26th June 2023

Spinal Cord Neuroanatomy

This will have been covered in greater detail in the neuroanatomy section; please refer to this accordingly. The following points are a quick recap to aid understanding of spinal cord disorders.

The intervertebral disc is made up of:

• Annulus fibrosus
• Nucleus pulposus

Compression on the spinal cord caused by intervertebral disc herniation is a result of the nucleus pulposus pushing through a defect in the annulus fibrosus. Reversible risk factors include high body weight, poor posture, occupations involving bending, sitting and lifting, lack of physical activity, smoking, and intrinsic risk factors such as the presence of diabetes mellitus and chondrodystrophies.

The layers of the spinal cord are continuous with the meninges:

• The dura mater has a periosteal and meningeal layer (on top of the spinal arachnoid mater) which separate caudal to the foramen magnum. It is this separation that forms the epidural space (a bit of a misnomer considering it is technically the intradural space.)
• Within the epidural space lie connective tissue, lymphatics, fat, nerve roots and vertebral venous plexus. Of note, this space does not contain any cerebrospinal fluid (CSF). It is this space that epidural anaesthesia targets.
• Beneath the spinal arachnoid mater is the subarachnoid space which contains CSF. It is this space that a lumbar puncture, intrathecal medication, or spinal anaesthesia targets.
• The pia mater forms denticulate ligaments which anchor the spinal cord.

The spinal cord ends at L3 at birth and L1-L2 in adulthood. Below this level is the cauda equina.

The C1-C7 spinal nerves exit above the atlas and above their respective vertebrae. C8 and below exit below their respective vertebrae.

The spinal cord is made of:

• Grey matter
  • Dorsal horn – sensory dorsal horn neurons
  • Lateral horn and lateral grey column – preganglionic visceral motor neurons that project to the sympathetic ganglia
  • Ventral horn – motor neurons supplying striated muscle

• White matter
  • Posterior columns – fasciculus cuneatus and gracilis – ascending sensory information from somatic mechanoreceptors
  • Lateral columns – lateral corticospinal tracts, posterior spinocerebellar tract, rubrospinal tract
  • Anterior columns – spinothalamic tracts, anterior spinocerebellar tract, vestibulospinal tract, olivospinal tract

For more information on the ascending and descending tracts, please refer to the ‘Basic neuroanatomy’ section.

The vascular supply of the spinal cord is composed of:

• Multiple radicular vessels
  • At each intervertebral foramen supplying the corresponding nerve root
  • C1 to T12 supplied by vertebral and thyrocervical trunk
  • T3 to T7 supplied by intercostal arteries
  • T8 downwards by the Great artery of Adamkiewicz
• Three longitudinal vessels:
  • One anterior spinal artery
  • Two posterior spinal arteries in the posterior lateral sulcus

Disruption of this vascular supply, e.g. by aortic dissection, vasculitis, or thrombus, can lead to spinal cord infarctions, which differ in presentation depending on the affected vessel and can be syndromic, e.g. anterior spinal artery syndrome, covered later in this section.