Week 27 - Spine and Spinal Cord

Question 1

Name the artery that passes through the transverse foramina of the cervical spine. At what cervical spinal level does it typically enter the foramen before coursing superiorly in the neck?

Answer 1

= Vertebral arteries

The vertebral arteries are paired vessels which arise from the subclavian arteries, just medial to the anterior scalenes. They ascend the posterior aspect of the neck, passing through holes in the transverse processes of the cervical vertebrae (known as foramen transversarium).

The vertebral arteries enter the cranium via the foramen magnum and converge to form the basilar artery – which continues to supply the brain. The vertebral arteries do not supply any branches to the neck or other extra-cranial structures.

Segments

• V1: pre-foraminal segment = ​origin to the transverse foramen of C6
• V2: foraminal segment = ​from the transverse foramen of C6 to the transverse foramen of C2
• V3: atlantic, extradural or extraspinal segment = starts from C2, where the artery loops and turns lateral to ascend into the transverse foramen
  
  • continues through C1 to pierce the dura
• V4: intradural or intracranial segment = ​from the dura at the lateral edge of the posterior atlanto-occipital membrane to their confluence on the medulla to form the basilar artery

Question 2

The spinal nerves exit the spine through which of the following openings?

• a) Intervertebral foramina
• b) Transverse foramina
• c) Lateral foramina
• d) Spinal foramen
• e) Supravertebral foramina

Answer 2

= a) Intervertebral foramina - spinal nerves exit the spine

Question 3

At what spinal level does the adult spinal cord end?

Answer 3

L1 - L2 at Conus medullaris

Question 4

List the layers pierced during a lumbar puncture.

Answer 4

1. Skin
2. Subcutaneous tissue
3. Supraspinous ligament
4. Interspinous ligament
5. Ligamentum flavum
6. Epidural space
7. Dura mater
8. Arachnoid mater → Subarachnoid space for CSF collection

Lumbar puncture, also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid for diagnostic testing.

In approximately 94% of individuals the spinal cord terminates at the level of the L1 vertebrae. In the further 6% of individuals the spinal cord can extend to the L2-L3 interspace. Therefore a lumbar puncture is generally performed at or below the L3-L4 interspace. As a general anatomical rule, the line drawn between the posterior iliac crests often corresponds closely to the level of L3-L4. The interspace is selected after palpation of the spinous processes at each lumbar level.

Question 5

The spinal nerves at the terminal end of the spinal cord form a loose bundle. This bundle of spinal nerves is the:

• a) Conus medullaris
• b) Filum terminale
• c) Epineurium
• d) Denticulate ligaments
• e) Cauda equina

Answer 5

• a) Conus medullaris
• b) Filum terminale = pia mater
• c) Epineurium
• d) Denticulate ligaments
• e) Cauda equina