peripheral nerve injuries

Question 1

what do A-alpha fibres do ?

Answer 1

large motor axons

muscle stretch and tension sensory axons

Question 2

what do A-beta fibres do ?

Answer 2

touch, pressure

vibration and joint position sensory axons

Question 3

what do A-gamma fibres do ?

Answer 3

gamma efferent motor axons

Question 4

what do A-delta fibres do ?

Answer 4

sharp pain, very light touch and temperature

Question 5

what do B fibres do ?

Answer 5

sympathetic preganglionic motor axons

Question 6

what do C fibres do ?

Answer 6

dull, aching, burning pain and temperature sensation

Question 7

what are classic nerve compression injuries ?

Answer 7

carpal tunnel syndrome - median nerve at wrist
sciatica - spinal root by intervertebral disc
Morton’s neuroma - digital nerve in 2nd/3rd web space of forefoot

Question 8

what are the different types of nerve trauma ?

Answer 8

direct - blow, laceration

indirect - avulsion, traction

Question 9

what are the different types of indirect nerve injury ?

Answer 9

neurapraxia
axonotmesis
neurotmesis

Question 10

what is neurapraxia ?

Answer 10

nerve stretched or bruised
nerve in continuity
reversible conduction block - ischaemia and demyelination
prognosis good - wks/mnths

Question 11

what is axonotmesis ?

Answer 11

very stretched or crushed or direct blow
endometrium intact, disruption of axons
degeneration follows
prognosis fair

Question 12

what is neurotmesis ?

Answer 12

complete nerve division - laceration or avulsion
no recovery unless repaired - suturing or grafting
endoneural tubes disrupted so high chance of misfiring
prognosis poor

Question 13

what is a closed nerve injury ?

Answer 13

usually nerve injuries in continuity
spontaneous recovery possible
surgery indicated after 3 months in no recovery
typically brachial plexus injury or radial nerve humeral fracture

Question 14

what is an open nerve injury ?

Answer 14

usually knives, glass
treated with early surgery
distal portion undergoes Wallerian degeneration - 2/3 weeks after injury

Question 15

what are the clinical features of a peripheral nerve injury ?

Answer 15

sensory - dysaethesiae
motor - weakness or paralysis +/- wasting, dry skin
reflexes - diminished or absent

Question 16

what are features of the nerve healing process ?

Answer 16

very slow 1mm/day
Wallerian degeneration distally
proximal budding after 4 days
pain is first modality to return
more proximal = worse prognosis

Question 17

what is the rule of 3 in surgical intervention of nerve injury ?

Answer 17

immediate surgery in 3 days for clean, sharp injury
early surgery in 3 weeks for blunt/contusion injury
delayed in 3 months for closed injury