Stroke Flashcards
What are the 4 things that must be present in the clinical diagnosis of stroke?
- Sudden onset
- Focal neurological deficit
- Of presumed vascular origin
- Symptoms lasting more than 24 hours or leading to death
excludes lesions associated with trauma, infection or tumour, retinal infarction and most cases of SAH
What is the main difference between stroke and TIA?
In a TIA, symptoms are lasting less than 24 hours
What aspect of stroke care is the most expensive?
Community care
this is looking after the disabled following a stroke
this is the largest proportion of the cost of caring for a stroke patient
How is the number of strokes likely to change in the future?
There has been progress in primary prevention, although the number of strokes is likely to increase in the future
this is due to the ageing population and greater proportion of the population being elderly
there is an exponential increase in stroke incidence in the elderly
What are the 2 different types of stroke?
Haemorrhagic or infarction
What types of stroke are shown in the images?
What are the two different causes of ischaemic stroke?
Thrombosis:
- large arteries (mainly extra-cranial e.g. vertebral, carotid)
- small arteries (mainly intra-cranial)
Embolism:
- a clot travels to the brain from elsewhere in the body
- from the heart - cardiogenic embolism
- from proximal arteries - artery to artery embolism
What are the stages involved in atheromatous-thrombo-embolism?
- Atheromatous plaque forms as the result of stenosis
This occurs due to sheer stresses on the artery wall at the point of bifurcation
- This leads to mural thrombus
- Part of the thrombus may break off and form an embolus
or
the artery can be occluded entirely by an occlusive thrombus
What arteries are most commonly implicated in ischaemic stroke?
Large arteries in the neck
e.g. Internal carotid artery
How do emboli form from a cardiac source?
- Atrial fibrillation is the main source of blood clots
- the atria contract at a different rate to the ventricles, leading to stasis of blood in the left atrium and clot formation
- clots dislodge, leading to ischaemic stroke
What are other cardiac sources of embolism?
- Endocarditis - an infection on the heart valve
- Tumours within the ventricles
- Thrombus may form at a site of previous MI
What vessel tends to be implicated in small vessel disease and how can it be identified?
The middle cerebral artery is injected with contrast
the arteries affected are the lenticular striate arteries which take blood to the internal capsule
even a small ischaemic stroke (lacunar stroke) can interrupt the motor pathway and lead to loss of function
What are the % of cases caused by different mechanisms of ischaemic stroke?
Large vessel atherosclerosis - 40%
cardioembolism - 30%
intracranial small vessel disease - 25%
other - 5%
What is the population attributable risk for stroke (modifiable factors)?
- Hypertension
- lifestyle factors - obesity, diet, lipids, exercise, smoking
- cardiac (AF)
- diabetes
- other
all of these risk factors can be modified
How does hypertension and atrial fibrillation change with age?
They both increase in prevalence with increasing age
ageing population in the country means that these will be seen more often in the future
if they are not controlled, the downstream effect will get worse i.e. development of atheromatous disease
What is meant by secondary stroke prevention?
Preventing any further events from occurring after a patient has already had a stroke
What does an odds ratio of 1 mean?
There is no benefit to one treatment over another
What does this diagram show about the effect of aspirin on treating stroke?
To the left:
this shows that there is a benefit in taking aspirin
even if there is a small benefit to an individual e.g. preventing vascular death, this may have large population benefits when given to lots of people
What does this graph show about the benefits of taking aspirin to prevent the early risk of recurrent ischaemic stroke?
- The benefit of taking aspirin is visible within the first few weeks following the initial stroke
- as endothelium forms over the embolus, the chance of recurrence is higher in the first 12 weeks
- the early use of aspirin is effective
- if symptoms have resolved within a few hours (TIA), this will never be due to haemorrhage
What does this diagram show?
It shows the annual risk of recurrent stroke in patients who are in atrial fibrillation
the clot forming on atheromatous plaque mainly consists of platelets
clot forming in the heart is more fibrin and more likely to respond to anticoagulants
12% risk of recurrence can be reduced to 4% through anticoagulantion
What does this graph show?
Treating patients early with “urgent” endarterectomy leads to a greater benefit
This procedure is given to a smaller population but has a large benefit
statins and blood pressure tablets can be given to a larger population but have a smaller overall benefit
What is meant F.A.S.T. Campaign for public education about stroke?
Face:
- has their face fallen on one side?
- can they smile?
Arms:
- can they raise both arms and keep them there?
Speech:
- is their speech slurred?
Time:
- it’s time to call 999 if you see any of these signs
*
What are the stages involved in the pathophysiology of acute ischaemic stroke?
When does intervention need to occur?
- Initial reduction in cerebral blood flow
- alterations in cellular chemistry caused by the ischaemia
- cellular necrosis
intervention needs to occur before cellular necrosis
What are the thresholds of cerebral ischaemia?
- Normal function
- Electrical function impaired
- Release of K+ and movement of water intracellularly
- Cell death
What do the thresholds of cerebral ischaemia show?
Where should intervention occur?
- A substantial drop in blood flow to the brain can occur without having any symptoms
- electrical function of neurones is impaired and the patient has symptoms but neurones are structurally intact
- cellular integrity begins to disappear
- point of intervention (blue) where the patient has symptoms but cell death has not yet occurred
Label the following features
What are they?
Core infarct - cells have irreversibly died here
penumbra - this is salvageable as there is reduced blood flow but no symptoms
How does the size of the core and penumbra change over time?
The core increases in size and the penumbra decreases in size as time continues
What is meant by a “clot-busting” cure for strokes?
An intravenous injection of a drug that dissolves the clot
this is known as thrombolysis
what does this graph show about the use of thrombolysis for acute ischaemic stroke?
If you were treated within 3 hours, your risk of becoming dead or dependent is reduced by 34%
1 in 10 patients who would walk out dead or dependent instead walk out symptomless
there is a risk of symptomatic intracranial haemorrhage as the drug thins the blood by large amounts
Why is stroke now considered an emergency?
Due to time dependency
even treating someone 5-10 minutes earlier can have large impacts on recovery
treatment under 3 hours increases the odds of a good outcome by 50%
What is shown in this scan?
What would the treatment be and how would it work?
The white dot occurs where the middle cerebral artery enters the fissure
there is an acute clot in the MCA that supplies the anterior 2/3 of the brain
IV thrombolysis would be given
opening up the arteries leads to a better outcome as oxygen and glucose are being delivered to the brain
this stops the core from expanding
How can recanalisation affect ischaemic stroke outcome?
Early recanalisation is strongly associated with improved functional outcome and reduced mortality
recanalisation within 6 hours of onset increases the odds of a non-disabled outcome 6 fold
What % of ischaemic stroke is caused by proximal anterior circulation large vessel occlusion?
What about deaths or severe disability?
Proximal anterior circulation large vessel occlusion accounts for 18 - 25% of all ischaemic stroke
but it accounts for 60-70% of deaths or severe disability
What is the problem with using IV thrombolyis on large vessel occlusion?
Larger clots will not dissolve as well with IV thrombolysis as well as small clots will
the large vessel occlusion may not respond to the only available acute treatment
What is the treatment for proximal anterior circulation large vessel occlusion?
Stentrievers
- place stent across the occlusion and leave in position for 10 mins
- reperfuse brain
- most clot will lose naturally or improves efficacy of IV tPA
- withdraw stent with smaller clot ‘core’
How do stentrievers work?
Catheter is inserted into the groin and fed into the artery
it is pushed through the clot to open up the occluded vessel and restore blood flow
it is similar to a stent, but it is not left inside the artery
The stentriever is removed and the clot comes with it
