Cerebral Vasculature Flashcards
What percentage of cardiac output is used by the brain?
10-20-%
What percentage of oxygen is consumed by the brain?
20%
What percentage of liver glucose is used by the brain?
66%
Why is the brain so vulnerable?
Very vulnerable if blood supply is impaired because it is so metabolically active
What three arteries supply the brain?
Common carotid
Internal carotid
Vertebral artery
What is the path of the common carotid?
branches from brachiocephalic
runs up the side of the neck
divides at the laryngeal prominence
What does the external carotid supply?
Supplies the structure of the face
What is the pathway of the internal carotid artery?
Passes through base of skull into cranial cavity
What is the first branch of the subclavian artery?
Vertebral artery
What is the path of the vertebral artery?
Goes up in the neck
Posteriorly through transverse foramen of the cervical vertebrae
Passes through the base of skull via foramen magnum into cranial cavity
What arteries comprises the circle of willis?
Anterior communicating artery Anterior cerebral artery Internal carotid artery Middle cerebral artery Posterior communicating artery Posterior cerebral artery Basilar artery Vertebral artery
What are the main feeding arteries to the circle of willis?
Internal carotid
Vertebral artery
Anatomically, where can you find the Basilar artery?
Sits on the base of the pons
What is the benefit of the arrangement of the circle of willis?
If you have a blockage in one of the internal carotids e.g. atherosclerotic build up
Chance of compensatory flow from the other side
How does blood exit the cranial cavity?
Cerebral vains
Venous sinuses in the dura mater
Internal jugular vein
What is the path of blood flow in the venous sinuses?
Superior sagittal sinus
drains down the back of the head to the occipital lobe to form the confluence of sinuses
then drains laterally down the transverse sinus through the sigmoid sinus into the internal jugular vein
What is the fold of the dura between the two hemisphere called?
Falx cerebri
What is the fold of the dura between the hemispheres and the cerebellum called?
Falx cerebelli
How does blood drain from the brain itself?
Great cerebral vein (of Galen) drains into straight sinus and then on to the confluence
What are the layers of the brain?
Dura mater
(Inner meningeal layer and Outer periosteal layer)
Arachnoid mater
Pia mater
Is there any extradural space?
No space between the skull and the dura mater
What are the 4 types of haemorrhage?
Extradural
Subdural
Subarachnoid
Intracerebral
What are main features of extradural haemorrhage?
trauma, immediate clinical effects (arterial, high pressure)
Can strip dura away from the skull
What does a fracture to the pterion result in?
Main artery supplying the dura is behind the pterion
Rupture of this artery causes a extradural haemorrhage
What are main features of subdural haemorrhage?
trauma, can be delayed clinical effects (venous, lower pressure)
which is why patients are often kept overnight after a head injury
What are main features of subarachnoid haemorrhage?
Ruptured aneurysms (congenital) Weaknesses in the blood vessel walls that burst and cause subarachnoid bleeds
What are main features of subarachnoid haemorrhage?
Spontaneous hypertensive
What is a CVA?
Cerebrovascualr accident (stroke)
What is the definition of a CVA?
rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration
What are the two types of stroke?
Thrombo-embolic (85%)
Haemorrhagic (15%)
What is a TIA?
Transient ischaemic attack
What is the definition of a TIA?
rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
can last seconds/minutes
What is an infarct?
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 does thrombosis mean?
formation of a blood clot (thrombus) causing a blockage
What does embolism mean?
plugging of small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid
Why is stroke a huge public health issue?
3rd commonest cause of death
100,000 deaths in UK per annum
50% of survivors are permanently disabled
70% show an obvious neurological deficit
What are the risk factors for stroke?
Age Hypertension Cardiac disease Smoking Diabetes mellitus
What are the three main cerebral arteries?
Anterior
Middle
Posterior
Which cerebral artery has the biggest perfusion field?
Middle cerebral artery
It also supplies many of the subcortical, deep structures of the brain
What does the anterior cerebral artery supply?
Midline structures
Perfuses all the way back to the parietal-occipital fissure
What does the posterior cerebral artery supply?
Inferior part of the temporal lobe
Occipital lobe
What are the anterior cerebral artery symptoms?
Paralysis of contralateral structures (leg > arm, face)
Disturbance of intellect, executive function and judgement (abulia)
Loss of appropriate social behaviour
What are the middle cerebral artery symptoms?
Classic stroke”
Contralateral hemiplegia: arm > leg
Contralateral hemisensory deficits
Hemianopia (loss of one side of the visual field)
Aphasia (L sided lesion)
What are the posterior cerebral artery symptoms?
Visual deficits
homonymous hemianopia
visual agnosia
How would atherosclerosis look on a specimen?
yellow discolouration in the walls of the vessels is a build-up of atheroma, fatty deposits that cause atherosclerosis or “hardening of the arteries”
How does fresh blood present on a CT scan?
White lesions
How does blood that has become a haematoma present (after time has passed)?
Black lesions
