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Flashcards in Peripheral nerve injuries Deck (27)
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Outline Seddon's classification of nerve injury

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


What is Wallerian degeneration?

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


Describe axonal regeneration

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


Outline the MRC scale for muscle power

5. Normal power
4. Active movement against gravity and resistance
3. Active movement against gravity alone
2. Active movement without gravity
1. Flicker of movement
0. No movement


Outline the treatment principles for nerve injuries

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


Name 2 causes of brachial plexus injury

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


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

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


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

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


What features suggest preganglionic avulsion injury to the brachial plexus?

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


In which situations do brachial plexus lesions require emergency surgery?

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


How can the long thoracic nerve be damaged?

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


What sign is seen with long thoracic nerve palsy?

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


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

Stab wounds
Operations in posterior triangle of neck


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

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


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

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


Describe the features of ulnar nerve plasy

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


Name 2 consequences of median nerve palsy

Carpal tunnel syndrome: flexor retinaculum
Hand of benediction: wrist or elbow


Describe the clinical features of carpal tunnel syndrome

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


Describe the presentation of Hand of Benediction

Present when attempting to make a fist
Loss of flexion at MCPJ and DIP joints of the middle and index fingers


Name 2 causes of femoral nerve injury

Gunshot wound
Bleeding into the thigh


Describe the clinical features of femoral nerve palsy

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


Name 2 causes of sciatic nerve injury

Local trauma: hip dislocation or fracture
Gunshot wounds


Describe the clinical features of sciatic nerve palsy

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


Name 2 causes of common peroneal nerve injury

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


Describe the clinical features of common peroneal nerve injury

Foot-drop: weakened dorsiflexion and eversion
Sensory loss over front and outer half of leg, and dorsum of the foot


What is the sensory supply of the superficial peroneal nerve?

Sensation over outer side of leg and foot


What is the sensory supply of the deep peroneal nerve?

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