Pathology of Cerebral-Vascular Disease

Question 1

Define ischaemia

Answer 1

Lack of blood flow

Question 2

Define hypoxia

Answer 2

Lack of oxygen

Question 3

What is the WHO definition of stroke?

Answer 3

Focal neurological deficit (loss of function affecting a specific region of the central nervous system) due to disruption of blood supply

Question 4

What is the basic cause of a stroke?

Answer 4

Interruption of supply of oxygen and nutrients, causing damage to brain tissue

Question 5

What are three factors that interrupt the supply of oxygen?

Answer 5

Virchows Triad - changes in:
• Vessel wall
• Blood flow (including blood pressure)
• Blood constituents

Question 6

Give examples of what changes that occur in the vessel wall?

Answer 6

• Abnormality of wall - atheroma

* Outside pressure - i.e. compression of spinal cord or veins, strangulation

Question 7

Give examples of what changes occur to blood flow and pressure

Answer 7

• Decreased - when a person is in shock (loss of blood)

* Increased pressure which can burst vessels

Question 8

Give examples of what changes occur to blood constituents

Answer 8

• Thrombosis or arteries and rarely veins

* Bleeding due to anticoagulation, reduced platelets and clotting factors

Question 9

What are the three main causes of LOCALISED interrupted blood supply?

Answer 9

• Atheroma + thrombosis of artery causing ischaemia
• Thromboembolism (i.e. from LA) causing ischameia
• Ruptured aneurysms of a cerebral vessel causing haemorrhage

Question 10

Where is a common place for an atheroma to form?

Answer 10

Bifurcation of common carotid artery

Question 11

How does an atheroma of the carotid sinus lead to stroke?

Answer 11

Thrombosis form by build of of platelets and fibrin, and if this dislodges and travels up ICA, it will travel into the middle cerebral artery and cause ischaemia in MCA territory

Question 12

Describe the importance of the duration of ischaemia

Answer 12

• Transient symptoms (<24 hours) – due to reversible ischaemia (transient ischaemic attack) = tissue still viable
• Longstanding symptoms (>24 hours) – due to irreversible ischaemia causing localised brain death = infarct

Question 13

Describe the pathogenesis of an ischaemic stroke

Answer 13

Brain is very sensitive to O2 ischaemia, and a few minuted of hypoxia or anoxia will cause it.

This can lead to infarction, which causes damage to neurones (permanent). Neurones do not regenerate.

Question 14

Why does ischaemia not immediately arise if the carotid arteries are fully occluded?

Answer 14

Due to vertebral arteries still supplying circle of willis (only for 3mins)

Question 15

What is a regional cerebral infarct?

Answer 15

A localised area of brain death reflecting arterial perfusion territory

Classically wedge-shaped, which starts soft and then becomes cystic.

Question 16

What is gliosis?

Answer 16

CNS equivalent of fibrosis - yellow colouration at edge of infarcted area caused by foamy macrophages

Question 17

Describe the change in histology after infarction?

Answer 17

• Loss of neurones

* Foamy macrophages - repair process leading to gliosis

Question 18

What do old infarct cause?

Answer 18

Loss of brain tissue, cystic spaces and gliosis

Question 19

Why is the location of ischaemia important?

Answer 19

Small affected area of one part of brain may not cause too much impairment, but a similar size of affected area in another part of brain may be devastating

Question 20

Describe how a thromboembolism can lead to infarction

Answer 20

Heart with atrial fibrillation can cause thrombosis of atrial appendages.

If it dislodges it will embolism to aorta and possibly carotid (or any other) arteries - but L common carotid is inline with ascending aorta.

Travels to MCA and occludes it.

Question 21

Describe how a ruptured vessel wall can lead to haemorrhage stroke

Answer 21

The cerebral arteries are thin walled, therefore hypertension causing the waking of the wall and formation of an aneurysm

Decreased blood blood flow vitally to brain due to spams of artery

Question 22

Why are cerebral arteries thin walled?

Answer 22

As your brain does not want to be affected by substances, like caffeine, to ensure constant blood flow

Question 23

What does rupturing of a vessel cause?

Answer 23

Haemorrhage (+/- distal ischaemia due to spasm of artery)

Whereas other two cause ischaemia

Question 24

Name two common sites of ruptures vessels causing haemorrhage stroke

Answer 24

• Basal gangli - microaneurysms form in hypertensive patients
• Circle of Willis - Berry aneurysm forms in hypertensive patient

Question 25

Name causes of GENERALISED interruption of blood supply

Answer 25

• Low O2 in blood (hypoxia with intact circulation
• Inadequate supply of blood (flow of blood not occuring)

• Rarely: Inabiloty to use O2 - i.e. cyanide poisoning

Question 26

What are three causes of hypoxia?

Answer 26

CO2 poisoning, drowning, respiratory arrest

Question 27

What are three causes of inadequate blood supply and/or hypoxia?

Answer 27

• Hypotension
• Cardiac arrest
• Complex case

Question 28

What is the effect of hypotension on perfusion of the brain?

Answer 28

It causes the central part of the artery territory to be perfused, but the edges in-between each territory (the watershed zones) are poorly perfused

This causes watershed infarcts (distinct zones between territories)

Question 29

How does a cardiac arrest cause infarction?

Answer 29

No circulation to brain and no oxygen in blood – all of brain deprived of blood flow and O2

Question 30

What is the effect of cardiac arrest on perfusion of the brain?

Answer 30

Causes large areas of grey matter thinning and necrosis –> cortical necrosis

Question 31

Complex case effect of perfusion:
75yr old 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.

What has happened?

Answer 31

Reperfusion with good circulation after cardiac arrest (no O2 or perfusion) comes with complication.

Combination of poor perfusion and atheroma in carotid arteries cause regional infarcts;
• Watershed infarcts
• Laminar cortical necrosis
• Region infarcted related to poor flow through cerebral vessels narrowed by atheroma