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Posterior intercostal arteries

The posterior intercostal arteries are paired segmental arteries that supply the intercostal spaces, thoracic wall, spinal cord, vertebrae, and overlying muscles/skin. There are typically eleven pairs on each side: the first two pairs arise from the highest intercostal artery (branch of the costocervical trunk), while the remaining nine pairs (3rd–11th) originate directly from the thoracic aorta.

Each artery runs laterally within its intercostal space, lying between the internal intercostal and innermost intercostal muscles, accompanied by the intercostal vein and nerve (neurovascular bundle: vein superior, artery middle, nerve inferior). The arteries provide collateral branches and anastomose with the anterior intercostal arteries (from the internal thoracic artery), ensuring robust blood supply to the thoracic cage.

Clinically, the posterior intercostal arteries are important in collateral circulation during aortic coarctation, and they may serve as feeding vessels in thoracic tumors, trauma, or hemothorax.

Synonyms

  • Intercostales posteriores

  • Aortic intercostal arteries

  • Thoracic segmental arteries

Function

  • Supply thoracic wall muscles (intercostals, serratus posterior, subcostals)

  • Supply parietal pleura and overlying skin

  • Contribute spinal branches to the vertebrae, meninges, and spinal cord

  • Provide collateral circulation with anterior intercostal arteries and other thoracic vessels

Branches

  • Dorsal branch: supplies spinal cord, vertebrae, meninges, and back muscles

  • Collateral branch: runs parallel to main artery in intercostal space

  • Lateral cutaneous branch: pierces muscles to supply skin of thorax and upper abdomen

  • Muscular branches: to intercostal muscles and thoracic wall

MRI Appearance

T1-weighted images:

  • Posterior intercostal arteries appear as flow voids (black tubular structures) in the thoracic wall

  • Surrounded by hyperintense fat planes, aiding identification

T2-weighted images:

  • Lumen also appears as a flow void

  • Useful for identifying adjacent edema, masses, or vascular compression

STIR (Short Tau Inversion Recovery):

  • Fat suppression enhances contrast between artery and thoracic wall

  • Wall inflammation, aneurysm, or surrounding edema appears hyperintense

T1 Post-Contrast (Gadolinium-enhanced):

  • Arteries enhance brightly and homogeneously

  • Improves visualization of branching, stenosis, aneurysm, or arteriovenous malformations

  • MR angiography clearly maps their origin from thoracic aorta or costocervical trunk

MRA (Magnetic Resonance Angiography):

  • Demonstrates segmental origin and course of intercostal arteries

  • Useful for identifying collateral circulation, vessel stenosis, or spinal artery supply

CT Appearance

Non-contrast CT:

  • Arteries appear as small soft tissue density structures within intercostal spaces

  • Calcifications may be present in older patients

CT Angiography (CTA):

  • Provides high-resolution visualization of origin, course, and branches

  • Demonstrates collateral circulation in coarctation of the aorta

  • Identifies aneurysm, traumatic injury, pseudoaneurysm, or arteriovenous malformations

  • Axial and multiplanar images show neurovascular bundle relationships in each intercostal space

MRI image

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CT image

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CT image

Posterior intercostal arteries anatomy CT axial image -img-00000-00000

CT images

Posterior intercostal artery

CT images

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