Pathology of Cerebrovascular Disease: Ischaemia (Atheroma and thrombosis, thromoboembolism, Raptured aneurysm) and hypoxia generalised problems Flashcards
what three arteries supply blood to the cerebral cortex?
anterior, middle and posterior cerebral arteries
do veins accompany arteries in the brain?
Veins do not accompany arteries
Large venous sinuses within dura
which sinuses are responsible for venous drainage of the brain?
superior sagittal sinus
transverse vein
what is ischaemia?
lack of blood flow
what is hypoxia?
lack of oxygen
what is the definition of stroke?
Focal neurological deficit (loss of function affecting a specific region of the central nervous system) due to disruption of blood supply
what is the cause of stroke?
Interruption of supply of oxygen and nutrients, causing damage to brain tissue
what can interruption of supply of oxygen be caused by?
Vessel wall
Blood flow (including blood pressure)
Blood constituents
how can the vessel wall cause an interruption of supply in oxygen?
(abnormality of wall eg atheroma or vasculitis, outside pressure [eg strangulation, spinal cord compression, compression of veins])
how can blood flow and pressure cause an interruption of supply in oxygen?
(eg decreased blood flow, increased blood pressure bursting vessels)
how can blood constituents and pressure cause an interruption of supply in oxygen?
(Thrombosis of arteries and rarely veins. Bleeding due to anticoagulation, reduced platelets and clotting factors)
what are the three main causes of localised interrupted blood supply?
Atheroma + thrombosis of artery causing ischaemia
Thromboembolism (for example, from left atrium) causing ischaemia
Ruptured aneurysm of a cerebral vessel causing haemorrhage
how does atheroma and thrombosis affect an artery?
narrowing of artery
atheroma causes some narrowing
thrombosis results in severely narrowed artery
ussually occurs near bifurcation
where is ischaemia found typically following internal carotid artery thrombosis?
typically get ischaemia in middle cerebral artery territory (but can affect elsewhere)
what are transient symptoms of ischaemia defined as?
(<24 hours) – due to reversible ischaemia (transient ischaemic attack) = tissue still viable
what are long standing symptoms of ischaemia defined as?
(>24 hours)– due to irreversible ischaemia causing localised brain death = infarct
describe the pathogenesis of an ischaemic stroke?
Brain is very sensitive to oxygen ischaemia
A few minutes hypoxia or anoxia will cause brain ischaemia
Can lead to infarction. If infarction then damage to neurones is permanent. Neurones do not regenerate
what is a localised area of brain death known as?
Regional cerebral infarct
how are regional cerebral infarcts characterised?
Classically wedge-shape reflecting arterial perfusion territory
Soft and then becomes cystic
how does an infarct present histologically?
Loss of neurones - causes clinical functional deficit
Microglia are brain macrophages that eat up dead tissue – repair process leading to gliosis
Gliosis is CNS equivalent of fibrosis
why is the location of ischaemia very important?
Small affected area of one part of brain may not cause too much impairment
Similar size of affected area in another part of brain may be devastating
who are thrombosis of atrial appendages most common in?
people with arrhythmias such as atrial fibrillation
how does a thromboembolism typically travel?
Heart with left atrial appendage thrombosis
Left atrium is connected directly to outflow of left side of heart
If thrombosis in left
atrial appendage breaks off it
will embolise to aorta and
possibly the carotid
(or any other) arteries
Right middle cerebral artery blocked by embolus - leads to ischaemia
what causes an aneurysm to form?
Beyond carotids and vertebral arteries the cerebral arteries have thin walls.
Weakening of wall + hypertension causes aneurysm to form
when is a vessel wall most liekly to rupture?
in severe hypertension
what does a ruptured vessel wall cause?
haemorrhage and distal ischaemia
Decreased blood flow
distally to brain due to
spasm of artery
what are two common sites of ruptured vessels which cause haemorrhagic stroke?
Basal ganglia
Circle of Willis
what type of aneurysms form in hypertesnive patients in the basal ganglia?
microaneurysms form in hypertensive patients
what type of aneurysms form in hypertesnive patients in the circle of willis?
Berry aneurysm forms in hypertensive patient
which three factors cause generalised interupted blood supply/ hypoxia?
Low O2 in blood (hypoxia with intact circulation of blood) – eg. C02 poisoning, near drowning, respiratory arrest
Inadequate supply of blood (flow of blood not occurring) – eg. cardiac arrest, hypotension, brain swelling (eg trauma)
Rarely: Inability to use O2 – eg cyanide poisoning
what causes Low O2 in blood (hypoxia with intact circulation of blood)?
C02 poisoning, near drowning, respiratory arrest
what causes inadequate supply of blood (flow of blood not occurring)?
cardiac arrest, hypotension, brain swelling (eg trauma)
what causes inability to use O2?
cyanide poisoning
what are 3 examples of brain injury caused by generalised interrupted blood supply and/or hypoxia?
Hypotension
Cardiac arrest
Complex case
Patient has coronary artery bypass with prolonged period of hypotension during operation – patient kept oxygenated by ventilation
which part of their brain is better perfused?
Central part of arteries territories are perfused
Watershed zones are poorly perfused
So patient has prolonged period of poor perfusion pressure of brain, but blood is oxygenated
Patient dies a few days after operation 🡪 autopsy - Zonal pattern of ischaemia and infarction at interface of territories
what are Zones of infarction at interface of artery perfusion territores known as?
Watershed’ infarcts
(Pure hypotension with oxygenated blood)
what are watershed infarcts?
Pure hypotension with oxygenated blood
60 year old male suffers myocardial infarct. Doing well then, Cardiac arrest followed several minutes later by resuscitation - what happens during those minutes?
no circulation to brain and no oxygen in blood – all of brain deprived of blood flow and O2
60 year old male suffers myocardial infarct. Doing well then, Cardiac arrest followed several minutes later by resuscitation - patient dies what will autopsy show?
Large areas of grey matter necrosis
60 year old male suffers myocardial infarct. Doing well then, Cardiac arrest followed several minutes later by resuscitation - id patient had lived longer what would have happened to grey matter?
laminar cortical necrosis
what is complete loss of perfusion and oxygen?
cortical necrosis (infarction)
75 year old woman with known coronary artery disease
Suffers bout of pneumonia
Periods of poor oxygenation but adequate circulation (due to pneumonia)
Then suffers cardiac arrest – period of no perfusion and no oxygen
Successful resuscitation then further arrest then dies
at autopsy what various types of infarcts may be seen?
watershed infarcts
laminar corticsl necrosis (infarction)
regional infarcts related to poor flow through cerebral vessels narrowed by atheroma?
