Cerebral vasculature Flashcards
Why is the brain very vulnerable if the blood supply is impaired?
it uses
10-20% cardiac output
20% of body O2 consumption
66% of the liver glucose
Relied very heavily on blood supply
How does blood get to the brain?
The common carotid from the brachiocelphalic artery.
It divides into external for the face and internal carotid to cranial cavity
Vertebral artery comes from subclavian, goes posteriorly up behind the verterbrae into cranial cvity
What us special about the circle of willis?
anastomatic circuit vessels are joined
Describe the venous drainage of the brain?
Cerebral veins –> venous sinuses in the dura mater –> internal jugular
Why is having anastomised circle of willis useful e.g. in carotid blockage?
If one branch is blocked and leads to a carotid atherlocarotid build up the posterior circulation and the other branch can continue circulation to the other side of the brain
- however posterior communicating arteries are very thin
Describe the dural venous sunuses?
Look at slide 8, many sinuses shown in the midsaggital section. Brain removed
What is an intracranial haemorrhage?
Bleed in the cranial cavity
What are the four types of haemorrhage?
Extradural
Subdural
Subarachnoid
Intracerebral
What causes extradural haemorrhage and what clinical effects are there?
- Trauma
- Immediate clinical effects :
Arterial, high pressured
What causes Subdural haemorrhage and what clinical effects are there?
- Trauma
- Can be delayed clinical effects :
Venous, lower pressure
What causes Subarachnoid haemorrhage and what clinical effects are there?
Ruptured aneurysms, usually in circle of willis
- generally congenital aneurysms -weaknesses in blood vessels. In hypertensive px it can burst and bleed
What causes Inrtacerebral haemorrhage and what clinical effects are there?
usually seen in chronic raised hypertensive
What is a stroke?
Cerebrovascular accident - CVA
Definition: “rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration”
Thrombo-embolic (85%) or haemorrhage (15%)
What is a transient ischaemic attack? TIA
- rapidly developing
- focus disturbance of brain function
- from presumed vascular origin
- resolves within 24 hours
: need to keep an eye out for future strokes
What is an infarction?
Degenerative chances which occur in tissue following occlusion of an artery
*ischaemia can cause infarction
What is a Cerebral Ischaemia?
Lack of sufficient blood supply to nervous tissue
–> permanent damage if not restored quick
What is a thromboembolic stroke?
thrombosis: formation of a blood clot
Embolism : plugging of a smaller vessel by something carried in a larger vessel
Give an example of material that can cause embolism?
- Thrombi from heart
- Atherosclerotic debri from internal carotid
- Air e.g. from iv injection air bubble
Why are strokes a major public health issue?
3rd commonest cause of death
100,000 deaths annually uk
50% survivors are permanently disabled
70% show obvious neurological deficit
What are the risk factors for stroke?
- age
- hypertension
- cardiac disease
- smoking
- diabetes mellitus
If anterior cerebral artery is affected (slide 26/27) what symptoms are seen?
- paralysis of contralateral structures , leg>arm, face
- Disturbance of intellect, executive function and judgement
- Loss of appropriate social behaviour
If Middle cerebral artery is affected what are the symptoms?
‘Classic stroke features’
- Contralateral hemiplagia : arm/leg
- contralateral hemisensory deficits
- Hemianopia
- Aphasia ( L sided lesion )
If posterior cerebral artery is affected, what are the symptoms?
Visual deficits:
- Homonymous hemianopia
- Visual agnosia
