Pathology of Cerebrovascular Disease Flashcards
A
anterior cerebral artery
B
middle cerebral artery
C
posterior cerebral artery
Describe the venous drainage of the brain
- Veins do not accompany arteries
- Large venous sinuses within dura
A
superior sagittal sinus
B
transverse sinus
C
jugular vein
What is Ischaemia?
lack of blood flow
What is hypoxia?
lack of oxygen
What is anoxia?
no oxygen what so ever
What does ischemia lead to?
hypoxia
Wha does a lack of blood flow cause?
lack of oxygen
WHat are the 2 different main ways a stroke could be caused?
- Focal or localised interrupted blood supply or hypoxia
- Generalised problem with blood supply or hypoxia
What is WHO definition of a stroke?
Focal neurological deficit (loss of function affecting a specific region of the central nervous system) due to disruption of blood supply
What is the cause of a stroke?
Interruption of supply of oxygen and nutrients, causing damage to brain tissue
Many causes of interruption of supply of oxygen
Interruption of supply of oxygen caused by what changes?
- Vessel wall
- Blood flow (including blood pressure)
- Blood constituents
(virchows triad)
What is an example of a change in the vessel wall leading to interruption of supply of oxygen?
abnormality of wall eg atheroma or vasculitis, outside pressure (eg strangulation, spinal cord compression, compression of veins)
What is an example of a change in blood flow and pressure leading to interruption of supply of oxygen?
decreased blood flow, increased blood pressure bursting vessels
What is an example of a change in blood constituents leading to interruption of supply of oxygen?
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 interrupted blood supply leading to a stroke?
- Atheroma + thrombosis of artery causing ischaemia
- Thromboembolism (for example, from left atrium) causing ischaemia
- Ruptured aneurysm of a cerebral vessel causing haemorrhage
What is a common area for a thromboembolism to form?
left atrium is a very common site, blocks an artery and causes distal ischemia
How can a atheroma cause a stroke?
Where is a common site for it to occur?
Narrowing (for example, atheroma) + thrombosis of artery
Can happen anywhere form the left ventricle upwards to vessels in their brain themselves
Common is the bifurcation of the carotid artery - often get a patch of atheroma as there is turbulent flow
Where would an internal carotid artery thrombosis typically effetc in the brain?
typically get ischaemia in middle cerebral artery territory
What is the texture of a infarct?
Soft and then becomes cystic
What histological changes happen when there is a brain infarct?
Loss of neurones - causes clinical functional deficit
Foamy macrophages –repair process leading to gliosis
Gliosis is CNS equivalent of fibrosis
Eventually: old infarct with loss of brain tissue
How does a thromboembolism form in the left atrium?
AF is the classic arrhythmia which causes stagnant blood to turn into a thrombosis
Any heart disease can cause arrhythmias so any heart disease can cause thrombosis
Heart is set up in humans to supply the brain
What is a common site for a thromboembolism form the brain to travel to?
the middle cereblar artery
What do the thin walls of the cerebral arteries make them susceptible to?
Weakening of wall + hypertension causes aneurysm to form
Don’t want cerebral vessels in spasm as they have thin walls and almost no smooth muscles (little) in them so makes them weaker and more susceptible to aneurysms
Wall can rupture and hemorrhage comes out of it
What can make cerebral arteries rupture easily?
Wall can then rupture, especially if severe hypertension
What do ruptured vessel walls cause?
Ruptured vessel wall causes haemorrhage and distal ischaemia
What are 2 common sites of ruptured vessels causing haemorrhagic stroke?
- Basal ganglia – microaneurysms form in hypertensive patients
- Circle of Willis – Berry aneurysm forms in hypertensive patient
Why may a haemorrhagic stroke in basal ganglia cause problems?
Internal capsule on the left takes all neuron output form one side so an infarct here would cause lots of problems
Extremely devastating thing to have
Haemorrhagic stroke due to bursting of Berry aneurysm affecting circle of Willis
(pictures)
A patient has coronary artery bypass with prolonged period of hypotension during operation – patient kept oxygenated by ventilation
Central part of arteries territories are perfused ok
So patient has prolonged period of poor perfusion pressure of brain, but blood is oxygenated
What does this all lead to?
Watershed zones are poorly perfused
Zonal pattern of ischaemia and infarction at interface of territories - leading to death
What are ‘watershed’ infarcts?
Zones of infarction at interface of artery perfusion territores are called ‘Watershed’ infarcts
Zonal pattern of ischaemia and infarction at interface of territories
Pure hypotension with oxygenated blood - watershed infarcts
Usually affects both sides
60 year old male suffers myocardial infarct
Cardiac arrest followed several minutes later by resuscitation
During those minutes – no circulation to brain and no oxygen in blood – all of brain deprived of blood flow and O2
What happens next?
patient dies
Large areas of grey matter thinning and necrosis
Laminar = lines of necrosis and thinning
So complete loss of perfusion and oxygen - cortical necrosis (infarction)
75 year old woman with known coronary artery disease
Suffers bout of pneumonia
Periods of poor oxygenation but adequate circulation (due to pneumonia)
Then suffers cardiac arrest – period of no perfusion and no oxygen
Successful resuscitation then further arrest then dies
What would an autopsy show?
Various types of infarcts
Mixture of different kinds all happening because of previous disease and because of complete loss of perfusion
So in practice many cases are complex and areas of ischaemia and infarction in brain may be very variable
