Hypoxia and Stroke

Question 1

What are the 3 main mechanisms of cerebrovascular disorders?

Answer 1

Thrombotic occlusion

Embolic occlusion

Vascular rupture

Question 2

What is hypoxia?

Answer 2

HYPOXIA is a reduction in either oxygen supply

or oxygen utilisation by the tissues

Question 3

What mechanisms can deprive the brain of oxygen?

Answer 3

Functional hypoxia:
Low partial pressur eof oxygen, impaired oxygen carrying capacity (eg CO poisoning), toxins that interfere with oxygen

Ischaemia:
Tissue hypoperfusion (transient or permanent), hypotension, vascular obstruction, or both.

Question 4

What is a combination of hypoxia and ischaemia called?

Answer 4

Hypoxic Ischaemic Encephalopathy. The combined term is not recommended. A reduction in oxygen can occur along several points of oxygen delivery to the brain.

Question 5

What is histotoxic hypoxia?

Answer 5

Inability of tissue to utilise oxygen.

Question 6

What causes histotoxic hypoxia?

Answer 6

Environmental toxins such as cyanide and sulfide bind to brain receptors but cause severe hypotension due to heart failure resulting in brain necrosis.

Question 7

What happens during carbon monoxide poisoning?

Answer 7

Oxygen on haemoglobin is displaced. This results in hypoxia that is irreversible.

Question 8

Which parts of the brain are most affected by CO poisoning?

Answer 8

High iron content areas

Question 9

What kind of syndrome is associated with low dose CO?

Answer 9

Amotivational state called psychic akinesia. This is seen more commonly in cases who survived attempted suicide in modern car.

Question 10

What are the types of necrosis of brain tissue?

Answer 10

Selective neuronal necrosis

Pan-necrosis.

Question 11

What does selective neuronal necrosis indicate in forensic findings?

Answer 11

The death must have happened after some time from the initial injury.

Question 12

Why must hypoxia and ischaemia be distinguished?

Answer 12

To be able to predict outcome of a global insult and coma.

Medico-legal determine whether a respiratory arrest or a cardiorespiratory arrest has occured. The clinical outcome is vastly different if the heart has not stopped and the blood pressure has been maintained.

Causes of pure hypoxia include infections of tracheobronchial tree and short lived anaesthetic errors. Hypoxic coma can be followed by complete recovery.

Question 13

What are the potential non-traumatic causes of subarachnoid haemorrhage?

Answer 13

Rupture of aneuryms

Arteriovenous malformations abnormal development of vessels

Other aneurysms

Mycotic (septic embolus that weakens the vessel wall where it lodges)

Question 14

What layer is missing in blood vessels that get aneurysms?

Answer 14

Tunica media (all that remains is the tunica intima and adventitia)

Question 15

Where do berry aneurysms occur most often?

Answer 15

90% of them occur in anterior circulation near major arterial branches. (20 - 30% of cases have multiple aneurysms)

Question 16

What are the major symptoms of berry aneurysm rupture (subarachnoid haemorrhage)?

Answer 16

Very intense headaches and vomiting with lucid interval.

Question 17

What conditions are aneurysms associated with?

Answer 17

Polycystic kidney disease

Coarctation of the aorta

Moyamoya

Fibromuscular dysplasia

Ateriovenous malformation

Question 18

What is the most common cause of mortality in people with subarachnoid haemorrhage?

Answer 18

Vasospasm which is a direct effect of the blood or blood products on the adventitia of the artery.

Question 19

What are the symptoms of an aneurysm?

Answer 19

Prior to rupture usually asymptomatic unless large enough to press on
vital structures.
Aneurysmal rupture has a high mortality .
Neurosurgical and endovascular intervention is available.
There is a risk of re- bleeding.
Some do return to a normal life and others are partially or severely
disabled ( variable).