Pathology of Cerebrovascular disease

Question 1

What arteries supply the areas on the diagram?

Answer 1

Question 2

What arteries supply the brainstem and cerebellum?

Answer 2

Vertebral and basilar arteries

Question 3

What is the difference between ischaemia and hypoxia?

Answer 3

Ischaemia is the lack of blood flow

Hypoxia is the lack of oxygen

Question 4

What is a stroke?

Answer 4

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

(WHO)

Question 5

What 3 ways can the blood flow and thus supply of oxygen be interrupted?

Answer 5

Changes in:

• vessel wall
• blood flow (incl. blood pressure)
• blood constituents

Think Virchow’s triad

Question 6

What changes in the vessel wall can cause interrupt the supply of oxygen?

Answer 6

Abnormality of the physical wall:

• Atheroma
• Vasculitis

Abnormality of outside pressure:

• Strangulation
• Spinal cord compression
• Compression of veins

Question 7

What can change the blood flow & pressure to interrupt oxygen supply?

Answer 7

decreased blood flow

increased blood pressure bursting vessels

Question 8

How can abnormal blood constituents lead to interrupted oxygen supply?

Answer 8

Thrombosis of arteries and rarely veins

Bleeding due to anticoagulation, reduced platelets and clotting factors

Question 9

In practice, what are the 3 main causes of localised interrupted blood supply?

Answer 9

Atheroma & thrombosis:

• Ischaemia

Thromboembolism:

• Ischaemia

Ruptured aneurysm:

• Haemorrhage

Question 10

What area of the brain most commonly becomes ischaemic due to atheroma & thrombosis?

Why?

Answer 10

An internal carotid artery thrombosis will cause ischaemia in the middle cerebral artery territory

This means parts of the Frontal, temporal and/or parietal lobes could be affected

Question 11

For how long must symptoms last before a stroke is a stroke?

Answer 11

>24 hours = stroke

<24 = Transient ischaemic attack

If TIA - the transient symptoms are due to reversible ischaemia - tissue is still viable

If stronk - longstanding symptoms mean tissue has infarcted causing localised brain death

Question 12

Why is infarction permanent in the brain?

Answer 12

Neurones don’t regenerate

Question 13

What shape/pattern does the infarcted area typically look like in stroke

Answer 13

An outward wedge - showing the normal perfusion territory

Question 14

What are the labels pointing at in this lovely photo

Answer 14

Infarcted tissue initially goes soft then cystic

Question 15

What happens in the inflammatory response seen in the previous photo

What process do the cells present contribute to?

Answer 15

There will be lots of foamy macrophages cutting about that are visible histologically

These make up the repair process which leads to gliosis

Gliosis is the CNS equivalent to fibrosis

Question 16

What is the long term structural changes to the brain after infarction?

Answer 16

The infarcted area jut kinda rots away - leaving a cyst-like cavity

The edges of these cavities have lots of yellow discolouration

Question 17

Why do some heart arrhythmias cause strokes?

Answer 17

Arrhythmias such as Atrial fibrillation can lead to a thrombosis forming in the atrium, for example, can embolize

They can end up in the carotid arteries and if they go up the ICA then they can occlude vessels such as the MCA

Question 18

What characteristic of the arteries in the brain allows aneurysms to form relatively easily?

Answer 18

Beyond the carotid & vertebral arteries - the cerebral arteries have quite thin walls

Slight weakening + hypertension can often lead to aneurysms

Question 19

When an aneurysm ruptures, obviously not much blood flows through the artery distal to the haemorrhage

How does the distal artery react to the rupture?

Answer 19

Distal artery will spasm

This will cause ischaemia distal to the site of haemorrhage

Question 20

What are the 2 common sites of aneurysm rupture in the brain?

Answer 20

Basal ganglia - microaneurysms form in hypertensive patients

Circle of Willis – Berry aneurysm forms in hypertensive patients

Question 21

What are some causes of generalised interruption to cerebral blood supply or hypoxia?

Answer 21

Low O₂ in blood:

• this would be hypoxia without ischaemia
• Eg - CO₂ poisoning, near drowning, Respiratory arrest

Inadequate supply of blood:

• regardless of whether or not blood is oxygenated
• Cardiac arrest, hypotension, brain swelling (trauma)

Rarely - some conditions prevent the usage of oxygen by tissues - eg cyanide poisoning

Question 22

How can hypotension lead to hypoxia/infarction in the brain?

Answer 22

Perfusion of the central areas of the arteries territories would be perfused okay

Perfusion of Watershedareas (where territories cross) would bepoor - at risk of infarction. Not enough oxygen delivered as these are like the end branches of the arteries tree

Question 23

What is shown below?

Answer 23

These are watershed infarcts - the typical outcome of pure hypotension with oxygenated blood

Notice that they are symmetrical - ie same area on both sides

Question 24

If a patient suffers a cardiac arrest and the brain suffers complete loss of blood flow and oxygen - what is the outcome?

Answer 24

Cortical necrosis (infarction)

This is characterised by large areas of grey matter thinning (necrosis) with a laminar appearance (lined)