Lecture 8: Neural Response to Ischemic Injury and Stroke Flashcards
What are modifiable risk factors of stroke?
- high BP
- High Body mass index
- high fasting glucose
- poor diet
- high LDL
- Kidney dyfunction
- air pollution
- alcohol use
- smoking
- low physical activity
What are Unmodifiable risk factors of stroke?
- Age
- Gender
- Genetics
- Head/ Neck Injuries
- Pregnancy
What is a stroke?
- Sudden loss of blood supply to brain tissue as a result of either a blocked or burst blood vessel
- Loss of oxygen and nutrients leads to neural cell death (infarction)
What are the two types of strokes?
- Hemorrhagic stroke (15%)
- Ischemic stroke (85%)
What are the two types of Hemorrhagic strokes?
- Intracerebral hemorrhage: in brain tissue
- Subarachnoid hemorrhage: btw pia layer and arachnoid layer-> bleeding in the space that surrounds the brain-> MOST DEADLY
What are the two types of ischemic stroke?
- Thrombotic strokes: caused by a blood clot that develops in the blood vessels inside the brain.
- Embolic strokes: Ouside of CNS-> when a blood clot or debris (embolus) travels from one part of the body and lodges in a narrower brain artery
Where do 65% of strokes occur in?
territory of the middle cerebral artery
Where do 15-25% of strokes occur? 10%?
15-25% occur in the Posterior circulation
- Occlusion supplying the brainstem often leads to death
- Otherwise effects are not as severe
- Occlusion supplying the brainstem (basilar artery) often leads to death
10% of strokes occur in watershed areas
- out towards the capillary bed and towards the system so it can have a global effect
- in watershed areas (near capillary beds)
After MCAO, regions which sustain damage include:
- Dorsolateral Striatum (usually damaged)
- Neocortex (usually damaged)
- Hippocampus (caused by larger strokes)
- Thalamus (secondary injury)
Is the middle cerebral artery or posterior circulation stroke worse? explain?
Posterior circulation stroke because there no no other way to get blood around the brain since all the arteries come together at the basilar artery -> EITHER MAJOR EFFECT OF NO EFFECT
Middle cerebral has another side to supply the brain
External carotid supplies what? which sends collaterals to the brain via what? (2)
- External Carotid supplies facial artery which sends collaterals to the brain via the internal carotid
- External Carotid supplies superficial artery which also sends collaterals to the brain via the internal carotid
Bold: how we connect the two
External to vertebral artery connects through what?
External Carotid supplies the occipital artery which sends collaterals into the vertebral artery
External to internal
1. external->
2. external->
- Facial
- superficial
External to Vertebral
- External->
occipital
what are the Leptomeningeal branches?
Watershed areas (Anastasomes)
- Anterior cerebral artery
- middle cerebral artery
- posterior cerebral artery
List all the collateral blood flow (5)
- External -> facial
- External -> superficial
- External -> occipital
- Circle of Willis
- Leptomeningeal-> anterior, middle, posterior
What is unique about the cicle of willis?
If you get damage on your right side, flow on the left may compensate for losses on the right side
What is the importance of collateral flow in Recannulation?
When you have high collateral flow, the infract will not be seen because blood will reach there
What are the regions that are damage after MCAO?
- NeoCortex , Dorsal-lateral striatum, corpus callsum, Hippocampus
- Thalamus-> considered a 2nd injury
The types and degrees of disability that follow a stroke depend upon what?
area of the brain is damage and how much damage is there
What are the five types of disabilities caused by stroke?
- Paralysis or problems controlling movement
- Sensory disturbances including pain
- Problems using or understanding language
- Problems with thinking and memory
- Emotional disturbances
What are the sensory distrubances after stroke?
- lose the ability to feel touch, pain, temperature, or position
- neuropathic pain-> nothing will stop it completely
What are problems using or understanding language after stroke?
- One-fourth of all stroke survivors experience language impairments
- Broca’s area, causes expressive aphasia (can understand words but cannot respond to them)
- Wernicke’s area, results in receptive aphasia (cannot understand but can talk)
What are the problems with thinking and memory after stroke?
shortened attention spans or may experience deficits in short- term memory
What are the emotional distrubances after stroke?
- fear, anxiety, frustration, anger, sadness, and a sense of grief -> depends on what area you damage
- clinical depression is common-> not sure if it is damage or just dealing with the stroke
What is the core of a stroke?
- the region that lost direct vascularization
- Cells within this region usually die within minutes and create an infarct
- Place that loses vascularization
What is the area surrounding the core?
Penumbra
What is happening in the penumbra from a stroke?
- Although this area did not directly lose blood flow, the damage caused at the core leads to inflammation and apoptosis.
- Compensatory reactions such as acidosis decrease protein synthesis, and selective gene expression within this region intensify inflammation and can eventually lead to cell death if left untreated.
What happens in the immediate phase?
- Vascular thrombosis
- Platelet embolization
- BBB permeability
- Metabolic stress -> Increase lactate, decrease ATP
- Ionic perturbations (Ca++, Na+, K+)
- Anoxic depolarization (cortical spreading depression)-> no O2 so trouble firing APs
- Cytokine release
What happens in the acute phase?
- Selective neuronal damage (necrosis)
- Inflammation (PMNLs, Macrophages, lymphocytes, microglia)
- Vascular reactivity abnormalities
- glial swelling
- secondary axotomy
Phase II
What happens in the subacute phase?
- Apoptosis
- Protein Aggregation
- Cell signaling perturbations
- Gene expression (HSP, Growth factors)
- Axonal Damage (permanent, transient, delayed)
- Axonal transport abnormalities
- Wallerian degeneration
phase III