L1 Flashcards
Cerebral Ischemia
[definition] impaired delivery of cerebral blood flow (CBF).
[types]
- focal ischemia: stroke
- global ischemia: from cardiac arrest, severe hypotension
[add.] while ischemia is more common, hemorrhagic is more devastating; and while ischemic strokes might restrict blood flow, which causes decreases in oxygen and glucose, there is more to them than hypoxia/hypoglycemia (such as, lack of waste removal).
Cerebral Hemorrhage
[definition] bleeding; hemorrhagic stroke
[types]
- intracerebral hemorrhage (ICH)
- subarachnoid hemorrhage (SAH)
Hypoxia/Anoxia
[types]
- anemic hypoxia: low blood hemoglobin
- histotoxic hypoxia: cells are unable to use oxygen (ie. cyanide poisoning)
Hypoglycemia
[definition] oxygen delivery is intact, but there are insufficient glucose levels (ie. overdose of insulin)
Hypoxic-Ischemic Encephalopathy (HIE)
[definition] a term encompassing other insults (ischemia, hypoxia, hypoglycemia) including a combination of them; if HIE is severe it leads to cardiac arrest. HIE is commonly a reference to insults in the perinatal period (use other terms when the insult is defined and known)
Focal Ischemic Stroke
Accounts for ~80% of all strokes
[causes]:
- Thrombus: blood clot forming at the site of occlusion (vessel damaged by atherosclerosis).
- Embolism: clot formed elsewhere and travelled to the site of occlusion.
Necrosis/pan-necrosis
[definition] area of dead tissue; a form of cell injury that results in the premature death of cells in living tissue by autolysis (pan-necrosis is widespread cell death, usually of neurons).
Necrosis differs from apoptosis in that apoptosis is a naturally occurring programmed and targeted cause of cellular death, while necrosis is caused by factors external to the cell or tissue (ie. infection, toxins, trauma) that results in the unregulated digestion of cell components.
Intracerebral Hemorrhage
Accounts for 10 - 15% of all strokes.
Has a high mortality rate and causes severe disabilities.
[causes]:
- hypertensive damage to cerebrovasculature
- amyloid angiopathy (commonly occurs in cortical regions; deposition of amyloid plaques)
- trauma, etc.
Types of ICH’s
Subcortical [common sites]: >> lobar >> basal ganglia >> thalamus >> cerebellum >> pons >> intraventricular
[primary factors influencing outcome: lobar]:
» size and location of the bleed
» re-bleeding
» intraventricular extension
Hematoma
[definition] a localized collection of blood outside the blood vessels, usually in liquid form within the tissue.
Mass Effect
Mass effect is an increased pressure in the brain which causes the blood leaking out of the vessels to push through tissue (causing mechanical destruction of tissue); this is difficult to treat due to the speed of the damage. Additionally, blood is toxic and erythrocyte degradation can increase blood toxicity.
Re-bleeding
Bleeding that occurs after the original bleed stops, usually due to popped clots. There’s also ongoing bleeding as well. These typically occur during the first three hours of the hemorrhagic bleed.
Intraventricular Extension
Blood pushing into the ventricals; a very bad sign in a stroke.
SAH
Accounts for ~5% of all strokes.
Has a high mortality rate, although recovery is better.
Usually caused by aneurysms at the base of the brain.
Compare and contrast the conditions of ICH, SAH, focal and global ischemic stroke.
- patient characteristics?
- survival rate?
- recovery?
- mechanism of injury and recovery?
- treatment strategies?
What is the vascularity of the brain?
Two main arteries coming from the heart:
- carotid arteries
- vertebral arteries
Within the brain there are two systems:
- carotid system
- vertebrobasilar system
The Circle of Willis: the basilar artery is connected to the carotid arteries via these communicating arteries (a posterior and anterior one). Everyone has this, and it acts as a back-up system in case on artery narrows (a different artery can then supply that territory).
» presence/disease of the CoW can affect how dramatic damage is due to stroke, and certain animal models may lack this anatomical feature.
Also: the MCA, PCA, ACA.
The middle cerebral artery (MCA) is most commonly affected in stroke; state two symptoms that you’d expect with a MCA territory stroke and why?
The MCA is most commonly affected because it’s so large; therefore there’s more flow going on and a higher statistical probability of a clot going here.
You’d expect to see motor deficits, sensory deficits, neglect, language damage, etc. (areas covered by the MCA).
How many new cases of strokes are there in Canada each year?
~50,000!
~20 - 25% of these die within the year, while many more are living with the consequences of stroke (over 1/4 million).
Numbers like these don’t even include covert strokes or related insults. There is a huge societal impact to the individual and their family, as well as enormous costs to health care systems at all levels.
What are some major RF’s of stroke?
- Age: more common in 60’s, 70’s, and 80’s.
- Gender: more common in women than men.
- Race: influences risk and type of stroke (ie. higher occurrence in Asia than Canada)
- Genetic predisposition
- Hypertension: sustained high blood pressure.
- Diabetes: both types
- Smoking
- Heart disease
- TIA’s: transient ischemic attacks (ischemic stroke in which symptoms resolve within twenty-four hours) — TIA’s predict problems, such as a clot which may have merely moved elsewhere.
What are some common symptoms of a stroke?
It depends on the location, severity, and any comorbidities.
BUT:
- weakness
- language difficulties
- vision problems
- headache (particularly in SAH)
- dizziness
(a combination of these things are usually warning signs of a stroke)
