Median nerve palsy
Encyclopedia
Injuries to the arm, forearm or wrist area can lead to various peripheral nerve disorders. One such disorder is median nerve palsy. If the median nerve
is damaged, the ability to abduct
and oppose the thumb may be lost due to paralysis of the thenar muscles. 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.
, which are on either side of the axillary artery
and fuse together to create the nerve anterior to the artery.
The median nerve is closely related to the brachial artery
within the arm. The nerve enters the cubital fossa
lateral 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 and the flexor digitorum superficialis. The median nerve emerges to lie between the flexor digitorum superficialis and the flexor carpi ulnaris 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
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
while the palmar digital branch supplies sensation to the palmar aspect of the lateral 3 ½ digits and the lateral two lumbricals.
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 median nerve
produce variable symptoms and/or syndromes. The areas are:
Palpation above the elbow joint may reveal a bony consistency. Radiography
images may show an abnormal bony spur outgrowth (supracondyloid process) just proximal to the elbow joint. Attached fibrous tissue (Struthers' ligament
) 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 bicipital aponeurosis
). This is sometimes misdiagnosed as elbow strain and medial or lateral epicondylitis.
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 median claw hand. Another test is the bottle sign—the patient is unable to close all their fingers around a cylindrical object.
Carpal tunnel syndrome
(CTS) is caused by compression of the median nerve as it passes under the carpal tunnel. Nerve conduction velocity
tests through the hand are used to diagnosis CTS. Physical diagnostic tests include the Phalen maneuver or Phalen test and Tinel's sign
. To relieve symptoms, patients may describe a motion similar to "shaking a thermometer", another indication of CTS.
Pronator teres syndrome
(also known as pronator syndrome) is compression of the median nerve between the two heads of the pronator teres muscle
. The Pronator teres test is an indication of the syndrome—the patient reports pain when attempting to pronate 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
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
", 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 remains intact, the flattening of the muscles causes the thumb to become adducted and laterally rotated. The opponens pollicis 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 first step is simply to rest and modify daily activities that aggravate the symptoms. Patients may be prescribed anti-inflammatory drugs, physical therapy, splints for the elbow and wrists, and corticosteroid
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
. 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 flexor digitorum superficialis 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
is an ideal transfer.
For high median nerve palsy, the brachioradialis
or the extensor carpi radialis longus transfer is more appropriate to restore lost thumb flexion and side-to-side transfer of the flexor digitorum profundus 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.
Median nerve
The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....
is damaged, the ability to abduct
Abduction (kinesiology)
Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist...
and oppose the thumb may be lost due to paralysis of the thenar muscles. 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.
Anatomy
The median nerve receives fibers from roots C6, C7, C8, T1 and sometimes C5. It is formed in the axilla by a branch from the medial and lateral chords of the brachial plexusBrachial plexus
The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...
, which are on either side of the axillary artery
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 and the upper limb...
and fuse together to create the nerve anterior to the artery.
The median nerve is closely related to the brachial artery
Brachial artery
The brachial artery is the major blood vessel of the 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 at the elbow. It then divides into the radial and ulnar arteries...
within the arm. The nerve enters the cubital fossa
Cubital fossa
The cubital fossa is the triangular area on the anterior view of the elbow of a human or other hominid animal. It is colloquially known as the "elbow pit".-Boundaries:...
lateral 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 and the flexor digitorum superficialis. The median nerve emerges to lie between the flexor digitorum superficialis and the flexor carpi ulnaris 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
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 middle compartment of the deep plane of the palm. The tunnel consists of bones and connective tissue...
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
Thenar eminence
The thenar eminence refers to the group of muscles on the palm of the human hand at the base of the thumb...
while the palmar digital branch supplies sensation to the palmar aspect of the lateral 3 ½ digits and the lateral two lumbricals.
Signs and symptoms
- Lack of ability to abduct and oppose the thumb due to paralysis of the thenar muscles. This is called "ape-hand deformityApe hand deformityApe hand deformity is a deformity in humans who cannot move the thumb outside of the plane of the palm. It is caused by inability to oppose the thumb and the limited abduction of the thumb...
". - Sensory loss in the thumb, index finger, long finger, and the radial aspect of the ring finger
- Weakness in forearm pronation and wrist and finger flexion
- Activities of daily livingActivities of daily livingActivities of Daily Living is a term used in healthcare to refer to daily self-care activities within an individual's place of residence, in outdoor environments, or both...
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 median nerve
Median nerve
The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....
produce variable symptoms and/or syndromes. The areas are:
- Underneath Struthers' ligamentStruthers' ligament320px|right|thumb|Diagram showing location of Struthers' ligamentStruthers' ligament is a ligament that extends between the shaft of the humerus and the medial epicondyle of the humerus. It is not a constant ligament, and can be acquired or congenital...
- Passing by the bicipital aponeurosisBicipital aponeurosisThe bicipital aponeurosis is a broad aponeurosis of the biceps brachii which is located in the cubital fossa of the elbow and separates superficial from deep structures in much of the fossa....
(also known as lacertus fibrosus) - Between the two heads of the pronator teres
- Compression in the carpal tunnel causes carpal tunnel syndromeCarpal tunnel syndromeCarpal Tunnel Syndrome is an entrapment idiopathic median neuropathy, causing paresthesia, pain, and other symptoms in the distribution of the median nerve due to its compression at the wrist in the carpal tunnel. The pathophysiology is not completely understood but can be considered compression...
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
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
images may show an abnormal bony spur outgrowth (supracondyloid process) just proximal to the elbow joint. Attached fibrous tissue (Struthers' ligament
Struthers' ligament
320px|right|thumb|Diagram showing location of Struthers' ligamentStruthers' ligament is a ligament that extends between the shaft of the humerus and the medial epicondyle of the humerus. It is not a constant ligament, and can be acquired or congenital...
) 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 bicipital aponeurosis
Bicipital aponeurosis
The bicipital aponeurosis is a broad aponeurosis of the biceps brachii which is located in the cubital fossa of the elbow and separates superficial from deep structures in much of the fossa....
). This is sometimes misdiagnosed as elbow strain and medial or lateral epicondylitis.
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
Hand of benediction
The hand of benediction results from a severed Median nerve at the level of the elbow or upper arm. The ability to flex the digits 2–3 at the metacarpophalangeal joints, proximal interphalangeal joints and distal interphalangeal joints is lost. This is due to the loss of innervation of the lateral...
or median claw 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
Carpal Tunnel Syndrome is an entrapment idiopathic median neuropathy, causing paresthesia, pain, and other symptoms in the distribution of the median nerve due to its compression at the wrist in the carpal tunnel. The pathophysiology is not completely understood but can be considered compression...
(CTS) is caused by compression of the median nerve as it passes under the carpal tunnel. Nerve conduction velocity
Nerve conduction velocity
Nerve conduction velocity is the speed at which an electrochemical signal propagates down a neural pathway. Many things can affect this, including axon diameter, myelination, the internal resistance of the axon, and temperature. Nerve conduction velocity differs from species to species, and to a...
tests through the hand are used to diagnosis CTS. Physical diagnostic tests include the Phalen maneuver or Phalen test and Tinel's sign
Tinel's sign
Tinel's sign is a way to detect irritated nerves. It is performed by lightly tapping over the nerve to elicit a sensation of tingling or "pins and needles" in the distribution of the nerve.It takes its name from French neurologist Jules Tinel .For example, in carpal tunnel syndrome where the...
. To relieve symptoms, patients may describe a motion similar to "shaking a thermometer", another indication of CTS.
Pronator teres syndrome
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 or isolated injury of the anterior interosseous branch of the median nerve .- Anatomy :The median nerve arises from the cubital fossa and passes between the two...
(also known as pronator syndrome) is compression of the median nerve between the two heads of the pronator teres muscle
Pronator teres muscle
The pronator teres is a muscle of the human body that, along with the pronator quadratus muscle, serves to pronate the forearm .-Structure:...
. The Pronator teres test is an indication of the syndrome—the patient reports pain when attempting to pronate 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
Wrinkle
A wrinkle is a fold, ridge or crease in the skin. Skin wrinkles typically appear as a result of aging processes such as glycation or, temporarily, as the result of prolonged immersion in water. Wrinkling in the skin is caused by habitual facial expressions, aging, sun damage, smoking, poor...
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
Ape hand deformity is a deformity in humans who cannot move the thumb outside of the plane of the palm. It is caused by inability to oppose the thumb and the limited abduction of the thumb...
", 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 remains intact, the flattening of the muscles causes the thumb to become adducted and laterally rotated. The opponens pollicis 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.
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 suffer from 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 surgerySurgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
. The first step is simply to rest and modify daily activities that aggravate the symptoms. Patients may be prescribed anti-inflammatory drugs, physical therapy, splints for the elbow and wrists, and corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
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
Flexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
. 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 flexor digitorum superficialis 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
Extensor indicis proprius
-External links: - "Extensor Region of Forearm and Dorsum of Hand: Deep Muscles of Extensor Region"...
is an ideal transfer.
For high median nerve palsy, the brachioradialis
Brachioradialis
Brachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm...
or the extensor carpi radialis longus transfer is more appropriate to restore lost thumb flexion and side-to-side transfer of the flexor digitorum profundus 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.