Peripheral nerve injuries

Question 1

where are the cell bodies of motor units found

Answer 1

in the anterior cell horn of the spinal colun

Question 2

where are the cell bodies of the sensory units located

Answer 2

in the dorsal root ganglia (outside of the spinal column)

Question 3

what cells are responsible for forming the myelin sheath in the PNS

Answer 3

Schwann cells

Question 4

how are peripheral nerves constructed

Answer 4

the axons are bundled into fascicles and these fascicles are bundles into nerves

Question 5

what are axons coated with

Answer 5

endoneurium

Question 6

what are nerve fascicles coated with

Answer 6

perineurium

Question 7

what are nerves coated with

Answer 7

epineurium

Question 8

what fibre type is the largest

Answer 8

A-alpha

Question 9

what fibre type is unmyelinated

Answer 9

C fibres

Question 10

what type of fibres transmit slow pain

Answer 10

C fibres

Question 11

what type of fibres are the sympathetic pre-ganglionic fibres

Answer 11

B fibres

Question 12

what nerve is compressed in carpal tunnel syndrome

Answer 12

median nerve

Question 13

what causes the compression in sciatica

Answer 13

IV discs

Question 14

what is Morton’s neuroma

Answer 14

compression of the digital nerve in the foot between the 2nd/3rd webspace of the forefoot

Question 15

what is neurapraxia

Answer 15

when the nerve is still intact by has been stretched and there is a temporary conductive blockage

Question 16

what is the prognosis of neurapraxia

Answer 16

good - full recovery within weeks/months

Question 17

what is axonotmesis

Answer 17

the endoneruium is intact but the axons are disturbed > Wallerian degeneration follows

Question 18

what is Wallerian degeneration

Answer 18

when the nerve distal to the site of injury degenerates due to laceration

Question 19

what is neurotmesis

Answer 19

when the nerve has been completely divided and surgical repair is necessary

Question 20

what is the difference between closed and open nerve injuries

Answer 20

closed injuries are not operated on immediately because there is a chance of natural healing (neurapraxia and axonotmesis) and open injuries are operated on immediately (neurotmesis)

Question 21

what are the surgical requirements for open and closed nerve injuries

Answer 21

closed - only after 3 months if there has been no improvement
open - early surgery

Question 22

what is the normal axonal growth rate

Answer 22

1mm/day - can be up to 3 in children

Question 23

describe the rule of 3

Answer 23

• surgery within 3 days for avulsions
• surgery within 3 weeks for blunt injuries
• surgery after 3 months in closed nerve injuries if there has been no improvement