4.7 Stroke

Question 1

When does a stroke occur

Answer 1

When blood supply to a part of the brain is blocked

Question 2

Describe the 3 types of stroke

Answer 2

Intracerebral haemorrhage stroke (10% of total strokes):
It is caused by bleeding into the brain due to a sudden rupture of an artery within the brain. The blood released into the brain compresses brain structures.

Subarachnoid haemorrhage stroke (5% of total strokes):
It is caused by bleeding around the brain due to a sudden rupture of an artery within the brain which leads to blood filling space around the brain.

Ischaemic stroke (85% of total strokes):
It is caused by a blood clot that occludes an artery in the brain. It is either a thrombotic occlusion where diseased/damaged cerebral vessels are blocked by blood clots. Or an embolic occlusion where a clot/emboli forms distal to the brain and travels to the brain to restrict the blood flow.

Question 3

What is ischaemia

Answer 3

A lack of blood flow

Question 4

Describe the stroke risk factors

Answer 4

unmodifiable: sex, age, ethnicity, genetics, transient ischaemic attack

modifiable: hypertension, diabetes, smoking, hypercholesterolaemia, atrial fibrilation, physical inactivity

Question 5

What are some of the physiological defects caused by stroke

Answer 5

A stroke causes defects such as excitotoxicity, oxidative stress, peri-infarct depolarisations, inflammation, apoptosis and blood brain barrier dysfunction. They all have different levels of importance on survival chances and different time frames of impact. The responses following stroke are interconnected and cause a cascade.

Question 6

What are 3 of the most important physiological defects caused by stroke

Answer 6

excitotoxicity, oxidative stress and inflammation

Question 7

Describe inflammation following stroke

Answer 7

Minutes (but peaking at hours) following stroke, immune cells release inflammatory cytokines to brain. This inflammation can worsen brain injury by damaging neurons and other brain cells. However, inflammation also has a dual role, as it may aid in tissue repair in later stages.

Question 8

Describe oxidative stress following stroke

Answer 8

Minutes following stroke (but peaking at around an hour), there is overproduction of reactive oxygen species (ROS). These ROS can damage lipids, proteins, and DNA in brain cells, leading to cell death and further neurological damage.

Question 9

Describe excitotoxicity following stroke

Answer 9

Minutes after stroke, there is an excessive release of glutamate which overstimulates neuron receptors causing influx of ca into neurons triggering harmful cellular processes and ultimately leading to neuronal death.

Question 10

What are some current stroke treatments

Answer 10

• a dedicated stroke unit
• antiplatelet therapy (aspirin)
• recombinant tissue plasminogen activator (rt-PA), is the only approved pharmacological intervention. Is a clot busting drug that activates plasmin to degrade fibrin clots