POSTERIOR CIRCULATION

Dr D Sudeepta RaoPG-General MedicineDCMS

Vertebrobasilar System

Vertebral arteries

Basilar artery

Posterior cerebral arteries

VERTEBROBASILAR SYSTEM

Blood Supply

Upper spinal cordBrain stemCerebellumOccipital lobePart of Temporal lobeThalamusHypothalamus

Vertebral artery(VA)Subclavian arteryAscend in foramina transversaria Upper six cervical vertebraEnter cranial cavity thro foramen

magnumAnterolateral aspect of medullaDivided into 4 parts: V 1 to V 4

DIVISIONS:

• Subclavian occluded proximal to origin of vertebral.

• Leads of reversal in the direction of blood flow in the ipsilateral vertebral artery.

• Exercise of ipsilateral arm may increase demand on vertebral flow, leading to posterior circulation TIAs.

“SUBCLAVIAN STEAL”

Branches of VAAnterior spinal artery

◦Join at mid medullary level◦Descend on ventral midline of spinal

cord◦Supply triangular area of medulla

oblongata

Branches of VA(contd…)Posterior inferior cerebellar

artery◦Largest branch◦Ascends behind the roots of the ix &

x cr. Nerves◦Turns laterally into cerebellar

vallecula◦Medial and lateral branches◦Supply medulla oblongata dorsal to

olivary nucleus & lateral to xii nucleus

Branches of VA(contd…)Posterior spinal artery

Arises from picaMinute medullary branches

Branches of VA:

BRANCHES OF VA

Blood supply of Medulla

Basilar artery(BA)Arise at Lower border of ponsExtend upto upper border of ponsLarge median vessel formed by

union of vertebral arteriesTerminates by dividing into 2

posterior cerebral arteries at the interpeduncular fossa

Branches of Basilar arteryPontine branchesAnterior inferior cerebellar artery

◦Lower part of BA◦Labyrinthine artery◦Supplies inferior cerebellar surface

anterolaterally◦Anastomose with PICA◦Few branches to inferolateral pons

Superior cerebellar artery

Branches of Basilar artery(contd..)Superior cerebellar artery

◦Distal portion of BA◦Oculomotor nerve separates it from

posterior cerebral artery◦Trochlear nerve laterally

Branches of Basilar artery

Branches of Basilar artery

Branches of Basilar artery

Posterior Cerebral Artery(PCA)Terminal branch of basilar arterySurgical nomenclature identifies

3 segments:◦P1 basilar bifurcation to post

communicating a◦P2 portion in perimesencephalic

cistern◦P3 portion in the calcarine fissure

Supplies temporal and occipital lobes◦Has cortical and perforate/central

branches

PCA: Cortical Branches

Temporal branches usually two supply◦Uncus◦Parahippocampus◦Medial and lateral occipetotemporal

gyriOccipital branches supply

◦Cuneus◦Lingual gyrus◦Posterolateral surface of the

occipetal lobe

Posterior Cerebral ArterySupplies visual areas of the

cerebral cortex

Concept of Macular sparring

Posterior Cerebral Artery

PCA: Central branchesSupply subcortical structuresPosteromedial central

branches(thalamo perforate)◦Ant thalamus, subthalamus, latral wall of

third ventricle and globus pallidusPosterolateral central

branches(thalamo geniculate)◦Supply peduncle posterior thalamus,

MGB, superior &inferior colliculiPosterior choroidal branch

◦LGB & ends in the lateral ventricle

PCA: Central branches

Thalamus blood supply

PCA: Cortical Branches

Blood supply of the spinal cordAnterior spinal artery in anterior

median fissureTwo Posterior spinal arteries in

the posterolateral sulcusArterial vasocorona an arterial

plexus in the pia mater

Blood supply of the spinal cord

Main source of bloodMain source of blood to spinal

arteriesVertebral arteries upto cervical

segmentsRadicular ateries that reach the

cord along spinal nerve roots

Main source of blood

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