Radial Mononeuropathy Clinical Presentation

Updated: May 22, 2017
  • Author: Wayne E Anderson, DO, FAHS, FAAN; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Presentation

History

Symptoms are dependent on the site of the lesion.

  • The most common reported symptom is wrist drop.
  • If the lesion is high above the elbow, then numbness of the forearm and hand may be an additional symptom.
  • If the lesion is in the forearm, sensation typically is spared despite the wrist drop.
    • Pain in the forearm resembling tennis elbow may be prominent.
    • This presentation is initially acute for several days to weeks.
  • If the lesion is at the wrist, patients report isolated sensory changes and paresthesias over the back of the hand without motor weakness.
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Physical

Radial neuropathy typically presents with weakness of wrist dorsiflexion (ie, wrist drop) and finger extension.

  • If the lesion is in the axilla, all radial-innervated muscles are involved.
    • The triceps and brachioradialis reflexes are decreased.
    • Sensation is decreased occur over the triceps, the posterior part of the forearm, and dorsum of the hand.
  • Acute compression of the radial nerve commonly occurs at the spiral groove. If the lesion is at this level, all radial-innervated muscles distal to the triceps are weak.
    • Triceps reflex is preserved, but brachioradialis is decreased.
    • Sensory loss is over the radial dorsal part of the hand and the posterior part of the forearm.
    • Numbness over the triceps area is variable.
  • In isolated posterior interosseous lesions, sensation is spared and motor involvement occurs in radial muscles distal to the supinator.
    • Brachioradialis reflex is intact.
    • The extensor carpi radialis sometimes is also spared, resulting in radial deviation with wrist extension.
    • Pain may occur with palpation at the proximal forearm and with forceful supination.
  • In distal radial sensory lesions at the wrist, no motor weakness occurs. Numbness of the dorsal hand is noted, sparing the fifth digit.
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Causes

See the list below:

  • Penetrating trauma can cause injury anywhere along the nerve.
  • Compressive lesions high in the axilla can occur from improper use of crutches.
  • Compression injuries at the humeral spiral groove occur in patients with sustained compression of this area over a period of several hours.
    • This is reported in patients who fall asleep in a drunken or drug-induced stupor with the arm over a chair. It also can occur in honeymooners.
    • Fracture of the humerus is a common cause of radial neuropathy due to compression or secondary laceration of the nerve as it wraps around the humerus near the spiral groove. [3]
    • Radial neuropathy has also been reported in wheelchair users, when the spiral groove of the humerus is compressed on a hard wheelchair surface. [4]
  • Subluxation of the radius can produce radial nerve injury in the proximal forearm.
  • The posterior interosseous syndrome typically occurs from compression of this division of the radial nerve as penetrates the supinator muscle within the proximal forearm. [5]
    • It is associated with repetitive supination of the forearm and hypertrophy of the supinator muscle.
    • It also can occur secondary to elbow synovitis, ganglion cysts [6] , enlarged bursa from the elbow, or tumors (especially lipomas at the entry of the radial nerve into the supinator muscle).
  • Isolated distal sensory radial neuropathy is associated with compression from handcuffs and tight bracelets.
  • Bilateral radial palsies suggest lead intoxication. Lead exposure may be occupational. [7]
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