Pathology of Cerebrovascular Disease Flashcards
Explain the blood supply to different parts of the cortex?
Do veins accompany arteries in the brain?
No they do not
What drains the dura mater?
Large venous sinuses
What is ischaemia?
Lack of blood flow
What is hypoxia?
Lack of oxygen
What is a stroke?
Focal neurological deficit (loss of function affecting a specific region of the central nervous system) due to disruption of blood supply
Vaugly, what is the cause of stroke?
Interruption of supply of oxygen and nutrients, causing damage to brain tissue
What can an interruption in oxygen to the brain be caused by changes in?
Vessel wall
Blood flow (including blood pressure)
Blood contituents
What changes in the vessel wall can cause an interruption of blood supply to the brain?
Atheroma or vasculitis
Outside pressure (strangulation)
Spinal cord compression
Compression of veins
What changes to blood flow can cause an interruption of oxygen delivery to the brain?
Decreased blood flow
Increased blood pressure bursting vessels
What changes to blood constituents can cause interruption to delivery of oxygen to the brain?
Thrombosis of arteries and rarely veins
Bleeding due to anticoagulation
Reduced platelets and clotting factors
In practice, what are the 3 main causes of localised interruptions of blood supply?
Atheroma and thrombosis of artery causing ischaemia
Thromboembolism (for example from left atrium) causing ischaemia
Ruptured aneurysm of cerebral vessel causing haemorrhage
What are the 2 kinds of ischaemia?
Transient symptoms
Longstanding symptoms
What are transient symptoms ischaemia?
Less than 24 hours
Due to reversible ischaemia (transient ischamia attack)
Tissue still viable
What are long standing sympotoms ischaemia?
More than 24 hours
Due to irreversible ischaemia
Causes localised brain death (infarct)
Explain the pathogenesis of ischaemic stroke?
Brian is very sensitive to oxygen ischaemia
Few minutes of hypoxia or anoxia will cause brain ischaemia
Can lead to infarction, it it does then damage to neurons is permanent as neurons do not regenerate
Classically wedge shaped reflecting arterial perfusion territory
How long is required to cause brain ischaemia?
Few minutes of hypoxia
What is a local area of brain death called?
Regional cerebral infarct
What is seen in histology of ischaemic stroke?
Loss of neurons (causes clinical functional deficit)
Foamy macrophages (repair process leading to gliosis)
Gliosis is CNS equilvalent of fibrosis
Why is the location of ischaemia important?
Small affected area of one part of brain may not cause too much impairment
Similar size of affected area in another part of brain may be devastating
What artery in the brain is often blocked due to an atheroma or maybe thromboembolism from the internal carotid artery?
Middle cerebral artery
What is the pathogenesis of a ruptured aneurysm causing ischaemic stroke?
1) Beyond carotids and vertebral arteries the cerebral arteries have thin walls
2) Weakening of wall and hypertension causes aneurysm to form
3) Wall can then rupture, especially if severe hypertension
4) Decreased blood flow distally to brain due to spasm of artery (haemorrhage)
What are 2 common sites of ruptured vessels causing haemorrhage stroke?
Basal ganglia (microaneurysm forms in hypertensive patients)
Circle of Willis (berry eneurysm forms in hypertensive patients)
Vaugly, what can cause strokes as well as local problems?
General problems
What are some examples of general problems that can cause stroke?
Low oxygen in blood
Inadequate supply of blood
Inability to use oxygen
What are examples of low oxygen in blood causing stroke?
Carbon dioxide poisoning
Near drowning
Respiratory arrest
What does low oxygen in blood causing stroke mean?
Hypoxia with intact circulation of blood
What does inadequate supply of blood causing stroke mean?
Flow of blood not occuring
Blood may be oxygenated or not
What are examples of things that cause inadequate supply of blood causing stroke?
Cardiac arrest
Hypotension
Brain swelling (such as trauma)
What is an example of inability to use oxygen?
Cyanide poisoning
This is rare
How does hypotension lead to stroke?
Central parts of arteries territory is better perfused
Leads to watershed zones that are poorly perfused, which are zonal patterns of ischaemia and infarction at interface of territories
How does cardiac arrest cause stroke?
Causes complete loss of perfusion and oxygen for a few minutes
Leads to laminar cortical necrosis (infarction)
What are the different patterns of infarction?
Watershed infarcts
Laminar cortical necrosis
Regional infarcts
