Posterior interosseous neuropathy

Background

• Posterior interosseous nerve (C7-8) is a branch of the radial nerve that supplies motor innervation to the forearm extensor muscles
• Compression or injury can cause an isolated PIN palsy
• More proximal pathologies can cause a combined palsy
• More common in body builders and laborers due to repetitive pronosupination

Causes

• Peripheral neuropathy
  • Repetitive microtrauma
  • Entrapment
  • Trauma
    • Forearm fracture
  • Space occupying lesions
    • Ganglion cyst
    • Lipoma
    • Bone tumor
• Iatrogenic

Clinical Features

Cutaneous innervation of the upper limb

• Forearm and wrist pain
• Weakness on finger and wrist extension

Differential Diagnosis

Upper extremity peripheral nerve syndromes

Median Nerve Syndromes

• Carpal tunnel syndrome
• Pronator teres syndrome
• Anterior interosseous neuropathy

Ulnar Nerve Syndromes

• Ulnar neuropathy at the elbow and wrist

Radial Nerve Syndromes

• Radial neuropathy at the spiral groove (ie. "Saturday night palsy")
• Posterior interosseous neuropathy

Proximal Neuropathies

• Suprascapular neuropathy
• Long thoracic neuropathy
• Axillary neuropathy
• Spinal accessory neuropathy
• Musculocutaneous neuropathy

Other

• Brachial plexopathy
• Cervical radiculopathy

Evaluation

Workup

• Plain films
• EMG (as outpatient)

Diagnosis

• Usually a clinical diagnosis (in ED)

Management

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

Disposition

• Discharge with orthopedic follow up

See Also

• Peripheral nerve syndromes