Peripheral nerve injuries

Question 1

Outline Seddon’s classification of nerve injury

Answer 1

Neurapraxia (I): reversible conduction block
Axonotmesis: axonal interruption
(II) full recovery
(III) partial recovery
(IV) no recovery
Neurotmesis (V): axonal and endoneurium interruption
-fibrosis of proximal end: neuroma formation
-irrecoverable without surgical intervention

Question 2

What is Wallerian degeneration?

Answer 2

Atrophy of denervated motor end-plates and sensory receptors. Irreversible motor and sensory loss if not re-innervated within 2 years.

Question 3

Describe axonal regeneration

Answer 3

Proximal stump sprouts unmyelinated tendrils
Tendrils spread towards Schwann cells, and return to an old endoneurial tube
Axon slowly regenerates at 1 mm/day
Eventually join to denervated end-organs
May result in full, partial, or no recovery of function

Question 4

Outline the MRC scale for muscle power

Answer 4

5. Normal power
6. Active movement against gravity and resistance
7. Active movement against gravity alone
8. Active movement without gravity
9. Flicker of movement
10. No movement

Question 5

Outline the treatment principles for nerve injuries

Answer 5

Open nerve injuries: explored and consider repair

• if cleanly cut: end-to-end suture
• ragged cut: paring of stump, then suture
• if nerve under tension when joined, consider mobilising the nerve or using nerve grafts or nerve conduits
• post-op physiotherapy

Closed nerve injury: wait and see if nerve recovers
-if no recovery: delayed repair

Motor function fails to recover: tendon transfer

Question 6

Name 2 causes of brachial plexus injury

Answer 6

Stab wound
Supraclavicular: motorcycle accidents
Infraclavicular: shoulder fracture or dislocation

Question 7

Describe the presentation of upper plexus injuries (C5 and C6)

Answer 7

Erb’s palsy
Motor paralysis of
-shoulder abduction: suprascapular n, axillary n
-shoulder external rotation: axillary n, suprascapular n
-forearm supination: musculocutaneous nerve
Sensory loss along outer aspect of arm and forearm

Suprascapular n: supraspinatus, infraspinatus
Axillary n: deltoid, teres minor
Musculocutaenous nerve: biceps, brachialis, coracobrachialis

Question 8

Describe the presentation of lower plexus injuries (C8 and T1)

Answer 8

Klumpke’s paralysis
Paralysis of intrinsic hand muscles: clawing
Sensory loss along inner aspect of arm

Question 9

What features suggest preganglionic avulsion injury to the brachial plexus?

Answer 9

Burning pain in an anaesthetic hand
Paralysis of scapular muscles or diaphragm
Horner’s syndrome
Severe vascular injury
Associated fractures of the cervical spine
Spinal cord dysfunction

N.B. preganglionic damage is irreparable

Question 10

In which situations do brachial plexus lesions require emergency surgery?

Answer 10

Penetration wounds
Vascular injury
Severe (high-energy) soft-tissue damage

Question 11

How can the long thoracic nerve be damaged?

Answer 11

Shoulder or neck injuries
Carrying heavy loads on the shoulder
Axillary node clearance

Question 12

What sign is seen with long thoracic nerve palsy?

Answer 12

Winging of the scapula: demonstrated by asking patient to push forcefully against a wall

Question 13

How can the spinal accessory nerve (CNXI) be damaged?

Answer 13

Stab wounds

Operations in posterior triangle of neck

Question 14

What typically causes axillary nerve injury, and how does the palsy present?

Answer 14

Shoulder dislocation
Humeral head fracture

Cannot abduct shoulder beyond 15 degrees
Sensory loss over regimental patch (C5)
Deltoid muscle wasting

N.B. Typically recovers within 8 weeks

Question 15

Name 3 causes of radial nerve palsy, and describe how it presents

Answer 15

Low: fracture or dislocation of elbow, surgery
High: humeral shaft fracture, Saturday night palsy
Very high: crutch palsy (compression at axilla)

Wrist drop
Sensory loss: dorsal side around base of thumb

Question 16

Describe the features of ulnar nerve plasy

Answer 16

Presents at rest
Clawing of ring and little finger
-interphalangeal flexion
-hyperextension of MCPJ
Wasting of intrinsic muscles
Sensory loss over medial aspect of hand, including medial 1.5 digits

Ulnar paradox: higher lesions produce a less clawed appearance due to paralysis of ulnar half of flexor digitorum profundus

Question 17

Name 2 consequences of median nerve palsy

Answer 17

Carpal tunnel syndrome: flexor retinaculum

Hand of benediction: wrist or elbow

Question 18

Describe the clinical features of carpal tunnel syndrome

Answer 18

Pain or paraesthesia: typically localised to median innervated fingers, but may involve entire hand or radiate into the forearm
Common at night and after repetitive movement
Relieved by hanging arm or shaking*
Late: clumsiness and weakness

Wasting of thenar eminence
Sensory deficit of lateral 3.5 digits
Sparing of lateral palmar sensation

Question 19

Describe the presentation of Hand of Benediction

Answer 19

Present when attempting to make a fist

Loss of flexion at MCPJ and DIP joints of the middle and index fingers

Question 20

Name 2 causes of femoral nerve injury

Answer 20

Gunshot wound
Traction/operation
Bleeding into the thigh

Question 21

Describe the clinical features of femoral nerve palsy

Answer 21

Weakness of knee extensors
Numbness of anterior thigh and medial aspect of leg
Knee jerk reflex absent

Question 22

Name 2 causes of sciatic nerve injury

Answer 22

Local trauma: hip dislocation or fracture
Gunshot wounds
Iatrogenic

Question 23

Describe the clinical features of sciatic nerve palsy

Answer 23

Foot-drop: loss of dorsiflexion
Numbness in leg and foot
Paralysis of muscles below knee
Wasting of calfs, trophic ulcers

Question 24

Name 2 causes of common peroneal nerve injury

Answer 24

Lateral ligament injuries: leg forced into varus, or pressure from splint/plaster, bumper car fractures
Lying with leg externally rotated

Question 25

Describe the clinical features of common peroneal nerve injury

Answer 25

Foot-drop: weakened dorsiflexion and eversion

Sensory loss over front and outer half of leg, and dorsum of the foot

Question 26

What is the sensory supply of the superficial peroneal nerve?

Answer 26

Sensation over outer side of leg and foot

Question 27

What is the sensory supply of the deep peroneal nerve?

Answer 27

Sensation around the first web space on the dorsum of the foot