What is Radial Neuropathy

Radial neuropathy is a type of mononeuropathy which results from acute trauma to the radial nerve that extends the length of the arm.

What is involved?

Radial Nerve


  • Most frequently at the Spiral Groove of the humerus
  • Could be at the Axilla (Saturday Night palsy)
  • Or in the Forearm (Posterior Interosseous Syndrome)

Common symptoms

  • Wrist drop, Patient unable to extend wrist or fingers up
  • Almost always unilateral
  • No associated pain
  • Occasional forearm/hand/thumb numbness
  • Symptoms always present no night/day preference


  • Sudden
  • Usually happens upon waking up one morning
  • Or, after a “Saturday Night” at the bar falling asleep with arm hanging over back of chair
  • Or following prolonged sitting in a position with arm leaning against sharp object
  • Or following misplaced intramuscular injection in the vicinity of the Radial nerve

Risk factors

  • No gender preference
  • Diabetes or family history of Diabetes, Alcoholism
  • Leaning on arms/axilla, sleeping in wrong position or with somebody leaning on arm, trauma


  • When first seen, weakness but no atrophy – Wrist drop with inability to extend wrist, fingers
  • Always check the three following muscles: Triceps, Brachio-Radialis, Extensor Indicis Proprius
  • Triceps: Ask subject to extend elbow
  • Brachio-Radialis: Ask subject, with thumb pointing to ceiling, to flex forearm. Make sure the belly of the Brachio-Radialis is easily visible (compare to healthy side)
  • Extensor Indicis Proprius: With hand flat on bed, ask subject to raise index finger up
  • Occasional numbness/decreased sensation over dorsum of hand/thumb area
  • Difficulty spreading fingers (pseudo-ulnar interosseii weakness)
  • Pseudo-Ulnar weakness correctible when wrist held level with forearm by examiner
  • Positive Tinel sign (tingling upon tapping nerve) at the humeral Spiral Groove when lesion at that location


Three possible locations determined by exam of Triceps, Brachio-Radialis and Extensor Indicis Proprius.

  • Axilla: Triceps, Brachio-Radialis and Extensor Indicis Proprius all weak, normal to decreased sensation over dorsum hand/thumb area
  • Humeral Spiral Groove: Triceps strength is normal, weak Brachio-Radialis (can barely see belly of muscle) and weak Extensor Indicis Proprius, normal to decreased sensation over dorsum hand/thumb area
  • Forearm (Posterior Interosseous Syndrome): Triceps and Brachio-Radialis normal, Extensor Indicis Proprius weak, normal sensation over dorsum hand/thumb area


  • Very Good for localization (Axilla, Spiral Groove, Forearm)
  • Very Good for Prognostic value: In pure myelin lesions (conduction block), recovery may occur after three weeks to a month
  • In moderate/severe axonal lesions, recovery may take from 6 months to a year
  • In mixed lesions, somewhere in between


  • Slowing, drop in Extensor Indicis Proprius amplitude across compression area in myelin lesions
  • Diffuse drop in Extensor Indicis Proprius amplitude with or without slowing in axonal lesions
  • Mixture of above in mixed lesions
  • Radial sensory spared only in forearm (posterior interosseous) lesions


  • Symptomatic treatment
  • Stop/decrease cause
  • Wrist/finger splint to keep fingers extended in moderate to severe axonal lesions
  • Passive wrist, fingers Range of Motion to maintain mobility

What else could it be?

  • If other nerves involved, could be Brachial Plexus lesion (do not make the mistake of diagnosing a superimposed Ulnar neuropathy because the interosseii “appear” weak)
  • Bilateral Radial palsies, always look for Lead poisoning
  • Very rarely, Myotonic Dystrophy can cause weak, wasted forearms and bilateral wrist drop

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