Cerebral Vasculature Flashcards
What are the perfusion demands of the brain and why is this significant?
10-20% of cardiac output
20% of body O2 consumption
66% of liver glucose
The brain is therefore very vulnerable if the blood supply is impaired
What are the two main arteries that supply the brain?
Internal carotid artery
Vertebral artery
Once the internal carotid artery enters the skull, what does it continue as?
Middle cerebral artery
Outline the venous drainage of the brain
Cerebral veins -> drain into the venous sinuses in the dura mater -> drain into the internal jugular vein
What are the different types of haemorrhage?
Extradural
Subdural
Subarachnoid
Intracerebral
Label the dural venous sinuses
What causes extradural haemorrhages and describe the nature of clinical effects?
Trauma - usually trauma to the side of the head e.g. pterion - directly beneath is middle meningeal artery – requires immediate treatment – build up of pressure compresses brain stem – shut down of cardio respiratory centres
Immediate clinical effects
What causes subdural haemorrhages and describe the nature of clinical effects?
Trauma
Clinical effects may be delayed
Why may the clinical effects of a subdural haemorrhage be delayed and what is the significance of this?
Rupture of a vein - lower pressure
Subdural so more space to fill
If a person has trauma to the head and is unconscious but wakes up feeling fine later, keep in hospital overnight as they may develop a subdural haematoma
What is a cause of subarachnoid haemorrhages?
Ruptured aneurysms - weakening in vessel wall ( likely congenital)
Usually an incidental finding
Big risk of rupture if patient is hypertensive
What can causes Intracerebral haemorrhages?
Spontaneous hypertensive cause
Identify a suitable diagnosis based on the image below
Subdural haematoma
Intracerebral haematoma
Identify a suitable diagnosis based on the image below
Extradural haematoma
Subarachnoid haemorrhage
What is a stroke?
Cerebrovascular accident - rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration
What are the two main causes of stroke?
Thrombo-embolic (85%)
Haemorrhage (15%)
Define a transient ischaemic attack?
A rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
Define infarction
Degenerative changes which occur in tissue following occlusion of an artery
What is cerebral ischaemia?
Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly
What is thrombosis?
Formation of a blood clot (thrombus)
Define embolism
Plugging of small vessel by material carried from a larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid
What are the risk factors for stroke?
Age
Hypertension
Cardiac disease
Smoking
Diabetes Mellitus
Label this diagram of cerebral artery perfusion fields
What are the symptoms of a stroke affecting the anterior cerebral artery?
Paralysis of contralateral structures (usually leg)
Disturbance of intellect, executive function and judgement (abulia)
Loss of appropriate social behaviour - aggression, hypersexuality
What are the symptoms of a stroke affecting the middle cerebral artery?
Known as the “Classic stroke”
Contralateral hemiplegia (usually arm)
Contralateral hemisensory deficits
Hemianopia
Aphasia (L sided lesion) - e.g. Wernicke’s area - receptive aphasia
What are the symptoms of a stroke affecting the posterior cerebral artery?
Visual deficits:
- homonymous hemianopia (affects same side - e.g. two left or two right visual field defects)
- visual agnosia
What major risk factor for stroke is evident in this specimen?
The yellow discolouration in the walls of the vessels is a build-up of atheroma, fatty deposits that cause atherosclerosis or “hardening of the arteries” - can cause blockages
Which cerebral artery has been occluded in this specimen?
Right middle cerebral artery
