Spinal cord function and dysfunction Flashcards
How many spinal segments are there?
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
What are the 31 pairs of spinal nerves?
8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal
Where do nerves leave the vertebral column?
Intervertebral foramina
Where are the two enlargements of the spinal cord?
Cervical C3-T1 - Extra motor neurones that supply the upper limbs
Lumbosacral L2-S3 - Extra motor neurones that supply the lower limbs
Define spinal segment
A portion of the spinal cord that gives rise to a pair of spinal nerves
What would happen if the spinal cord was severed just below the lumbosacral enlargement?
Loss of control to the bladder and bowl = incontinent
What is the collection of nerves at the bottom of the spinal cord called?
Corda equina. Lumbar cistern (sub-arachnoid space) can be used to sample CSF
What would happen if the spinal cord was severed in the mid thoracic region?
Loss of voluntary control of lower limbs - paraplegia
What would happen if the spinal cord was severed above C3-C5?
The person would not be able to breath because the phrenic nerve arises from this point
Where do the nerves emerge from below C8?
All the nerves emerge below their corresponding vertebrae. From C1-C7 they emerge above their corresponding vertebrae
What are the layers of the meninges?
Dura matter, arachnoid mater and pia mater
Where does the CSF lie?
In the subarchnoid spance
What holds the spinal cord in the middle of the subarachnoid space?
Small protrusions of pia matter called denticulate ligaments. They attach to the dura mater
What lies between the dura and the vertebral bone?
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
Define dermatome
Area of skin innervated by a single spinal nerve or spinal segment
Define myotome
Muscles innervated by one single spinal nerve or spinal segment
What is the difference between ramus and roots?
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.
What can be used to tell whether the view of the spinal cord is ventral or dorsal?
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
What is the anterior median fissure?
Divides the anterior surface of the spinal cord into halves
What is the exit point for anterior motor nerve root called?
Anterolateral sulcus
What is the entry point of the posterior sensory nerve root called?
Posterolateral sulcus
What divides the posterior surface of the spinal cord?
The posterior median sulcus
If the sensory neurones come in and synapse…
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.
What are the major tracts of the spinal cord?
Fasciculus gracilis Fasciculus cuneatus Spinocerebellar tract Lateral corticospinal tract Spinothalamic tract
See diagram
What is the main voluntary motor pathway?
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.
Describe the sensory pathway
See diagram
1,2 and 3 order sensory neurone
Describe the dorsal column pathway
This is the discriminative (fine) touch, vibration, proprioception. See diagram
Describe the spinothalamic tract
See diagram
What are the three most important tracts in spinal cord injury?
Lateral corticospinal tract - MOTOR (important for fine movements)
Dorsal Columns - Sensory (touch, vibration, pressure)
Spinothalamic tract - Sensory (pain, temperature)
Reflex pathways
See diagram
Describe the stages of injury to the lateral corticospinal tract
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
What are the factors affecting the severity of a spinal lesion?
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
