Flashcards in 27. Stroke Deck (22):
What is stroke?
Interruption of blood flow to a region of the brain, causing ischaemia and hypoxia
Third most common cause of death in the UK
What are the symptoms of stroke and what is important about these symptoms?
Sudden numbness or weakness on one side of the body - face, arm, leg
Sudden trouble seeing in one or both eyes
Sudden trouble walking or dizziness, loss of balance or coordination
Sudden severe headache with no known cause
With stroke, important to note that all the symptoms occur suddenly
What pneumonic is used to recognise the symptoms of stroke?
Face - is their a loss of tone or a weakness of any of the facial muscles?
Arms - can they raise both their arms equally?
Speech - any changes e.g. slurring/slowness
Time - The faster the person receives help, the more the brain function can be preserved
Golden hour - interventions within an hour of the stroke onset can make significant differences to the outcome
What are the different types of stroke?
Thrombotic (form of ischaemic stroke)
Embolitic (form of ischameic stroke)
Ischaemic strokes form about 85% of strokes and haemorrhagic strokes form about 15% of strokes
What is a TIA?
Transient Ischaemic attack
This is a transient stroke which does not last
Presumed to be the result of the release of small emboli from a thrombus
Temporarily block downstream vessel but then quickly dissolve
The symptoms of these generally resolve within an hour but always last no longer than 24 hours
What is meant by thrombotic stroke?
This is where there is an atheroma formation within a cerebral vessel (i.e. rather than within a carotid vessel)
The vessel gets narrower and narrower until the atheroma ruptures and this produces a local clot
About 60% of thrombotic strokes occur during sleep
What is meant by an embolic stroke?
This is the same as a thrombotic stroke apart from the fact that the blockage forms elsewhere e.g. in the heart and then moves and gets stuck in an artery which then causes the ischaemia to the brain
The source of this is almost always from the left side of the heart
Hence, risk factors are e.g. MI, AF
What is meant by haemorrhagic stroke?
This is where a blood vessel ruptures and causes a bleed
Rather than just a stop in blood flow (ischaemic), there is a leak of blood into the inctracranial space
This leads to an increased intracranial pressure which prevents with a severe headache
Can be due to hypertension or poor clotting
What is a lacunar stroke?
This is where there is an occlusion of blood supply to the deep structures of the brain e.g. basal ganglia
Most ischaemic strokes result in a lack of perfusion to the superficial structures of the brain
What are the risk factors for stroke?
Hypertension!!!!! - accounts for 25-50%
Heart disease - especially AF
Diet low in potassium
Thiazides and loop diuretics
What is the main artery that is impacted by strokes and why?
Most strokes occur in the branches of the middle cerebral artery (continuation of the internal carotid)
This is because this artery is highly tortuous (twists and turns a lot)
What is the importance of the sodium pump in the brain?
The sodium pump is present in nerve cells
It has a vital role in maintaining nerve cell size and shape
What happens if the sodium pump is not working effectively?
SO the brain is protected within the cranial vault
If the sodium pump does not get enough O2/ATP then it will stop pumping out sodium (followed by water) and so the sodium will leak into the nerve cells (followed by water)
This means that the neurones will swell
Due to the cranial vault, the skull cannot expand to accommodate this so this leads to an increase in intracranial pressure
Nb. This is why the brain requires such a high volume of blood all the time - to deliver O2 to these constantly working sodium pumps
What are the other effects of the swelling of the neurones?
There is generally an extracellular space between neurones through which blood can flow to deliver materials - this becomes compromised and the exchange of fluid is disrupted
The neurones expanding causes them to press against each other and can cause physical damage to themselves
Can also cause physical damage to the veins that are between them as these do not have muscle to protect them - disrupts overall blood flow
Leads to overall death of neurones and raised intracranial pressure
What is a severe effect of raised intracranial pressure?
Can lead to tonsillar herniation
The raised pressure causes the cerebellum to expel through the foramen magnum
This can compress the lower brainstem and damage respiratory and blood pressure control - person can go into a coma
What is the role of potassium in the brain?
How is this affected in stroke?
Generally potassium is removed from extracellular space by glial cells to prevent depolarisation of cells
BUT in hypoxic brain, potassium is not removed and there is an increased extracelullar potassium causing depolarisation
This results in the release of excitatory neurotransmitter glutamate
What happens when glutamate is released into the extracellular space?
Increased glutamate levels result in excitotoxicity - the conditions are toxic for the brain and this overstimulates and kills the neuronal cells
What are the treatment options for stroke?
Restoration of blood flow
Combat excitotoxicity - this kills more cells than hypoxia does so this is an important one BUT is currently being worked on - has not yet proved to be effective
Combat free radical damage
How can you restore the blood flow following a stroke?
Give an example
Attempt to dissolve the blood clot in an ischaemic stroke
E.g. use of tissue plasminogen BUT this can only be used within the first hour of stroke onset
How can you combat free radial damage?
Free radicals are powerful oxidising agents SO need to introduce a powerful reducing agent i.e. antioxidants
E.g. vitamin C and E
When should free radicals be used as treatment?
To be used if someone has a history of stroke or has had a TIA
Cannot be used in someone who has just suffered a stroke bc the vitamins need to be carried to the brain by the blood