Peripheral nerve injuries

Question 1

what cells myelinate the PNS?

Answer 1

Schwann cells

Question 2

schwann cells vs satellite cells

Answer 2

schwann cells form myelin sheath around axons to insulate, speed up conduction & guide regrowth
satellite cells encode cell bodies of PNS & regulate internal environment

Question 3

In the UL, what peripheral nerves are most commonly damaged in order?

Answer 3

1. radial nerve
2. ulnar nerve
3. median nerve

Question 4

what are the most commonly damaged LL peripheral nerves?

Answer 4

1. sciatic nerve
2. peroneal nerve

Question 5

list some causes of PNS injury

Answer 5

trauma
compression
toxic chemicals
Iatrogenic (caused by medicine)
medical conditions

Question 6

how is peripheral nerve injury classified?

Answer 6

Question 7

what is neuropraxia?

Answer 7

-usually due to compression pathology
-mildest form of peripheral nerve injury
-can completely recover in 6-12 weeks
-a focal segment of the nerve is demyelinated without any damage to the axon
-symptoms include pain, numbness, muscle weakness, no muscle wasting

Question 8

what is axonotmesis?

Answer 8

-damage to axon + myelin sheath
-however the endoneuroium, perineurium and epineurium are intact
-damage to the axons leads to wallerian degeneration

Question 9

what is neurotmesis?

Answer 9

-disruption of the axon and endoneurium. when this occurs the perineurium and epineurium remain intact.
-Disruption of the axon and perineurium is considered a 4th-degree injury.
-And a complete disruption of the entire nerve trunk is classified as a 5th-degree injury.
-no spontaneous recovery, surgery is indicated

Question 10

what are 2 types of peripheral nerve degeneration?

Answer 10

-anterograde / wallerian
-retrograde

Question 11

describe anterograde degeneration

Answer 11

the axon degenerates distal to the lesion
-begings within hours of injury
-occurs when axon is damaged or severed

Question 12

describe retrograde degeneration

Answer 12

-some and dendrites (proximal to the lesion) show a change in size and breakdown in architecture
-cell death may occur

Question 13

describe the pathophysiology of nerve injury

Answer 13

1. at the injury site, there is immediate inflammatory changes
2. there is an increase in mRNA and protein synthesis, and increase in Ca2+ in the cell body
   -schwann cells cause wallerian degeneration distal to the injury
   -there is shrinkage of muscle cells and sensory receptors are less sensitive to generation

Question 14

explain peripheral nerve regeneration

Answer 14

• wallerian degeneration happens
  -macrophages clear the axonal and myelin debris
  -schwann cells help to rebuild and form “regeneration” tracks
  -the healthy part of the axon nearest to the cell body sends little sprouts and growth cones and regrows
  -axon will grow to reach its target to have function again eg muscle, skin etc

Question 15

what does the functional recovery of the peripheral nerve regeneration depend on?

Answer 15

-axon guidance specificity
-reinnervation of the end organ
-timing of the nerve injury
-distance to the target organ

Question 16

how is a peripheral nerve injury diagnosed?

Answer 16

-physical and neuro testing
-EMG
-nerve conduction studies
-MRI/CT
-ultrasound

Question 17

open vs closed nerve injuries

Answer 17

open: nerve is damaged with open skin eg glass laceration
closed: nerve is damaged without a break in the skin

Question 18

what can cause an axillary nerve injury?

Answer 18

-shoulder dislocation
-traction injury
-compression eg tumour or cyst

Question 19

what are the main features of an axillary nerve injury?

Answer 19

-loss of deltoid + muscle wasting
-loss of sensation over the regimental badge area

Question 20

what is obstetric brachial plexus injury?

Answer 20

injury to the brachial plexus that can occur during childbrith
-if the babies neck or shoulder is pulled
-risk factors include breech presentation

eg Erbs palsy (C5-C7), Klumpe’s paralysis (C8/T1)

Question 21

Other than obstetrics, what other MOIs can cause a brachial plexus injury?

Answer 21

-trauma
-RTA

Question 22

how are peripheral nerve injuries treated?

Answer 22

-conservate
-surgical - nerve repair, graft, scar release etc
-depends on whether PNI is closed or open

Question 23

describe ulnar nerve injuries/ lesions

Answer 23

-symptoms depend on the location of the injury eg distal vs proximal
-if proximal (elbow) - sensory loss + claw hand deformity
-if distal, sensory loss to superficial branch only, more pronounced claw hand

Question 24

describe median nerve injury

Answer 24

roots: C5-T1
note: innervates most forearm flexors
-caused by upper arm fractures, shoulder dislocation, penetrating wounds
-can happen in upper arm, elbow or wrist
-carpal tunnel syndrome at the wrist can compress the median nerve

Question 25

what are some features of median nerve injuries?

Answer 25

-loss of thumb opposition -weak pronation, wrist and finger flexion -sensory loss

Question 26

what things can cause a radial nerve injury?

Answer 26

-axilla- pressure from axillary crutches -saturday night palsy -fracture

Question 27

what hand deformity is common with radial nerve injury?

Answer 27

wrist drop

Question 28

what can cause sciatic nerve injuries?

Answer 28

-pelvic and thigh wounds -hip dislocation

Question 29

what can cause common perineal nerve injuries?

Answer 29

-fracture of neck of fib -pressure from plaster cast

Question 30

what does the physio Ax of peripheral nerve injuries involve including database, sub and objective ?

Answer 30

database: investigations, HPC, medical hx, smoking -subjective: pain, sensory changes, activity limitations -objective: muscular changes, scarring, posture, pain behaviours, odema, skin condition, ROM, tone, power, sensation

Question 31

what are trophic changes post PNI?

Answer 31

structural and functional changes that occur to skin etc post nerve injury - warm phase: first 3 weeks - skin is warm and flushed, may have sweating -cold phase: cold skin, shiny and smooth, brittle fingernails, dryness and ulceration

Question 32

what is complex regional pain syndrome?

Answer 32

a condition that typically develops after an injury, such as a fracture, sprain, surgery, or nerve damage, but the pain and symptoms it causes are often disproportionate to the initial injury. It often affects the distal parts of the limb, such as the hands, fingers, feet, or toes. -characterised by severe burning pain, changes in skin colour, temperature, sweating

Question 33

what are the goals of physio management?

Answer 33

-control pain - MDT, TENS, nerve glides -maintain / increase ROM -maintain / increase power -reduce oedema -educate re care of limb -prevent and manage deformity via splinting and PROM -retrain sensation -retrain normal movement and function - motor learning

Question 34

how is physiotherapy involved post surgical nerve repair?

Answer 34

-reduce swelling -control pain -in later phases, do sensorimotor training and desensitisation

Question 35

what does sensory reeducation involve?

Answer 35

-daily stimulation 10-15 mins -different textures eg cotton wool, brushes, sharp and blunt, sandpaper etc