Spinal Cord Function and Dysfuntion

Question 1

What are the enlargements of the spinal cord?

Answer 1

1. Cervical enlargement: C3->T2 - has extra motor neurones that go to the muscles of the upper back.
2. Lumbosacral enlargement: T11->S2 - has extra motor neurones that go to the muscles of the lower limbs.

Question 2

What would severing the spinal cord below the lumbrosacral region affect? What would a lesion above C3-C5 result in?

Answer 2

lumbrosacral - bladder and bowel control

lesion - loss of breathing ability

Question 3

What is paraplegia?

Answer 3

loss of voluntary control of lower limbs

Question 4

What is used to sample CSF?

Answer 4

lumbar cistern

Question 5

What is a difference between the spinal cord and the vertebral column?

Answer 5

sc tops developing early - vc continues to grow in adulthood

Question 6

What is the difference between the meningeal covering of the spinal cord and the brain?

Answer 6

sc also has three layers but dura only has one layer not two - no epidural space

CSF located in subarachnoid space

Question 7

What are denticulate ligaments?

Answer 7

small protrusions of pia mater that tether the spinal cord

Question 8

What are the features of the extradural space?

Answer 8

There is a unique extradural space between the outside of the dura and the bone (not in cranial meninges).

The space is full of venous plexuses and fatty tissue.

This space is used clinically to inject anaesthetic.

Question 9

What is the corticospino tract? What would a lesion here cause?

Answer 9

major voluntary movement pathway

Injury to this tract results in a 2 stage response:

1. SPINAL SHOCK:
   - Lose ALL reflex activity below the level of the lesion (no direct damage, just stop working).
   - Results in flaccid paralysis–limbs become floppy with no muscular tone.
2. RETURN OF THE REFLEXES (hyperreflexia)
   - Reflexes become over exaggerated (i.e. large knee jerk).
   - High muscle tone becomes apparent, known as rigid paralysis.
   - Due to the lower cut off motor neurones reducing their normal activating pathway and thus are activated with a lower threshold.

Neurones here decussate (cross) at the level of the medulla and so a lesion below this level would produce a deficit on the same side.

Question 10

What is the spinothalamic tract? What would a lesion here cause?

Answer 10

pain and temperature pathway (sensory)

Lateral = mainly limbs
Neurones here decussate at the SAME LEVEL as the entry point of the sensory nerve into the spinal cord.

This means a lesion on the left at the mid-thoracic level will cause a loss of pain sensation in the right leg.

Anterior = trunk

Question 11

What are the dorsal columns?

Answer 11

fine touch, vibration and pressure

neurones here decussate at the level of the medulla

fasciculus gracillis (more medial) - sensory from ipsilateral lower limb

fasciculus cuneatus (more lateral) - sensory from ipsilateral upper limb