Peripheral Nerve Injury

Question 1

Causes of peripheral nerve injury

Answer 1

compression
traction
laceration

Question 2

Types of PNI

Answer 2

Neurapraxia
Axonotmesis
Neurotmesis

Question 3

Neurapraxia

Answer 3

usually caused by nerve compression - like when you leave your arm hanging over the back of your chair and it goes numb
axon and nerve sheath are in contact but lose normal conduction

Question 4

Axonotmesis

Answer 4

axon damaged and demyelination
endoneurium (nerve sheath) is intact
ability for regrowth via Wallerian Degeneration
proximal injuries may require surgery as muscle will atrophy before the connection is re-established
moderate conduction block

Question 5

Neurotmesis

Answer 5

whole nerve trunk cut
degenerative cause
axon damage, demyelination and endoneurium damage occurs
lose conduction
Wallerian Degeneration occurs to attempt to repair however axon has nothing to grow along due to damage to endoneurium
requires surgery

Question 6

Wallerian Degeneration/Process of PN Repair

Answer 6

Degeneration of remaining axon, myelin sheath and schwann cells in the portion of the nerve distal to the site of injury

Regeneration/Repair
macrophages remove the debris
remaining neurilemma and endoneurium form a tunnel from the point of injury to the effector
new schwann cells grow inside the tunnel
cell body produces proteins needed for axon regrowth
axon sprouts appear
once sprout reaches the tunnel its growth rate increases
skeletal muscles cells atrophy until the nerve regrowth reaches them and connection is re-established

Question 7

Axonal Polyneuropathy

Answer 7

normally related to toxic and metabolic causes 
diabetic neuropathy 
alcoholic neuropathy 
vitamin deficiency 
neurotoxic agents 
bacterial infections 
viral infections

Question 8

Hereditary Polyneuropathy

Answer 8

very rare
Charco Marie Tooth disease
hypertrophic polyneuropathy

Question 9

Demyelinating Polyneuropathy

Answer 9

Guillian Barre Syndrome

Chronic inflammatory demyelinating polyneuropathy

Question 10

Effects of a PNL

Answer 10

Motor

• lose tone
• lose reflexes
• muscle paralysis
• muscle atrophy
• deformity due to imbalance between muscles

Sensory

• loss of cutaneous sensation
• lose proprioception
• homunculi changes to compensate for loss, nearby regions expand into the affected area

Autonomic
- sympathetic paralysis only occurs with axonotmesis and neurotmesis
Vasomotor changes - skin colour and temperature
Sudomotor - anhydrosis
Pilomotor - absent goosefles response
Trophic - skin, hair and nail quality changes

Question 11

Physio Treatment

Answer 11

If no repair

• educate
• maintain integrity and avoid infection
• positioning and ROM to avoid muscle contracture

If surgery to repair

• facilitate regaining muscle and sensory function
• educate
• positioning and ROM exercises to avoid contracture