Pathology of cerebro-vascular diseases Flashcards
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 is the overall cause of a stroke
Interruption of supply of oxygen and nutrients and causing damage to brain tissue
either due to ischaemia or haemorrhage
What is virchows train components that if changed can cause interruption of supply of oxygen
Vessel wall
Blood flow and pressure
Blood constituents
What changes in the vessel wall can result in interrupted blood supply
Abnormality of wall
(atheroma, vasculitis)
Outside pressure (strangulation, spinal cord compression, compression of veins)
What changes in the blood flow and pressure can result in interrupted blood supply,
Decreased blood flow,
Increased blood pressure bursting vessels
What changes in the blood constituents can result interrupted blood supply,
Thrombosis of arteries and rarely veins
Bleeding due to anticoagulation,
Reduced platelets and clotting factors
What is the three main causes of localised interrupted blood supply
Atheroma + thrombosis of artery causing ischaemia
Thromboembolism (for example, from left atrium) causing ischaemia
Ruptured aneurysm of a cerebral vessel causing haemorrhage
What is the pathophysiology of atheroma and thrombosis
There is a narrowing of the artery wall due to atheroma then the formation of a thrombosis (from platelets and fibrin) forming on top reducing the blood flow and resulting in ischaemia
Where does atheroma and thrombosis typically occur cause ischaemia to the brain
The internal carotid artery
In internal carotid artery thrombosis where do you typically get ischaemia
In the middle cerebral artery territory (which is on the lateral side of the brain)
What is the two category of symptoms that can arrises from ischaemia (lack of oxygen) to the brain
Transient symptoms
<24hours
Long standing symptoms >24 hours (stroke)
Why does a stroke result in irreversible ischaemia
As the brain tissue is no longer viable as long term ischameia has causes localised brain death (infarct) which is irreversible as neurones cant regenerate
What is the pathogenies of ischaemic stroke
Brain is very sensitive to oxygen ischaemia
A few minutes hypoxia or anoxia will cause brain ischaemia
which can lead to infarction
What is a localised area of brain death caused
Regional cerebral infarct
What is the morphology of regional cerebral infarct
Classically wedge-shaped reflecting arterial perfusion territory
is Soft and then becomes cystic
Which then leads to loss of brain tissue
What is the features of regional cerebral infarct when its has a wedge shape reflecting arterial territory appearance
Tissue degeneration
Yellow colouration
Congested vessels
Swelling of surrounding brain tissue
What is seen in the histology of an infarct
Gliosis - the CNS equivalent of fibrosis
How does gillosis occur in cerebral infarct
Foamy marocphages try to repair the loss of neurones and cause clinical deficit of gliosis
What additional features are seen with loss of brain tissue
Cyst like spaces
Yellow colouration to edge of infarcted area
Why is the location of ischaemia in the brain very important
Small affected area of one part of brain may not cause too much impairment however
Similar size of affected area in another part of brain may be devastating
Where is a thrombo-embolism most likely to arise from
Left atrium appendage of the heart
How does the thrombo-embolism result in ischaemia type infarct
thrombsis in the left atrial appendage breaks offand embolises to the aorta and then in the direction of the carotid, which eventually block right middle cerebral artery as are smaller arteries
The thromboembolsim ischaemic type infarct is similar to what
Atheroma/thrombosis iscahemic type infarct
Why do patient with thrombo-embolism and arrhythmias have a higher risk of further embolisation
Due to arrhythmias causing stagnant blood
How do aneurysm form beyond carotid and vertebral arteries
Due hypertension, expanding and weakening the thin cerebral arteries wall
Why is the cerebral arteries walls thin and weak, what is the benefit of this
As have no muscle - so the vessels in the brain don’t constrict - therefore nothing will affect cerebral inflow
What causes the aneurysm to rupture in the cerebral arteries
If severe hypertension
What is the affect of rupture aneurysm in the cerebral arteries
Haemorrhage - decreased blood flow to the brain
Spasm of artery - decrease blood flow distally leading to additional ischaemia
What is the two common sites of ruptured vessels causing haemorrhagic stroke
Basal ganglia
circle of willis
What causes haemorrhage strokes to occur in the basal ganglia
Microanueysms from in hypertensive patient
What causes haemorrhoid stroke to occur in the circle of willis
Berry aneurysm to form in hypertensive patient
where are berry aneurysm visible
visible outside brain tissue
What is three overall reasons for 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)
Inability to use O2
The inability t to use O2 is a rare occasion, what is an example of this occasion
Cyanide poisoning
What is cause of low O2 in blood
C02 poisoning, Near drowning, Respiratory arrest
What is causes of inadequate supply of blood
Cardiac arrest with immediate resus’n,
Hypotension,
Brain swelling (eg trauma)
What pattern of ischaemia and infarct can be caused by hypotension
Zonal pattern of ischaemia leading to watershed infarcts
How does zonal pattern of ischaemia occur due to hypotension
Low pressure blood means the central part of the artery territory are better perfused but the water shed areas (at the periphery) are poorly perfused, prolonged poor perfusion leads to watershed infarcts
How does a cardiac arrest result in infarction
During cardiac arrest there is no perfusion and oxygen reaching the brain this can cause laminar cortical necrosis resulting in infarction
How does brain swelling cause infarction
vessels compressed due to trapped in a skull leads to ischameia to the brain
What is the main cause of watershed infarcts
Poor perfusion due to hypotension
What is the main cause of regional infarcts (complex patten)
decreased blood flow caused by narrowed cerebral vessels due to atheroma
What causes laminar cortical infarction
Complete loss of perfusion e.g. cardiac arrest
What can be seen in laminar infarction
Lines of necrosis and thinning
