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What is a stroke?
- - ischaemic event leading to lack of blood supply to the brain
- - lack of blood means- deficit of O2, glucose, lack of waste removal
- - depending on the duration of symptoms if < 24hr-a transient ischaemic attack, if > 24hrs- a stroke
What are the two main types of stroke?
- - ischemic strokes
- - hemorrhagic strokes
What is an ischemic stroke?
- caused by an interruption of blood flow in a cerebral vessel and are the most common type of stroke- accounting for 70-80% of strokes
What is a hemorrhagic stroke?
- caused by bleeding into brain tissue usually from a blood vessel rupture
What are the dysfunctions that follow a stroke?
- - vary according to region deprives
- - characteristic regions can be affected but the only definitive diagnosis comes from CT and MRI scanning
- - small branches of arteries most often affected; symptoms may ass unnoticed
- - multiple very small strokes may not be noticed individually, but combine to produce cerebral vascular dementia
How much does the brain weight?
How much glucose does the brain need each day?
How much O2 does the brain need each day?
Blood supply to the brain
- - no storage of glucose, blood and O2 in the brain
- - about 500ml?min of blood is delivered to the arteries supply the brain
- - arterioles in brain are highly chemosensitive, and dilate/ contract according to local )2 and CO2 concentrations as tissues uses oxygen
What arteries supply the brain?
- - vertebral
- - internal carotid
What areteries are in the circle of wilis?
What cardiovascular abnormalities may cause ischemic stroke?
Which cardiovascular abnormalities may cause hemorrhagic stroke?
- - hypertension
- - aneurysms
- - arteriovenous malformations
- - head injury
- - blood dyscrasias
What happens in the brain tissue after a stroke occurs?
- 30 sec- metabolism alters and slows
- 1 min - neurons stop functioning
- 5 min- anoxia- leads to the start of infarction- vasodilation and blood stasis, oedema, necrosis (softening tissue removal)
- 5-7 min: excitotoxis processes begin to kill neurons
What is the anatomy of stroke: care and penumbra
- core- dead, infarcted brain tissue
- penumbra- threatened, potentially salvageable tissue surrounding the infart core soon after stroke
What are the cellular mechanisms of excytotoxic lesions?
What are the signs and symptoms of stroke
- sudden onset- combination of sensory, motor and cognitive deficits
- Most common signs (indicate damage to sensory and motor pathways in the brain)
- - loss of sensations and numness in one side of the body
- - hemiplegia (same side as sensory dissorders) and mm weakness of the face
- - initial reduction of mm tone (flaccidity) replaced by mm rigidity/ spasticity and hyperreflexia on the same side
Why are clinical signs on the opposite side to the side of a stroke?
- as the sensory and motor pathways cross over as they move up and down the spine
How clinical signs depend on the vessel involved
Which other signs of a stroke?
- brainstem damage- manifests as a deficit in function of cranial nerves:
- - altered smell, taste, hearing or vision
- - decreased sensation on thee face
- -ptosis (drooping of eyelid) and weakness of ocular mm
- - weakness in tounge (deviation to one side)
- - decreased reflexes (swallow, pupil reactivity to light)
- - possibly altered respiration
signs and symptoms for cerebellum damage
- - altered equilibrium
- - altered coordination of movements
What are cortical signs of damage
- - depends on the area of damage
- - aphasia
- - dysartia
- - defect of visual field
- - disorganized thinking, confusion
- - hemineglect
How can you diagnose a stroke?
How do you treat a stroke?
- - thrombolysis
- -body cooling
What is brain plasticity?
The ability of the brain to adapt and change throughout life
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