Neuro - Cerebral Vasculature Flashcards
Body weight of brain
2%
Cardiac output of brain
10-20%
Liver glucose of brain
66%
Oxygen consumption of brain
20%
Two main arteries suppling brain
Vertebral arteries and internal carotid arteries
Path of vertebral arteries
Travel up the neck via the transverse cervical process (protected) and enter via the foramen magnum
Path of internal carotid
Common carotid emerges from the brachiocephalic/arch of aorta and bifurcates at the level of the laryngeal prominence. The internal carotid then travels via the carotid canal into the cerebral cavity.
Advantage of circle of willis anastomotic circuit?
If the carotid artery is obstructed - there may be compensation from the posterior supply
What is the problem with the circuit from circle of willis?
There is weak compensation due to the posterior communicating artery connecting the anterior and posterior supplies
What is the main branch of the internal carotid?
Middle cerebral artery
Describe how blood is drained in the brain
From cerebral veins, into venous sinuses and then into the internal jugular vein back to the SVC
What are sinuses
Vessesl carrying venous blood from the brain to the internal jugular vein, formed between the meningeal and the periosteal layers of dura mater
What is the fold of dura separating the two hemishperes
Falx cerebri
What is the fold of dura separating the cerebellum hemishperes
Falx cerebelli
What dural layer separates cerebellum from cerebrum
Tentorium cerebelli
Pathway of sigmoid sinus
Travels out the cranial cavity through the jugular foramen and is continuous with the internal jugular vein
What are the 4 types of intracranial haemorrhage
Extradural
Subdural
Subarachnoid
Intracerebral
Onset of extradural haemorrhage
Rapid onset due to high arterial pressure
What commonly causes extradural haemorrhage
Often trauma related
if the pterion is hit, what artery is at risk of haemorrhage?
Middle meningeal artery - main supply to the meninges
How do we treat an extradural haemorrhage?
Urgen burr hole surgery or craniotomy
What does extradural haemorrhage look like on CT
Lemon shaped - blood is limited by the sutures of the skull
What is the onset of a subdural haemorrhage?
Slow onset
Why is a subdural haematoma slow onset
Due to space between the dura and the arachnoid layer, and also because of the low venous pressure
What does subdural haematoma look like on CT
Banana shaped - blood not limited by the sutures of the skull
When does a sub arachnoid haemorrhage occur?
When aneurysms rupture
Where does blood fill with a sub arachnoid haemorrhage
Subarachnoid space
What location in the brain is most commonly affected by sub arachnoid haemorrhage
Circle of Willis
What is an aneurysm
Weakness in the blood vessel wall - often congenital and benign. In patients with hypertension, aneurysm may rupture and blood can fill SAS
Where does blood fill in an intracerebral haemorrhage
In the substance of the brain itself
What patients are more prone to an intracerebral haemorrhage
Patients with hypertension
What is the onset of a intracerebral haemorrhage
Spontaneous
Why is an extradural haemorrhage a surgical emergecny
Blood pressure can build up rapidly and can cause function deficit to shut down cardiorespiratory system, thus resulting in death.
What is another name for a stroke?
Cerebrovascular accident
CVA definition
Rapid developing focal disturbance of brain function with presumed vascular origin and lasting longer than 24 hours
What does a rapid onset mean in clinical presentation?
Often means that the cause is vascular, but we should rule out other causes first
What is the most common type of stroke?
Thrombo embolic stroke (85%)
What is the other type of stroke?
Haemorrhagic stroke (15%)
What is a TIA?
Rapid developing focal disturbance of brain function often presumed vascular in origin, but resolves completely within 24 hours
What can a TIA be a sign of?
An oncoming stroke
What is infarction?
Degenerative changes that occur when a tissue loses blood supply (death)
What is cerebral ischaemia?
Lack of sufficient blood supply to nervous tissue resulting in permanent brain damage if blood flow is not quickly restored
What is the difference between anoxia and ischaemia?
Anoxia is a loss of oxygen, however ischaemia involves not only a loss of oxygen but a loss of glucose and everything else in the blood
What is thrombosis?
Formation of a blood clot (thrombus). Can be from stasis or material from other parts e.g. from the heart, ending up in the brain.
What is an embolism?
When a small vessel is obstructed by material carried from a large vessel e.g. a thrombus from the internal carotid ending up in the brain
Iatrogenic example of an embolism
Air from an IV injection
Epidemiology of strokes
3rd most common cause of death
100,000 deaths in Uk/year
50% of survivors left permanently disabled
70% show obvious neurological deficit
Signs of stroke?
Face fallen on one side
Can’t raise both arms and keep them there
Slurred speech
Risk factors for stroke? (5)
Age Hypertension Diabetes mellitus Cardiac disease Smoking
DCASH
Which cerebral artery has the biggest perfusion field
MCA
What does the MCA supply
Deep structures in the brain e.g. deep motor structures.
Outer brain surface
Anterior temporal lobe
What does the ACA supply
Mid line structures all the way to the parietal occipital fissure.
Structures at the top of the brain
What does the PCA supply
Occipital lobe and inferior temporal lobe
What artery presents with a classic stroke
MCA
What does an ACA result in (3)
Contralateral paralysis
Abulia
Inappropriate social behaviour
What limb is affected with ACA stroke
Legs
What does MCA stroke present with
Maybe complete contralateral hemiplegia
Contralteral hemisensory deficit
Hemianopia
Aphasia (if left sided lesion)
Why may MCA stroke cause complete hemiplegia
MCA supplies deep motor structures
What does a PCA stroke present with
homonymous hemianopia
visual agnosia
What is abulia?
Lack of judgement, intellect and executive function
