Peripheral nerve injuries

Question 1

What diameter do peripheral nerves range from

Answer 1

0.2-22 um

Question 2

What coats the axons

Answer 2

Endonurium

Question 3

What coats the fascicles

Answer 3

Perineurium

Question 4

What coats the nerve itself

Answer 4

Epineurium

Question 5

What are Aa function

Answer 5

Large motor axons
Muscle stretch
Tension sensory axons

Question 6

What are Ab function

Answer 6

Touch
Pressure
Vibration
Joint sensory position

Question 7

What are Ay function

Answer 7

Gamma efferent motor axons

Question 8

What are A (delta) function

Answer 8

Sharp pain
Very light touch
Temperature sensation

Question 9

What are B function

Answer 9

Sympathetic preganglionic motor axons

Question 10

What are C function

Answer 10

Dull, aching burning pain

temperature sensation

Question 11

How can injury to a peripheral nerve occur

Answer 11

Compression

trauma

Question 12

What can compress nerves

Answer 12

Nerve entrapment

Compression conditions

Question 13

What are Classical compression conditions

Answer 13

Carpal tunnel syndrome

Sciatica

Morton’s neuroma

Question 14

What is compressed in carpal tunnel syndrome

Answer 14

median nerve

Question 15

What is compressed in sciatica

Answer 15

Spinal root compression by intervertebral disc

Question 16

What is compressed in mortons neuroma

Answer 16

digital nerve in 2nd or 3rd web space of forefoot are compressed in sole of foot)

Question 17

What nerve damage can trauma cause

Answer 17

• Neurapraxia
• Axonotmesis
• neurotmesis

Question 18

What is neupraxia

Answer 18

• Nerve in continuity in neuropraxia.
• Stretched (8% will damage microcirculation) or bruised
• You get a Reversible conduction block due to local ischaemia and demyelination
• For a short area in the nerve you cannot get conduction.
• Prognosis good (weeks or months)

Question 19

What is axonotmesis

Answer 19

• Endoneurium intact (tube in continuity), but disruption of axons within it;

Question 20

what causes axonotmesis

Answer 20

• Can occur by the nerve being stretched (15% elongation disrupts axons) or severly crushed or direct blow

Question 21

What is pathophysiology of axonotmesis

Answer 21

• Wallerian degeneration follows (distal to sight of injury. The nerve fibre disappears but the endoneurial tube remains. Proximally the nerve shrinks back to the last node of ranvier.

Question 22

what is prognosis of axonotmesis

Answer 22

• Prognosis fair (sensory recovery often better than motor - often not normal but enough to recognise pain, hot & cold, sharp & blunt)

Question 23

What is Neurotmesis

Answer 23

• Complete nerve division and loss of endoneurium (possibly perineurium)

Question 24

What typically causes Neurotmesis

Answer 24

Laceration or Avulsion

Question 25

What is prognosis of Neurotmesis

Answer 25

Poor prognosis No recovery unless repaired (by direct suturing or grafting)

Question 26

What are closed nerve injuries

Answer 26

Neuropraxis | axonotmesis,

Question 27

What is treatment for closed nerve injuries

Answer 27

Surgery indicated after 3 months if it has not recovered If no recovery is identified - Clinical - Electromyography-

Question 28

What is the Axonal growth rate

Answer 28

Axonal growth rate (1–3 mm/day)

Question 29

What are open nerve injuries

Answer 29

Neurotmesic injuries

Question 30

what is wallerian degeneration

Answer 30

Changes (death) of axons distal to the sight of a nerve injury

Question 31

What are motor changes seen in nerve injury

Answer 31

- Paresis (weakness) or paralysis ± wasting - Dry skin o Loss of tactile adherence since sudomotor nerve fibres not stimulating sweat glands in skin

Question 32

What are sensory changes in a nerve injury

Answer 32

``` - Dysaethesiae (disordered sensation) o Anaesthetic (numb), hypo- & hyper-aesthetic, paraesthetic (pins & needles) ```

Question 33

What happens about 4 days after a peripheral nerve injury

Answer 33

Proximal axonal budding occurs after about 4 days

Question 34

What does the Prognosis for recovery depend on:

Answer 34

- whether nerve is o “pure” (only sensory or only motor) o “mixed” (both sensory and motor within same nerve) - how distal the lesion is (proximal worse)

Question 35

Does a pure nerve or mixed nerve have a better prognosis

Answer 35

pure nerve tends ro receoer better because in general even if there is miswiring and they grow and miss their own tube but grow down to antoher oenen. They will all grow down to motor end plates of sensory end plates

Question 36

Why do mixed nerves have a worse prognosis

Answer 36

mixed nerves have a variable recovery as the senory nerves (some) can gorw back down the motor tubes and the motor axons down the sensry tubes and you will therefore get a much more imcomplete recovery.

Question 37

Why does the nerve recover better if the injury is more distal

Answer 37

Distal better recovery due to the 1mm growth a day. If it’s a long distance to grow back down then you get degeneration of the endplates to when the nerve gets to the end plate it doesn’t function as well.

Question 38

What can be used to monitor recovery of a nerve

Answer 38

Tinnel' sign | Electrophysiological Nerve Conduction Studies