• Clinical science

Radial neuropathies

Abstract

Radial neuropathies are conditions caused by acute or chronic injury to the radial nerve. Clinical presentations vary with the mechanism, site, and extent of nerve injury. The radial nerve arises from the posterior cord of the brachial plexus, which comprises cervical roots C5–T1. Within the upper extremity, the radial nerve has lateral cutaneous sensory branches and innervates extensors. When injured, radial neuropathies are therefore characterized by sensory symptoms of pain, paresthesia, and numbness, as well as motor symptoms of weakness of extension at the elbow, wrist (“wrist drop”), and/or fingers. Several risk factors are associated with subtypes of radial neuropathies, including crutch use, intoxication, fracture of the humerus or radius, use of tight watch bands or handcuffs, and repetitive pronation and supination. The patient history and examination, including Tinel's sign, may be sufficient for diagnosis in some cases, but x-ray is necessary in the presence of trauma, and electrodiagnostics, though less useful than in carpal tunnel syndrome, may be considered if symptoms persist. Conservative management, consisting of local corticosteroid injections and counseling to reduce risk factors, is typically the treatment of choice in nontraumatic cases. Surgical decompression, with approach varying by location, may be considered in refractory cases.

Etiology

  • Risk factors vary according to the location of the injury:
    • Axilla: improper crutch use
    • Mid-arm (Saturday night or Honeymoon palsy):
      • Fracture of humerus (radial nerve runs in spiral groove)
      • Compression of the radial nerve due to draping of arm over furniture or pressure on mid-arm; more likely in the setting of intoxication, anesthesia, or sleep
    • Elbow: radial tunnel syndrome (controversial diagnosis) due to chronic compression within the radial tunnel:
    • Deep forearm: posterior interosseous nerve syndrome due to fracture of the radial head or chronic soft tissue compression
    • Superficial forearm or wrist: superficial radial nerve compression, called “cheiralgia paresthetica,” often due to tight wristwatches or handcuffs or repetitive pronation and supination

References:[1][2][3][4][5][6]

Clinical features

Anatomy

The radial nerve innervates all of the extensors of the forearm, hand, and fingers. It courses through the radial groove between the brachioradialis and brachialis muscles, then winds around the shaft of the humerus to reach the elbow, where it splits into a deep (motor) branch and a superficial (sensory) branch. The deep branch passes through the supinator muscle (radial tunnel) and courses through the posterior compartment of the forearm before reaching the wrist. The superficial branch courses along the radial side of the forearm and ends as a sensory nerve on the radial aspect of the dorsal hand, where it innervates the thumb, the index finger, and the radial half of the middle finger.

Clinical features

Site of lesion Sensory symptoms Motor symptoms
Axilla
  • All below
  • All below
  • Paralysis of the triceps muscle may occur if the radial nerve is injured in the axilla.
Mid-arm
  • All below
  • Numbness, paresthesia, pain along lateral posterior arm
  • All below
  • Wrist drop
    • Paralysis or weakness of the hand and finger extensors (decreased grip strength)
    • The patient cannot extend their hand at the wrist joint.
Elbow (radial tunnel)
  • Pain and tenderness following extension or repetitive pronation/supination
  • Sometimes weakness of extension and supination, secondary to pain (not to missing innervation!)
Deep Forearm (proximal posterior interosseous nerve)
  • None
  • Paralysis of the finger extensors (no true wrist drop!)
Superficial forearm and wrist (superficial radial nerve)
  • Deficits on the radial side of the dorsum of the hand (thumb, index finger, and the radial half of the middle finger)
  • None


The higher (more proximal) the lesion, the greater the number of extensor muscles involved!

References:[2][3][5][6][4]

Diagnostics

  • History: Inquire about risk factors, including substance use, trauma, and causes of compression. Ask the patient to describe the timeline of symptoms, history of similar symptoms, and associated symptoms such as joint pain.
  • Physical examination: Focus the exam on the most proximal location of injury, if known (see “Clinical Features”)
  • Instrumental diagnostics: x-ray, electromyography (EMG), nerve conduction studies, ultrasound, MRI

References:[3][5][6][7]

Treatment

  • The treatment of choice depends on the severity and persistence of symptoms.
  • Conservative therapy
  • Surgical therapy in severe and treatment-resistant cases: nerve decompression, neurorrhaphy, nerve transplantation, tendon transfer
  • Orthopedic repair of fractures, dislocations, or other traumatic injury

References:[2][3][5][8]

  • 1. Le T, Bhushan V. First Aid for the USMLE Step 1 2015. McGraw-Hill Education; 2014.
  • 2. Anderson WE. Radial Mononeuropathy. In: Radial Mononeuropathy. New York, NY: WebMD. http://emedicine.medscape.com/article/1141674. Updated March 30, 2016. Accessed April 7, 2017.
  • 3. Stern M. Radial Nerve Entrapment. In: Radial Nerve Entrapment. New York, NY: WebMD. http://emedicine.medscape.com/article/1244110. Updated September 13, 2016. Accessed April 7, 2017.
  • 4. Loh YC, Lam WL, Stanley JK, Soames RW. A new clinical test for radial tunnel syndrome: the Rule-of-Nine test: a cadaveric study. J Orthop Surg. 2004; 12(1): pp. 83–86. doi: 10.1177/230949900401200115.
  • 5. Donofrio PD. Textbook of Peripheral Neuropathy. Demos Medical; 2012.
  • 6. Brazis PW, Masdeu JC, José Biller J. Localization in Clinical Neurology. Lippincott Williams & Wilkins; 2006.
  • 7. Birch R. Surgical Disorders of the Peripheral Nerves. Springer; 2011.
  • 8. Grinsell D, Keating CP. Peripheral nerve reconstruction after injury: a review of clinical and experimental therapies. Biomed Res Int. 2014; 2014. doi: 10.1155/2014/698256.
  • Le T, Bhushan V, Sochat M, Petersen M, Micevic G, Kallianos K. First Aid for the USMLE Step 1 2014. McGraw-Hill Medical; 2014.
  • Szekeres M. Tenodesis extension splinting for radial nerve palsy. Tech Hand Up Extrem Surg. 2006; 10(3): pp. 162–165. doi: 10.1097/01.bth.0000231968.51170.6b.
  • Nanjundaiah K, Jayadevaiah ShM, Chowdapurkar Sh. Long head of triceps supplied by axillary nerve. Int J Anat Var. 2012; 5: pp. 35–37. url: http://www.pulsus.com/scholarly-articles/long-head-of-triceps-supplied-by-axillary-nerve.html.
last updated 11/19/2018
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