Radial Nerve Palsy

Nerve supply

• Motor
  • Triceps
  • Brachioradialis
  • Extensor carpi radialis longus and brevis
  • Extensor carpi ulnaris
  • Supinator
  • Extensor digitorum (metacarpophalangeal joint extension)
  • Extensor indicis
  • Extensor digiti minimi
  • Extensor pollicis brevis and longus
  • Abductor pollicis longus
• Sensory
  • Dorsal aspect of radial 3½ digits
  • Posterior aspect (in the midline) of the forearm
  • Posterior aspect of the distal arm

Examination

• Inspection
  • Wrist drop (ECR, ECU weakness)
  • Scars – axilla, arm, elbow, forearm
  • Wasting of the posterior compartment of the forearm
• Reflexes
  • Triceps jerk only affected in lesions at the axilla, otherwise preserved
• Power
  • Radial nerve
    • Elbow extension (radial nerve lesion in the axilla)
    • Elbow flexion with forearm held between supination and pronation (brachioradialis, spiral groove or axillary lesions)
    • Forearm supination (supinator, spiral groove or axillary lesions)
    • Wrist extension (ECR, ECU, spiral groove or axillary lesions)
    • MCPJ extension (extensor digitorum, extensor indicis, extensor digiti minimi, lesions at the radial neck, spiral groove lesions or axillary lesions)
  • Ulnar nerve
    • Normal extension of IPJs
    • Normal thumb adduction
  • Median nerve
    • Normal thumb flexion
    • Normal thumb abduction
• Sensation
  • Affected over the first dorsal web
  • Palmar aspect of thumb is supplied by the median nerve / C6
  • Palmar aspect of the middle finger is supplied by median nerve / C7
  • Little finger is supplied by ulnar nerve / C8

Differential diagnosis

• C7 lesion (sensation over palmar aspect of middle finger affected)
• Plexopathy

Causes of a radial nerve palsy

• Axillary
  • Crutch palsy
  • Trauma
• Spiral groove
  • Mid-shaft humerus fracture
  • Saturday night palsy
• Proximal forearm (posterior interosseous nerve is a pure motor nerve)
  • Neck of radius fracture
  • Elbow dislocation
  • Rheumatoid nodules
  • Tight cast
• Wrist
  • Tight watches / jewelry / handcuffs
  • Distal radius fracture
• Mononeuritis multiplex

Localizing the radial nerve lesion

Function	Axillary	Spiral Groove	Proximal Forearm	Wrist
Elbow extension	Weak	Normal	Normal	Normal
Elbow flexion	Weak	Weak	Normal	Normal
Forearm supination	Weak	Weak	Normal	Normal
Wrist extension	Absent  (ECR, ECU)	Absent (ECR, ECU)	Weak (ECU)	Normal
MCPJ extension	Weak	Weak	Weak	Normal
Sensation	Dorsal 1st web, posterior arm	Dorsal 1st web	Normal	Dorsal 1st web

Investigations

• Nerve conduction studies to confirm diagnosis
• Radiographs of wrist and elbow if underlying fracture suspected

Management

• Multidisciplinary approach
• Analgesia if needed
• Splinting, physiotherapy to maximize and regain function
• Consider surgical exploration