peripheral nerve injuries

Question 1

motor unit (efferent)

Answer 1

anterior horn cell (in grey matter spinal cord)
motor axon
muscle fibres (NMJ)

Question 2

sensory unit

Answer 2

cell bodies in posterior root ganglia (outside spinal cord)

Question 3

nerve fibres join to form..

Answer 3

anterior (ventral) motor roots

posterior (dorsal) sensory roots

Question 4

spinal nerves

Answer 4

anterior and posterior roots combine to form a spinal nerve
exit vertebral column via intervertebral foramen
start of peripheral nerve

Question 5

axons: what are they and what they covered with

Answer 5

long processes of neurons

coated with endoneurium

Question 6

fascicles: what are they and what they covered with

Answer 6

groups of axons: nerve bundles

covered with perineurium

Question 7

nerve: what are they and what they covered with

Answer 7

groups of fasicles

covered with epineurium

Question 8

what do schwann cells do

Answer 8

surround neurones

Question 9

A-alpha fibres

Answer 9

14 microns
60-100m/s

large motor axons
muscle stretch and tension sensory axons

Question 10

A-beta fibres

Answer 10

12-14microns
30-60m/s

touch, pressure, vibration and joint position sensory axnos

Question 11

A-delta fibres

Answer 11

6-8microns
10-15m/s

sharp pain, light touch and temp sensation

Question 12

B fibres

Answer 12

2-5microns
3-10m/s

sympathetic preganglionic motor axons

Question 13

C fibres

Answer 13

<1micron
<1.5m/s

dull, aching, burning pain and temp sensaton

Question 14

types of trauma no peripheral nerve

Answer 14

direct: blow, laceration
indirect: avulsion, traction

Question 15

different types of nerve injuries

Answer 15

neurapraxia
axonotmesis
neurotmesis

Question 16

classical conditions of nerve compression

Answer 16

carpal tunnel: median nerve at wrist

sciatica: spinal root ocmpressed IV disc

morton’s neuroma: digital nerve 2nd/3rd web space forefoot

Question 17

neurapraxia injury

Answer 17

nerve in continuity

stretched, bruised or compression

reversible conduction block: localised ischaemia and demyelination, area of nerve

prognosis good

Question 18

axonotmesis

Answer 18

endoneurium in tact (tube in continuity) but disruption of axons

stretched ++++, crushed or direct blow

Question 19

what follows axonotmesis

Answer 19

wallergian degerneration

distal to site of injury, nerve fibre dissapears but endoneurium tube remails. Nerve shrinks back

Question 20

axonotmesis prognosis

Answer 20

prognosis fair

sensory recovery often bettrer than motor (often not normal but enough to recognise pain, hot + cold, sharp + blunt_

Question 21

neurotmesis

Answer 21

complete nerve division

laceration or avulsion

Question 22

repairing neurotmesis

Answer 22

no recovery unless repaired - direct suturing or grafting

endoneural tubes disrupted to high change of mis-wiring during degeneration - sensory nerves going down motor pathways etc.

Question 23

closed nerve injuries

Answer 23

nerve injuries in continuity - neuropraxis, axontmesis

spontaneous recovery possible, surgery indicated after 3motnths

Question 24

examples closed nerve injuries

Answer 24

brachial plexus injuries - falling onto shoulder

radial nerve - humeral fractures

Question 25

open nerve injuries

Answer 25

assoc with nerve division - neurotmesis treated w early surgery

Question 26

nerve injuries clinical features: sensory

Answer 26

dysathesiae (disordered sensation) anasethesis (numb), hypo+hyper-aesthetic, paraesthetic

Question 27

nerve injuries clinical features: motor

Answer 27

parasis (weakness), or paralysis, wasting dry skin: loss of tactile adherence since sudomotor fibres not stimulating sweat glands in skin

Question 28

nerve injuries clinical features: reflexes

Answer 28

diminished or absent

Question 29

healing of nerve injuries

Answer 29

slow starts with initial death of axons distal to site of injury - Wallerian degeneration, then degredation of myelin sheath proximal axonal budding after ~4days regeneration process rate 1mm/day pain first modality to reurn

Question 30

prognosis for recovery depends on

Answer 30

whether nerve is pure (only sensory/motor) or mixed how distal lesion is (proximal worse)

Question 31

direct repair of nerve

Answer 31

laceration with ends close together | no loss nerve tissue

Question 32

nerve grafting

Answer 32

nerve loss | late repair

Question 33

UMN lesion vs LMN lesion: strength

Answer 33

U: decreased L: decreased

Question 34

UMN lesion vs LMN lesion: tone

Answer 34

U: increased L: decreased

Question 35

UMN lesion vs LMN lesion: reflexes

Answer 35

U: increased L: decreased

Question 36

UMN lesion vs LMN lesion: ankle clonus

Answer 36

U: present L: absent

Question 37

UMN lesion vs LMN lesion: Babinski's sign

Answer 37

U: present L: absent

Question 38

UMN lesion vs LMN lesion: atrophy

Answer 38

U: absent L: present