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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
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What are the two main types of stroke?
- - ischemic strokes
- - hemorrhagic strokes
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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
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What is a hemorrhagic stroke?
- caused by bleeding into brain tissue usually from a blood vessel rupture
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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
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How much does the brain weight?
1500g
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How much glucose does the brain need each day?
- 150g
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How much O2 does the brain need each day?
- 72L
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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
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What arteries supply the brain?
- - vertebral
- - internal carotid
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What areteries are in the circle of wilis?
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What cardiovascular abnormalities may cause ischemic stroke?
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Which cardiovascular abnormalities may cause hemorrhagic stroke?
- - hypertension
- - aneurysms
- - arteriovenous malformations
- - head injury
- - blood dyscrasias
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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
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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
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What are the cellular mechanisms of excytotoxic lesions?
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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
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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
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How clinical signs depend on the vessel involved
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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
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signs and symptoms for cerebellum damage
- - altered equilibrium
- - altered coordination of movements
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What are cortical signs of damage
- - depends on the area of damage
- - aphasia
- - dysartia
- - defect of visual field
- - disorganized thinking, confusion
- - hemineglect
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How can you diagnose a stroke?
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How do you treat a stroke?
- - thrombolysis
- -thrombectomy
- -body cooling
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What is brain plasticity?
The ability of the brain to adapt and change throughout life
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