2.4 Cerebral Vasculature Flashcards
What % of cardiac output does the brain require?
10-20%
What % of body O2 consumption does the brain require?
20%
Why is the brain so vasularised?
high metabolic demands
What % of liver glucose does the brain require?
66%
Where does the basilar artery sit?
the base of the pons
How does venous blood drain from the brain?
cerebral veins
venous sinuses into the dura mater
internal jugular vein
heart
How would blood drain from the superior sagittal sinus?
into the confluence of sinuses into the transverse sinus into the sigmoid sinus through the jugular foramen then becomes the internal jugular vein
Where are the venous sinuses?
lie in-between the two layers of the dura mater
outer periosteal layer of dura mater
inner meningeal layer of dura mater
Is there space in between the dura and the skull?
no
What are the 3 layers of the meninges?
skull dura (split into two layers) arachnoid pia brain
What are the 4 types of haemorrhage?
extradural
subdural
subarachnoid
intracerebral
Where is the most likely place of an extradural haemorrhage?
the pterion
where the frontal, parietal, temporal, and sphenoid bones join
What is an extradural haemorrhage?
arterial bleed (bleeding from arterial supply to dura) high pressure so forces blood inbetween dura and skull leads to very high intercranial pressure --> immediate clinical effects
What is an extra-dural haemorrhage caused by?
trauma
What is an subdural haemorrhage caused by?
trauma
What is an subarachnoid haemorrhage caused by?
ruptured aneurysms
aneurysms often congenital
What is an intracerebral haemorrhage caused by?
spontaneous hypertensive
often those with chronic hypertension
Where is a subdural haemorrhage?
bleeding in between the dura and arachnoid
What is the presentation of a subdural haemorrhage?
loss of consciousness then wake up
delayed onset symptoms slowly getting worse
venous, lower pressure
What is a stroke?
Cerebrovascular accident (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%) (blockages)
haemorrhage (15%)
What is a transient- ischaemic attach (TIA)?
rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
(>24 hr = stroke, <24 = TIA)
What is an infarction?
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
Why should you investigate a TIA?
warning sign for stroke further down the line
What is 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 athesclerotic debris from the internal carotid, air
Why is stroke a major public health issue?
50% survivors permanently disabled
70% show obvious neurological deficit
3rd commonest death
FAST (face, arms, speech, time)
What are the risk factors for stroke? (5)
age
hypertension
cardiac disease (leads to forming of clots)
smoking
diabetes mellitus
–> many are risk factors due to effects on vasculature
What are the 3 main cerebral arteries?
anterior cerebral artery
middle cerebral artery
posterior cerebral artery
Which artery has the biggest perfusion field?
middle cerebral artery
What is the perfusion field of the anterior cerebral artery?
midline structures all the way until the parietal occipital fissure
What is the perfusion field of the middle cerebral artery?
temporal fossa area (covering part of the temporal, parietal and frontal) part of brain
What is the perfusion field of the posterior cerebral artery?
occipital lobe and inferior part of temporal lobe
What are the symptoms of a stroke of the anterior cerebral artery?
paralysis of contralateral (opposite structure) (leg> more than arm, face) (motor cortex)
disturbances of intellect, executive function and judgement = abulia (frontal lobe)
loss of appropriate social behavior (frontal lobe)
What are the symptoms of a stroke of the middle cerebral artery?
classic stroke
paralysis of contralateral structures (hemiplegia): usually arm not leg, could be whole side of body as deep motor structures
contralateral hemisensory defects (sensory cortex)
hemianopia loss of one half of visual field.
aphasia if left sided lesion
What are the symptoms of a stroke of the posterior cerebral artery?
Mostly visual field defects homonymous hemianopia (cannot see left half of field in both eyes for example) visual agnosia (cannot visually process)
