Blood Supply to the Central Nervous System Flashcards
What percentage of cardiac output goes to the brain?
10-20%
What percentage of liver glucose does the brain use?
66%
State the 2 main sources of blood supply to the brain?
Vertebral arteries (posteriorly) Internal carotid arteries (anteriorly)
State the major artery that the vertebral arteries branch off and describe the path of the vertebral arteries to the brain.
Subclavian artery
VA’s pass through the transverse foramina of the cervical vertebrae + through the foramen magnum into the brain
Describe the circle of Willis (posterior to anterior)
2 vertebral arteries form Basilar artery (just infront of pons)
Basilar splits to produce 2 posterior cerebral arteries
Each has a branch (posterior communicating artery) to the middle cerebral artery
Branching off the MCA are the anterior cerebral arteries (which are joined by the anterior communicating artery)
State the names of the venous sinuses that are at the top and bottom of the falx cerebri.
Superior sagittal sinus
Inferior sagittal sinus
What is the name given to the place where all the sinuses meet?
Confluence of sinuses
What connects the inferior sagittal sinus to the confluence of sinuses?
Straight sinus
What vessel does the inferior sagittal sinus join with to form the straight sinus?
Great cerebral vein
Which sinus ascends to join the confluence of sinuses?
Occipital sinus
Which 2 sinuses run along the temporal bone?
Superior petrosal sinus
Inferior petrosal sinus
Which main sinus drains into the internal jugular vein through the jugular foramen?
Sigmoid sinus
Which sinus connects the confluence of sinuses to the sigmoid and superior petrosal sinuses?
Transverse sinus
Which sinus runs along the sphenoid and parietal bones?
Sphenoparietal sinus
Which sinuses run on either side of the pituitary stalk?
Anterior + posterior intercavernous sinuses
Which extension of dura mater separates the cerebellum from the inferior portion of the occipital lobe?
Tentorium cerebelli
Define Stroke.
A rapidly developing focal disturbance of brain function of presumed vascular origin that lasts > 24 hours
Define Transient Ischaemic Attack (TIA).
A rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
What percentage of strokes are caused by infarction and what percentage are caused by haemorrhage?
85% infarction
15% haemorrhage
State 2 causes of occlusions.
Thrombus (formation of a blood clot)
Embolus (plugging of a small vessel by material carried from a larger vessel)
Describe the perfusion fields of the brain.
ACA: medial part of both hemispheres
MCA: extends laterally, emerges through the lateral fissure between the frontal and temporal lobes – supplies the front 2/3 of the lateral part of the hemisphere
PCA: occipital lobe + inferior part of temporal lobe
Describe the features of a disturbance in the anterior cerebral artery.
Paralysis of contralateral leg > arm, face
Disturbance of intellect, executive function + judgement
Loss of appropriate social behaviour
Describe the features of a disturbance in the middle cerebral artery.
"CLASSIC STROKE" Contralateral hemiplegia: arm > leg Contralateral hemisensory deficits Hemianopia Aphasia- left-sided lesion as language centres are more on the left than the right
Describe the features of a disturbance in the posterior cerebral artery.
Visual deficits: Homonymous hemianopia (loss of visual field on same side of both eyes) Agnosia (unable to recognise what you are seeing)
Which parts of the brain are involved in speech and understanding language?
Broca’s area: speech
Wernicke’s area: understanding language
What are lacunar infarcts?
Small cavities that appear in the brain due to small vessel occlusion
Clinical deficit is dependent on location of the small vessel occlusion
Associated with Hypertension
State the 4 types of haemorrhagic stroke and their likely causes.
Extradural: rapid onset, caused by trauma
Subdural: slow onset, caused by trauma
Subarachnoid: ruptured aneurysms
Intracerebral: spontaneous hypertensive rupture of small vessels
What is the difference between the dura in the vertebral column compared to the brain?
Dura in the vertebral column has 1 layer
Dura in the skull has 2 layers
What are the 2 layers of dura in the skull called?
Periosteal and Meningeal
What is the name given to the fold of dura that extends between the medial surfaces of the two hemispheres?
Falx Cerebri
Why are extradural haemorrhages more rapid onset than subdural haemorrhages?
They are caused by rupture of a meningeal ARTERY (blood strips dura away from skull, increasing pressure) whereas subdural haemorrhages are caused by rupture of veins in the skull
Define infarction
Degenerative changes which occur in tissue following occlusion of an artery
Define cerebral ischaemia
Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly
List 5 main risk factors for stroke
Age Hypertension Cardiac disease Smoking Diabetes mellitus
