Blood Supply of the Spine and Spinal Cord

Segmental arteries:

• The vertebral column's fundamental blood supply pattern is segmental, with a paired artery at each level giving off branches to the vertebral body, the posterior elements (laminae, spinous/transverse processes), the adjacent intrinsic back muscles, and a spinal branch entering the intervertebral foramen to supply the spinal cord/meninges/nerve roots at that level, the specific named artery providing this segmental supply varies by region.

Vertebral arteries:

• Supply the cervical spine's segmental branches, given their course through the C1-C6 transverse foramina, small branches arise along this course to supply the adjacent cervical vertebrae.

Posterior intercostal arteries:

• Supply the thoracic spine's segmental branches, arising from the descending thoracic aorta, each posterior intercostal artery gives off a dorsal branch, which in turn gives a spinal branch entering the corresponding intervertebral foramen.

Lumbar arteries:

• Supply the lumbar spine's segmental branches, arising directly from the abdominal aorta (typically four paired lumbar arteries), following the same segmental branching pattern as the posterior intercostal arteries above.

Lateral sacral arteries:

• Supply the sacral spine's segmental branches, arising from the internal iliac artery's posterior division, entering the anterior sacral foramina to supply the sacral canal contents and the sacrum itself.

• The spinal cord's own dedicated blood supply is distinct from (though anatomically continuous with, via the segmental radicular/medullary artery contributions below) the vertebral column's segmental supply.

Anterior spinal artery:

• A single, midline vessel, formed by the union of small branches from each vertebral artery near the foramen magnum, descending along the spinal cord's anterior median fissure for its entire length, supplies the anterior two-thirds of the spinal cord's cross-sectional area (the anterior and lateral white columns, including the corticospinal and spinothalamic tracts, and the anterior/lateral grey matter horns), a single vessel supplying a disproportionately large territory, making it comparatively more vulnerable to ischaemic injury than the paired posterior spinal arteries.

Posterior spinal arteries (paired):

• Two vessels, also arising from the vertebral arteries (or, more variably, from the posterior inferior cerebellar arteries), descending along the posterolateral spinal cord surface, supplying the posterior one-third of the cord (predominantly the dorsal columns/DCML pathway), being paired, with a naturally richer anastomotic network between the two vessels along the cord's length, the posterior spinal arteries provide somewhat more robust collateral protection to their territory than the single anterior spinal artery provides to its own, larger territory.

Radicular arteries:

• Small segmental arteries accompanying the individual nerve roots through the intervertebral foramina, arising from the vertebral column's segmental supply (vertebral, posterior intercostal, lumbar, lateral sacral arteries, depending on level), most radicular arteries supply only the nerve root itself and do not reach or significantly reinforce the anterior/posterior spinal arteries, remaining functionally distinct from the following category.

Segmental medullary arteries:

• A smaller subset of the segmental (radicular-level) arteries that, unlike the majority (purely radicular) arteries above, do extend inward to actually reach and reinforce the anterior or posterior spinal artery, these segmental medullary arteries are relatively few in number (typically only around 6-8 significant anterior segmental medullary arteries reinforce the anterior spinal artery along the cord's entire length) and are irregularly, unpredictably distributed, making the anterior spinal artery's blood supply pattern a series of watershed zones between these few significant reinforcing contributions, a key anatomical vulnerability.

Typical origin:

• The largest and most clinically significant of the anterior segmental medullary arteries, typically arising from a lower thoracic or upper lumbar posterior intercostal/lumbar artery (most commonly around T9-T12, though with recognised anatomical variation ranging from T5 to L2 in different individuals), and (in the majority of people) arising from the left side.

Contribution to lower spinal cord:

• Provides the dominant, and in many individuals the sole substantial, blood supply to the lower two-thirds of the spinal cord (the thoracolumbar and lumbosacral enlargement regions) via its reinforcement of the anterior spinal artery at this level, given the relatively sparse distribution of other significant segmental medullary arteries in this specific region (a recognised anatomical watershed zone), the artery of Adamkiewicz's contribution here is disproportionately critical compared to its single-vessel status might otherwise suggest.

Clinical importance:

• Injury to, or interruption of, the artery of Adamkiewicz (most classically during thoracoabdominal aortic aneurysm surgery, where the vessel's origin may need to be sacrificed or is inadvertently compromised during aortic cross-clamping or graft placement) risks catastrophic anterior spinal artery syndrome affecting the lower spinal cord, producing bilateral lower limb paralysis (corticospinal tract involvement) and bilateral loss of pain/temperature sensation (spinothalamic tract involvement) below the level of ischaemia, with relative sparing of proprioception/vibration sense (dorsal columns, supplied separately by the posterior spinal arteries), this specific vulnerability is a major, well-recognised consideration in the surgical planning of thoracoabdominal aortic procedures, sometimes prompting pre-operative imaging specifically to identify the artery's precise origin level and side, in an effort to minimise the risk of this devastating complication.

Internal vertebral venous plexus:

• An extensive, valveless venous network within the epidural space, running the vertebral canal's full length.

External vertebral venous plexus:

• A corresponding venous network located outside the vertebral canal, surrounding the vertebral column's external surface (around the vertebral bodies and posterior elements), communicating segmentally with the internal vertebral venous plexus through the vertebral bone itself and via the intervertebral foramina.

Basivertebral veins:

• Veins draining the vertebral body's internal cancellous bone, emerging through a foramen on the vertebral body's posterior surface (within the gap in the posterior longitudinal ligament's attachment) to drain into the internal vertebral venous plexus, a distinctive, large-calibre venous channel visible as a characteristic finding on spinal imaging.

Connections with systemic veins:

• The internal and external vertebral venous plexuses together connect extensively with the segmental veins at each level (intercostal, lumbar veins, draining to the azygos system and IVC respectively), and, via this connectivity, form part of the broader valveless venous network sometimes collectively termed Batson's (vertebral venous) plexus.

Spinal cord ischaemia:

• Given the anterior spinal artery's single-vessel, watershed-zone-dependent supply pattern (with the artery of Adamkiewicz as the dominant, often sole, significant reinforcement to the lower cord), the spinal cord is vulnerable to ischaemic injury from systemic hypotension (a global "watershed" ischaemic insult, most likely to manifest at the anatomical watershed zones between segmental medullary artery territories, often around the mid-thoracic region, a second, less individually dominant watershed zone distinct from the lower cord's Adamkiewicz-dependent territory) or from direct vascular injury/interruption (surgical, traumatic, or embolic) affecting the artery of Adamkiewicz or its parent vessel specifically.

Aortic surgery relevance:

• Thoracoabdominal aortic aneurysm repair (open surgical or, increasingly, endovascular) carries a recognised risk of spinal cord ischaemia via interruption of the artery of Adamkiewicz's blood supply, modern surgical/anaesthetic strategies to reduce this risk include pre-operative imaging to identify the artery's origin, intraoperative spinal cord perfusion pressure optimisation, cerebrospinal fluid drainage (to reduce intraspinal pressure and thereby improve relative spinal cord perfusion pressure), and staged/sequential aortic segment repair (rather than prolonged single-stage cross-clamping), all directly informed by the anatomical vulnerability pattern described in this section.

Vertebral venous spread of malignancy:

• The valveless internal vertebral venous plexus's extensive connectivity with the pelvic venous system provides a direct, lung-bypassing route for haematogenous metastatic spread from pelvic malignancies (classically prostate cancer) directly to the vertebral column, explaining the characteristic pattern of vertebral/axial skeletal metastasis seen in this and related cancers, a theme directly paralleling the equivalent cranial venous connectivity (via the dural venous sinuses and their own emissary vein connections).