Vertebrobasilar System

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Vertebrobasilar System

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TERMINOLOGY

Abbreviations

• Vertebrobasilar (VB), vertebral artery (VA), basilar artery (BA)
• Superior cerebellar arteries (SCAs), posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA)
• Internal carotid artery (ICA)
• Anterior spinal artery (ASA), posterior spinal artery (PSA)

GROSS ANATOMY

Overview

• 4 VA segments

Extraosseous (V1) segment (arch → C6)

Foraminal (V2) segment (C6 → C1)

Extraspinal (V3) segment (C1 → foramen magnum)

Intradural (V4) segment (intracranial)

IMAGING ANATOMY

Overview

• Ectasia, tortuosity, off-midline course, variations in configuration/branching patterns common

Anatomy Relationships

• VA

V1 : Arises from subclavian artery and courses posterosuperiorly to enter C6 transverse foramen

V2

– Ascends through C6-C3 transverse foramina

– Turns superolaterally through inverted L-shaped transverse foramen of axis (C2)

– Courses short distance superiorly through C1 transverse foramen

V3

– Exits top of atlas (C1) transverse foramen

– Lies on top of C1 ring, curving posteromedially around atlantooccipital joint

– As it passes around back of atlantooccipital joint, turns sharply anterosuperiorly to pierce dura at foramen magnum

V4

– After VA enters skull through foramen magnum, courses superomedially behind clivus

– Unites with contralateral VA at/near pontomedullary junction to form BA
• BA

Courses superiorly in prepontine cistern (in front of pons, behind clivus)

Bifurcates into its terminal branches, posterior cerebral arteries (PCAs), in interpeduncular or suprasellar cistern at/slightly above dorsum sellae

Branches

• VA

V1

– Segmental cervical muscular, spinal branches

V2

– Anterior meningeal artery, unnamed muscular/spinal branches

V3

– Posterior meningeal artery

V4

– ASA, PSA

– Perforating branches to medulla

– PICA : Arises from distal VA, curves around/over tonsil, gives off perforating medullary, choroid, tonsillar, cerebellar branches
• BA

Pontine, midbrain perforating branches (numerous)

AICA

– Lies ventromedial to CNVII and CNVIII

– Often loops into internal auditory meatus

SCAs

– Arise from distal BA and course posterolaterally around midbrain below CNIII, tentorium

– Lie above CNV and often contact it

PCAs (terminal BA branches)

Vascular Territory

• VA

ASA: Upper cervical spinal cord, inferior medulla

PSA: Dorsal spinal cord to conus medullaris

Penetrating branches: Olives, inferior cerebellar peduncle, part of medulla

PICA: Lateral medulla, choroid plexus of 4th ventricle, tonsil, inferior vermis/cerebellum

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Tags: Imaging Anatomy Brain and Spine

Mar 13, 2021 | Posted by admin in NUCLEAR MEDICINE | Comments Off

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