| Patient Education |
|
Click here for patient education.
|
|
You are in: eMedicine Specialties >
Neurology > Electromyography and Nerve Conduction Studies
Radial Mononeuropathy
Article Last Updated: Sep 26, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Wayne E Anderson, DO, Assistant Professor of Internal Medicine/Neurology, Western University of Health Sciences; Assistant Professor of Family Medicine, Touro University College of Osteopathic Medicine; Consulting Staff in Pain Management, Department of Neurology, California Pacific Medical Center
Wayne E Anderson is a member of the following medical societies: American Academy of Neurology, American Medical Association, American Society of Law Medicine and Ethics, California Medical Association, and San Francisco Medical Society
Coauthor(s):
Elizabeth A Sekul, MD, Associate Professor, Department of Neurology, Medical College of Georgia
Editors: Aashit K Shah, MD, Associate Professor of Neurology, Wayne State University; Program Director, Clinical Neurophysiology Fellowship, Department of Neurology, Detroit Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Neil A Busis, MD, Chief, Division of Neurology, Department of Medicine, Head, Clinical Neurophysiology Laboratory, University of Pittsburgh Medical Center-Shadyside; Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital; Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Author and Editor Disclosure
Synonyms and related keywords:
radial mononeuropathy, Saturday night palsy, honeymooner's palsy, wrist drop, radial neuropathy
Background
Radial neuropathies result from injury due to penetrating wounds or fractures of the arm, compression, or ischemia. Most commonly, they present with a wrist drop. The pattern of clinical involvement is dependent on the level of injury.
Radial neuropathies can occur from surgical procedures such as humeral nailing performed to stabilize an acute humeral fracture.1
The terms Saturday night palsy and honeymooner's palsy refer to the concept of placing one's arm over another chair, with the resultant pressure causing injury to the radial nerve.
Pathophysiology
An introduction to radial nerve anatomy is essential for understanding the common mechanisms and location of its injury. The radial nerve branches from the posterior cord of the brachial plexus. It receives root innervation from C5-T1 spinal roots. In the upper arm, the radial nerve gives off a branch to the triceps muscle before it wraps around the humerus at the spiral groove. Three sensory branches, which supply the skin over the triceps and posterior forearm, also are given off at this level. Here, its proximity to the humerus makes it susceptible to compression and/or trauma. After exiting the spiral groove, the radial nerve supplies the brachioradialis muscle before dividing into the posterior interosseous branch and a sensory branch. The posterior interosseous branch is a pure motor nerve that supplies the supinator. It then dives into the supinator through the fascia to supply the muscles of the wrist and finger extension. This fascia is another common site for nerve damage to occur. The sensory branch that arises approximately at the elbow travels down the forearm, becoming superficial at the wrist before it supplies the lateral aspect of the dorsum of the hand.
Frequency
United States
Radial neuropathy is the fourth most common mononeuropathy.
Race
No racial preponderance is known.
Sex
No gender predilection has been observed.
Age
Radial neuropathy is reported in all age groups.
History
Symptoms are dependent on the site of the lesion.
- The most common complaint is wrist drop.
- If the lesion is high above the elbow, then numbness of the forearm and hand may be an additional complaint.
- 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 complain of isolated sensory changes and paresthesias over the back of the hand without motor weakness.
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.
Causes
- 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.
- 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.
- 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, 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
Median Neuropathy
Multifocal Motor Neuropathy With Conduction Blocks
Ulnar Neuropathy
Other Problems to be Considered
Lesion of the posterior cord of the brachial plexus
Cervical disk syndromes
Imaging Studies
- A recent study showed that ultrasound examination can localize radial neuropathy more rapidly than standard electrophysiological testing.2
- Occasionally, imaging of the elbow region or the humeral area is indicated to determine if any mass or bony lesions are compressing the nerve. Plain radiographs may show bony causes of compression, such as fractures, dislocations, callus formations, or osteophytes. MRI is particularly helpful for soft tissue evaluation and more direct imaging of the nerve.
Other Tests
- Nerve conduction studies and needle electromyography (EMG) are essential for specific localization and to rule out a more generalized process.
Medical Care
Therapy is dependent on the site and cause of the lesion.
- When the lesion is due to external compression at the spiral groove, removing the source of the compression and conservative management is indicated.
- Physical therapy and wrist splinting helps in reestablishing functional use of the hand.
- If the lesion is due to a humeral fracture, the fracture must be carefully reduced and set to avoid further injury. This may require external fixation.
- If no recovery is noted within several months, then exploration for the site of compression or transection with possible surgical re-anastomosis may be indicated.
- With posterior interosseous neuropathies, repetitive supination of the forearm should be avoided.
- In distal radial sensory nerve lesions, management is typically conservative.
Surgical Care
Surgical exploration may be considered for a chronic compressive lesion or transection.
- Surgical exploration frequently is indicated for release of the nerve from tethered points in the forearm.
- Localizing the lesion prior to surgery via EMG is important to assist the surgeon in identifying which section of the nerve is most likely involved.
- When transection is suspected as the mechanism of injury, conservative management for several months is indicated to assure that no nerve regrowth has occurred either clinically or by electrodiagnostic measures.
- If no regeneration or inadequate regeneration is confirmed, surgical exploration with possible re-anastomosis may be indicated.
- Selective tendon transfer may allow for finger extension and thumb extension in cases of long-standing, irreparable radial nerve lesions.3
Consultations
Electrodiagnostic consultation is important in radial mononeuropathy in order to:
- Localize the lesion
- Provide useful prognostic information in traumatic radial neuropathy
Although there are no medications specifically designed for radial mononeuropathy, in cases of neuropathic pain related to the neuropathy, it is appropriate to consider various agents that may help reduce neuropathic pain.
Further Outpatient Care
- Physical therapy may accelerate improvement after tendon transfer for irreversible radial nerve injury.
Prognosis
- Prognosis depends on the degree and type of radial nerve injury. In most cases of mild injury, recovery after several months is expected.
- In cases where recovery fails, tendon transfer surgery may provide adequate hand function.
- Electromyographic testing may help not only to localize the lesion but also to provide prognostic information.
Patient Education
- In patients with posterior interosseous lesions, discuss avoidance of repetitive supination of the forearm.
Medical/Legal Pitfalls
- Lead poisoning should be considered in cases of isolated radial nerve palsy.
- In cases of irreparable radial nerve injury, tendon transfer still may provide adequate hand function.
| Media file 1:
The Radial Nerve from Gray's Anatomy (published 1918, public domain, copyright expired). |
 |  View Full Size Image | |
Media type: Illustration
|
- Rommens PM, Kuechle R, Bord T, Lewens T, Engelmann R, Blum J. Humeral nailing revisited. Injury. Apr 14 2008;[Medline].
- Lo YL, Fook-Chong S, Leoh TH, Dan YF, Tan YE, Lee MP. Rapid ultrasonographic diagnosis of radial entrapment neuropathy at the spiral groove. J Neurol Sci. May 10 2008;[Medline].
- Krishnan KG, Schackert G. An analysis of results after selective tendon transfers through the interosseous membrane to provide selective finger and thumb extension in chronic irreparable radial nerve lesions. J Hand Surg [Am]. Feb 2008;33(2):223-31. [Medline].
- Campbell WW. Focal neuropathies. In: Campbell WW, ed. Essentials of Electrodiagnostic Medicine. Baltimore, Md: Williams & Wilkins; 1999:255-278.
- Fardin P, Negrin P, Sparta S, et al. Posterior interosseous nerve neuropathy. Clinical and electromyographical aspects. Electromyogr Clin Neurophysiol. Apr-May 1992;32(4-5):229-34. [Medline].
- Fluri F, Lyrer P, Gratwohl A, Raetz-Bravo AE, Steck AJ. Lead poisoning from the beauty case: neurologic manifestations in an elderly woman. Neurology. Aug 28 2007;69(9):929-30. [Medline].
- Hanz KR, Saint-Cyr M, Semmler MJ, Rohrich RJ. Extensor tendon injuries: acute management and secondary reconstruction. Plast Reconstr Surg. Mar 2008;121(3):109e-120e. [Medline].
- Leis AA, Wells KJ. Radial nerve cutaneous innervation to the ulnar dorsum of the hand. Clin Neurophysiol. Mar 2008;119(3):662-6. [Medline].
- Malikowski T, Micklesen PJ, Robinson LR. Prognostic values of electrodiagnostic studies in traumatic radial neuropathy. Muscle Nerve. Sep 2007;36(3):364-7. [Medline].
- Pollock FH, Drake D, Bovill EG, et al. Treatment of radial neuropathy associated with fractures of the humerus. J Bone Joint Surg Am. Feb 1981;63(2):239-43. [Medline].
- Shapiro BE, Preston DC. Entrapment and compressive neuropathies. Med Clin North Am. May 2003;87(3):663-96, viii. [Medline].
- Stone DA, Laureno R. Handcuff neuropathies. Neurology. Jan 1991;41(1):145-7. [Medline].
- Turner OA, Taslitz N, Ward S. The radial nerve. In: Handbook of Peripheral Nerve Entrapments. Clifton, NJ: Humana Press; 1990:79-91.
- Walczyk S, Pieniazek M, Pelczar-Pieniazek M, Tabasz M. Appropriateness and effectiveness of physiotherapeutic treatment procedure after tendon transfer in patients with irreversible radial nerve injury. Ortop Traumatol Rehabil. Apr 30 2005;7(2):187-97. [Medline].
Radial Mononeuropathy excerpt Article Last Updated: Sep 26, 2008
|
