Computed Tomography

Computed Tomography

Lubdha M. Shah, MD

CT myelogram demonstrates severe spinal stenosis with nerve root encroachment at the L4-L5 level due to a combination of disc protrusion image and ligamentum flavum thickening image.

Axial CT fluoroscopic image shows the needle tip in the dorsal epidural space confirmed with nonionic contrast image. The hypodense epidural fat is easily delineated from ligamentum flavum & the thecal sac.



  • CT


  • Computed tomography plays complementary role to MR in preprocedural planning

    • Assessment of osseous etiologies of back/neck pain

    • Plan treatment approach


General Anatomic Considerations

  • Alignment

    • Scoliosis

    • Spondylolisthesis

Critical Anatomic Structures

  • Normal conus medullaris level of termination at L2-L3 or above

Anatomic Relationships

  • Arterial supply

    • Radicular arteries arising from vertebral arteries tend to course in anteromedial portion of foramen

      • Deep cervical artery (division of costocervical trunk) provides spinal branches from levels C7 to T1, cervical radiculomedullary arteries

      • At cervical enlargement (C5 or C6), larger medullary branch joins anterior spinal artery

      • These radiculomedullary arteries traverse entire length of foramen medially & can be compromised during injection

    • Blood supply to thoracic spinal cord is predominantly from anterior spinal artery & poor collateral network with smaller posterior spinal arteries

      • At every level in thoracolumbar spine, radicular branches off segmental, intercostal, or lumbar arteries supply exiting nerve root & foraminal structures

      • At as many as 5-6 levels, radicular arteries also contribute to anterior spinal artery: Radiculomedullary arteries

      • Dominant radiculomedullary artery (artery of Adamkiewicz) is primary blood supply to thoracic cord

      • Artery of Adamkiewicz originates between T9 & L2 on left in 85% of people, though aberrant origins from every lumbar level & S1 have been reported

    • Lumbar spine: Radicular arteries primarily supply nerve root, entering intervertebral foramina just inferior to exiting spinal nerve, and travel tortuous path in anterior inferior aspect of foramina


Key Concepts or Questions

  • Nerve root tunnel

    • Begins at point where sheath of nerve root comes off dural sac and ends where nerve root emerges from intervertebral foramen

      • Bounded by undersurface of proximal vertebral pedicles superiorly & superior surface of caudal vertebral pedicle inferiorly

      • Ventrally, posterior surface of vertebral body & annulus of disc form proximal portion of tunnel wall

      • Posterior portion is articular joint, in particular anterior surface of superior articular facet

      • Inner foramen & outer foramen; within inner foramen and nerve-root tunnel is where nerve root is implicated in most of its pathological syndromes

Imaging Approaches

Sep 22, 2016 | Posted by in EMERGENCY RADIOLOGY | Comments Off on Computed Tomography
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