describe a treatment to prevent vasospasm and delayed cerebral ischemia
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
What are the risks of Stellate Ganglion Block treatment after SaH
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)
What happened to Bob Saget
- 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
