Spinal Cord Function and Dysfunction Flashcards
What are the two enlargements in the spinal cord and what is their significance?
Cervical enlargement (C3-T1) – has extra motor neurons that go to the muscles of the upper limb Lumbosacral enlargement (L1-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 – this can be used for injecting anaesthetics
What are the three most important tracts in spinal cord injury? State their roles.
Lateral corticospinal tract – fine motor movements of limbs
NB there is an anterior corticospinal tract too but it controls axial musculature (head and torso) rather than limbs see slide 11
Dorsal columns – touch, pressure, vibration, proprioception NB fasciculus gracilis and fasciculus cuneatus are both part of the dorsal columns pathway. (slide 11)
Spinothalamic tract – pain and temperature
What are the two stages of lateral corticospinal tract damage?
stage 1: 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 = FLACCID paralysis
stage 2: RETURN OF REFLEXES – you get hyperreflexia and spasticity(muscles are constantly contracted). The patient experiences spontaneous muscle contraction and there is very high muscle tone= RIGID paralysis
Note these symptoms occur on the same side as the lesion becomes the lateral corticospinal tracts dessucate at the level of medulla
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
Pyramidal decussation also occurs at the level of medulla but on the anterior side
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 selectively affects the spinothalamic fibres that are crossing at the level of the lesion and it does not affect fibres that have alreadycrossed 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 because these fibres have to cross at that level across the central canal. However, not the legs (because those fibres would already have crossed and would be ascending in the spinothalamic tract away from the central canal)
2 locations for anaesthetic?
Epidural anaesthesia
Spinal (aka subarachnoid) anaesthesia/spinal block
3 factors that affect the severity of spinal lesion
- degree of loss of neural tissue
- Vertical level, the further up the worse
- Transverse plane
