Flashcards in Stroke Deck (56):
What is a stroke?
Sudden death of brain tissue due to lack of oxygen and glucose delivery arising from an interrupted blood supply (ischaemia)
How many deaths per year are caused by strokes in the UK?
1 every 3.5 minutes
How many first time strokes were there worldwide in 2010/
1 every 2 seconds
Whats the difference in men and women and the likelihood of getting a stroke?
Men are 25% higher risk of having stroke compared to women
However, incidence of stroke in women is higher due to longer lifespan
How many stroke survivors are there in the UK?
Around 1.2 million
How many strokes are fatal within the first 30 days?
1 in 8
How many strokes are fatal within the first year?
1 in 4
What are modifiable risk factors towards a stroke?
Hypertension- single most important modifiable risk factor
Waist to hip ratio
Diet (i.e. obesity)
Alcohol intake (>30 drinks per month)
Psychological factors (stress, depression)
Cardiac causes (Atrial fibrillation, Previous transient ischaemic attack)
o All 10 combined about for 90% of risk of stroke
What are non-modifiable risk factors towards a stroke?
Age- most important risk factor
Ethnicity- Black and south Asian origin
What is stroke the leading cause of?
How many stroke survivors are dependent on others?
More than half
42% will be independent
22% have mild disability
14% have moderate disability
10% have severe disability
12% have very severe disability
What are the stroke warning signs?
What are the stroke subtypes?
15% primary intracerebral haemorrhage
5% subarchanoid haemorrhage
What are the subtypes of ischaemic stroke?
What is a thrombotic stroke caused by?
A blood clot in an artery supplying the brain
What is the most common cause of thrombotic stroke?
Atherosclerosis- results in narrowing of arteries
Accounts for half of all strokes
How is an embolic stroke caused?
Blood clot forms elsewhere in the body and travels to the brain
What is the most common cause of embolic stroke?
Atrial fibriliation- increased risk of clots
Air bubbles, plaque form in an artery wall
When does a haemorrhagic stroke occur?
Occurs when a blood vessel within the brain ruptures
What can cause a haemorrhagic stroke?
What is an aneurysm?
Ballooning of weakened region of blood vessel
What is arteriovenous malformation?
Abnormal connection between arteries and veins. Increased risk of bleeding due to increased pressure
What happen in a haemorrhagic stroke?
The blood accumulates and causes compression of brain tissue and increased pressure within brain (intracranial pressure)
What is there an increased mortality for?
Haemorrhagic stroke than ischaemic stroke
What is a Transient Ischaemic Attack (TIA)?
Sometimes referred to as mini-stroke
Brief period of symptoms similar to stroke
At greater risk of subsequent stroke
What is TIA caused by?
Caused by a temporary decrease in blood supply to a particular brain region
Caused by a clot or other debris blocks blood flow temporarily
What happens to ischaemic core in ischaemic stroke?
Irreversibly damaged and cells are destined to die within 2 mins
What happens to ischaemic penumbra in ischaemic stroke?
Tissue does not function normally but is still viable and may recover if blood flow is restored or drugs given to support survival
Who introduced the ischaemic penumbra?
Originally by Astrup and Symon 1981
What is the the ischaemic penumbra?
A region of reduced CBF with impaired electrical activity but still maintained ionic homeostasis and transmembrane electrical potentials. This definition further evolved to include preserved energy metabolism and increased oxygen extraction faction (OEF)
Where do most ischaemic strokes occur?
What is the composition of the forebrain?
22 billion neurones
84,500 miles of myelinated fibres
157 trillion synapses
What is the timeframe of brain damage associated with occlusive stroke/
Occurs roughly a 10 hour time frame
What happens if the patient is left untreated?
Patient will lose
1.9 million neurones (every minute)
13.8 billion synapses (every minute)
7 miles of axonal fibres (every minute)
What is infarction dependent on?
Severity and duration of ischaemia
What is acute ischaemic stroke treatment?
Thrombolysis (clot buster) (recombination tissue plasminogen activator; Alteplase)
Can only be used in specialist stroke units
What is a CT scan essential to exclude?
In thrombolysis how long before treatment?
Treatment within 4.5 hours of stroke onset
What are the side effects of thrombolysis?
Bleeding- must not be used in haemorrhagic stroke
How many patients are eligible for thrombolysis?
What happens in Thrombolysis?
Tissue plasminogen activator (t-PA) binds to fibrin on clot surface
t-PA (Alteplase) activates Plasminogen → Plasmin
Plasmin is a proteolytic enzyme
Plasmin breaks down fibrin molecules and results in clot dissolving
t-PA preferentially binds fibrin bound plasminogen
What is a thrombectomy?
Used for acute stroke treatment?
Stent retriever into cerebral vessel
Five different clinical trials have shown efficacy of mechanical thrombectomy in acute stroke (MRCLEAN, ESCAPE, EXTEND-IA, SWIFT PRIME, REVASCAT)
What is the efficacy of thrombectomy?
Up to 6 hours post stroke
What is thrombectomy often used in combination with?
What does Ischaemic penumbra contain?
What is acute treatment of ischaemic penumbra?
Selection of patients for acute treatment
Acute treatment futile in patients without salvageable tissue
Patients with penumbra most likely to benefit from “clotbuster” therapy
What is penumbra the main target tissue for?
What does Computerised Tomography (CT) scans use?
What does Magnetic Resonance Imaging (MRI) scans use?
Signals are generated by nuclei with a positive charge (i.e. H, P)
MRI most commonly uses the signal from hydrogen atoms
Hydrogen most abundant atom in body (approx. 70-90% of body)
What are the purposes of imagining a stroke?
To discriminate between irreversibly damaged brain tissue and tissue at risk of infarction
To identify location of stroke
To identify patients that will benefit from thrombolysis
What are the benefits of CT scans?
Very good at detecting haemorrhage
Quicker than MRI
Cheaper and more widely available
What are the disadvantages of CT scans?
CT scanning not very sensitive for detecting early ischaemic damage following stroke
What are the advantages of MRI?
More detail than CT
MRI sequences can be used to detect very early brain damage due to stroke
Diffusion weighted imaging (DWI) an MR sequence which is sensitive to motion of water molecules can detect ischaemic damage within minutes of stroke
Perfusion weighted MRI can be used to assess the tissue at risk
What is perfusion?
Delivery of blood to capillary bed for supply of nutrients and oxygen
What information can be obtained by MRI?
Information about the perfusion status of the brain can be obtained (blood flow)