6.03 Cerebrovascular accident

Question 1

Common causes of collapse

Answer 1

Fainting (syncope), cardiovascular disease, epilepsy

Question 2

Syncope

Answer 2

Sudden, brief loss of consciousness

Associated with loss of postural tone

Recovery is rapid and complete

Question 3

3 causes of syncope

Answer 3

1. Vasovagal syncope - neurally mediated, results from reflex-mediated changes in vascular tone or heart rate
2. Orthostatic hypotension
3. Primary cardiac conditions (e.g. large MCI, aortic stenosis), arrhythmias

Question 4

When can cerebrovascular disease cause collapse?

Answer 4

When the reticular formation is involved in a brainstem stroke

In large cerebral strokes with raised ICP (e.g. intracranial haemorrhage.)

Question 5

What is the difference between a cerebrovascular-caused collapse than the other causes (epilepsy and syncope)?

Answer 5

The collapse in cerebrovascular disease is usually of longer duration and is often accompanied by neurological defects

Question 6

Stroke

Answer 6

Describes a prolonged neurological deficit that has a sudden onset and a vascular basis.

Question 7

TIA

Answer 7

Episodes of neurological deficit with a vascular basis that last a short time (only a few minutes)

Question 8

Strokes can be caused by

Answer 8

1. Cessation of blood flow - leading to ischaemic necrosis (infarction)
2. Break in blood vessels - leading to haemorrhage

Question 9

Causes of most cerebral infarcts

Answer 9

Atherothrombosis (atheroma + superimposed thrombus).

The thrombus that forms on the atheroma can either occlude the artery at the point of its generation, or can break off and embolise to a distal branch of the artery

Question 10

Where can thromboembolic material arise from?

Answer 10

Internal carotid, aortic arch
Cardiac chambers (especially after MCI)

Question 11

What are the superficial parts of the brain supplied by?

Answer 11

The large arteries (anterior, middle and posterior cerebral arteries)

Question 12

What are the deep parts of the brain supplied by?

Answer 12

Small penetrating arteries.

Question 13

How are haemorrhages in the brain cause?

Answer 13

1. Rupture of a berry aneurysm at the base of the brain, giving rise to a SAH
2. Rupture of a small penetrating artery that gives rise to a haematoma deep in the brain (intracerebral haemorrhage).

Question 14

What are neuroprotective agents?

Answer 14

Drugs that target the cellular disturbances that lead to brain infarct after stroke

Question 15

What does current drug therapy for strokes involve?

Answer 15

Primarily it is preventive, with the aim of reducing thrombus formation using anticoagulants and anti-platelet agents.

Agents that lyse blood clots e.g. thrombolytic agents like t-PA are used to increase perfusion of the affected areas

Question 16

What is the enzyme system inhibited by aspirin?

Answer 16

Cyclo-oxygenase (converts arachidonic acid to prostaglandins and thromboxane)

Question 17

What is thromboxane A2

Answer 17

It is the major metabolite in platelets, which is pro-aggregatory

Question 18

What is prostacyclin?

Answer 18

PGI2 - the major metabolite in endothelial cells. It inhibits platelet aggregation

Question 19

How does aspiring work in platelets?

Answer 19

It binds irreversibly to cyclo-oxygenase (check) to inhibit thromboxane synthesis for the lifespan of the platelets