Stoke Flashcards
(57 cards)
What is a stroke?
Neurological deficit of sudden onset which lasts more than 24 hours
Also of vascular origin
What is a transient ischaemic attack?
Less than 24 hours
Neurological deficit (loss of function)
What happens to cause a stroke?
A blocked or ruptured blood vessel causing a failure of neuronal function leading to some deficit in brain function
Death to neurovascular unit
What are the causes of stroke?
Blockage by thrombus or clot
Disease of vessel wall
Disturbance of normal properties of blood
Rupture of vessel wall - haemorrhage
What are the 2 types of stoke?
Haemorrhagic stroke - blood leaks into brain tissue Ischaemic stroke - occlusion causing cell death as lack of blood supply
What are types of large artery disease?
Carotid stenosis
Carotid disease - plaque ruptures
Cardioembolic stroke - atrial fibrillation is the commonest cause
Describe lacunar stroke
Small vessel stroke
Affects very small areas of the brain and is associated with hypertension
Blockage or rupture in medial and lateral lenticulostriate arteries
What is a rarer cause of stoke?
Carotid dissection - idiopathic or trauma
Lining of blood vessel tears and causes thrombosis which breaks off and travels to brain vessels
What are the causes of brain infarction?
Intracranial atherosclerosis, carotid plaque with arthritogenic emboli, aortic arch plaque, cardiogenic emboli, valve disease, atrial fibrillation, carotid stenosis and penetrating artery disease
Why does haemorrhage happen?
Hypertension, amyloid, excess alcohol, hypocholesterolaemia and haemorrhagic transformation
Is haemorrhagic stroke or ischaemic stroke more deadly?
Haemorrhagic
Explain penumbra
Area of brain which surrounds ischaemic brain tissue but is getting enough blood to not die but not enough to carry out function
Still some supply from collateral vessels
What is lost every minute in a patient with large vessel ischaemic stroke?
1.9 million neurons
13.8 billion synapses
12km of axonal fibres
What does ischaemia result in?
Varying degrees of hypoxia and hypoglycaemia
What hours of a stroke are essential for threshold of preservation?
First 2-3 hours
What does prolonged hypoxia lead to?
Hypoxia stresses metabolic machinery of brain cells
Becomes Anoxia (no oxygen)
What is the result of anoxia?
Results in infarction and this is a completed stroke
Further damage can be result of oedema, size and location of stroke and haemorrhage
Explain oedema in the brain
Oedema can push parts of brain and damage rest of brain tissue because of pressure
Vessels can move and midline can be shifted
How is lactic acid produced in brain?
Lack of O2 and glucose means brain cells lose ability to make energy
Cells in affected area switch to anaerobic metabolism so lesser ATP production and lactic acid production
What does lactic acid do in the ischaemic cascade?
Acts as an irritant which has potential to destroy cells by disruption of normal acid-base balance in the brain
Describe the influx of Ca2+ and efflux of potassium in the ischaemic cascade?
ATP-reliant ion transport pump fails so membrane depolarises, influx of Ca2+ and efflux of K+
Intracellular calcium level become too high and trigger release if excitatory amino acid neurotransmitter glutamate
What is the role of glutamate in the ischaemic cascade?
Stimulates AMPA receptors and Ca-permeable NMDA receptors which leads to more Ca influx into cells
Excess Ca entry overexcites cells and activates proteases, lipases and free radical formed in process called excitotoxicity
What happens when the cells membrane is broken down by phospholipids?
Becomes more permeable so more ions and harmful chemicals enter cells
Mitochondria break down and release toxins ad apoptotic factors into cell so cells undergo apoptosis
What happens when a cell dies through necrosis?
Release glutamate and toxic chemicals into environment.
Toxins poison nearby neurons and glutamate overexcites them
