User:Eeb11288/Median Nerve Palsy

Eeb11288/Median Nerve Palsy

Median Nerve Palsy

Anatomy of Median Nerve

File:MedianNerveAnatomy.jpg

Median Nerve 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 plexus, 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.

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.

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 thumb, index finger, long finger, and the radial aspect of the ring finger
• Weakness in forearm pronation and wrist and finger flexion

Treatment

The option of treatment for Median Nerve Palsy is a tendon transfer. 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 need 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 dn 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.

References

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