Flashcards in Blood Supply Deck (30)
What is an aneurysm?
dilation of vessel of wall
-common at branch points (ex: ACA, Acomm, Basilar)
-lead to subarachnoid hemorrhage
-mass effects on other things
What is a vascular territory?
region of tissue supplied by an artery
What are the 2 major arteries that supply brain? where?
Internal carotids As: antero-superior cerebrum, ant. diencephalon
Vertebral As: posteroinferior, brainstem, cerebellum, post. diencephalon
Where does the ICAs enter brain? What are its branches?
through carotid canals - over foramen lacerum
-SIPHON @ cavernous sinus
-PComms, ACAs, anterior choroidal As, MCAs
Where does the vertebral Arteries enter the brain? What are its branches
-from Subclavin As in transverse foramena > foramen magnum > merge => Basilar A on ventral pons
>Basilar : AICA, PCA, Superior Cerebellar As
>Anterior spinal artery
Name the vessels involved in Circle of Willis
2 Posterior Cerebral As
2 Posterior Communicating As
2 Anterior Cerebral As
1 Anterior Communicating A
2 Internal Carotid As
What are 2 common variations in Circle of Willis
1 large Acomm > most ACA comes from 1 ICA
or large Pcomm and small PCA > ICA supplies PCA territory instead of VAs
Terriotory of ACAs
medial surface, frontal pole
Territory of PCAs
inferior surface, occipital pole
Territory of MCAs
superior-lateral surface, temporal pole
What is a watershed area? What is the relevance?
-border zone of tissue receiving blood from 2 major vessels
-but at the end so loss of blood > perfusion deficit
-these areas are first to suffer
(30% perfussion loss > electrical activity fails
10% loss > neurons die)
What is the blood supply for spinal cord?
What are segmental medullary arteries?
-vessels connecting radicular As around cord to the ASAs and 2PSAs on cord
Aorta > intercostal A > Spinal Branches > Radicular As > ASAs and PSAs < Vertebral arteries
What are dura sinuses?
folds of dura - contain CSF and blood
Distinguish 3 types of Intracranial bleeds
-where? give ex.
1. extradural: aka epidural > lens shape lesion
ex: tearing meningeal A
ex: tearing cerebral vein as it cross bt subarachnoid space to venous sinus > opens the space bt arachnoid and dura matters
ex: cerebral A
-fast onset, immediate headache because of ICP
What are arteriovenous malformations?
direct a-v connections with no cap beds
-rupture > hemmorhage
What is embolism?
-occlusion of vessel from anything blocking blood flow
> infarction, ischemia
Thrombus = embolism from a clot
What is CSF? fnc?
-buoyancy - prevent compression, protect brain from impact, equalize pressure
-turned over 3x/day
-clear, colourless, low in protein, cells, IgG
-continuous with interstitial fluid
-ventricles lined with ependymal cells (have NO tight junctions)
-total volume = 140ml, most in subarachnoid space
How is the blood-brain barrier maintained?
2: blood-ISF barrier and blood-CSF barrier
-continuous capillaries with tight jncs bt endothelial cells: prevent leaking
-water, gases, lipid-soluble can diffuse through
-transporters required for others
What is hydrocephalus?
-increase CSF, enlarged ventricles, increase pressure
1. Noncommunicating (Obstruction) > enlarged lateral/3rd ventricles
ex: narrowing of aqueduct
2. Communicating (impaired absorption) > all ventricle enlarged
-caused by agenesis of arachnoid granulations, blockage
(usually cause 2)
What happens with blood-brain barrier breaks down?
What are possible causes?
-leaky > vasogenic edema - increase ICP
-mass effect > midline shift
-on MRI, see gadolinium outside of blood vessel
ex cause: tumour, inflammation
Describe CSF production.
Choroid plexus in lateral, 3rd, 4th ventricles
-invagination of vessels through ependymal cells into ventricles > villi
-have FENESTRATED capillaries
-tight junctions bt ependymal cells
How is CSF reabsorbed?
1. via arachnoid granulations in dura sinuses > venous space
2. into lymphatics
What is monro-kellie doctrine?
1. skull is closed compartment: brain, blood, CSF
2. intracranial space is fixed
3. changes to contents > change intracranial pressure nd redistribute contents
What is the ICP?
intracranil pressure = 5-7mmhg/9-12 mmhg
-formed by CSF movement from ventricle to subrachnoid space
-INCREASE > dysfnc > organ failure (sleepiness, confusion, LOC, coma, death)
How much blood goes to the brain?
15% of CO
if blood flow decrease> ischemia > neuronal cell death
Normal cerebral blood flow = 50-55ml.min.100g brain
Cell death @ 8-10ml/min/100g
What are causes of intracranial htn?
-CSF obstruction (hydrocephalus): aqueduct stenosis; subarachnoid hemorrhage
-increase content: tumour, hemorrhage
-brain edema: trauma, encephalopathy
-small changes autoregulated (vi moving CSF from intracranial space)
How can we lower ICP?
1. decrease CSF
2. decrease CBV: normalize pCO2 and PO2, maximize venous flow
3. relieve mass effect
Where are cerebral veins located? What do they cross to empty to dura sinus?
Subarachnoid space. Cross subdural space to go to sinus (invagination of dura)
Why is the confluence of sinus not a true confluence?
Where does straight and superior sinus empty?
It doesn't all meet at confluence.
Straight > left transverse
Superior sagital> rt transverse