Vertebral Arteries

Overview

• Vertebral artery (VA): 4 segments

  • V1 segment (extraosseous segment)

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      Arises from 1st part of subclavian artery

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      Courses posterosuperiorly to enter C6 transverse foramen

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      Branches: Segmental cervical muscular, spinal branches

  • V2 segment (foraminal segment)

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      Ascends through C6-C3 transverse foramina

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

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      Courses short distance superiorly through C1 transverse foramen

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      Branches: Anterior meningeal artery, unnamed muscular/spinal branches

  • V3 segment (extraspinal segment)

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      Exits top of atlas (C1) transverse foramen

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

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

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      Branches: Posterior meningeal artery

  • V4 segment (intradural/intracranial segment)

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

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      Unites with contralateral VA at or near pontomedullary junction to form basilar artery (BA)

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      Branches: Anterior, posterior spinal arteries (ASA, PSA), perforating branches to medulla, posterior inferior cerebellar artery (PICA)

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      Arises from distal VA, curves around/over tonsil, gives off perforating medullary, choroid, tonsillar, cerebellar branches

• 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 or slightly above dorsum sellae

  • Branches: Pontine, midbrain perforating branches (numerous), anterior ICA (AICA), superior cerebellar arteries (SCAs), PCAs (terminal branches)