Stoke Flashcards
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
What does loss of structural integrity result in?
Breakdown of protective blood brain barrier and contributes to central oedema which can cause secondary progression of brain injury
Explain the extension of infarction over time in a stroke?
First tiny area of dead tissue and large penumbra
Then as time increases, dead tissue increases and area of salvageable tissue decreases
Swelling also increases with time
What symptoms does a patient get with a stroke?
Motor - clumsy or weak limb, Sensory - loss of feeling, Speech - dysarthria/ dysphagia, visuospatial problems, gaze palsy, loss in one eye, hemianopia, ataxia, vertigo, incoordination
Describe the vascular supply of the brain
Carotid system supplies most of the hemispheres and cortical deep white matter
Vertebra-basilar system supplies brainstem, cerebellum and occipital lobes
What is hemianopia?
Both eyes can only see left side as right side is blacked out
What is ataxia?
Cant control movement
Impaired coordination
What is dysarthria?
Slow or slurred speech as weakened muscles
What are the symptoms of anterior cerebral artery occlusion?
Paralysis of contra-lateral foot and leg, sensory loss over contra-lateral toes, foot and leg, and impairment of gait and stance
What are the symptoms of middle cerebral artery occlusion?
Contra-lateral paralysis of face/arm/leg, sensory impairment and homonymous hemianopia
Gaze paralysis to opposite side, aphasia if on dominant side (left) and unilateral neglect for half of external space if non-dominant
What are some lacunar stroke syndromes?
Lack of cortical signs
Pure motor stroke
Pure sensory stroke
Dysarthria - clumsy hand syndrome
Ataxia hemiparesis
Where will a small stroke cause major deficit?
At internal capsule and pons
Fibres are packed together very closely
What is the anatomy involved in posterior circulation?
Brainstem, cerebellum, thalamus, parts of occipital and temporal lobes
What are symptoms of brainstem dysfunction?
Coma, drop attacks, vertigo, nausea, vomiting, cranial nerve palsies and ataxia
Hemiparesis, hemisensory loss, crossed sensory-motor deficits and visual field deficits
What are the stroke subtypes?
TACS - total anterior circulation stroke
PACS - partial anterior
LACS - lacunar stroke
POCS - posterior circulation stroke
Which stroke subtype has highest mortality and recurrence rate?
Mortality is highest after a year in TACS
Recurrence rate is highest in POCS and PACS (part of MCA)
What are the risk factors of stroke?
Age, hypertension, cardiac disease, diabetes, smoking, Family history, cholesterol (apoA and apoB) and bleeding disorders
Obesity
What are some associated disease with strokes?
Previous TIAs or strokes, angina, MI, blood pressure poorly controlled, PVD, aortic aneurysm, carotid bruits and renovascular disease
Possible cocaine or alcohol abuse
What is the most important modifiable risk factor for stroke?
Hypertension - associated with small vessel stroke and haemorrhage
Describe diabetes and strokes
Diabetes mellitus increases incidence of stroke up to 3-fold
Small vessel, lagre vessel and cardioembolic strokes
Describe smoking and strokes
Have a 2 fold increased risk of ischaemic stroke
Describe lipids and strokes
High plasma level of low density lipoprotein results in excessive amounts of LDL within arterial wall
Hypertension, cigarette smoking and diabetes contribute to LDL deposition on arterial walls
What are some other less common risk factors?
Impaired cardiac function, oral contraceptives with high oestrogen content and hypercoagulable states (malignancy and genetic)
What is the aim of stroke treatment?
Protect the damaged brain before ischaemia becomes cell death, get rid of clot and prevent the clot happening in the first place
Why are stroke units important?
Physiotherapy, aspirin and can get imaging done fast
Also specialised staff
What shoulds acute stroke therapies do?
Restore blood flow, prevent extension of ischaemic damage, protect vulnerable brain tissue, avoid reperfusion injury and be non-toxic
What medication if given for strokes?
Thrombolysis - alteplase
Try give in 30 mins of arriving at hospital
Has risk of bleeding but has more benefits
Describe the acute stroke triage
Pre-alert, stroke centre, ED/stroke physician initial evolution, perform CT and IV tPA
What investigation is first choice in ED?
Plain CT
MRI are good for areas of infarction but take longer
What are some advanced imaging that will help is available?
Perfusion CT, CT angiogram, MRA, Diffusion CT
Explain fast field cycling MRI
Lower magnetic field
PUFFINS trial
Ultra low magnetic field
Assesses new contrast mechanisms based onT1 dispersion
Infarct is clearer at lowest magnetic field
Explain clot retrieval
Catheter pulls clot out safely
Trials show positive outcomes with clot retrieval
Challenges are no thrombectomies in Scotland right now
What are some other treatments for strokes?
Antiplatelets, statins, blood pressure management and anticoagulation if atrial fibrillation
What is the treatment for primary intracerebral haemorrhage?
BP management to <140mmHg
