Pathology of Cerebrovascular Disease Flashcards
How does the vasculature of the brain differ from other parts of the body?
Vein do not accompany arteries
How are the veins arranged in the brain?
There are large venous sinuses within the dura
Give examples of the venous sinuses found within the brain.
- Superior sagittal sinus
- Inferior sagittal sinus
- Transverse sinus
- Sigmoid sinus
- Straight sinus
What is the WHO definition of stroke?
Focal neurological deficit (loss of function affecting a specific region of the central nervous system) due to disruption of blood supply
What causes a stroke??
Interruption of supply of oxygen and nutrients, causing damage to brain tissue
Interruption of supply of oxygen caused by changes in…
- Vessel wall
- Blood flow (including blood pressure)
- Blood constituents
What can cause changes in the vessel wall?
Abnormality of wall
- Atheroma
- Vasculitis
Outside pressure
- Strangulation
- Spinal cord compression
- Compression of veins
What can cause changes in blood flow?
- Decreased blood flow
- Increased blood pressure bursting vessels
What can cause changes in blood constituents?
- Thrombosis of arteries and rarely veins
- Bleeding due to anticoagulation, reduced platelets anc clotting factors
What are the 3 main causes of localised interrupted blood supply?
- Atheroma and thrombosis of artery causing ischaemia
- Thromboembolism (for examples from the left atrium) causing ischaemia
- Ruptured aneurysm of cerebral vessel causing haemorrhage
Where is a common place for atheroma and thrombosis?
Carotid artery bifurcation
What is a thrombosis formed from?
Platelets and fibrin
What does atheroma and thrombosis of a vessel lead to?
Severe narrowing of the vessel
Where does ischaemia typically occur with internal carotid artery thrombosis?
Middle cerebral artery territory
Ischaemia
Relative of absolute lack of blood supply In a tissue or organ
What is the outcome of ischaemia causing transient symptoms?
- Last <24 hours
- Due to reversible ischaemia (TIA)
- Tissue still available
What is the outcome of ischaemia causing longstanding symptoms?
- Last >24 hours
- Due to irreversible ischaemic causing localised brain death
- Infarction
What is the brain very sensitive to?
Oxygen ischaemia
What will a few minutes of hypoxia or anoxia cause?
Brain ischaemia which can lead to infarction
Why is the damage permanent of infarction occurs?
The damage to the neurones is permanent. Neurons do not regenerate
How does localised area of brain death appear?
-There will be regional cerebral infarct-Classically wedge shaped reflecting arterial perfusion territory-Soft and then becomes cystic
What does the histology of infarct look like?
- Loss of neurones which cause clinical functional deficit
- Foamy macrophages: repair process leading to gliosis
- Gliosis is CNS equivalent of fibrosis
Why is the location of ischaemia very 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
Who is thromboembolism of atrial appendage common in?
People with arrhythmias such as AF
How does thromboembolism occur from the left atrium?
- Heart with left atrial appendage thrombosis
- Left atrium is connected directly to outflow of left side of the heart
- If thrombosis in left atrial appendage breaks off it will embolise to aorta and possibly the carotid (or any other) arteries
How can vessel walls rupture to cause a stroke?
- Beyond carotids and vertebral arteries the cerebral arteries have thin wall.
- Weakening of wall and hypertension causes aneurysm to form
- Wall can then rupture, especially if severe hypertension
- Decreased blood flow distally to brain due to spasm of artery
What are 2 common sites of ruptured vessels causing haemorrhagic stroke?
- Basal ganglia: microaneursyms form in hypertensive patients
- Circle of Willis: Berry aneurysm forms in hypertensive patient
What are the causes of generalised interrupted blood supply or hypoxia?
- Low O2 in blood (hypoxia with intact circulation of blood)
- Inadequate supply of blood (flow of blood not occurring) (blood may be oxygenated or not)
- Rarely: Inability to use O2 such as cyanide poisoning
What can cause low O2 levels in the blood?
- CO poisoning
- Near drowning
- Respiratory arrest
What can cause inadequate supply of blood?
- Cardiac arrest with immediate resuscitation
- Hypotension
- Brain swelling (trauma)
Describe the what would happen if someone experience a prolonged period of hypotension but was kept well oxygenated?
- There is prolonged period of poor perfusion but blood is oxygenated
- Central part of arteries territories are perfused OK
- Watershed zones are poorly perfused
- Zonal pattern of ischaemia and infarction at interface of territories
What are watershed zones?
Zones at interface of artery perfusion territories
What does pure hypotension with oxygenated blood lead to?
Watershed infarcts
What may found on autopsy of someone with a period of no oxygenation and no circulation to the brain?
- Large areas of grey matter thinning and necrosis
- Laminar appearance
What does complete loss of perfusion and oxygen lead to?
Cortical necrosis
What will a complex case lead to?
Complex pattern
