Stroke Flashcards
What is a stroke? What are its symptoms?
stroke refers to a sudden loss of oxygen delivery to a brain region due to the interruption of blood flow.
symptoms - depend on the artery involved
- paralysis = MAIN
- sudden loss or blurring of vision
- dizziness, confusion
- difficulty understanding speech, slurred speech = MAIN
- problems with balance and co-ordination
- difficulty swallowing (dysphagia)
- sudden and very severe headache
- loss of consciousness
use fast (facial drop, arm drop, slurred speech)
What are the types of stroke? What are they caused by? What is the most common?
ischemic stroke
- occlusion due to thrombosis or embolism
= is the most common in the UK (85%)
haemorrhagic stroke
- rupture of a weakened blood vessel
= not very common (15%)
What are the types of haemorrhagic stroke?
- different types
subarachnoid bleeding = bleeding on the SURFACE
- rupture of a blood vessel leading to bleeding in the subarachnoid space
= space between the arachnoid mater and pia mater (meninges which cover the brain)
intracerebral bleeding = bleeding WITHIN the brain
- rupture of a blood vessel leading to bleeding within the cerebrum
What causes haemorrhagic strokes?
rupture of a weakened blood vessel
cerebral aneurysm
- localised dilatation resulting in the abnormal widening of a blood vessel
= rupture causes subarachnoid bleeding (SURFACE)
arteriovenous malformation
- abnormal tangle of blood vessels connecting arteries and veins
= rupture causes intracerebral bleeding (WITHIN)
What are the pathophysiological processes that occur as a result of haemorrhagic stroke?
leads to haematoma formation which can lead to cell injury
- haematoma = localised bleeding outside a blood vessel
methods of causing cell injury
haematoma increases intracranial pressure
causes compression of the brain
leads to ischemia and cell injury
haematoma can cause coagulation and expansion
leads to inflammation which results in cell injury
haematoma undergoes lysis and releases haemoglobin bound iron
haemoxygenase digests the haemoglobin releasing neurotoxin iron
iron causes oedema which leads to inflammation and cell injury
How does an ischemic stroke cause brain injury?
excitotoxicity
- damages neurones and glial cells
inflammation
apoptosis
What is NMDA receptor mediated excitotoxicity?
occluded blood vessel causes decreased energy supply - depleted oxygen and glucose failure of the Na/K ATPase pump causes neuronal depolarisation excessive glutamate release (excitotoxic neurotransmitter) over-activation of the NMDA receptor calcium entry thorough the NMDA overactive enzyme systems - proteases and lipases damage membrane oxidative stress/damage mitochondrial dysfunction - cytochrome c release apoptosis
What are the two different effects an ischemic stroke can have?
occlusion due to thrombosis or embolism
can form an ischemic core
- an infarction core representing irreversibly injured brain tissue
= withe areas of diminished blood flow, cell death occurs within minutes (core)
can form an ischemic penumbra
- peripheral zone of brain tissue that may be clinically symptomatic but can be rescued if blood flow is restored
= are supported by collateral circulation
with time, the infarct core expands at the expense of the penumbra
- as the infarct core increases, the penumbra decreases
What is golden hour for strokes?
the first hour after a stroke is the best time for treatment
- higher chance of survival if treated within 1 hour of onset
What are the different treatments for a haemorrhagic stroke?
- pharmacological and non-pharmacological
non-pharmacological
- surgery
= craniotomy where a section of the skull is removed to allow the site of bleeding to be seen, repair of blood vessels and removal of haematoma
reversal of anticoagulopathy
- prescribed to prevent blood clots
= anticoagulants
blood pressure medication
- should be given to patients presenting with high systolic pressure between 150-220mmHg
= beta blockers, ace inhibitor, angiotensin receptor blockers
anticonvulsants
Why is reversal of coagulopathy needed for haemorrhagic strokes? What can be used?
anti cogulants (warfarin, dabigatran) prevent blood clots but increase risk of haemorrhage
can use clotting factors (prothrombin complex concentrate), vitamin K, fresh frozen plasma or attack the anticoagulants and their fragments
idarucizumab
- human monoclonal antibody fragment binds to dabigatran and its metabolites
Why are anticonvulsants used for haemorrhagic strokes?
is associated with a risk of post-stroke seizures
- used to control this
Carbamazepine
How can an ischemic stroke be treated? What is the goal?
occlusion due to thrombosis or embolism
aim is to:
- restore perfusion = save the brain tissue of the penumbra
- increase resistance of brain cells to ischemic damage
How you restore perfusion in ischemic stroke?
- pharmacological
alteplase (acute ischemic stroke treatment)
- tissue plasminogen activator (tPA)
converts plasminogen to plasmin
activated plasmin can degrade fibrin and fibrinogen to break up the blood clot
must be administered i.v. within 3 hours (and up to 4.5 hours in certain eligible patients)
- otherwise, there is a significant risk of bleeding that outweighs the thrombolytic effects of the drug
What is tenecteplase?
is a genetically modified variant of alteplase that has been shown to have greater fibrin specificity and a longer half-life than alteplase
- has better reperfusion than alteplase
- better functional outcome
not approved for acute ischemic stroke
- it is approved for acute myocardial infarction
