peripheral nerve injury

Question 1

motor unit

Answer 1

anterior horn cell
motor axon
muscle fibres

Question 2

sensory unit

Answer 2

cell bodies in posterior root ganglia

Question 3

peripheral nerve

Answer 3

part of spinal nerve distal to nerve roots
schwann cells form a thin cytoplasmic tube around
larger fibres in multilayered insulating membrane (myelin sheath)

Question 4

structure

Answer 4

axons are coated with endoneurium and grouped with perineurium; these are group to from the nerve covered by epineurium

Question 5

injury

Answer 5

compression
trauma- neurapraxia
axonotmesis
neurotmesis

Question 6

compression

Answer 6

entrapment
classical conditions
carpal tunnel syndrome
sciatica
morton's neuroma

Question 7

neurapraxia

Answer 7

nerve in continuity
stretched or bruised
reversible conduction block
good prognosis

Question 8

axonotmesis

Answer 8

endoneurium intact but disruption of axons; more severe injury
stretched , crushed or direct blow
wallerian degeneration follows
prognosis fair ( sensory recovery often better than motor)

Question 9

neurotmesis

Answer 9

complete nerve division
laceration or avulsion
no recovery unless repaired
endoneural tubes disrupted so high chance of miswiring during regeneration
prognosis poor

Question 10

sunderland grade 3 - 5

Answer 10

neurometsis

Question 11

closed nerve injuries

Answer 11

typically stretching of nerve

brachial plexus injuries, radial nerve humeral fracture

Question 12

open nerve injuries

Answer 12

treated with early surgery, distal portion of nerve undergoes wallerian degeneration

Question 13

clinical features

Answer 13

sensory dysaethesiae
anaesthetic, numbing, pins and needles
motor
paresis & dry skin (loss of tactile adherence since sudomotor nerve fibres not stimulating sweat gland
diminished reflexes

Question 14

healing

Answer 14

proximal axonal budding occurs after 4 days
regeneration rate 1mm/day
pain is first modality to return
more proximal worse healing
Tinel’s sign can moniter recovery- parasethesia felt distal to regeneration
nerve conduction studies

Question 15

the rule of three

Answer 15

surgical timing
immediate surgery within days for clean and sharp injuries
early surgery within 3 weeks for contusion/blunt injuries
delayed surgeries, performed 3 months after injury for closed injury

Question 16

UMN vs LMN lesions

Answer 16

UM
decreased strength
increased tone
increased deep tendon reflexes
present clonus
babinski's sign present
atrophy absent