Blood Supply of the Spinal Cord

Overview

Extrinsic (Extramedullary) System

Three Longitudinal Arteries

• The ASA runs along the anterior median fissure from the level of the olivary nucleus to the tip of the conus medullaris.
• The PSAs run along the dorsal surface and also extend throughout the cord's length.
• At the conus medullaris, the ASA and PSAs are joined by an anastomosing ansa of the conus medullaris.

Radiculomedullary Arteries (Segmental Feeders)

• Segmental branches of the aorta (intercostal and lumbar arteries)
• Subclavian arteries (via vertebral, ascending, and deep cervical branches)
• Hypogastric arteries

Three Vascular Zones

1. Cervicothoracic Region (C1–T2) — richly vascularized

• C1–C4: supplied by the ASA with limited radiculomedullary input
• C5–T2: supplied by 2–4 large radicular arteries from the vertebral, ascending cervical, and deep cervical arteries
• The artery of the cervical enlargement (typically C4–C8, often entering with C7 or C8 root) is the most important feeder here

2. Midthoracic Region (T3–T8) — poorly vascularized (watershed zone)

• Most vulnerable to ischemia
• Receives only 1 radiculomedullary artery, usually entering with the T6, T7, or T8 root
• Fed by branches of the intercostal arteries

3. Thoracolumbosacral Region (T9–S) — richly vascularized

• The dominant feeder is the Artery of Adamkiewicz (AKA) — great anterior radicular artery / artery of the lumbar enlargement
• Usually arises from the left side (in ~75% of cases) with the T9–T12 root (75% of cases); occasionally from T6–T8 or upper lumbar roots
• It is the only major artery supplying the caudal 2/3 of the ASA — making it a critical watershed zone
• Has a characteristic "hairpin" configuration on imaging
• The sacral cord also receives supply from the median sacral artery anteriorly

Intrinsic (Intramedullary) System

• Sulcocommissural (central) arteries: largest branches of the ASA; enter the ventral median fissure and supply the anterior horns, lateral horns, central gray matter, and basal posterior horn
• Perforating pial branches: from the perimedullary plexus; supply white matter
• Posterior spinal arteries + perforating branches: supply dorsal horns and dorsal funiculi

Gray matter is more richly vascularized than white matter.

Clinical Relevance

Anterior Spinal Artery Syndrome

• Bilateral motor loss (corticospinal tract damage → paraplegia/quadriplegia)
• Loss of pain and temperature (spinothalamic tract damage)
• Preserved vibration and proprioception (dorsal columns supplied by PSAs are spared)

Why the ASA Is More Vulnerable Than PSAs

• The single ASA receives fewer collateral feeders than the paired PSAs
• The midthoracic zone (T3–T8) is a watershed and lacks robust collaterals
• AKA occlusion (e.g., aortic surgery, dissection, atherosclerosis) can devastate the lower thoracic/lumbar cord

Aortic Surgery Risk

• Miller's Anesthesia, 10e — Spinal Cord Blood Supply
• Localization in Clinical Neurology, 8e — Extraspinal & Intraspinal Systems
• Neuroanatomy through Clinical Cases, 3e — Spinal Cord Blood Supply