Stroke Flashcards
Name the two main arteries supplying the brain
Carotid arteries & vertebral arteries
What do the carotid arteries divide into?
The external and internal carotid arteries
What do the vertebral arteries join together to form?
The basilar artery
What areas of the brain are supplied by the carotid system?
most of the hemispheres and cortical deep white matter
Which areas of the brain are supplied by the vertebro-basilar system?
brain stem, cerebellum and occipital lobes
What is a stroke?
a neurological deficit of sudden onset & vascular origin lasting more than 24 hours
What is a TIA?
A transient ischaemic attack is a “mini-stroke” that lasts less than 24 hours `
What % of people will suffer a stroke worldwide?
1 in 4 (25%)
What fraction of stroke patients die within the first 30 days following a stroke?
1 in 8
What fraction of stroke patients will die within a year following a stroke?
1/3
What causes a stroke?
A blocked or ruptured vessel in the brain
List three things that can cause an ischaemic stroke
- A thrombus or clot
- Disease of vessel wall
- Disturbance of normal properties of blood
What is the more common type of stroke: ischaemic or haemorragic?
Ischaemic
What % of strokes are caused by an infarction?
85-90%
What is the most significant risk factor associated with stroke?
Hypertension
What are the risk factors associated with stroke?
- Hypertension
- Age
- Cardiac Disease (esp atrial fibrillation)
- Diabetes
- Smoking
- Family history
- Cholesterol
- Bleeding disorders
- Alcohol intake
- Stress/depression
- Waist to hip ratio
- Poor diet
- No regular physical activity
What is the systolic blood pressure above which the risk of stroke increases dramatically?
160mmHg
What impact does diabetes have on stroke risk?
Diabetes increases the risk of stroke by up to 3 fold in both sexes
What impact does smoking have on stroke risk?
Smoking increases the risk of ischaemic stroke by up to 2 fold and increases the risk of haemorragic stroke by up to 3 fold
What impact does alcohol consumption have upon stroke risk?
- Small amounts of alcohol decrease stroke risk .
- Heavy drinking increases the risk 2.5 fold.
What impact does obesity have upon stroke risk?
Increases stroke risk
Where are the 2 most common sites of origin for a thrombus causing an ischaemic stroke?
Carotid (thrombus breaks off from a stenosed carotid OR from a carotid dissection )
Clots forming in the heart as a result of AF
What is a cardioembolic stroke?
A stroke caused by a clot that has come from the heart
What % of all strokes are cardioembolic?
20%
In ischaemic stroke:
What is the difference between a stroke and a lacunar stroke?
A stroke is usually caused by a blockage in one of the large vessels supplying the brain so a large region of the brain is affected
a lacunar stroke is the blockage of one of the small vessels which has branched off a large vessel so a small, more focused area of the brain tends to be affected
What % of all strokes are lacunar?
25%
What health problems are associated with lacunar stroke?
Hypertension and thickening of the small artery walls
How many
A) Neurons
B) Synapses
C) Km of axonal fibres
are lost every minute following an ischaemic stroke?
A) 1.9 million neurons
B) 13.8 billion synapses
C) 12Km of axonal fibres
Describe the structure of a region of ischaemia (e.g. what are the different aspects of an ischaemic focus called)
An ischaemic region is made up of the ischaemic core (the part of the brain which is directly affected by a lack of blood supply) and a region around the outside of the ischaemic core called the ischaemic penumbra which is affected by the occlusion but is still able to get a small amount of blood supply from nearby vessels
What is anoxia?
No oxygen
What causes anoxia?
When a region of hypoxia runs out of oxygen
What does anoxia lead to?
Cell death and necrosis
What is a “completed stroke”
A necrotic infarction
Does localised oedema occur folliowing a stroke?
Yeah
Describe the ischaemic cascade
- Loss of blood supply, cells loose their ability to produce ATP
- Cells switch to anaerobic metabolism and release lactic acid
- Lactic acid upsets the normal acid-base balance of the brain
- ATP reliant ion transport pump fails
- Cell membrane depolarizes
- There is an influx of calcium into the cell, and efflux of potassium out of the cell.
- Intracellular calcium levels become too high and trigger the release of the excitatory amino acid neurotransmitter glutamate.
- Glutamate stimulates AMPA receptors and calcium-permeable NMDA receptors, which leads to even more calcium influx into cells.
- Excess calcium entry overexcites cells and activates proteases (enzymes which digest cell proteins), lipases (enzymes which digest cell membranes) and free radicals formed as a result of the ischaemic cascade in a process called excitotoxicity.
- As the cell’s membrane is broken down by phospholipases, it becomes more permeable, and more ions and harmful chemicals enter the cell.
- Eventually the mitochondria break down, releasing toxins and apoptotic factors into the cell.
- Cells undergo apoptosis.
What does the cell release if it dies via necrosis rather than apoptosis and what impact do the released factors have upon the surrounding tissue?
releases glutamate and toxic chemicals into the environment around it. Toxins poison nearby neurons, and glutamate can overexcite them.
What are the symptoms associated with Anterior Cerebral Artery (ACA) occlusion?
Paralysis of contra-lateral foot and leg
Sensory loss over contra-lateral toes, foot and leg
Impairment of gait and stance.
What are the symptoms associated with Middle Cerebral Artery (MCA) occlusion?
Contra-lateral paralysis of face/arm/leg
Contra-lateral sensory impairment
Contralateral homonymous hemianopia
Gaze paralysis to the opposite side
Aphasia if stroke on the dominant (left) side
Unilateral neglect for half of external space if non-dominant stroke (usually right side).
Are the recurrence and mortality rates of Middle Cerebral Artery (MCA) occlusion low, medium or high?
Low recurrence rate, high mortality rate
Where in the brain do lacunar strokes occur?
Deep in the white matter
What signs would you NOT see if the patient is suffering from a lacunar stroke?
no ‘cortical’ signs (no dysphasia, neglect, hemianopia)
What are the signs of a lacunar stroke?
- Pure motor stroke
- Pure sensory stroke
- Dysarthria - clumsy hand syndrome
- Ataxic hemiparesis
Why can lacunar strokes cause such a significant deficit when they affect such a small area?
there are so many densely packed fibres in the white matter coming from the cortex `
What is the recurrence and mortality rates of lacunar stroke?
Mortality at one year is around 11%
Recurrence rate is low (around 9%)
What regions of the brain are supplied by the basilar artery?
the posterior aspect of the brain which encompasses;
Brain Stem / Cerebellum / Thalamus
Parts of occipital and temporal lobes
What artery is affected in a posterior circulation stroke?
Basilar
List some of the signs you may see in a patient with a posterior circulation stroke
Coma, drop attacks, vertigo, nausea, vomiting, cranial nerve palsies, ataxia.
Hemiparesis, hemisensory loss
Crossed sensori-motor deficits
Visual field deficits
What is the recurrence and mortality rates of a posterior circulation stroke?
Mortality is around 19% at one year
The recurrence rate for this type of stroke is high
How long is the thrombolysis window for an ischaemic stroke?
4.5 hours from onset of symptoms
What is the expected door-to-needle time when treating an ischaemic stroke patient in A&E?
30 mins
How soon after arrival to A&E must a stroke patient be seen by an ED /stroke physician
10 minutes maximum
What is the first line imaging technique used in stroke patients?
CT scan
What is the thrombolytic of choice for ischamic stroke patients presenting to ED within 4.5 hours of symptom onset?
Alteplase
What is the main risk associated with alteplase?
Bleeding
Why is thrombolysis not administered after 4.5 hours?
because the risk of harm (bleeding) outweighs the chance of benefit.
Name the minimally invasive procedure that can be used to treat an ischamemic stroke under specific circumstances
Clot Retrieval (- A catheter is fed up into the affected vessel, an umbrella is fed through the clot and opened on the other side of the clot The open umbrella is pulled back with the catheter, taking the clot along with it There are small holes in the umbrella which allow the blood to get through but do not allow clot debris to escape)
Which type of stroke carries the higher risk of mortality: ischamic or haemorragic?
Haemorrhagic
List 5 risk factors associated with haemorrhagic stroke
- Hypertension (60-70%)
- Amyloidosis of vessels (15 -20%)
- Excess alcohol consumption
- Hypocholesterolaemia
- Haemorrhagic transformation
What is the target blood pressure in stroke patients and patients at risk of stroke?
> 140mmHg
What kind of necrosis occurs in the brain and what kind of necrosis occurs elsewhere in the body?
Brain= colliquitive necrosis
Body= Coagulative necrosis
