Anatomy Brain and It’s Blood Supply:
Brain:
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Telencephalon (cerebrum) becomes cerebral hemisphers (gyri and sulci) separated by
longitudinal fissure
Diencephalon = thalamus and hypothalamus (most rostral part of brain stem)
Mesencephalon (midbrain) = first part of brainstem seen, jxn between middle and posterior
cranial fossa
Metencephalon becomes cerebellum and pons (against clivus and dorsum sellae)
Myelencephalon (medulla oblongata) = causal most part of brainstem, ends at foramen
magnum (CN VI and XII attached)
Blood Supply:
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Vertebral and internal carotid arteries connect at cerebral arterial circle (of Willis)
o Internal carotids enter via carotid canals
 Branches = ophthalmic artery, posterior communicating artery (PComms),
middle cerebral artery (MCA) and anterior cerebral artery (ACA)
o Verterbral arteries from subclavian artery passing though transvers foramina of upper 6
cervical vertebrae
 Give off small meningeal branch on entering foramen magnum
 Gives off anterior spinal artery (descends in anterior median fissure) and
posterior spinal artery (descends on posterior SC) and posterior inferior
cerebellar artery before becoming basilar artery
 PSA commonly directly from PICA
Basilar artery passes anterior to bones
o Branches = AICA, pontine arteries, superior cerebellar arteries (SCA) and bifurcates as
posterior cerebral arteries (PCA)
Circle of Willis:
o Anterior communicating artery connects L and R ACAs
o PComms connect internal carotid and PCA
Stroke:
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Acute development of focal neurological deficit (hypoperfusion)
Causes: cerebral thrombosis or hemorrhage, subarachnoid hemorrhage, and cerebral embolus
from atherosclerotic plaque at bifurcation of common carotid (most common)
o Stenosis from plaque causes eddy currents making emboli
Transient ischemic attacks (TIAs) -> recovery complete within 24 hours
Intervention: lifestyle change, hypertension control, platelet aggregation inhibitor (aspirin)
Intracerebral aneurysms:
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Typically in ACA, PCA, branches of MCA, distal end of basilar artery, and PICA
Rupture = “thunderclap” headache with neck stiffness and vomiting
o Blood within subarachnoid space
o Treatment -> catheterization via femoral artery packs microcoils in aneurysm sealing it
Venous drainage:
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Dural venous sinuses between outer periosteal and inner meningeal layers of dura -> internal
jugular vein
o Diploic veins (in bones of skull) and emissary veins (outer cranium to inside) also empty
in dural venous sinus
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Emissary veins allow infection to enter cranial cavity (no valves)
Dural sinus
Location
Receives
Superior sagittal
Superior border of falx cerebri
Superior cerebral, diploic, and emissary veins and CSF
Inferior sagittal
Inferior margin of falx cerebri
A few cerebral veins and veins from the falx cerebri
Straight
Junction of falx cerebri and tentorium
cerebelli
Inferior sagittal sinus, great cerebral vein, posterior cerebral veins,
superior cerebellar veins, and veins from the falx cerebri
Occipital
Confluence of sinuses
In falx cerebelli against occipital bone
Communicates inferiorly with vertebral plexus of veins
Dilated space at the internal occipital
Superior sagittal, straight, and occipital sinuses
protuberance
Horizontal extensions from the
Drainage from confluence of sinuses (right-transverse and usually superior sagittal sinuses;
confluence of sinuses along the posterior left-transverse and usually straight sinuses); also superior petrosal sinus, and inferior cerebral,
and lateral attachments of the tentorium cerebellar, diploic, and emissary veins
cerebelli
Transverse (right and left)
Sigmoid (right and left)
Continuation of transverse sinuses to
internal jugular vein; groove of parietal,
temporal, and occipital bones
Transverse sinuses, and cerebral, cerebellar, diploic, and emissary veins
Cavernous (paired)
Lateral aspect of body of sphenoid
Cerebral and ophthalmic veins, sphenoparietal sinuses, and emissary veins from
pterygoid plexus of veins
Intercavernous
Crossing sella turcica
Interconnect cavernous sinuses
Sphenoparietal (paired)
Inferior surface of lesser wings of
sphenoid
Diploic and meningeal veins
Superior petrosal (paired)
Superior margin of petrous part of
temporal bone
Cavernous sinus, and cerebral and cerebellar veins
Inferior petrosal (paired)
Groove between petrous part of
Cavernous sinus, cerebellar veins, and veins from the internal ear and brainstem
temporal bone and occipital bone ending
in internal jugular vein
Basilar
Clivus, just posterior to sella turcica of
sphenoid
Connect bilateral inferior petrosal sinuses and communicate with vertebral plexus of veins
Cavernous Sinuses:
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Against lateral aspect of sphenoid bone on either side of sella turcica
o Gets blood form cerebral veins, ophthlamic veins, and emissary veins (pterygoid plexus)
providing path for infections
Intercavernous sinuses connect R and L cavernous sinus
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Sphenoparietal sinuses drain into anterior end of each cavernous sinus (lesser wing of sphenoid
with blood from diploic and meningeal veins)
Superior and Inferior petrosal sinuses:
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Drain cavernous sinuse into transverse sinus with blood from cerebral and cerebellar veins
Inferior petrosal sinuses pass between temporal and occipital bone ending in internal jugular
(get blood from internal ear and brainstem)
Basilar sinuses connect inferior petrosal sinuses and vertebral plexus (on clivus)
Head injury:
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Always suspect in patients with multiple injuries (50% die from it)
2 processes: 1) primary axonal and cellular damage, intracerebral hemorrhage and penetrating
injuries, 2) secondary injuries of scalp laceration, fracture, disruption of arteries and veins,
intracerebral edema and infection
Intracranial hemorrhage:
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Primary brain hemorrhage: aneurysm rupture, hypertension, and bleeding after infarction
Extradural hemorrhage: arterial damge and tearing of middle meningeal artery (at pterion)
o Blow to head with minor unconsciousness (lucid interval), semilunar image on MRI
Subdural hematoma: between dura and arachnoid, venous bleeding (torn veins entering
superior sagittal sinus)
o Young and elderly (from cerebral atrophy), cresent shape on MRI
Subarachnoid hemorrhage: ruptured aneurysm
Clinical assessment:
o Document circumstances of injury (for legal purposes), determine severity, CNS and PNS
system exam,
o Glasgow coma scale = evaluates level of consciousness; score of 15 paints (15/15 = alert
and oriented, 3/15 = fully coma)
 Motor response 6 point, verbal response 5 points, Eye movement 4 points
Treatment:
o Swellling compresses blood supply (↑ BP), may squeeze brain through foramen
magnum (coning) or herniate beneath falx cerebri (falcine herniation)
 Hyperventilation and IV corticosteroids decrease swelling