Injuries to the arm, forearm or wrist area can lead to various

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

disorders. One such disorder is median nerve palsy. The median nerve controls the majority of the muscles in the forearm. It controls abduction of the thumb, flexion of hand at wrist, flexion of digital

phalanx The phalanx ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particularly use ...

of the fingers, is the sensory nerve for the first three fingers, etc. Because of this major role of the median nerve, it is also called the eye of the hand. If the

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has contr ...

is damaged, the ability to abduct and oppose the thumb may be lost due to paralysis of the

thenar muscle The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the muscles of the thumb#Intrinsic, intrinsic group of muscles of the thumb. The skin overlying this region is the area stimulated when trying to elicit ...

s. Various other symptoms can occur which may be repaired through surgery and tendon transfers. Tendon transfers have been very successful in restoring motor function and improving functional outcomes in patients with median nerve palsy.http://www5.aaos.org/oko/description.cfm?topic=HAN027&referringPage=mainmenu.cfm

Signs and symptoms

*Lack of ability to abduct and oppose the thumb due to paralysis of the thenar muscles. This is called " ape-hand deformity". *Sensory loss in the thumbs, index fingers, long fingers, and the radial aspect of the ring fingers. *Weakness in forearm pronation and wrist and finger flexion *

Activities of daily living Activity may refer to: * Action (philosophy), in general * Human activity: human behavior, in sociology behavior may refer to all basic human actions, economics may study human economic activities and along with cybernetics and psychology may st ...

such as brushing teeth, tying shoes, making phone calls, turning door knobs and writing, may become difficult with a median nerve injury.

Causes

Median nerve palsy is often caused by deep, penetrating injuries to the arm, forearm, or wrist. It may also occur from blunt force trauma or neuropathy. Median nerve palsy can be separated into 2 subsections—high and low median nerve palsy. High MNP involves lesions at the elbow and forearm areas. Low median nerve palsy results from lesions at the wrist. Compression at the different levels of the

produce variable symptoms and/or syndromes. The areas are: * Underneath

Struthers' ligament Struthers' ligament is a feature of human anatomy consisting of a band of connective tissue at the medial aspect of the distal humerus. It courses from the supracondylar process of the humerus (also known as ''avian spur'') to the medial humeral ...

* Passing by the

bicipital aponeurosis The bicipital aponeurosis (also known as lacertus fibrosus) is a broad aponeurosis of the biceps brachii, which is located in the cubital fossa of the elbow. It separates superficial from deep structures in much of the fossa. Structure The bicip ...

(also known as lacertus fibrosus) * Between the two heads of the pronator teres * Compression in the carpal tunnel causes

carpal tunnel syndrome Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic compression of the median nerve as it travels through the wrist at the carpal tunn ...

Anatomy

The median nerve receives fibers from roots C6, C7, C8, T1 and sometimes C5. It is formed in the

axilla The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superior ...

by a branch from the medial and lateral chords of the

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in th ...

, which are on either side of the

axillary artery In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit) and the upper limb. Its origin is at the lateral margin of the first rib, before which it is ...

and fuse together to create the nerve anterior to the artery. The median nerve is closely related to the

brachial artery The brachial artery is the major blood vessel of the (upper) arm. It is the continuation of the axillary artery beyond the lower margin of teres major muscle. It continues down the ventral surface of the arm until it reaches the cubital fossa ...

within the arm. The nerve enters the

cubital fossa The cubital fossa, chelidon, or elbow pit, is the triangular area on the anterior side of the upper limb between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow (Latin ) when in standard anatomical position ...

medial to the brachialis tendon and passes between the two heads of the pronator teres. It then gives off the anterior interosseus branch in the pronator teres. The nerve continues down the forearm between the

flexor digitorum profundus The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Together t ...

and the

flexor digitorum superficialis Flexor digitorum superficialis (''flexor digitorum sublimis'') is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints. It is in the anterior compartment of the forearm. It is sometimes considered to be the deepest pa ...

. The median nerve emerges to lie between the

and the

flexor carpi ulnaris The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist joint. Structure Origin The flexor carpi ulnaris has two heads; a humeral head and ulnar head. The humeral head originates from the medial epicondyle o ...

muscles which are just above the wrist. At this position, the nerve gives off the palmar cutaneous branch that supplies the skin of the central portion of the palm. The nerve continues through the

carpal tunnel In the human body, the carpal tunnel or carpal canal is the passageway on the palmar side of the wrist that connects the forearm to the hand. The tunnel is bounded by the bones of the wrist and flexor retinaculum from connective tissue. Normall ...

into the hand, lying in the carpal tunnel anterior and lateral to the tendons of the flexor digitorum superficialis. Once in the hand, the nerve splits into a muscular branch and palmar digital branches. The muscular branch supplies the

thenar eminence The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the intrinsic group of muscles of the thumb. The skin overlying this region is the area stimulated when trying to elicit a palmomental reflex. The word ...

while the palmar digital branch supplies sensation to the palmar aspect of the lateral digits and the lateral two lumbricals.

Diagnosis

Because lesions to different areas of the median nerve produce similar symptoms, clinicians perform a complete motor and sensory diagnosis along the nerve course. Decreased values of nerve conduction studies are used as indicators of nerve compression and may aid in determining the localization of compression. Palpation above the elbow joint may reveal a bony consistency.

Radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

images may show an abnormal bony spur outgrowth (supracondyloid process) just proximal to the elbow joint. Attached fibrous tissue (

) may compress the median nerve as it passes underneath the process. This is also known as supracondylar process syndrome. Compression at this point may also occur without the bony spur; in this case, aponeurotic tissue found at the location of where Struthers' ligament should be is responsible for the compression. If patients mention reproduction of symptoms to the forearm during elbow flexion of 120–130 degrees with the forearm in maximal supination, then the lesion may be localized to the area underneath the lacertus fibrosus (also known as

). This is sometimes misdiagnosed as elbow strain and medial or

lateral epicondylitis Tennis elbow, also known as lateral epicondylitis or enthesopathy of the extensor carpi radialis origin, is a condition in which the outer part of the elbow becomes painful and tender. The pain may also extend into the back of the forearm. Onset ...

. A lesion to the upper arm area, just proximal to where motor branches of forearm flexors originate, is diagnosed if the patient is unable to make a fist. More specifically, the patient's index and middle finger cannot flex at the MCP joint, while the thumb usually is unable to oppose. This is known as hand of benediction or Pope's blessing hand. Another test is the bottle sign—the patient is unable to close all their fingers around a cylindrical object.

Carpal tunnel syndrome Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic compression of the median nerve as it travels through the wrist at the carpal tunn ...

(CTS) is caused by compression of the median nerve as it passes under the carpal tunnel."Carpal Tunnel Info". Carpal Tunnel Info. Web 28 October 2010. < http://www.carpal-tunnel.org>

Nerve conduction velocity In neuroscience, nerve conduction velocity (CV) is an important aspect of nerve conduction studies. It is the speed at which an electrochemical impulse propagates down a neural pathway. Conduction velocities are affected by a wide array of factors ...

tests through the hand are used to diagnosis CTS. Physical diagnostic tests include the

Phalen maneuver Phalen's maneuver is a diagnostic test for carpal tunnel syndrome by an American orthopedist named George S. Phalen. Technique The patient is asked to hold their Wrist, wrists in complete and forced flexion (pushing the dorsal surfaces of bot ...

or Phalen test and

Tinel's sign Tinel's sign (also Hoffmann-Tinel sign) is a way to detect irritated nerves. It is performed by lightly tapping ( percussing) over the nerve to elicit a sensation of tingling or " pins and needles" in the distribution of the nerve. Percussion is u ...

. To relieve symptoms, patients may describe a motion similar to "shaking a thermometer", another indication of CTS.

Pronator teres syndrome Pronator teres syndrome is a compression neuropathy of the median nerve at the elbow. It is rare compared to compression at the wrist (carpal tunnel syndrome) or isolated injury of the anterior interosseous branch of the median nerve (anterior inte ...

(also known as pronator syndrome) is compression of the median nerve between the two heads of the

pronator teres muscle The pronator teres is a muscle (located mainly in the forearm) that, along with the pronator quadratus, serves to pronate the forearm (turning it so that the palm faces posteriorly when from the anatomical position). It has two attachments, to ...

. The Pronator teres test is an indication of the syndrome—the patient reports pain when attempting to

pronate Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

the forearm against resistance while extending the elbow simultaneously. The physician may notice an enlarged pronator teres muscle. Tinel's sign the area around the pronator teres heads should be positive. The key to discerning this syndrome from carpal tunnel syndrome is the absence of pain while sleeping. More recent literature collectively diagnose median nerve palsy occurring from the elbow to the forearm as pronator teres syndrome. In uncooperative patients, the skin

wrinkle A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on skin or fabric. Skin wrinkles typically appear as a result of ageing processes such as glycation, habitual sleeping positions, loss of ...

test offers a pain-free way to identify denervation of the fingers. After submersion in water for 5 minutes, normal fingers will become wrinkled, whereas denervated fingers will not. In "

Ape hand deformity Ape hand deformity is a deformity in humans who cannot move the thumb away from the rest of the hand. It is an inability to abduct the thumb. Abduction of the thumb refers to the specific capacity to orient the thumb perpendicularly to the ventra ...

", the thenar muscles become paralyzed due to impingement and are subsequently flattened. This hand deformity is not by itself an individual diagnosis; it is seen only after the thenar muscles have atrophied. While the

adductor pollicis In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath ...

remains intact, the flattening of the muscles causes the thumb to become adducted and laterally rotated. The

opponens pollicis The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles. It lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis. Structure The opp ...

causes the thumb to flex and rotate medially, leaving the thumb unable to oppose. Carpal tunnel syndrome can result in thenar muscle paralysis which can then lead to ape hand deformity if left untreated. Ape hand deformity can also be seen in the hand of benediction deformity. The Anterior Interosseus Nerve (AIN), a branch of the median nerve, only accounts for the movement of the fingers in hand and does not have any sensory capabilities. Therefore, the AIN syndrome is purely neuropathic. AINS is considered as an extremely rare condition because it accounts for less than 1% of neuropathies in the upper limb. Patients with this syndrome have impaired distal interphalangeal joint, because of which they are unable to pinch anything or make and "OK" sign with their index finger and thumb. The syndrome can either happen from pinched nerve, or even dislocation of the elbow.

Prevention

One way to prevent this injury from occurring is to be informed and educated about the risks involved in hurting your wrist and hand. If patients do have median nerve palsy, occupational therapy or wearing a splint can help reduce the pain and further damage. Wearing a dynamic splint, which pulls the thumb into opposition, will help prevent an excess in deformity. This splint can also assist in function and help the fingers flex towards the thumb. Stretching and the use of C-splints can also assist in prevention of further damage and deformity. These two methods can help in the degree of movement the thumb can have. While it is impossible to prevent trauma to your arms and wrist, patients can reduce the amount of compression by maintaining proper form during repetitive activities. Furthermore, strengthening and increasing flexibility reduces the risk of nerve compression.

Treatment

Depending on the severity of the lesion, physicians may recommend either conservative treatment or

surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...

. The first step is simply to rest and modify daily activities that aggravate the symptoms. Patients may be prescribed anti-inflammatory drugs, Physical or Occupational therapy, splints for the elbow and wrists, and

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...

injections as well. This is the most common treatment for CTS. Especially involving compression at the wrist, such as in CTS, it is possible to recover without treatment. Physical therapy can help build muscle strength and braces or splints help recover. In pronator teres syndrome, specifically, immobilization of the elbow and mobility exercise within a pain-free range are initially prescribed. However, if the patient is not relieved of symptoms after a usual 2 to 3 month refractory period, then decompression surgery may be required. Surgery involves excising the tissue or removing parts of the bone compressing the nerve. Many tendon transfers have been shown to restore opposition to the thumb and provide thumb and finger

flexion Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

. In order to have optimal results the individual needs to follow the following principles of tendon transfer: normal tissue equilibrium, movable joints, and a scar-free bed. If these requirements are met then certain factors need to be considered such as matching up the lost muscle mass, fiber length, and cross-sectional area and then pick out muscle-tendon units of similar size, strength, and potential excursion. For patients with low median nerve palsy, it has been shown that the

of the long and ring fingers or the wrist extensors best approximate the force and motion that is required to restore full thumb opposition and strength. This type of transfer is the preferred method for median nerve palsy when both strength and motion are required. In situations when only thumb mobility is desired, the

extensor indicis proprius In human anatomy, the extensor indicis roprius'' is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it exte ...

is an ideal transfer. For high median nerve palsy, the

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way o ...

or the

extensor carpi radialis longus A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "hand ...

transfer is more appropriate to restore lost thumb flexion and side-to-side transfer of the

of the index finger are generally sufficient. To restore independent flexion of the index finger could be performed by using the pronator teres or extensor carpi radialis ulnaris tendon muscle units. All of the mentioned transfers are generally quite successful because they combine a proper direction of action, pulley location, and tendon insertion.

Rehabilitation

In high median nerve palsy patients, recovery time varies from as early as four months to 2.5 years. Initially, patients are immobilized in a neutral position of the forearm and elbow flexed at 90° in order to prevent further injury. Additionally, gentle exercises and soft tissue massage are applied. The next goal is strengthening and flexibility, usually involving wrist extension and flexion; however, it is important not to overuse the muscles in order to prevent re-injury. If surgery is required, post operative therapy initially involves decreasing pain and sensitivity to the incision area. Adequate grip and elbow strength must be achieved before returning to pre-operative activity.

Epidemiology

* The number of discharges related to median nerve injuries decreased from 3,402 in 1993 to 2,737 in 2006. * The mean hospital charges in nominal dollars increased from $9,257 to $27,962 between 1993 and 2006. * 37.1% of patients in 2006 presenting with median nerve injuries needed acute repair. * Median nerve injuries were the least likely to be admitted to the emergency room out of all peripheral nerve injuries (median nerve 68.89%, ulnar nerve 71.3% and radial nerve 77.06%). * The highest percentage of patients discharged with median nerve injuries in 2006 were between the ages of 18–44. * Out of all the patients in 2006 presenting with median nerve injuries, 77.76% were male and 21.75% were female.

References

External links

{{PNS diseases of the nervous system Myoneural junction and neuromuscular diseases Overuse injuries