Cerebrovascular Disease Flashcards
what is the blood supply to the brainstem and the cerebellum?
vertebral and basilar arteries
in the brain do veins accompany the arteries?
no they are in large venous sinuses within the dura
define stroke
focal neurological deficit (loss of function affecting a specific region of the central nervous system due to disruption of blood supply
what are the causes of stroke?
interruption of supply of:
> oxygen
> nutrients
causing brain damage
what causes interruption to the supply of oxygen to the brain?
changes in:
> vessel wall
> blood flow (increased or decreased pressure)
> blood constituents
what changes in the vessel wall can cause interruption in oxygen supply?
> atheroma
vasculitis
outside pressure- spinal cord, strangulation
give some examples of changes in the constituents of the blood that leads to altered oxygen supply to the brain
> thrombosis of arteries and (rarely) veins
> bleeding due to anticoagulation, reduced platelets and clotting factors
name the three main causes of localised interrupted blood supply
> atheroma and thrombosis (causing ischaemia)
thromboembolism (causing ischaemia)
ruptured aneurysm (haemorrhage)
describe the pathology of atheroma and thrombosis
> often at a bifurcation of an artery
atheroma causes narrowing
thrombosis (on top of the atheroma), made from platelets and fibrin, resulting in severely narrowed artery
define ischaemia
a relative or absolute lack of blood supply in a tissue or organ
is tissue still viable in a transient ischaemic attack?
yes as it is reversible
what can longstanding symptoms due irreversible ischaemia lead to?
infarct, localised brain death
describe the pathogenesis of ischaemic stroke
> brain is sensitive to ischaemia, a few minutes of hypoxia/anoxia will cause ischaemia
this can lead to infarction where the damage to neurones is permanent as they do not regenerate
describe a regional cerebral infarct
> localised area of brain death
classically wedged shaped reflecting arterial perfusion territory
soft then becomes cystic
eventually there is a loss of brain tissue
swelling of surrounding brain tissue
describe the histology of an infarct
> loss of neurons (causing clinical functional deficit)
> foamy macrophages (repair process leading to gliosis-fibrosis)
why is the location of ischaemia very important?
> small area of brain affected in the periphery would cause less impairment than a similar sized area in another part of the brain
why does thromboembolism lead to stroke?
when the thrombus embolises to the cerebral blood supply oxygen content to tissues is lowered
why do cerebral arteries have thin walls?
they have less muscle so that there is no constriction with large amounts of angiotensin ensuring that the cerebral blood flow is not disturbed
what can cause aneurysms to form?
> weakening of walls
> hypertension
what is the affect on brain distal to the haemorrhage of an artery?
decreased blood flow due to spasm of the artery = ischaemia
name two common sites of ruptured vessels In the brain
> basal ganglia (microaneurysms)
> circle of willis (berry aneurysms)
name three things that can lead to generalised interrupted blood supply or hypoxia
> low O2 in blood- hypoxia will intact circulation
inadequate blood supply - blood flow not occurring
inability to use o2 (cyanide poisoning)
what can cause hypoxia with intact circulation of blood?
> CO poisoning
near drowning
respiratory arrest
what can cause in adequate supply of blood to the brain?
> cardiac arrest with immediate ressus
hypotension
brain swelling (trauma)
what are watershed infarcts?
zones of infarction at interface of artery perfusion territories
what can lead to watershed infarcts?
pure hypotension with oxygenated blood
what leads to cortical necrosis?
when there is no circulation to the brain and no oxygen in the blood so all the brain is derived of blood flow and o2 (cardiac arrest)
what is cortical necrosis?
large areas of grey matter thinning and necrosis
what is laminar necrosis?
lines of necrosis and thinning
a patient with coronary artery disease and pneumonia suffers a heart attack. what infarcts would you expect to see?
> watershed infarcts (periods of hypoxia due to pneumonia)
laminar cortical necrosis (due to total lack of oxygenation)
regional infarcts (cerebral vessels narrowed by atheroma)
