2o. Brain Repair - PNS

Question 1

Nerve Structure

- Surrounding Structures

Answer 1

Endoneurium surrounds axons

Perineurium surrounds fascicles, which are groups of axons

Epineurium surrounds nerves, which are groups of fascicles

Question 2

2 Types of Nerve Injury

Answer 2

• Crush

- Cut

Question 3

Wallerian Degeneration

Answer 3

Degeneration of the distal stump of an axons and its myelin, distal to a cut or crush injury

Question 4

Distal Axons Regeneration

- 2 Reasons

Answer 4

• Nerve cell body survives and re-expresses genes for axonal growth
• Schwann cells react adaptively, alongside macrophages to:
  • Promote regeneration
  • Promote phagocytosis of myelin
  • Promote secretion of cytokines and growth factors

Question 5

Proximal Axons Regeneration

Answer 5

Proximal axons can regenerate if a tube of Schwann cells (endometrial tube) is present to guide them

Question 6

Complete Break >1cm

Answer 6

If there is complete break in a peripheral nerve >1cm then the axons sprout into a local swelling called a neuroma.

Neuromas can produce intractable pain.

Question 7

Crush Injury

Answer 7

Endoneurial tube remains intact so regeneration is accurate

Question 8

Cut Injury

Answer 8

Endoneurial tube is severed so regeneration is inaccurate and neurones grow into different endoneurial tubes causing them to innervate targets they did not previously innervate

Question 9

2 Challenges for Functional Recovery

Answer 9

• Axons growing into the wrong endometrial tube so innervating structures they did not previously innervate
• Chronic ataxy where regenerating axons haven’t reached their targets. Denervated schwann cells progressively lose their growth supportive phenotype

Question 10

3 Surgical Manipulations to Improve Functional Recovery

Answer 10

• Nerve transfer
• Tendon transfer
• Acellular bridges

Question 11

2 Developing Manipulations to Improve Functional Recovery

Answer 11

• Tissue engineering

- Stem cell-based approaches