Peripheral nerve injuries Flashcards
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
- Normal power
- Active movement against gravity and resistance
- Active movement against gravity alone
- Active movement without gravity
- Flicker of movement
- 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
Traction/operation
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
Iatrogenic
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
