1B cerebral vasculature Flashcards
How much cardiac output, O2 and glucose consumption does the brain use and what does this mean?
- Only makes up 2% of body weight but uses:
- 10-20% cardiac output
- 20% body O2 consumption
- 66% of liver glucose
- Brain is therefore very vulnerable if blood supply is impaired
What is the blood supply to the brain from the heart?
- Common carotid form brachiopulmonary artery splits into external and internal carotid arteries at level of laryngeal prominence
- Internal carotid artery goes through carotid canal into cranial cavity
- First branch of subclavian artery from brachiopulmonary artery is vertebral artery which goes through transverse foramen of cervical vertebrae and goes through foramen magnum into cranium
What is the advantage of the arrangement of arteries in the brain?
If you have blockage in one of the internal carotid arteries for example, there’s a chance of compensatory flow from other side
What is the venous drainage of the brain?
- Cerebral veins in brain drain into venous sinuses in dura mater which drains into the internal jugular vein
- Superior sagittal sinus → occipital confluence of sinuses → drains transversally through sigmoid sinus into IJV back to heart
Describe venous drainage to brain in depth
- Blood goes from superior sagittal sinus to confluence
- Also from inferior sagittal sinus (along bottom of falx cerebri) to confluence
- Also from great cerebral vein down straight sinus to confluence
- Also through transverse into sigmoid sinus and goes through jugular foramen and becomes IJV
What are the four types of intercranial haemorrhage?
- Extradural (red)
- Subdural (blue)
- Subarachnoid (purple)
- Intracerebral (yellow)
What happens in extradural haemorrhage?
- Trauma, immediate clinical effects
- Arterial, high pressure
What happens in subdural haemorrhage?
- Trauma, can be delayed clinical effects
- venous, lower pressure
What happens in subarachnoid haemorrhage?
- Ruptured aneurysms- generally congenital
- Usually happens near circle of Willis and can burst due to hypertension
- Called the ‘thunderclap headahce’
What happens in intracerebral haemorrhage?
Spontaneous hypertensive
Identify this haemorrhage
Subdural
Dura has been reflected and blood clot is underneath the dura
Blood has spread through space over whole hemisphere
Identify this haemorrhage
Intracerebral
Due to rupture in vessel of hypertensive patient
Identify this haemorrhage
Extradural
Blood clot is outside the dura
Identify this haemorrhage
Subarachnoid
Often called berry aneurysm- congenital
What is a stroke aka cerebrovascular attack (CVA)?
A rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration
What two reasons are strokes caused by?
- 85% are thrombo-embolic (blockages in vessels)
- 15% are haemorrhagic
What is a transient ischaemic attack (TIA)?
A rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
What is an infarction?
Degenerative changes which occur in tissue when it loses its blood supply after 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
- Ischaemia is a lack of everything in blood, not just oxygen
What is a thrombosis?
Formation of a blood clot (thrombus)
What is an embolism?
- Plugging of small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid
- Fat and air (from syringe) could cause an embolism
What are the risk factors for stroke?
- Age
- Hypertension
- Diabetes mellitus
- Smoking
- Cardiac disease
What happens if anterior cerebral artery has a problem?
- Paralysis of contralateral structures (leg more than arm or face)- due to primary motor cortex damage
- Disturbance of intellect, executive function and judgement (breakdown of frontal lobe function is called abulia)- due to frontal lobe damage
- Loss of appropriate social behaviour- due to frontal lobe damage
What happens if middle cerebral artery has a problem?
- ‘classic stroke’
- Contralateral hemiplegia (paralysis) → arm more than leg- due to motor cortex damage
- Contralateral hemisensory deficits- due to somatosensory cortex damage
- Hemianopia- loss of one half of visual field- due to occipital lobe damage
- Aphasia (Left sided lesion)- loss of speech- due to Broca’s/Wernicke’s area damage
