Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, Neuroscience (NEU) module.
Cerebral ischaemia: an interruption in the blood supply causing disruption of brain function, usually leading to a permanent sensory, motor or cognitive deficit. It is calculated that in Eng...
! haemorrhagic & hemorrhagic !
Cerebral ischaemia
- in UK, 1 in 6 ppl have a stroke in their lifetime
Blood flow in the brain
- 2 pairs of arteries supply blood to the brain:
=> vertebral arteries: running at back of the neck
=> carotid arteries: running at front of the neck
=> form ring of arteries at base brain: the Circle of Willis
=> collateral circulation if blocked artery (nearby vessel...)
join right & left anterior supply medial surface of the
cerebral arteries frontal & parietal lobes
join internal carotid system
extension of internal carotid MIDBRAIN
w/ vertebral-basilar system
=> supply lateral surface of
j
brain + deep structures
supply medial surfaces of
the occipital & temporal
rise in the front of the neck & form
lobes + thalamus
middle + anterior cerebral arteries
PONS
- smaller arteries run above the pia mater
=> send penetrating arteries/ arterioles into brain tissue
Als
-
- blood flow interrupted/ decreased below the metabolic requirements of O2 & nutrients
=> interruption in a cerebral vessel occluded = focal (localised) ischaemia => affect defined area
=> interruption of blood flow to the whole brain = global ischaemia => faster cell death
, What is a stroke?
- stroke (= cerebrovascular accident CVA) = localised
=> rapidly developing focal disturbance of brain function of presumed vascular origin
=> >24h duration
=> second most common cause of death, leading cause of disability
=> permanent sensory, motor & cognitive deficits
=> symptoms depends on area affected BUT severity doesn’t correlate with amount of tissue lost
=> ex: loss in motor cortex => overlap in innervation => small impairment
- 2 types:
=> ischemic stroke (focal ischaemia): 85%
=> haemorrhagic stroke: 15% (not focal ischaemia)
=> develops more slowly but also ischaemic tissue
Ischaemic stroke
- caused by an occlusion in an artery that interrupts blood supply
=> platelet plug that forms in the vessel: thrombosis
=> blood clot (thromboembolus)/ other material moving through vessels until occlusion: embolism
=> tissue served by vessel starved of O2 + glucose
=> damage (degree depends on extent, duration of occlusion & presence of collaterals)
calso in
haemorrhage↳
L
- core tissue: irreversible damage during ischaemic stroke
=> neurons & glial cells suffer necrotic cell death in minutes
=> resulting dead tissue called ‘infarct’
- around infarct: penumbra => reduction in blood flow BUT collateral flow keeps cells alive for hours
=> after that, cell death spreads from core to penumbra
- transient ischaemic attack (TIA): ischaemic stroke resolving completely within 24h (= not a stroke)
=> blood supply briefly interrupted (similar symptoms but shorter) => no permanent damage
=> at risk for serious stroke
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