L10 - Peripheral nerve injuries Flashcards
What are the three CT layers covering nerves?
Endoneurium - cover axons and myelin sheath
Perineurium - cover bundles of axons (fasicles)
Epineurium - cover bundles of fasicles (nerves)
What are the types of peripheral nerve injuries?
Elongation - 10-20% elongation before damage
Laceration
Compression
What are the grades of injury?
Neuropraxia - little structural damage, no loss of nerve continuity
Axonotmesis - complete interruption of axon and myelin sheath
Neurotomesis - disconnection of nerve and surrounding stroma - no spontaneous recovery
What is the difference between PNS and CNS injury repair?
PNS actively promotes repair where CNS actively inhibits
What are the current treatments for nerve damage
Direct surgical recon - ischemia after 15% stretch
Nerve grafts
- Autologous: Low risk of rejection but LOF at donor site
- Allogeneic: No second surgery/LOF higher risk of rejection and limited avaliability
Nerve conduits - guide regen of axon
What happens when a nerve conduit is introduced to damaged tissue?
- Conduit fills with plasma (HOURS)
- Fibrin cable forms (DAYS)
- Cell migration and axonal regen (MONTHS)
- Nerve reconnects - thinner (YEARS)
What are the two types of conduits?
Decellularised and bioengineered
What considerations must be made when producing bioengineered construct?
Must have; electrical activity, intraluminal channels, oriented nerve substratum, biochemical signals, support cells, biodegradability and porosity
What is the critical gap length?
The length at which regeneration occurs 50% of the time
What increases critical gap length?
- ECM components - matrices with high water content, laminin, fibronectin and collagen
- Intraluminal support
- Neurotrophic factors - need controlled release
- Inclusion of cells in conduit - Schwann cells and SC for grafting
