Blood Supply to the Brain and the Clinical Relevance Flashcards
how long duration of anoxia to the brain causes unconsciousness
20 seconds
how long duration of anoxia causes permanent unconsciousness and neurone death
5 mins
normotensive cerebral bloodflow
~50ml/100g brain per min
how does CO2 and O2 content in blood affect bloodflow to brain
incr CO2 or decr O2 increases bloodflow
what does autoregulation of cerebral bloodflow ensure
enough bloodflow to brain over wide range of BP and sO2
what mean arterial pressures can sufficient cerebral bloodflow be regulated over
60-160 mmHg
why is venous return from the brain more reliant on gravity than other bodyparts
no valves, muscles, or elasticity to help return
2 arteries supplying total cerebral bloodflow
carotid arteries
vertebral arteries
are the anterior and posterior communicating arteries usually open or closed
closed
does each vertebral artery supply 1 or 2 hemispheres
1 unless artery blockage opens communicating arteries
which cerebral artery has the largest territory
middle cerebral artery
3 arteries supplying the cerebral cortex
posterior cerebral artery
middle cerebral artery
anterior cerebral artery
what creates watershed regions in brain bloodsupply
anastomoses between arteries
posterior cerebral circulation main 3 branches
vertebral arteries
basilar artery
posterior cerebral artery
what does PICA branch from and supply
branches from vertebral artery
supplies dorsal medulla of brainstem
what does the basilar artery supply
pons
cerebellum
what does the posterior cerebral artery supply
inferior ad medial aspects of temporal and occipital cortex
thalamus
posterior internal capsule
midbrain
arteries supplying the midbrain
posterior cerebral artery
superior cerebellar artery
posterior communicating artery
interpeduncular rami of posterior cerebral artery
arteries supplying the pons
basilar artery - long circumferential, short circumferential, and paramedian branches
arteries supplying the medulla
posterior inferior cerebellar artery
anterior inferior cerebellar artery
anterior spinal artery
which veins cross the subarachnoid space
superficial cerebral veins (become bridging veins)
which veins pierce the dura and enter the dural venous sinuses
bridging veins
which way do arachnoid granulations allow CSF to flow between dural sinuses and the subarachnoid space
into sinuses
prevent blood backflow into subarachnoid space
which dural sinus controls 80% of venous return from the brain
superior sagittal sinus
which 3 sinuses converge and the confluence of sinuses
superior sagittal sinus, straight sinus, and occipital sinus
dural venous sinuses
superior sagittal sinus
inferior sagittal sinus
straight sinus
signmoid sinus
occipital sinus
transverse sinus
comfluence of sinuses
is right or left dominance more common in cerebral venous drainage
right
what can cause spontaneous cerebral haemorrhage
arterio venous malformation
aneurism
causes of haemorrhagic stroke
hypertension
aneurism
elderly
trauma
alcoholism
arteriovenous malformation
how does age and alcoholism increase haemorrhagic stroke risk
brain atrophy and neurone loss -> bridging veins sink -> higher tension on bridging veins -> increased risk of breakage
effect of MCA stroke in left hemisphere
global aphasia
sensorimotor loss on contralateral face, upper limb, and trunk
effect of MCA stroke in right hemisphere
neglect syndrome
neglect syndrome
contralateral hemispatial neglect - ignore 1/2 of everything
why does neglect syndrome generally improve over time
other parts of brain take over from damaged part
effects of ACA stoke
contralateral sensorimotor loss below waist
urinary incontinence
personality defects - unemotional then impulsive
split brain syndrome
why does ACA stroke cause split brain syndrome
ACA supplies corpus callosum
TIA
transient episode of neurological dysfunction caused by focal brain, spinal cord, or retina ischaemia without acute infarction
what is a TIA a warning sign of
heart attack
stroke
anterior circulation TIA symptoms
motor weakness
hemi sensory loss
dysarthria
transient monocular blindness - blocked opthalmic artery
posterior circulation TIA symtoms
vertigo
diplopia
ataxia
amnesia
do TIA symptoms always return to normal within 24 hours
no - multiple TIAs could cumulate in permanent damage
where does blood collect in an epidural, subdural, and subarachnoid haematoma
epidural - between skull and dura mater
subdural - between dura mater and arachnoid mater
subarachnoid - between arachnoid mater and pia mater
where is extra axial bleeding
outside brain tissue - epidural, subdural, and subarachnoid
which type of extra axial bleed is most common
subarachnoid
rupture of which veins causes subdural haematoma
bridging veins
causes of extra axial bleeds
trauma
aging
ruptured aneurysm
ruptured arteriovenous malformation
how may a traumatic epi/extradural haematoma present
lucid period immediately after trauma then unconsciousness
which blood vessels commonly cause epi/extradural haematoma
middle meningeal artery
anterior ethmoidal artery
large venous sinuses
do epi/extradural haematomas cross suture lines
no - dura more tightly attached at sutures
epi/extradural haematoma symptoms
contralateral weakness of extremities
contralateral visual field loss
CN3 compression
how do epi/extradural haematomas cause symptoms
blood collection compresses intracranial structures
3 types of subdural haematoma
acute
subacute
chronic
what source of subdural haematoma has the slowest onset
venous bleeds - can take days to weeks
subdural haematoma symptoms
irritability
seizures
headache
numbness
disorientation
do subdural haematomas cross suture lines
yes
subarachnoid haemorrhage symtoms
thunderclap headache
vomiting
confusion
lowered/fluctuating consciousness
extra/epidural, subdural, and subarachnoid haematoma appearance on CT
extra/epidural - biconvex hyperdense
subdural - crescent hyperdense
subarachnoid - white diffuse signal over sulci
which type of extraaxial bleed can cause blood or bilirubin to be present in lumbar puncture
subarachnoid
xanthochromia
presence of bilirubin in the cerebrospinal fluid
2 types of cerebral aneurysm
saccular
fusiform
what type of extra axial bleed is caused by aneurysm rupture
subarachnoid
where do brain aneurysms tend to form
junction points
is a berry aneurysm a type of saccular or fusiform anaurysm
saccular
how can a saccular aneurysm be prevented from rupturing
stent vessel
clip aneurysm
fill with coil
risks from brain arteriovenous malformations
damage to surrounding tissue
leakage
weak spots in vascular system
how can arteriovenous malformations be treated
radiotherapy
surgical resection
embolisation
