Spinal Cord And Spinal Nerves Flashcards
What 4 aspects of the vertebral column make up the neural arch?
- Pedicle
- Transverse process
- Lamina
- Spinous process
Narrowing of the vertebral canal (stenosis) can impinge on the ___ ___/___ __
Spinal nerves/spinal cord
What soft tissue structure sits in line with the transverse processes?
Ureters
What does the change in size of the vertebral foramen reflect? Give an example of a large and small vertebral foramen.
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
Why is there no seperate vertebra in the sacrum?
They fuse together in a process called ossification
What is the structure of the spine from the top to the bottom?
Cervical (C1-C7) Thoracic (T1-T12) Lumbar (L1-L5/sometimes L1-L6) Sacral (S1-S5) Coccyx (2 small vertebra)
What are the general areas of exit of spinal nerves from their corresponding vertebrae?
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
What do spinal nerves usually contain?
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))
What structures in the spinal cord do spinal nerves emerge from?
Emerge via intervertebral foramen (pedicle, IV disc, articular processes + synovial joints) so issues/diseases affecting these structures can affect the spinal nerve
What is the grey and white matter of the spinal cord?
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
When will the lateral horn be seen in the spinal cord, along with the ventral + dorsal horn & central canal?
If autonomic nerves are present i.e. T1-L2 (SN) or S2-S4 (PN) as this is their pre-ganglionic region
In what orientation are sections of the spinal cord normally viewed?
The opposite way round to cross sections and CTs (back at the top whilst front is at the bottom)
Why would a part of the spinal cord have a large area of ventral grey matter?
Because it contains high motor function e.g. lumbar + sacral regions look after legs but cervical region looks after arms
Why is the white matter in the sacral region so small?
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)
Where are the cell bodies of motor neurons and sensory neurons?
Motor: Grey matter
Sensory: Dorsal root ganglion
What does the doral roots and ventral roots contain?
Dorsal roots: somatic or visceral sensory afferents
Ventral roots: Somatic or autonomic motor efferents
What does the posterior ramus supply?
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
What are ventral and dorsal ramus’?
Branches off of vertebral column containing mixed nerves either towards the front or back
What does the root value assigned to a given nerve refer to?
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
What are the 3 meningeal layers of the CNS and what is in between them? List them from the inside going out.
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
What can happen to the subdural space in a disease process?
2 layers can seperate and patients can get subdural haematomoas particularly in the cranium for e.g.
What is the epidural space full of?
Fat and veins so if epidurals (anaesthesia) is introduced here, it fuses through the space and bathes the spinal nerves
Why does the spinal cord have a extensive internal venous plexus in the extradural space with valve-less veins?
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.
What is radiculopathy and what can cause it? What are the associated symptoms?
Compressed nerve in spine caused by inflammation or injury
Symptoms include radicular pain, weakness, numbness or difficulty controlling muscle
What is the blood supply to the spinal cord? What would happen if these became blocked?
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
Why is the ability of the vertebral arteries to supply the inferior area poor?
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
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?
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.
Where does the adult spinal cord terminate in comparison to at birth?
L1/L2 in adulthood
L3/L4 at birth
Where does the subarachnoid space, and thus the CSF, terminate at? What colour is CSF shown on an MRI and why?
S2 (varies from S1-4)
White because the white shows hydrogen and water
What is the cauda equina?
Collection of lumbar and sacral spinal nerves running down to exit their vertebrae that supply the lower limbs, pelvic floor, urinary + anal sphincters
What does vertebral levels actually refer to?
A vertebral body, which is DIFFERENT to the part of the spinal cord from which spinal nerves arise
Where do the sacral and lumber nerves run through and exit the vertebral column?
Run through the subarachnoid space to exit below their correspondingly numbered vertebrae
What joins adjacent vertebral bodies and what is it made of?
The intervertebral disc which is made up of a shock absorbing jelly cord surrounded by a fibrous tissue to support it
What happens if the intervertebral disc is diseased?
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
Why does intervertebral (IV) disc prolapse/herniation compress the spinal nerve of the IV foramen one level below?
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
Why is disc prolapse more common in the lumbar region?
Because the lower back supports much of the bodies weight and facilitates a fairly wide range of motion so lumbar vertebrae are relatively flexible
What is cauda equina syndrome?
Compression of sacral spinal nerves (S1-S5) caused by disc herniation, tumour (metastatic spread), spinal stenosis, spondylolisthesis + vertebral canal stenosis
What are the possible symptoms/presenting complaints of cauda equina syndrome?
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!
How can you access the correct space for a lumbar puncture procedure i.e. surface landmarks?
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
Why are lumbar puncture procedures performed?
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
Why might you need to monitor blood oxygen saturation in the young, sick and those with significant comorbidities in a lumbar puncture procedure?
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
What are the 4 layers that a needle insertion in the midline (midvertebral line) will penetrate?
Skin
Supraspinous ligaments
Interspinous ligaments
Ligamentum flavum (provides significant resistance to needle so stop inserting the needle once past this point)
Why must you tilt the needle antero-superiorly in a lumbar puncture?
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
What other space for what other procedure can be accessed via almost the same route as for a lumbar puncture?
The lumbar epidural space can be accessed for anaesthetic administration but access is performed via L3/L4 to L5/S1
When you insert a needle into the spine where must you make sure to stop?
Before you go through the dura which contains fat + veins
What does spinal anaesthesia have a fast onset and how can the levels of anaesthesia be controlled?
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
Which procedures use the spinal route of anaesthetic delivery?
Major surgeries
Where is caudal anaesthesia performed?
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
Caudal anaesthesia is essentially a __ ___ if done right but can become a __ ___ by accident if you do not puncture the needle low enough.
Epidural Spinal anaesthetic (if you go into subarachnoid space which terminates ~ 3.5 cm from sacral hiatus)
How is the needle introduced in a caudal anaesthesia?
Introduced through ligament and subsequently angled toward the head and advanced
