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MSK > peripheral nerve injuries > Flashcards

peripheral nerve injuries Flashcards

1
Q

motor unit (efferent)

A

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

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2
Q

sensory unit

A

cell bodies in posterior root ganglia (outside spinal cord)

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3
Q

nerve fibres join to form..

A

anterior (ventral) motor roots

posterior (dorsal) sensory roots

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4
Q

spinal nerves

A

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

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5
Q

axons: what are they and what they covered with

A

long processes of neurons

coated with endoneurium

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6
Q

fascicles: what are they and what they covered with

A

groups of axons: nerve bundles

covered with perineurium

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7
Q

nerve: what are they and what they covered with

A

groups of fasicles

covered with epineurium

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8
Q

what do schwann cells do

A

surround neurones

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9
Q

A-alpha fibres

A

14 microns
60-100m/s

large motor axons
muscle stretch and tension sensory axons

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10
Q

A-beta fibres

A

12-14microns
30-60m/s

touch, pressure, vibration and joint position sensory axnos

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11
Q

A-delta fibres

A

6-8microns
10-15m/s

sharp pain, light touch and temp sensation

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12
Q

B fibres

A

2-5microns
3-10m/s

sympathetic preganglionic motor axons

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13
Q

C fibres

A

<1micron
<1.5m/s

dull, aching, burning pain and temp sensaton

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14
Q

types of trauma no peripheral nerve

A

direct: blow, laceration
indirect: avulsion, traction

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15
Q

different types of nerve injuries

A

neurapraxia
axonotmesis
neurotmesis

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16
Q

classical conditions of nerve compression

A

carpal tunnel: median nerve at wrist

sciatica: spinal root ocmpressed IV disc

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

17
Q

neurapraxia injury

A

nerve in continuity

stretched, bruised or compression

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

prognosis good

18
Q

axonotmesis

A

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

stretched ++++, crushed or direct blow

19
Q

what follows axonotmesis

A

wallergian degerneration

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

20
Q

axonotmesis prognosis

A

prognosis fair

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

21
Q

neurotmesis

A

complete nerve division

laceration or avulsion

22
Q

repairing neurotmesis

A

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.

23
Q

closed nerve injuries

A

nerve injuries in continuity - neuropraxis, axontmesis

spontaneous recovery possible, surgery indicated after 3motnths

24
Q

examples closed nerve injuries

A

brachial plexus injuries - falling onto shoulder

radial nerve - humeral fractures

25
Q

open nerve injuries

A

assoc with nerve division - neurotmesis

treated w early surgery

26
Q

nerve injuries clinical features: sensory

A

dysathesiae (disordered sensation)

anasethesis (numb), hypo+hyper-aesthetic, paraesthetic

27
Q

nerve injuries clinical features: motor

A

parasis (weakness), or paralysis, wasting

dry skin: loss of tactile adherence since sudomotor fibres not stimulating sweat glands in skin

28
Q

nerve injuries clinical features: reflexes

A

diminished or absent

29
Q

healing of nerve injuries

A

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

30
Q

prognosis for recovery depends on

A

whether nerve is pure (only sensory/motor) or mixed

how distal lesion is (proximal worse)

31
Q

direct repair of nerve

A

laceration with ends close together

no loss nerve tissue

32
Q

nerve grafting

A

nerve loss

late repair

33
Q

UMN lesion vs LMN lesion: strength

A

U: decreased
L: decreased

34
Q

UMN lesion vs LMN lesion: tone

A

U: increased
L: decreased

35
Q

UMN lesion vs LMN lesion: reflexes

A

U: increased
L: decreased

36
Q

UMN lesion vs LMN lesion: ankle clonus

A

U: present
L: absent

37
Q

UMN lesion vs LMN lesion: Babinski’s sign

A

U: present
L: absent

38
Q

UMN lesion vs LMN lesion: atrophy

A

U: absent
L: present

MSK (33 decks)

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