Cerebral Vasculature Flashcards
The brain is about 2% of a person’s mass.
What percentage of the cardiac output does it take?
What percentage of the liver’s glucose does it take?
Brain uses 10-20% of cardiac output - 20% of body’s oxygen consumption
Brain uses 2/3 of the liver’s glucose
Why is the brain so vulnerable to blood supply?
Because it requires so much of the body’s oxygen and glucose supply
What are the main vessels that supply blood to the brain?
Internal carotid artery (a branch off the common carotid, which is a branch off the brachiocephalic)
Vertebral artery (a branch off the subclavian artery, which is a branch off the brachiocephalic)
Fill in the missing labels on the Circle of Willis diagram below:
2 main arteries feeding the Circle of Willis: internal carotid and vertebral arteries
Vertebral arteries come up via the foramen magnum, then fuse to form the basilar artery (which sits on the pons)
Basilar divides into the posterior cerebral arteries
There are also the anterior and middle cerebral arteries
Anterior and posterior communicating arteries connect the cerebral arteries
What is the advantage of having the Circle of Willis (where the arteries are connected)?
If there are blockages in any of the arteries, there is theoretically compensatory flow from the other side
How does the blood exit the brain via venous drainage?
Cerebal veins found in the brain, venous blood in the cranial cavity drains via the dural sinuses
This then drains down the back of the head into the confluence of sinuses, which then drains into the sigmoid sinus and into the side of the neck down the internal jugular vein
What forms the venous sinuses?
The two layers of the dura mater
Fill in the diagram below with the missing dura fold labels and sinus labels:
Falx cerebri - divides cerebral hemispheres
Falx cerebelli - divides cerebellum hemispheres
Sigmoid sinus = ‘S’ shaped going through the jugular foramen, via which venous blood drains into the internal jugular vein
What are the 3 meninges of the brain?
2 layes of the dura mater (outmost layer)
Arachnoid mater (with sub-arachnoid space beneath)
Pia mater - sticks onto the cerebral cortex
What are the 4 types of intracranial haemorrhages and what are they usually caused by?
- Extradural: trauma, arterial bleed, (often at the pterion), immediate clinical effects, raised intracranial pressure due to lack of epidural space in the cranium
- Subdural: trauma, delayed effects due to slight space between dura and arachnoid mater
3: Subarachnoid: ruptured aneurysms (often due to hypertension)
4: Intracerebral: bleed in the brain itself, spontaneous hypertensive bleed
What type of bleed does this image show?
Subdural bleed, due to large blood clot under the dura
Due to subdural space, blood has spread
What type of bleed does this image show?
Intracerebral bleed - within the brain itself
What type of bleed does this image show?
Extradural haemorrhage - large blood clot outside the dura, large sudden rise in intracranial pressure
What type of bleed does this image show?
Subarachnoid haemorrhage - rupture of one of the vessels in the Circle of Willis
What is a stroke?
What are the causes of a stroke?
Rapidly developing focal disturbance of brain function believed to be of vascular origin and of greater than 24hrs duration
85% of the time - thrombo-embolic (blockage of a vessel); 15% of the time - haemorrhage
What is a transient ischaemic attack (TIA)?
Rapidly developing focal disturbance of brain function believed to be of vascular origin and resolves itself within 24hrs Indicative of future strokes
What is meant by infarction?
An area of tissue that has lost its blood supply, leading to necrosis
What is meant by cerebral ischaemia?
Lack of sufficient blood supply to nervous tissue, which if not restored quickly, can lead to permanent damage
Thrombo-emoblic stroke:
What is meant by the terms thrombosis and embolism?
Thrombosis: formation of blood clot that ends up in the brain, blocking an artery
Embolism: plugging of a small vessel by material carried from a larger vessel (e.g. atherosclerosis, fat, air, blood clots etc.)
Thrombus (blood clot) is a type of embolism
How to spot a stroke with the F.A.S.T. acronym?
F = Face - drooping on one side
A = Arms - can they lift both arms and leave it there?
S = Speech - impaired / slurring speech
T = Time to call 999
What are the risk factors for strokes?
Age
Hypertension
Cardiac Disease
Smoking
Diabetes Mellitus
Label which cerebral arteries supply the perfusion fields onto the diagram below:
Left lateral view
Middle cerebral = largest perfusion field
Label which cerebral arteries supply the perfusion fields onto the diagram below: Mid-saggital view
Why is it important to learn the perfusion fields of the arteries?
Can help workout where a stroke has occurred in the brain
