Chapter 28 - Nerve Injuries and nerve Transfers

Question 1

What is the mot important prognostic factor for nerve recovery?

Answer 1

Patient age

Question 2

Nerve layers

Answer 2

nerve fiber -> endoneurium -> fasicle -> perineurium -> multiple fasicles -> epineurium

Question 3

what layers of the nerve are intact in neuropraxia

Answer 3

All - epineurium, perineurium, endoneurium. NO wallerian degeneration occurs

Question 4

Axontomesis

Answer 4

axons are disrupted, connective tissue layers are grossly intact

Wallerian degeneration DOES occur

Fibrillations and sharp waves present on EMG distally

Question 5

what happens to nerve degradation products following wallerian degeneration?

Answer 5

they are removed via phagocytosis

Question 6

steps of nerve regeneration

Answer 6

schwann cell migration to the basement membrane, form endoneurial tube, nerve cell body enlarges, proximal axon forms growth cone (1mm/day)

Question 7

Nerve conduction velocities - how are they used?

Answer 7

incomplete injury (demyelination) - looks like decreased NCV, diminished amplitude, increased latency

complete (transected) injury - no response

Question 8

EMG

Answer 8

measures axonal function at the NMJ

Question 9

EMG - how is it used?

Answer 9

acute denervation - reduced motor recruitment

3 weeks - fibrillations, positive sharp waves, fasiculations

early reinnervation - emergence of polyphasic motor unit potentials

chronic denervation - absence of motor unit potential recruitment

Question 10

role of nerve conduit in nerve repair

Answer 10

only indicated in gaps <10mm, and only for sensory nerves, not motor or mixed

Question 11

what factor is necessary in redundancy of nerve graft

Answer 11

the nerve conduit should be at least 10% larger than the measured gap

Question 12

role of allograft nerve

Answer 12

evidence supporting its use in sensory (and some evidence of major nerves) nerve repair up to a gap of 70mm

Question 13

Common motor nerve transfers in the upper extremity:
motor loss - hand intrinsics

Answer 13

donor: AIN

recipient: ulnar motor fascicle

Question 14

Common motor nerve transfers in the upper extremity:
motor loss - wrist/digital extension

Answer 14

donor: median branches to the FCR/FDS

recipient: PIN

Question 15

Common motor nerve transfers in the upper extremity:
motor loss - elbow flexion

Answer 15

donor: ulnar fascicle to the FCU and/ormedian fascicle to the FCR/FDS

recipient: musculocutaneous to biceps and/or brachialis

Question 16

Common motor nerve transfers in the upper extremity:
motor loss - shoulder flexion, abduction, ER

Answer 16

donor: radial nerve to medial triceps or medial pectoral

recipient: axillary

Question 17

Common motor nerve transfers in the upper extremity:
motor loss - shoulder abduction, ER

Answer 17

donor: spinal accessory nerve (XI)

recipient: suprascapular