Spinal cord function and dysfunction

Question 1

How many spinal segments are there?

Answer 1

31
Levels of injury that occur to the spinal cord are often different to the level of vertebra that was actually broken in the accident. So when you mention C1 you must clarify spinal nerves or vertebral levels

Question 2

What are the 31 pairs of spinal nerves?

Answer 2

8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccygeal

Question 3

Where do nerves leave the vertebral column?

Answer 3

Intervertebral foramina

Question 4

Where are the two enlargements of the spinal cord?

Answer 4

Cervical C3-T1 - Extra motor neurones that supply the upper limbs
Lumbosacral L2-S3 - Extra motor neurones that supply the lower limbs

Question 5

Define spinal segment

Answer 5

A portion of the spinal cord that gives rise to a pair of spinal nerves

Question 6

What would happen if the spinal cord was severed just below the lumbosacral enlargement?

Answer 6

Loss of control to the bladder and bowl = incontinent

Question 7

What is the collection of nerves at the bottom of the spinal cord called?

Answer 7

Corda equina. Lumbar cistern (sub-arachnoid space) can be used to sample CSF

Question 8

What would happen if the spinal cord was severed in the mid thoracic region?

Answer 8

Loss of voluntary control of lower limbs - paraplegia

Question 9

What would happen if the spinal cord was severed above C3-C5?

Answer 9

The person would not be able to breath because the phrenic nerve arises from this point

Question 10

Where do the nerves emerge from below C8?

Answer 10

All the nerves emerge below their corresponding vertebrae. From C1-C7 they emerge above their corresponding vertebrae

Question 11

What are the layers of the meninges?

Answer 11

Dura matter, arachnoid mater and pia mater

Question 12

Where does the CSF lie?

Answer 12

In the subarchnoid spance

Question 13

What holds the spinal cord in the middle of the subarachnoid space?

Answer 13

Small protrusions of pia matter called denticulate ligaments. They attach to the dura mater

Question 14

What lies between the dura and the vertebral bone?

Answer 14

Epidural space - used to inject anaesthetic by giving an epidural.
Contains venous plexuses and fatty tissue
This space doesn’t exist in the cranial meninges

Question 15

Define dermatome

Answer 15

Area of skin innervated by a single spinal nerve or spinal segment

Question 16

Define myotome

Answer 16

Muscles innervated by one single spinal nerve or spinal segment

Question 17

What is the difference between ramus and roots?

Answer 17

Ramus carries mixed fibres and a branch of the spinal nerve where as roots depending on whether it is ventral or dorsal carry either motor or sensory fibres.
Dorsal rami innvervate the posterior aspect while the ventral rami innervate the anterior aspect.

Question 18

What can be used to tell whether the view of the spinal cord is ventral or dorsal?

Answer 18

Look to see if there is a fissure or sulcus. Fissures are very deep divisions while sulcus divisions are not deep. The anterior median fissure is more anterior to the sulcus

Question 19

What is the anterior median fissure?

Answer 19

Divides the anterior surface of the spinal cord into halves

Question 20

What is the exit point for anterior motor nerve root called?

Answer 20

Anterolateral sulcus

Question 21

What is the entry point of the posterior sensory nerve root called?

Answer 21

Posterolateral sulcus

Question 22

What divides the posterior surface of the spinal cord?

Answer 22

The posterior median sulcus

Question 23

If the sensory neurones come in and synapse…

Answer 23

It will cross over to the other side and go up the spinal cord whereas if it doesn’t synapse it will go straight up the spinal cord. When it synapses it crosses over to the other side. So this can happen in the medulla as well.

Question 24

What are the major tracts of the spinal cord?

Answer 24

Fasciculus gracilis
Fasciculus cuneatus
Spinocerebellar tract
Lateral corticospinal tract
Spinothalamic tract

See diagram

Question 25

What is the main voluntary motor pathway?

Answer 25

The corticospinal tract - A motor neurone in the left motor cortex will supply the right side because it crosses over in the medulla. It then travels down the lateral corticospinal tract and synpases with a lower motor neurone that emerges from the spinal cord.

Question 26

Describe the sensory pathway

Answer 26

See diagram

1,2 and 3 order sensory neurone

Question 27

Describe the dorsal column pathway

Answer 27

This is the discriminative (fine) touch, vibration, proprioception. See diagram

Question 28

Describe the spinothalamic tract

Answer 28

See diagram

Question 29

What are the three most important tracts in spinal cord injury?

Answer 29

Lateral corticospinal tract - MOTOR (important for fine movements)
Dorsal Columns - Sensory (touch, vibration, pressure)
Spinothalamic tract - Sensory (pain, temperature)

Question 30

Reflex pathways

Answer 30

See diagram

Question 31

Describe the stages of injury to the lateral corticospinal tract

Answer 31

Stage 1. Spinal shock: loss of reflex activity below the lesion, lasting for days or weeks = flaccid paralysis

Stage 2. Return of reflexes: hyperreflexia and/or spasticity = rigid paralysis

Question 32

What are the factors affecting the severity of a spinal lesion?

Answer 32

Loss of neural tissue - Usually small if due to trauma
Can be more extensive e.g. metastases, degenerative disease

Vertical level - Higher the lesion the greater the disability

Transverse plane