Spinal Cord Function and Dysfunction

Question 1

What are the two enlargements in the spinal cord and what is their significance?

Answer 1

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

Question 2

What are the little protrusion of pia mater around the spinal cord called?

Answer 2

Denticulate ligaments

Question 3

Which space is present in the spinal meninges but not in the cranial meninges?

Answer 3

Epidural space – this can be used for injecting anaesthetics

Question 4

What are the three most important tracts in spinal cord injury? State their roles.

Answer 4

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

Question 5

What are the two stages of lateral corticospinal tract damage?

Answer 5

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

Note these symptoms occur on the same side as the lesion becomes the lateral corticospinal tracts dessucate at the level of medulla

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

Question 6

Where do the upper motor neurons within the lateral corticospinal tract decussate?

Answer 6

Pyramidal decussation in the medulla

Question 7

If you have a unilateral lesion of the lateral corticospinal tract in the mid-thoracic region, where will the deficit be?

Answer 7

Ipsilateral – on the same side as the lesion because the fibres decussate at the pyramidal decussation in the medulla

Question 8

Where do the sensory fibres of the dorsal columns decussate?

Answer 8

Sensory decussation in the medulla

note this is NOT the pyramidal decussation for the motor fibres in the lateral corticospinal tract

Pyramids are actually on the anterior side of the brainstem whereas the dorsal columns are on the posterior side of the brainstem

Question 9

How are pain neurons arranged differently to other sensory and motor neurons?

Answer 9

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

Question 10

What is syringomyelia? Describe and explain its features.

Answer 10

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)

Question 11

2 locations for anaesthetic?

Answer 11

Epidural anaesthesia

Spinal (aka subarachnoid) anaesthesia/spinal block

Question 12

3 factors that affect the severity of spinal lesion

Answer 12

• degree of loss of neural tissue
• Vertical level, the further up the worse
• Transverse plane