Updated: May 31, 2009
Entrapment neuropathies of the upper extremity are common problems. A wide range of physicians, from primary care providers to specialists such as orthopedic surgeons, plastic surgeons, or neurosurgeons, are sought to care for these problems.
What has traditionally been attributed to features of normal aging (eg, weakness, loss of function or sensation) has been subsequently recognized in younger patients whose vocations require repetitive motion to complete work-related tasks. Repetitive motion, force, posture, and vibratory influences on the peripheral nerves of the upper extremity are poorly understood but are blamed as contributing factors to the development of neuropathic symptoms.1
Currently, patterns of symptomatology, objective measures of nerve function (eg, electromyelogram [EMG] evaluation, nerve conduction studies), and the anatomy associated with nerve compression have been well outlined. Despite attempts at conservative medical and functional management, surgical decompression has become the choice for definitive treatment.2
For excellent patient education resources, visit eMedicine's Hand, Wrist, Elbow, and Shoulder Center and Procedures Center. Also, see eMedicine's patient education articles Repetitive Motion Injuries and Carpal Tunnel Syndrome.
The median nerve
The main nerve entrapments in the upper extremity involve the median nerve, ulnar nerve, or radial nerve. The median nerve forms the junction of the lateral medial cords. It travels lateral to the brachial artery to approximately the mid humerus or junction of the proximal two thirds to distal one third of the humerus. At this level, the median nerve crosses over the brachial artery to lie in a more medial anatomic position.
The nerve is superficial to the brachialis muscle and usually lies in a groove with the brachial artery, between the brachialis and biceps muscle. It travels across the antecubital fossa, underneath the bicipital aponeurosis, and between the biceps tendon and the pronator teres. At this level, the median nerve is on the distal aspect of the brachialis muscle. The nerve then travels underneath the 2 heads of the flexor digitorum sublimis (FDS) muscle to lie between this muscle and the flexor digitorum profundus (FDP) muscle. The median nerve emerges between these 2 muscles in the distal forearm to then travel ulnar to the flexor carpi radialis and radial to the sublimis tendons, usually directly underneath the palmaris longus tendon, and enters the carpal tunnel in a more superficial plane to the flexor tendons.
The motor branch emerges at variable sites but most frequently at the distal aspect of the carpal ligament to service the thenar musculature. Just beyond the end of the carpal ligament, the median nerve trifurcates to become the common digital sensory nerves to the fingers. The palmar cutaneous branch of the median nerve is a sensory branch that comes from the main body of the nerve approximately 6 inches above the rest of the nerves and services an elliptical area at the base of the thenar eminence. This superficial nerve does not lie within the carpal tunnel.
Just distal to the antecubital fossa, the median nerve branches into the anterior interosseous nerve, which travels on the interosseous membrane and innervates the flexor pollicis longus (FPL), the FDP to the radial 2 digits, and the pronator quadratus at its termination. The nerve innervates the pronator teres, flexor capri radialis, the FDS, and the 2 radial FDP tendons. It also supplies the FPL and the pronator quadratus.
Within the hand, the motor branch of the median nerve supplies the opponens pollicis, the flexor pollicis brevis, and the abductor pollicis brevis musculature. It also supplies the 2 radial lumbrical muscles in the hand. The median nerve supplies sensation to the 3.5 digits on the radial aspect.
The ulnar nerve
The ulnar nerve arises from the medial cord of the brachial plexus. The ulnar nerve travels posterior to the brachial artery and remains within the flexor compartment of the upper extremity until it reaches the medial epicondyle. The nerve travels behind the medial epicondyle back into the flexor compartment underneath the flexor musculature. Above the elbow, the ulnar nerve lies on the long head and then the medial head of the triceps muscle, directly posterior to the medial intermuscular septum between the brachialis and the triceps muscles.
The fascial bands over the median nerve constitute the Struthers arcade. The nerve passes within the cubital tunnel posterior to the medial epicondyle. It is directly underneath a tight fascial roof known as the Osborne band, which is contiguous with the leading fascial heads of the flexor carpi ulnaris (FCU) muscle. Just above the elbow branches, the nerve branches to the superficial head of the FCU. The nerve lies directly over the top of the FDS muscle and beside the FDP muscle at the elbow.
As the ulnar nerve travels down the forearm, it is wedged between the FDS and the FDP muscle bellies to exit in the distal forearm just ulnar to the ulnar artery and the FDP tendons. The FCU tendon protects the nerve on its ulnar aspect. The ulnar nerve travels within the Guyon canal at the wrist to supply the hypothenar muscles, including the opponens digiti quinti and the abductor digiti quinti. It also supplies the 2 ulnar lumbrical muscles and the interossei to the hand and the deep branch to the flexor pollicis brevis muscle. The ulnar nerve supplies sensation to the 1.5 digits of the ulnar aspect. The dorsal cutaneous branch of the ulnar nerve supplies sensation to the dorsal ulnar half of the hand and fingers. This nerve arises from the main ulnar nerve approximately 6 cm proximal to the wrist.
The radial nerve
The radial nerve emerges from the posterior aspect of the humerus in the spiral groove between the brachialis and brachioradialis muscles above the elbow. It leaves the extensor compartment to travel in front of the elbow underneath the brachioradialis muscle, sending branches of innervation to it just above the elbow. The radial nerve divides at the level of the radial capitellar joint into the deep motor branch of the radial nerve (ultimately becoming the posterior interosseous nerve) and the superficial radial nerve. At this point, it branches to the extensor carpi radialis brevis.
The superficial radial nerve continues to travel underneath the brachioradialis muscle to ultimately emerge between that muscle and the extensor carpi radialis longus tendon. The superficial radial nerve supplies sensation to the radial half of the dorsum of the hand. The deep motor branch of the radial nerve travels within the fat pad and runs below the supinator muscle to emerge the supinator and become the posterior interosseous nerve in the distal dorsal aspect of the forearm. The posterior interosseous nerve travels at the level of the interosseous membrane to ultimately provide sensation to the posterior aspect of the wrist. This nerve innervates the extensor indicis proprius, extensor digiti quinti, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis brevis, and extensor digitorum communis muscles.
The phrase compressive neuropathy implies that the peripheral nerves are being impinged upon by adjacent anatomic structures. The resultant injury is assumed to be related to reduced epineural blood flow. The relative ischemia decreases axonal transport and, in turn, the nerve's ability to conduct impulses. Long-standing disease can produce irreversible damage, in the form of scarring or fibrosis, and loss of motor endplates, causing muscle atrophy. The double-crush theory predicts that a compressive lesion at one point along a peripheral nerve lowers the threshold for occurrence of compression at another site secondary to internal derangement of nerve cell metabolism. Examples of some pathogenic factors inciting neural compression are as follows:
Many of the findings of peripheral nerve irritation or entrapment are identified during the physical examination and are discussed here in relation to each of the individual syndromes. Reproducing symptoms via provocative maneuvers or diagnosing deficits in strength or sensation can be accomplished in the office or with the aid of hand therapists.
Two-point discrimination testing, Semmes-Weinstein monofilament testing, and grip strength measurements are simple and inexpensive means of evaluation. Findings from imaging studies (eg, plain radiographs, MRIs) are occasionally helpful for excluding cervical ribs, lung tumors, or extremity masses, which may be contributing to neural compression.
Electrodiagnostic studies (eg, EMG, nerve conduction studies) remain the criterion standard for objective evaluations of neuropathic conditions. These studies are not without flaws; they are highly operator-dependent and the results do not always correlate with the severity of symptoms or patient outcomes. Despite these drawbacks, they may help confirm equivocal physical examination findings or help isolate the specific site of compression preoperatively. EMGs also may be used to verify progression or resolution in neurophysiology following surgical release.
Median nerve
Ulnar nerve
Radial nerve
Pronator syndrome
Anterior interosseous syndrome
Carpal tunnel syndrome
Cubital tunnel syndrome
Ulnar tunnel syndrome (Guyon canal)
Radial tunnel syndrome
Posterior interosseous syndrome
Superficial radial nerve syndrome (Wartenberg syndrome)
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hand nerve compression, compressive syndrome, entrapment neuropathy, repetitive motion syndromes, surgical decompression, nerve decompression, nerve entrapment, compressive neuropathy, median nerve entrapment syndrome, pronator syndrome, anterior interosseous syndrome, carpal tunnel syndrome, ulnar nerve entrapment syndrome, cubital tunnel syndrome, ulnar tunnel syndrome, radial nerve entrapment syndrome, radial tunnel syndrome, posterior interosseous syndrome, superficial radial nerve syndrome, Wartenberg's syndrome, Wartenberg syndrome
Bradon J Wilhelmi, MD, Professor and Endowed Leonard J Weiner, MD, Chair of Plastic Surgery, Residency Program Director, University of Louisville School of Medicine
Bradon J Wilhelmi, MD is a member of the following medical societies: Alpha Omega Alpha, American Association for Hand Surgery, American Association of Clinical Anatomists, American Association of Plastic Surgeons, American Burn Association, American College of Surgeons, American Society for Aesthetic Plastic Surgery, American Society for Reconstructive Microsurgery, American Society for Surgery of the Hand, American Society of Plastic Surgeons, Association for Surgical Education, Plastic Surgery Research Council, and Wound Healing Society
Disclosure: Nothing to disclose.
Ryan Naffziger, MD, Consulting Staff, Department of Plastic Surgery, San Juan Regional Medical Center
Ryan Naffziger, MD is a member of the following medical societies: Alpha Omega Alpha, American Society of Plastic Surgeons, and Phi Beta Kappa
Disclosure: Nothing to disclose.
Michael Neumeister, MD, FRCSC, Professor & Chairman - FACS - Director Hand/Microsurgery Fellowship - Division of Plastic Surgery, Southern Illinois University School of Medicine
Michael Neumeister, MD, FRCSC is a member of the following medical societies: American Association for Hand Surgery, American Association of Plastic Surgeons, American Burn Association, American College of Surgeons, American Medical Association, American Society for Reconstructive Microsurgery, American Society for Surgery of the Hand, American Society of Plastic Surgeons, Association of Academic Chairmen of Plastic Surgery, Canadian Society of Plastic Surgeons, Illinois State Medical Society, Illinois State Medical Society, Ontario Medical Association, Plastic Surgery Research Council, Royal College of Physicians and Surgeons of Canada, and Society of University Surgeons
Disclosure: Nothing to disclose.
Anthony E Sudekum, MD, Consulting Staff, Department of Plastic Surgery, St John's Mercy Health Center of Saint Louis
Anthony E Sudekum, MD is a member of the following medical societies: American College of Surgeons, American Society for Surgery of the Hand, and Missouri State Medical Association
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.
David W Chang, MD, FACS, Associate Professor, Department of Plastic Surgery, MD Anderson Cancer Center, The University of Texas
Disclosure: Nothing to disclose.
Nicolas (Nick) G Slenkovich, MD, Director, Colorado Plastic Surgery Center
Nicolas (Nick) G Slenkovich, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American College of Surgeons, American Medical Association, American Society of Aesthetic Plastic Surgery, American Society of Plastic Surgeons, and Colorado Medical Society
Disclosure: Nothing to disclose.
Subhas Gupta, MD, PhD, CM, FRCSC, FACS, Chief of Surgical Services, Professor of Surgery, Chairman, Department of Plastic Surgery, Director of Plastic Surgery Residency, Director of Comprehensive Wound Service, Department of Plastic Surgery, Loma Linda University School of Medicine
Subhas Gupta, MD, PhD, CM, FRCSC, FACS is a member of the following medical societies: American Association of Plastic Surgeons, American Burn Association, American College of Phlebology, American College of Surgeons, American Medical Association, American Medical Informatics Association, American Society of Plastic Surgeons, California Society of Plastic Surgeons, Canadian Medical Association, Canadian Society of Plastic Surgeons, Canadian Society of Plastic Surgeons, College of Physicians and Surgeons of Ontario, Plastic Surgery Research Council, Quebec Medical Association, Royal College of Physicians and Surgeons of Canada, and Wound Healing Society
Disclosure: Nothing to disclose.
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