week 6- Peripheral nerve

Question 1

Name the layers of connective tissue that surround spinal nerves?

Answer 1

Endoneurium (innermost)
Perineurium
Epineurium (outermost)

Question 2

Name the mechanisms of injury?

Answer 2

compression
crush/traction
laceration (cut)

Question 3

under the Seddon and Sunderlands classification of nerve injury, state the order?

Answer 3

grade 1 = neuropraxia- conduction block
grade 2= axonotmesis
grade 3= neurotmesis= with preservation of perineurium
grade 4= neurotmesis= with preservation of epineurium
grade 5= neurotmesis= with complete transection of nerve trunk

Question 4

explain, grade 1- Neuropraxia?

Answer 4

conduction block only, is temporary and completely reversible.
both axon and connective tissue remain intact

Question 5

explain grade 2- Axonotmesis?

Answer 5

loss of axonal continuity, all connective layers intact
Wallerian degeneration 
> distal cell death
> axonal regeneration 
>weeks- months (2-4mm per day)

Question 6

describe an overall summary of what is neurotmesis?

Answer 6

> structure of the nerve is destroyed by cutting, severe scarring or prolonged severe compression
loss of continuity of axon and all/some elements of endoneurial tubes, perineurium and epineurium
Degeneration of distal segment of nerve
prognosis: depends on extent of injury and success of surgery

Question 7

explain grade 3- Neurotmesis axon + endoneurium?

Answer 7

> damage to axon and endoneurium
> perineurium  and epineurium remain intact
Wallerian degeneration
Axonal regeneration 
> misdirection 
> intrafasicular scar formation 
> incomplete recovery

Question 8

explain grade 4- Fascicular rupture

Answer 8

> damage to axon, endoneurium and perineurium 
> epineurium remains intact
Wallerian degeneration 
Axonal regeneration
> gross misdirection 
> neuroma formation 
> apoptosis
> poor recovery 
> fascicle graft

Question 9

explain grade 5- nerve transection

Answer 9

> complete disruption of the nerve, all connective tissues discontinuous
Wallerian degeneration
Axonal regeneration
no direction as no connective tissues guidance
no natural recovery
some recovery of function with nerve graft