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Median nerve: want to learn more about it?

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Median nerve

The median nerve is the branch of the brachial plexus that supplies most of the superficial and deep flexors in the forearm, thenar and lumbrical muscles. It also gives sensation to certain areas of the skin of the hand.

Due to its innervation field, the median nerve enables us to perform both coarse and fine movements of the upper limb, such as opposing our thumb which is important to do precision handling and perform lots of activities like writing, threading a needle or winding a watch. In this article we will discuss the anatomy of the median nerve as well as the clinical points related to it.

Key facts about the median nerve
Origin Brachial plexus (C6-T1)
Motor supply

Flexor muscles in the forearm except flexor carpi ulnaris and the ulnar head of flexor digitorum profundus;

Muscles of the thenar eminence and the radial two lumbricals.

Sensory supply

The skin of the:

- Palmar and distal dorsal aspects of the lateral three-and-the-half digits and adjacent palm
- Palmar and distal dorsal aspects of the thumb and radial half of 2nd digit
- Palmar and distal dorsal aspects of the adjacent sides of 2nd–4th digits
- Central palm

Clinical relations Carpal tunnel syndrome, hand of Benediction, simian/ape hand deformity, pronator syndrome

Recommended video: Median nerve
Anatomy, distribution and function of the median nerve.

Innervation

The median nerve is a major peripheral nerve and supplies the flexor muscles in the forearm except flexor carpi ulnaris and the ulnar head of flexor digitorum profundus, which is supplied by the ulnar nerve. It also supplies the thenar muscles as well as the radial two lumbricals.

Median has an interesting sensory supply of the skin in the hand:

  • The skin of the palmar and distal dorsal aspects of the lateral three-and-the-half digits and adjacent palm
  • The skin of the palmar and distal dorsal aspects of the thumb and radial half of 2nd digit
  • The skin of palmar and distal dorsal aspects of the adjacent sides of 2nd–4th digits
  • The skin of the central palm

Hand skin supply: Sensory supply areas of the median, radial and ulnar nerves

Learn more about the median nerve with out video tutorial and quiz.

Origin and nerve roots

The nerve roots of the median nerve are from the ventral rami of the C6-T1 nerves. The median nerve is formed by the unification of the medial and lateral roots. It can be seen as the central line of an ‘M Shaped’ brachial plexus, the cords of which surround the axillary artery.

Brachial plexus in cadaver: Median nerve seen arising from medial and lateral roots. The roots are recognized as they form an M-structure with musculocutaneous and ulnar nerves over the axillary artery.

Course

Arm

After its formation from the medial and lateral cords of the brachial plexus, the median nerve descends down the centre of the arm in a superficial course. Initially it is lateral to the brachial artery but as it descends it eventually becomes medial. It gives no branches in the arm.

Forearm

Just before it enters the forearm, the median nerve passes between the tendons of biceps brachii and brachialis. At this point it becomes lateral to the brachial artery. Next, in order to gain access to the forearm, it passes between the deep and superficial heads of the pronator teres muscle. Once it passes this point it dives deeper and runs between the flexor digitorum profundus and superficialis. It gives: 

  • muscular branches to pronator teres, palmaris longus, flexor digitorum superficialis and flexor carpi radialis
  • the anterior interosseus nerve
  • the cutaneous nerve of the palm

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The anterior interosseous nerve supplies the flexor pollicis longus and radial part of flexor digitorum profundus. This branch runs on the interosseous membrane with anterior interosseous artery passes deep to the pronator quadratus and supplies it. It terminates by giving articular branches to the distal radio ulnar, radiocarpal and carpal joints. It also supplies to the proximal part of the palm, via the palmar cutaneous branch. This branch does not enter the carpal tunnel and is hence spared in carpal tunnel syndrome.

Hand

Median nerve passes through the carpal tunnel beneath the flexor retinaculum, and divides to form two common palmar digital nerves, the first of which supplies the radial two lumbricals and a common branch between the index and middle fingers. The second runs between the ring and middle finger, and divides to give the proper digital nerves. The branch also provides sensation to the radial three and a half fingers on their palmar aspect as well as the nail beds of the index, middle and half the ring finger, via the proper digital nerves.

Dissected carpal tunnel showing median nerve traversing the carpal tunnel with the nine flexor tendons; the flexor pollicis longus, the four flexor digitorum superficialis and the four flexor digitorum profundus.

The median nerve also gives off a recurrent branch to the muscles of the thenar eminence (flexor pollicis brevis, abductor pollicis brevis, opponens pollicis). It is also known as the ‘million dollar nerve’ to signify its importance for basic hand function. The reason it is referred to as the recurrent branch is due to the course it takes. It wraps around the flexor pollicis brevis and then arches back to pass into the thenar eminence. This does not include adductor pollicis, which although moves the thumb is not a part of the thenar eminence and is supplied by a deep branch of the ulnar nerve.

Clinical notes

Carpal tunnel syndrome

The median nerve passes within the carpal tunnel and runs deep to the flexor retinaculum. If the tendons of the long finger flexors become swollen due to overuse (typist), or oedema (pregnancy), then the median nerve becomes compressed. This results in pain, paresthesia and numbness (tingling and pins and needles) of the lateral three and a half fingers. Tapping over the median nerve in the carpal tunnel (‘Tinel’s maneuver’) results in numbness or pain in the median nerve distribution. Flexion of the wrist for 60 seconds will also elicit pain or numbness. Symptoms include thenar muscle wasting and weakness. Treatment is with surgical compression.

Hand of Benediction

The median nerve is vulnerable to be damaged at the elbow, commonly from a supracondylar fracture. This results in the radial head of flexor digitorum profunda being denervated. The forearm is constantly supinated and the lateral two lumbricals have also been denervated, the flexion at the metacarpophalangeal and interphalangeal joints of 2 & 3 digits is lost. There is inability to make a fist as both of these fingers are extended and the hand is in a classic position known as the ‘hand of benediction’ (when the person tries to flex their fingers).

Simian/ape hand deformity

If the recurrent motor branch of the median nerve is damaged, the muscles of the thenar eminence become denervated. This includes abductor pollicis brevis, flexor pollicis brevis, opponens pollicis and the two radial lumbricals. This results in the person becomes unable to oppose the thumb i.e. bring the tip of the thumb to the tip of the other fingers. The appearance is that of an ape’s hand, due to the unopposable thumb. This is distinguished from the hand of benediction as the radial head of flexor digitorum profundus is still functional.

Pronator syndrome

The median nerve can become trapped between the two heads of pronator teres, resulting in wrist flexor wasting.

Median nerve: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,168,736 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Frank H.Netter MD: Atlas of Human Anatomy, 5th Edition, Elsevier Saunders, Chapter 1 Head and Neck.
  • Chummy S.Sinnatamby: Last’s Anatomy Regional and Applied, 12th Edition, Churchill Livingstone Elsevier.
  • Richard L. Drake, A. Wayne Vogl, Adam. W.M. Mitchell: Gray’s Anatomy for Students, 2nd Edition, Churchill Livingstone Elsevier.

Author, review and layout:

  • Shahab Shahid
  • Uruj Zehra
  • Catarina Chaves

Illustrations:

  • Hand skin supply - Irina Münstermann, Abdulmalek Albakkar
  • Brachial plexus (cadaver dissection) - Prof. Carlos Suárez-Quian
  • Carpal tunnel (cadaver dissection) - Prof. Carlos Suárez-Quian
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

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