Blood Supply Spine
62 segmental arteries as 31 paired structures branches
- aorta
- subclavian
- vertebral
- internal iliac arteries
Cervical spine
- vertebral artery (77%)
- additional supply is from branches of the subclavian artery (thyrocervical and costocervical)
Cervicothoracic spine
- branch from ascending pharyngeal in 60%
- vertebral artery responsible for only 36% of supply
Thoracic and lumbar spine
- aorta gives segmental arteries
- divide into lateral and dorsal branches
Sacral spine
- internal iliac gives rise to iliolumbar artery (5th lumbar segmental artery) and lateral sacral artery
- additional supply from middle sacral artery
Blood Supply of the Spinal Cord
General Features
- cord dependant on all three longitudinal vessels
- metabolic demands of grey matter greater than that of white matter
- longitudinal arterial trunks larger in cervical and lumbar regions due to ganglionic enlargements
Anterior Spinal Artery / ASA
- formed by union of anterior spinal branches of vertebral arteries at foramen magnum
- runs in anterior median fissure from medulla oblongata to conus medullaris
- narrows and may become absent in thoracic cord
- variable segmental supply
- probably supplies entire cord except posterior columns
Posterior Spinal Artery / PSA
- smaller than anterior spinal artery
- bilateral
- aries from posterior inferior cerebellar arteries or vertebral arteries at foramen magnum
- usually double running in between and behind posterior rootlets of spinal nerve
- anastomoses with anterior spinal artery particularly at conus
- may be noncontiguous areas
- variable segmental supply but more numerous and smaller than ASA
Segmental Supply
- average of 8 ASA radicular arteries (range 2-17)
- average 12 paired PSA radicular arteries (range 6-25)
- T4-T8 is narrowest portion of longitudinal supply and usually is fed by a single radicular artery
- thoracolumbar cord supplied by one or more prominent arteries
Artery of Adamkiewicz
- originates on left from T9-T11 in 80% of cases (range T7-L4)
Cord Distribution
- ASA and PSAs give off central end arteries and peripheral branches
- central branches penetrate the cord via sulci
- peripheral branches anastomose with small pial branches of segmental vessels
- supply the periphery of the cord and are responsible for sacral sparing in ASA lesions
Venous Drainage
External venous plexus
- anterior to vertebral bodies
Internal venous plexus
- in epidural space
- anterior median spinal veins drains anterior cord
Posterior spinal veins are double and receive small radial veins from the posterior columns
- subsequent drainage into anterior and posterior medullary veins
- unite to form a segmental vein which anastomoses with the external plexus
- ultimate drainage into vertebral, azygous and lumbar veins and IVC
Surgical Considerations
T4-T9 is the critical vascular zone in which interference with the circulation is most likely to result in paraplegia
Principles of anterior spinal surgery
- ligate segmental spinal arteries only as necessary to obtain exposure
- ligate segmental spinal arteries at aorta rather than cord
- ligate segmental arteries on one side only
- limit dissection in vertebral foramina to a single level to preserve anastomoses