Contents of the Vertebral Canal SDL

Question 1

The spinal cord, spinal nerve roots and their meningeal coverings are the primary contents of the canal. However, because of differential growth between the spinal cord and the vertebral column, they do not maintain the same relationship throughout life.

In adulthood, why is the spinal cord is much shorter than the length of the vertebral column?

Answer 1

Due to the differential growth between the spinal cord and the vertebral column

Question 2

A which vertebral level does the spinal cord end in the newborn?

Answer 2

Approx L3

Question 3

A which vertebral level does the spinal cord end in adults?

Answer 3

Between L1-L2

Question 4

Due to the spinal cord ending around L1-L2 in adults, what does this mean for the lower spinal nerve roots?

Answer 4

At the end of the spinal cord, it tapers to form a cone called the conus medullaris. At the bottom of the spinal cord (conus medullaris) is the cauda equina. The cauda equina is a bundle of spinal nerves and spinal nerve rootlets, consisting of the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord.

Question 5

What is the conus medullaris?

Answer 5

The tapered end of the spinal cord from which a thin pial thread the filum terminale, continues downwards to attach to the coccyx

Question 6

What is the filum terminale?

Answer 6

A delicate strand of fibrous tissue, about 20 cm in length, proceeding downward from the apex of the conus medullaris. It is one of the modifications of pia mater.

Question 7

What is the cauda equina? What is it made up of?

Answer 7

A bundle of spinal nerves and spinal nerve rootlets, made up of lower lumbar, sacral and coccygeal nerve roots descending through the lumbar cistern

Question 8

What is the lumbar cistern?

Answer 8

The region of subarachnoid space between the level of termination of the cord and the level at which the dura and arachnoid coverings terminate (about S2).

Question 9

Complete the labelling in the diagrams below:

Answer 9

Question 10

The spaces between the dura and arachnoid, and the arachnoid and pia, are called the subdural and subarachnoid spaces, respectively.

• What does the subdural space contain?
• What does the subarachnoid space contain?

Answer 10

• Subdural: potential space
• Subarachnoid: CSF

Question 11

There is also a space between the dura and vertebra called the epidural (or extradural) space. What does this contain?

Answer 11

Fat

Question 12

Vertebral level of:

1. Termination of cord in adult?
2. Termination of cord in neonate?
3. Termination of subarachnoid space?
4. Termination of epidural space:
   
   1. inferiorly?
   2. superiorly?

Answer 12

1. L1-L2
2. Around L3
3. S2
4. …
   
   1. S2
   2. Base of skull (C1)

Question 13

What does the spinal cord receive its arterial supply from?

Answer 13

3 small longitudinally running arteries: one anterior and two posterior spinal arteries.

Question 14

Where do the anterior and posterior spinal arteries originate? Describe the areas of the spinal cord supplied by these arteries.

Answer 14

• The anterior spinal artery is formed rostrally from paired branches of the intracranial vertebral arteries that descend from the level of the medulla. These two arteries fuse to form a single anterior spinal artery that overlies the anterior longitudinal fissure of the spinal cord.
  
  • Supplies the anterior side of the spinal cord
• The posterior spinal arteries arise from the vertebral artery in 25% of humans or the posterior inferior cerebellar artery (PICA) in 75% of humans, adjacent to the medulla oblongata.
  
  • It supplies the grey and white posterior columns of the spinal cord.

Question 15

The anterior and posterior spinal arteries are small. What are they reinforced by?

Answer 15

Are reinforced by radicular branches of the intercostal and lumbar arteries which enter the vertebral canal through the intervertebral foramina.

Question 16

How are the veins that drain the spinal cord orientated?

Answer 16

Longitudinally

Question 17

What fissure/sulcus in the spinal cord does the:

• Anterior spinal vein parallel?
• Posterior spinal vein parallel?

Answer 17

• The anterior spinal vein parallels the anterior median fissure
• The posterior spinal vein parallels the posterior median sulcus

Question 18

What do the posterior and anterior spinal veins drain into?

Answer 18

These veins drain into the internal vertebral plexus embedded in the extradural/epidural fat of the vertebral canal.

Question 19

On the following diagram label the:

• Anterior spinal vein
• Posterior spinal vein
• Internal vertebral plexus
• Epidural/extradural fat
• Dura mater

Answer 19

Question 20

At each vertebral level, what does the internal vertebral plexus drain into?

Answer 20

There is drainage from the internal vertebral plexus into segmental thoracic, abdominal and intercostal veins and the external vertebral venous plexus to eventually connect with the major systemic veins.

Question 21

Do spinal veins have any valves?

Answer 21

No - blood passes directly into the systemic venous system

Question 22

Which aspect of spinal veins plays a role in metastasisation?

Answer 22

No internal valves allows the blood to flow in both directions, facilitating the spread of malignant tumours that invade blood vessels. The continuity of the vertebral venous plexuses with the prostatic plexus is probably the path along which prostatic neoplastic cells metastasise to the central nervous system.

Question 23

What is the prostatic plexus continuous with?

Answer 23

The vertebral venous plexuses

Question 24

What is the functional difference between the dorsal and ventral nerve roots?

Answer 24

• Dorsal root: sensory fibres enter spinal cord
• Ventral root: motor fibres leave spinal cord

Question 25

Where do the dorsal and ventral roots unite to form the spinal nerves?

Answer 25

join just lateral to the dural sheath to form the spinal nerve

Question 26

In the upper part of the vertebral canal, how does each spinal nerve exit the vertebral vana? What do they emerge as?

Answer 26

Via the intervertebral foramen --\> emerge as the anterior primary ramus and posterior primary ramus

Question 27

What do the ventral and dorsal rami consist of?

Answer 27

both sensory and motor fibres

Question 28

What does the dorsal rami innervate?

Answer 28

Innervate the: * skin of the back * intrinsic muscles of the back * sympathetics to the skin

Question 29

What does the ventral rami innervate?

Answer 29

Innervate all other muscles and cutaneous regions of the body. Visceral pain.

Question 30

The spinal nerves are named according to the region of the vertebral column from which they emerge. How many spinal nerves are associated with each region: * Cervical * Thoracic * Lumbar * Sacral * Coccygeal

Answer 30

* Cervical: 8 pairs of spinal nerves * Thoracic: 12 pairs of spinal nerves * Lumbar: 5 pairs of spinal nerves * Sacral: 5 pairs of spinal nerves * Coccygeal: 1 pair of spinal nerves

Question 31

If the diagram above represents the **third and fourth vertebrae** in each of the **cervical**, **thoracic** and **lumbar** regions, which spinal nerve emerges through the intervening intervertebral foramen?

Answer 31

* C4 * T3 * L3

Question 32

Name 3 conditions in which the composition of CSF is altered

Answer 32

1. Meningitis 2. Autoimmune disorders, such as Guillain-Barré Syndrome and multiple sclerosis (MS) 3. Bleeding in the brain

Question 33

In adults, where is is the most common site from which CSF is sampled?

Answer 33

Lumbar cistern using a procedure called a lumbar puncture

Question 34

Describe the position of the patient during a lumbar puncture. Between which vertebrae is the needle usually inserted?

Answer 34

The patient is positioned on one side, perpendicular to the bed and curled up as much as possible. A needle is then inserted in the mid-line, usually between the L3/L4 vertebrae or L4/L5 vertebrae.

Question 35

What surface landmarks would you use to determine the point at which to insert the needle during a lumbar puncture?

Answer 35

The anatomical landmark which is used to identify the correct level for lumbar puncture is the **line connecting both iliac crests**. This crosses the vertebra column at the level of the L4-L5 intervertebral space or L4 vertebra.

Question 36

Why are patients asked to curl up during lumbar punctures?

Answer 36

In these positions, the patient bends their back and stretches the ligaments between the vertebrae (specifically the ligamentum flavum) so their is more room to insert the needle

Question 37

Starting with the skin**, list the layers** pierced by the lumbar puncture needle.

Answer 37

1. Skin 2. Subcutaneous tissue 3. Supraspinous ligament 4. Interspinous ligament 5. Ligamentum flavum 6. Epidural space 7. Dura 8. Arachnoid 9. Finally into the subarachnoid space

Question 38

Oten, clinicians describe feeling a ‘pop’ or ‘give’ when the lumbar cistern is reached. Moving the needle through which ligament causes this?

Answer 38

Ligamentum flavum

Question 39

Complete the labelling of the diagram (note: the meninges have been omitted in order to avoid making the diagram too complex).

Answer 39

Question 40

From the diagram, which segmental spinal nerve would be compressed by herniation of the disc indicated by stippling? What signs and symptoms would the patient show?

Answer 40

The cauda equina * Severe low back pain. * Motor weakness, sensory loss, or pain in one, or more commonly both legs. * Saddle anesthesia (unable to feel anything in the body areas that sit on a saddle) * Recent onset of bladder dysfunction (such as urinary retention or incontinence) * Recent onset of bowel incontinence.

Question 41

In what way is bladder function affected by compression of the cauda equina, eg. by a tumour?

Answer 41

The cauda equina nerves supply muscle sensation to the bladder --\> compression can lead to loss of bladder control

Question 42

**Examine** the following **photographs** taken from four levels of the spinal cord: cervical, thoracic, lumbar and sacral. These sections were stained so that the white matter appears blue-black. In descending order; cervical, thoracic, lumbar and sacral. Which sections contain: * Dorsal, ventral and lateral grey horns * Dorsal, ventral and lateral white matter (white columns) * Central canal * Dorsal and ventral rootlets (if present)

Answer 42

* Cervical: * ???

Question 43

Which cross section has the most white matter? Why?

Answer 43

Cervical region - this pattern is caused by the many **axons going up to the brain from all levels of the spinal cord** AND there are many **axons traveling from the brain down to different segments** of the spinal cord.

Question 44

In which section(s) is the dorsal white matter subdivided into two columns on each side? What type of information runs in these columns?

Answer 44

Is located laterally in the upper thoracic and cervical (C1 to T6) spinal cord segments - it contains afferents from the upper trunk and extremities.

Question 45

In which spinal cord segments is the ventral grey horn enlarged due to the accumulation of motor neurons for innervation of the limbs?

Answer 45

Cervical and lumbar enlargements