1b Cerebral Vasculature Flashcards
What percentage of the bodies oxygen consumption does the brain use?
20% - therefore the brain is very vulnerable if the blood supply is impaired
Describe the blood supply to the brain?
The common carotid artery is a branch of the brachiocephalic trunk - this splits into the internal and external carotid artery
What is the point where the cerebral veins converge?
Point of confluence
What are the four types of haemorrhages?
- Extradural
- Subdural
- Subarachnoid
- Intracerebral
What is the most common cause of an extradural haematoma?
Trauma = blow to the pterion - rupture the middle meningeal artery
Why is an extradural haematoma a surgical emergency?
arterial bleed, therefore high pressure and loss of blood is fast
Why can the clinical effects of a subdural haematoma be delayed?
venous bleed therefore lower pressure so less of a clinical emergency
What will patients with a sub arachnoid bleed experience?
Thunderstorm headache
What causes subarachnoid bleeds?
ruptured aneurysms
What causes an intracerebral bleed?
Spontaneous hypertension
What is a stroke?
A rapidly developing focal disturbance of brain function of presumed vascular origin and greater than 24 hours in duration
What are the two main types of strokes?
Thrombo-embolic or haemorrhage
What is a TIA?
Transient Ischaemic Attack - rapidly reveloping focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
What is an infarction?
Degenerative changes which occur in the tissue following an occlusion of an artery
What is cerebral ischaemia
Lack of sufficient blood supply to the nervous tissues resulting in permanent damage if blood flow is not restored properly
What is thrombosis?
formation of a blood clot
What is an embolism?
plugging of a small vessel by material carried from a larger vessel eg thrombi from the heart or atherosclerotic debris from the internal carotid
What are some key signs of a stroke?
Loss of symmetry
slurred speech
drooping of face and mouth - one side
What are the risk factors for stroke?
Diabetes mellitus
smoking
Age
Hypertension
Cardiac Disease
Draw a diagram showing the cerebral artery perfusion fields?
What symptoms would be experienced by patients if they have an anterior cerebral artery blockage?
Paralysis of contralateral structures with a tendancy for lower limbs over arm
Disturbance of intellect, executive function and judgment (Abulia)
Loss of appropriate social behaviour
What symptoms would be experienced by patients if they have an MIDDLE cerebral artery blockage?
“Classic stroke”
Contralateral hemiplagia (upper limbs over the lower limbs)
Contralateral hemisensory deficits
Hemaniopia
Aphasia (L Sided lesion)
Why is hemiplagia common in middle cerebral artery conditions?
the middle cerebral artery supplies all pathways to the spinal cord, therefore there is likely to be subcortical damage
What type of aphasia ill damage to Broca’s area produce?
Expressive Aphasia - they can understand but not reply
What type of aphasia will damage to Wernicke’s area produce?
Receptive Aphasia - cannot understand but can speak
What does damage to the posterior cerebral artery result in?
Visual defects - homonymous hemaniopia and visual agnosia
What is agnosia?
Inability to recognise faces
What is a major risk factor for stroke?
Atherosclerosis - yellow discolouration in the walls of the vessel represent atherosclerosis or hardening of the arteries
Draw the circle of willis
What is the benefit of the circle of willis?
Compensatory flow - if one of the arteries is lacking - the others can compensate
What is the treatment for Subdural Haematoma?
Burr Holes - remove skull flap and then remove blood
How can you distinguish a SDH from other bleeds?
Delayed presentation = as SDH is a venous bleed therefore lower presure and hence slower presentation
Why do you have a persistent headache in SDH?
Due to sheering of the delicate bridging veins in the subdural space
What pathologies are seen on a scan of a SDH?
the bleed
compressed ventricles on the side of the bleed
Other ventricle large as filled with alot of CSF to compensate
What are the signs of an intra-cerebellar bleed?
Drowsy, slurred speech, wobbly eye movements, ataxia, broad based gait
Which type of bleed is due to hypertension usually?
Intra-parenchymal bleed
What is the treatment for Intra-parenchymal bleeds?
Manage hypertension - usually difficult to remove surgically as it is inside the brain
Which cerebral artery has the largest perfusion field?
Middle cerebral artery
Stroke of which artery results in a disturbance of intellect, executive function and judgement?
Anterior cerebral artery
What causes a venous haemorrhage?
Shearing of bridging veins
What is the presentation of a subdural haemorrhage?
Gradually worsening headache - due to pressure building up
Drowsiness / loss of consciousness due to pressure on the brainstem
If a lemon shaped bleed is on a CT, which type of bleed is this?
Extradural bleed
What are the clinical symptoms of cerebellar bleeding?
Dysarthia (slurred speech)
Wobbly eye movements
Ataxia (clumsy hands)
Broad based gait
How is an intraparenchymal bleed treated?
Manage the risk factors
May try remove the bleed via surgery
