Spinal Cord And Spinal Nerves

Question 1

What 4 aspects of the vertebral column make up the neural arch?

Answer 1

1. Pedicle
2. Transverse process
3. Lamina
4. Spinous process

Question 2

Narrowing of the vertebral canal (stenosis) can impinge on the ___ ___/___ __

Answer 2

Spinal nerves/spinal cord

Question 3

What soft tissue structure sits in line with the transverse processes?

Answer 3

Ureters

Question 4

What does the change in size of the vertebral foramen reflect? Give an example of a large and small vertebral foramen.

Answer 4

The amount of neural tissue
Cervical region: large vertebral foramen as it contains a lot of blood supply
Lumbar region: Small foramen because the vertebral body is bigger due to weight bearing

Question 5

Why is there no seperate vertebra in the sacrum?

Answer 5

They fuse together in a process called ossification

Question 6

What is the structure of the spine from the top to the bottom?

Answer 6

Cervical (C1-C7)
Thoracic (T1-T12)
Lumbar (L1-L5/sometimes L1-L6)
Sacral (S1-S5)
Coccyx (2 small vertebra)

Question 7

What are the general areas of exit of spinal nerves from their corresponding vertebrae?

Answer 7

Cervical spine nerves exit above their correspondingly numbered vertebra (why C8 is an anomaly)
All spinal nerves from T1 down exist below their correspondingly numbered vertebrae

Question 8

What do spinal nerves usually contain?

Answer 8

They are mixed i.e. can contain somatic sensory, somatic motor, visceral sensory and/or autonomic nerves (only in T1-L2 (SN) or S2-S4 (PS))

Question 9

What structures in the spinal cord do spinal nerves emerge from?

Answer 9

Emerge via intervertebral foramen (pedicle, IV disc, articular processes + synovial joints) so issues/diseases affecting these structures can affect the spinal nerve

Question 10

What is the grey and white matter of the spinal cord?

Answer 10

Grey matter: Cell bodies
White matter: axons of neurons arranged in bundles of similar function so white due to fatty myelin sheath (surrounds grey matter)
However if spinal cord is stained, colours are opposite way round

Question 11

When will the lateral horn be seen in the spinal cord, along with the ventral + dorsal horn & central canal?

Answer 11

If autonomic nerves are present i.e. T1-L2 (SN) or S2-S4 (PN) as this is their pre-ganglionic region

Question 12

In what orientation are sections of the spinal cord normally viewed?

Answer 12

The opposite way round to cross sections and CTs (back at the top whilst front is at the bottom)

Question 13

Why would a part of the spinal cord have a large area of ventral grey matter?

Answer 13

Because it contains high motor function e.g. lumbar + sacral regions look after legs but cervical region looks after arms

Question 14

Why is the white matter in the sacral region so small?

Answer 14

Its the end of the spinal cord so there are fewer axons going up or down at this point (therefore, there is more white matter as you ascend cord as more axons going to brain)

Question 15

Where are the cell bodies of motor neurons and sensory neurons?

Answer 15

Motor: Grey matter
Sensory: Dorsal root ganglion

Question 16

What does the doral roots and ventral roots contain?

Answer 16

Dorsal roots: somatic or visceral sensory afferents

Ventral roots: Somatic or autonomic motor efferents

Question 17

What does the posterior ramus supply?

Answer 17

An adjacent section of the back muscles and a small part of the overlying dermatome
Compression/injury can cause localised back pain
Passes close to facet joint so joint pathology can affect nerve

Question 18

What are ventral and dorsal ramus’?

Answer 18

Branches off of vertebral column containing mixed nerves either towards the front or back

Question 19

What does the root value assigned to a given nerve refer to?

Answer 19

The spinal nerve of origin of its component neurons i.e. pudendal + pelvic splanchnic nerve both innervate S2-4 because they originate from that level in the spinal cord

Question 20

What are the 3 meningeal layers of the CNS and what is in between them? List them from the inside going out.

Answer 20

Spinal cord
1. Pia matter (applied to spinal cord)
Subarachnoid space (full of CSF)
2. Arachnoid mater (lines dura)
Subdural space
3. Dura mater (thick outer layer)
Epidural space

Question 21

What can happen to the subdural space in a disease process?

Answer 21

2 layers can seperate and patients can get subdural haematomoas particularly in the cranium for e.g.

Question 22

What is the epidural space full of?

Answer 22

Fat and veins so if epidurals (anaesthesia) is introduced here, it fuses through the space and bathes the spinal nerves

Question 23

Why does the spinal cord have a extensive internal venous plexus in the extradural space with valve-less veins?

Answer 23

So the blood of the vertebral bodes, spinal cord + meninges is drained no matter what position the patient is in e.g. standing up, lying down etc.

Question 24

What is radiculopathy and what can cause it? What are the associated symptoms?

Answer 24

Compressed nerve in spine caused by inflammation or injury

Symptoms include radicular pain, weakness, numbness or difficulty controlling muscle

Question 25

What is the blood supply to the spinal cord? What would happen if these became blocked?

Answer 25

1/3 of supply from 2 posterior spinal arteries
2/3 from 1 anterior spinal artery
So if these became blocked, there would be death of grey matter (motor), autonomic problems + some sensory problems

Question 26

Why is the ability of the vertebral arteries to supply the inferior area poor?

Answer 26

The vertebral arteries do not supply the anterior or posterior spinal arteries at every level or on both sides so if the segmental/supplying arteries are blocked in an area, there is ischaemic damage to
a section of the spinal cord

Question 27

The venous plexus runs the length of the vertebral column into the cranium & vertebral bodies but also communicate with pelvic veins. Why is this problematic?

Answer 27

This is a route for cancer spread from the prostate for e.g. into the vertebral bodies. At this point you would see the bone structure change and become weaker so patient may present with fracture or slight compression fractures in the form of back pain.

Question 28

Where does the adult spinal cord terminate in comparison to at birth?

Answer 28

L1/L2 in adulthood

L3/L4 at birth

Question 29

Where does the subarachnoid space, and thus the CSF, terminate at? What colour is CSF shown on an MRI and why?

Answer 29

S2 (varies from S1-4)

White because the white shows hydrogen and water

Question 30

What is the cauda equina?

Answer 30

Collection of lumbar and sacral spinal nerves running down to exit their vertebrae that supply the lower limbs, pelvic floor, urinary + anal sphincters

Question 31

What does vertebral levels actually refer to?

Answer 31

A vertebral body, which is DIFFERENT to the part of the spinal cord from which spinal nerves arise

Question 32

Where do the sacral and lumber nerves run through and exit the vertebral column?

Answer 32

Run through the subarachnoid space to exit below their correspondingly numbered vertebrae

Question 33

What joins adjacent vertebral bodies and what is it made of?

Answer 33

The intervertebral disc which is made up of a shock absorbing jelly cord surrounded by a fibrous tissue to support it

Question 34

What happens if the intervertebral disc is diseased?

Answer 34

Degeneration (due to posture for e.g.) -> prolapse -> extrusion -> sequestration
This can suppress spinal nerves at any stage causing focal back pain or pain that radiates along the distribution of a spinal nerve

Question 35

Why does intervertebral (IV) disc prolapse/herniation compress the spinal nerve of the IV foramen one level below?

Answer 35

Lumbar nerves pass lateral + superior to disc forming IV foramen so lateral prolapse affects the spinal nerve travelling to the inferiorly located IV foramen e.g. patient will present with L5 nerve symptoms when a disc has prolapsed at L4

Question 36

Why is disc prolapse more common in the lumbar region?

Answer 36

Because the lower back supports much of the bodies weight and facilitates a fairly wide range of motion so lumbar vertebrae are relatively flexible

Question 37

What is cauda equina syndrome?

Answer 37

Compression of sacral spinal nerves (S1-S5) caused by disc herniation, tumour (metastatic spread), spinal stenosis, spondylolisthesis + vertebral canal stenosis

Question 38

What are the possible symptoms/presenting complaints of cauda equina syndrome?

Answer 38

Patient may not feel self going to the toilet (compression of parasympathetics + pudendal nerves (S2-4) used to keep you sociable + sexual)
Reduced angle jerk (S1/S2)
Lower limb sensory loss/changes
N.B. these symptoms are red flags so act immediately!

Question 39

How can you access the correct space for a lumbar puncture procedure i.e. surface landmarks?

Answer 39

Subarachnoid space accessed below termination of spinal cord between L3/L4 or L4/L5 spinous processes if needle is angled antero-superiorly
Can be identified at highest point of iliac crest i.e. supracristal plane at L4
Make sure to flex vertebral column to open up space between spinous processes before needle insertion

Question 40

Why are lumbar puncture procedures performed?

Answer 40

Take sample of CSF to measure fluid’s pressure to aid diagnosis
Remove fluid to reduce pressure in the skull/spine
Inject medications e.g. painkillers, antibiotics, chemotherapy
Inject a spinal anaesthetic (epidural) to numb lower body before op

Question 41

Why might you need to monitor blood oxygen saturation in the young, sick and those with significant comorbidities in a lumbar puncture procedure?

Answer 41

Because the positioning of the patient curled over, laying down with their vertebral column flexed may mean oxygen does not get to the brain as well so they may struggle to breath after a while

Question 42

What are the 4 layers that a needle insertion in the midline (midvertebral line) will penetrate?

Answer 42

Skin
Supraspinous ligaments
Interspinous ligaments
Ligamentum flavum (provides significant resistance to needle so stop inserting the needle once past this point)

Question 43

Why must you tilt the needle antero-superiorly in a lumbar puncture?

Answer 43

You must tilt the needle upwards towards the belly button (~15 degree cephalad orientation) because without this angle, the needle will hit bone, usually the lamina of the neural arch

Question 44

What other space for what other procedure can be accessed via almost the same route as for a lumbar puncture?

Answer 44

The lumbar epidural space can be accessed for anaesthetic administration but access is performed via L3/L4 to L5/S1

Question 45

When you insert a needle into the spine where must you make sure to stop?

Answer 45

Before you go through the dura which contains fat + veins

Question 46

What does spinal anaesthesia have a fast onset and how can the levels of anaesthesia be controlled?

Answer 46

Because it is administered directly into the CSF so it bathes the spinal nerves forming the cauda equina = quick + targeted
Level of anaesthesia can be controlled by adjusting the volume/density of the solution + position of patient

Question 47

Which procedures use the spinal route of anaesthetic delivery?

Answer 47

Major surgeries

Question 48

Where is caudal anaesthesia performed?

Answer 48

Via the sacral hiatus which is located at the inferior apex of an equilateral triangle measured between the posterior superior iliac spines (back versions of ASIS) - sits in upper part of the natal cleft (bum crack) - dimples of venus sit over this area

Question 49

Caudal anaesthesia is essentially a __ ___ if done right but can become a __ ___ by accident if you do not puncture the needle low enough.

Answer 49

Epidural
Spinal anaesthetic (if you go into subarachnoid space which terminates ~ 3.5 cm from sacral hiatus)

Question 50

How is the needle introduced in a caudal anaesthesia?

Answer 50

Introduced through ligament and subsequently angled toward the head and advanced