Anterior interosseous neuropathy


  • Anterior interosseous nerve (C5-T1) is a branch of the median nerve that supplies motor innervation to the deep forearm muscles
  • Compression or injury can cause an isolated AIN palsy
  • Brachial plexopathy or cervical spine pathologies may present with combined median nerve palsies


Clinical Features

  • May have forearm pain although not as common in other median nerve compression syndromes[1]
  • Weakness of finger flexion (FDL), thumb flexion (FPL), and pronation (pronator quadratus)
  • Inability to hold a piece of paper between index and thumb fingertips (can't make "OK" sign)
  • No sensory loss

Differential Diagnosis

Upper extremity peripheral nerve syndromes

Median Nerve Syndromes

Ulnar Nerve Syndromes

  • Ulnar neuropathy at the elbow and wrist

Radial Nerve Syndromes

Proximal Neuropathies



  • Clinical diagnosis
  • Plain films
  • Outpatient EMG or MRI


  • Nonoperative: rest, activity modification, NSAIDs, splinting
  • Operative decompression: compressive masses


  • Discharge with orthopedic follow up

See Also


  1. Dang AC et al. Unusual Compression Neuropathies of the Forearm, Part 2: Median Nerve. JHS. 2009;34A:1915-1920.
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