Spinal cord function and dysfunction Flashcards
What are the two enlargements in the spinal cord and what is their significance?
Cervical enlargement (C4-T1) – has extra motor neurons that go to the muscles of the upper limb
Lumbosacral enlargement (L2-S3) – has extra motor neurons that go to the muscles of the lower limb
What are the little protrusion of pia mater around the spinal cord called?
Denticulate Ligaments
Which space is present in the spinal meninges but not in the cranial meninges?
Epidural space (useful for injection)
What are the most important tracts in spinal cord injury? State their roles.
Anterior corticospinal tract - ispsi and contralateral anterior horn (mostly axial muscles)
Lateral corticospinal tract – ipsilateral anterior horn (mostly limb muscles)
Dorsal columns – touch, pressure, vibration, proprioception
Spinothalamic tract – pain and temperature
What are the two stages of lateral corticospinal tract damage?
SPINAL SHOCK – you get loss of reflexes below the level of the lesion leading to flaccid paralysis. The limbs become floppy and there is little muscle tone
RETURN OF REFLEXES – you get hyperreflexia and spasticity. The patient experiences spontaneous muscle contraction and there is very high muscle tone – rigid paralysis
Where do the upper motor neurons within the lateral corticospinal tract decussate?
Pyramidal decussation in the medulla
If you have a unilateral lesion of the lateral corticospinal tract in the mid-thoracic region, where will the deficit be?
Ipsilateral – on the same side as the lesion because the fibres decussate at the pyramidal decussation in the medulla
Where do the sensory fibres of the dorsal columns decussate?
Sensory decussation in the medulla
How are pain neurons arranged differently to other sensory and motor neurons?
The first order neurons synapse in the dorsal horn and then the second order neuron crosses to the contralateral side immediately (at the level of the synapse with the first order neurone)
The second order neurons then ascend on the contralateral side
What is syringomyelia? Describe and explain its features.
Enlargement of the central canal (the space is called a syrinx)
This first affects the spinothalamic fibres that are crossing at the level of the lesion as the anterior white commisure of the spinothalamic tract is closest to the central canal. It does not affect fibres that have already crossed at that stage.
So if the enlargement of the central canal is in the region of the cervical enlargement, you could get loss of pain/temperature sensation in the arms but not the legs (because those fibres would already have crossed and would be ascending in the spinothalamic tract away from the central canal)
How many spinal segments are there?
31 (Same as pairs of spinal nerves because segment is section where pair of spinal nerves arise from)
What are the categories of spinal nerves?
8 Cervical 12 Thoracic 5 Lumbar 5 Sacral (Parasympathetic) 1 Coccygeal
Describe the discrepancy between spinal levels and vertebral levels.
Travelling inferiorly, spinal nerves emerge from the vertebral column more inferiorly in respect to where they arise from spinal cord (Line up fairly well superior, but gap grows inferiorly – large part due to C8 spinal nerve while only 7 Cervical vertebrae.)
What is the difference between a ramus and root?
Both have anterior and posterior divisions; however, the roots are separate nerve fibres (anterior = motor, posterior = sensory) prior to forming the spinal nerves while rami are anterior and posterior branches of the spinal nerves containing both sensory and motor fibres.
What are the simplest motor and sensory nerve pathways?
Motor – One motor nerve, one synapse
Sensory – Three sensory nerves, Three synapses (In spinal cord – pain, temp or medulla -touch )
