Median Nerve

Median Nerve, superficial palmar nerves showing the terminal branches of the median nerve, gray’s anatomy plate 815
Superficial palmar nerves showing the terminal branches of the median nerve, Gray’s Anatomy plate 815. Image by Henry Vandyke Carter, Wikimedia Commons, Public domain.

Anatomy

  • Formed from the lateral (C5 to C7) and medial (C8, T1) cords
  • Passes under the lacertus fibrosus, between the heads of pronator teres and under the FDS arch
  • AIN arises just distal to the elbow and supplies FPL, FDP to index and middle, and pronator quadratus
  • Palmar cutaneous branch arises proximal to the wrist, superficial to the transverse carpal ligament
  • Recurrent motor branch is extraligamentous, subligamentous or transligamentous
  • Hand supply to radial two lumbricals, opponens pollicis, APB and superficial head of FPB

Clinical Features

Low lesion

  • Thenar wasting with loss of thumb abduction and opposition (ape hand)
  • Sensory loss over the radial three and a half digits

High lesion

  • Adds loss of FPL, FDP to index and middle, FDS and weak pronation
  • Benediction attitude on attempted fist and a positive Ochsner clasp test

AIN syndrome

  • Pure motor palsy with no sensory loss
  • Cannot make an O sign, pinching with thumb IP and index DIP hyperextended
  • Causes include deep head pronator teres bands, the FDS arch and Gantzer muscle
  • AIN is the nerve most often injured in paediatric supracondylar fractures
  • Parsonage-Turner syndrome often presents as AIN palsy after severe shoulder pain
  • Intact tenodesis effect excludes FPL rupture

Pronator syndrome

  • Compression at ligament of Struthers, lacertus fibrosus, pronator teres or FDS arch
  • Volar forearm ache and paraesthesia including the palm, usually without nocturnal symptoms
  • Provoked by resisted pronation, resisted elbow flexion in supination or resisted middle finger PIP flexion

Carpal tunnel syndrome

  • Most common compression neuropathy, tunnel holds the median nerve and nine flexor tendons
  • Nocturnal paraesthesia, positive Phalen and Durkan tests, thenar wasting when advanced
  • Nerve conduction studies confirm the diagnosis and grade severity

Management

  • AIN palsy without structural cause recovers with observation over several months
  • Pronator syndrome, nonoperative care then release of all potential sites
  • Carpal tunnel syndrome, night splints and corticosteroid injection, then open or endoscopic release

Complications

  • Carpal tunnel release risks palmar cutaneous or recurrent motor branch injury

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.