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Median nerve
Nerves of the left upper extremity.gif
Diagram from Gray's anatomy, depicting the peripheral nerves of the upper extremity, amongst others the median nerve
Details
From Lateral cord and Medial cord
Innervates Anterior compartment of the forearm (with two exceptions), Thenar eminence, Lumbricals, skin of the hand
Identifiers
Latin Nervus medianus
MeSH Median+Nerve
Dorlands
/Elsevier
n_05/12566162
TA A14.2.03.031
FMA 14385
Anatomical terms of neuroanatomy

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 contributions from ventral roots of C5-C7(lateral cord) and C8 & T1 (medial cord).

The median nerve is the only nerve that passes through the carpal tunnel. Carpal tunnel syndrome is the disability that results from the median nerve being pressed in the carpal tunnel.

Structure[edit]

After receiving inputs from both the lateral and medial cords of the brachial plexus, the median nerve enters the arm from the axilla at the inferior margin of the teres major muscle. It then passes vertically down and courses with the brachial artery on the medial side of the arm between biceps brachii and brachialis. At first it is lateral to the artery and lies anterior to the elbow joint; it then crosses anteriorly to run medial to the artery in the distal arm and into the cubital fossa.

Inside the cubital fossa the median nerve passes medial to the brachial artery, in front of the point of insertion of the brachialis muscle and deep to the biceps.

The median nerve gives off an articular branch in the upper arm as it passes the elbow joint. A branch to pronator teres may arise from the median nerve immediately proximal to the elbow joint.

Forearm[edit]

The median nerve arises from the cubital fossa and passes between the two heads of pronator teres. It then travels between flexor digitorum superficialis and flexor digitorum profundus before emerging between flexor digitorum superficialis and flexor pollicis longus.

The unbranched portion of the median nerve (which arises from the cubital fossa) innervates muscles of superficial and intermediate groups of the anterior(flexor) compartment except flexor carpi ulnaris.

The median nerve does give off two branches as it courses through the forearm:

Hand[edit]

The median nerve enters the hand through the carpal tunnel, deep to the flexor retinaculum along with the tendons of flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus.

From there it sends off several branches:

Variation[edit]

There are multiple naturally occurring anomalies of the median nerve.

  • Bifurcation of the median nerve typically occurs after the nerve exits the carpal tunnel; however, in a small percentage (5%-10%) of individuals, the median nerve bifurcates more proximal in the carpal tunnel, wrist, or forearm.[2]
  • During gestation, a median artery that serves the hand retracts. However, in some individuals the median artery does not retract and follows the course next to the median nerve into the hand.
  • Martin-Gruber anastomoses can occur when branches of the median nerve cross-over in the forearm and merge with the ulnar nerve to innervate portions of the forehand.
  • Riche-Cannieu anastomoses can occur when there is connection between recurrent branch of the median nerve and deep branch of the ulnar nerve of the hand.

Function[edit]

Arm[edit]

The median nerve has no voluntary motor or cutaneous function in the brachium. It gives vascular branches to the wall of the brachial artery. These vascular branches carry sympathetic fibers.

Forearm[edit]

It innervates all of the flexors in the forearm except flexor carpi ulnaris and that part of flexor digitorum profundus that supplies the 4th and 5th digits. The latter two muscles are supplied by the ulnar nerve (specifically the Muscular branches of ulnar nerve).

The main portion of the median nerve supplies the following muscles:

Superficial group:

Intermediate group:

The anterior interosseus branch of the median nerve supplies the following muscles:

Deep group:

Hand[edit]

The cutaneous innervation of the right hand. Areas supplied by the median nerve are colored green, the radial nerve red and the ulnar nerve blue. It appears that the borderline has been mistakenly drawn through the middle finger, rather than through the ring finger on the dorsal side of the hand!

In the hand, the median nerve supplies motor innervation to the 1st and 2nd lumbrical muscles. It also supplies the muscles of the thenar eminence by a recurrent thenar branch. The rest of the intrinsic muscles of the hand are supplied by the ulnar nerve.

The median nerve innervates the skin of the palmar side of the thumb, the index and middle finger, half the ring finger, and the nail bed of these fingers. The lateral part of the palm is supplied by the palmar cutaneous branch of the median nerve, which leaves the nerve proximal to the wrist creases. This palmar cutaneous branch travels in a separate fascial groove adjacent to the flexor carpi radialis and then superficial to the flexor retinaculum. It is therefore spared in carpal tunnel syndrome.

The muscles of the hand supplied by the median nerve can be remembered using the mnemonic, "LOAF" for Lumbricals 1 & 2, Opponens pollicis, Abductor pollicis brevis and Flexor pollicis brevis. (NB: OAF are the thenar eminence)[3]

Clinical significance[edit]

Injury[edit]

Injury of median nerve at different levels causes different syndromes with varying motor and sensory deficits.

Above the elbow

  • Common mechanism of injury: A supracondylar humerus fracture
  • Motor deficit:
    • Loss of pronation of forearm, weakness in flexion of the hand at the wrist, loss of flexion of radial half of digits and thumb, loss of abduction and opposition of thumb.
    • Presence of an ape hand deformity when the hand is at rest, due to an hyperextension of index finger and thumb, and an adducted thumb.
    • Presence of benediction sign when attempting to form a fist, due to loss of flexion of radial half of digits.
  • Sensory deficit: Loss of sensation in lateral 3 12 digits including their nail beds, and the thenar area.

At the elbow

Within the proximal forearm: Anterior interosseous syndrome

  • Injury to the anterior interosseous branch in the forearm causes the anterior interosseous syndrome.
  • Common mechanisms: Tight cast, forearm bone fracture
  • Motor deficit: Loss of pronation of forearm, loss of flexion of radial half of digits and thumb.
  • Sensory deficit: None

At the wrist

  • Common mechanism: Wrist laceration
  • Motor deficit:
    • Weakness in flexion of radial half of digits and thumb, loss of abduction and opposition of thumb.
    • Presence of an ape hand deformity when the hand is at rest, due to an hyperextension of index finger and thumb, and an adducted thumb.
    • Presence of benediction sign when attempting to form a fist, due to weakness in flexion of radial half of digits.
  • Sensory deficit: Loss of sensation in lateral 3 12 digits including their nail beds, and the thenar area.

Within the wrist: Carpal tunnel syndrome

  • Common mechanism: Carpal tunnel syndrome, an injury by compression in the carpal tunnel, without transection of the median nerve, due to overuse by activities such as keyboard typing and cooking.
  • Motor deficit:
    • Weakness in flexion of radial half of digits and thumb, weakness in abduction and opposition of thumb.
    • Absence of an ape hand deformity or when attempting to form a fist, the benediction sign, due to compression of the median nerve, as opposed to complete median nerve palsy.
  • Sensory deficit: Numbness and tingling in lateral 3 12 digits including their nail beds but excluding the thenar eminence which is supplied by the palmar cutaneous branch of the median nerve .[4] Unlike in wrist laceration, there is no loss of sensation in the area of the central palm, as the palmar cutaneous branch runs above the flexor retinaculum, and is not affected in compression in carpal tunnel syndrome.[1]

Additional images[edit]

See also[edit]

This article uses anatomical terminology; for an overview, see Anatomical terminology.


References[edit]

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

  1. ^ a b "Anatomy Tables - Hand". Retrieved 2008-01-06. 
  2. ^ "Sonographic Representation of Bifid Median Nerve and Persistent Median Artery" Roll, SC. JDMS, 27: 89-94.
  3. ^ "Median nerve: Supply to hand". LifeHugger. Retrieved 2009-12-14. 
  4. ^ Figure 6.86, Moore Clinically Orientated Anatomy 7th Edition

External links[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Median_nerve — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
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994 news items

The Herald-News

The Herald-News
Tue, 26 Apr 2016 07:03:45 -0700

Wrist pain, numbness, tingling, and weakness in grip strength may be signs of carpal tunnel syndrome (CTS), according to doctors at Ostir Physical Medicine in Joliet. CTS develops when the median nerve, which travels from the forearm into the hand, ...

IEEE Spectrum

IEEE Spectrum
Thu, 28 Apr 2016 12:00:39 -0700

Anxiously, we turned it on and activated a contact on Spetic's median nerve. “Wow!” he said. “That's the tip of my thumb. That's the first time I've felt my hand since the injury.” It was one of those moments a researcher lives for. Further testing ...
 
Caribbean News Now (press release) (blog)
Thu, 28 Apr 2016 17:31:41 -0700

This syndrome, which affects the hand and wrist, is caused by excessive pressure on the median nerve, which then causes a numbness and tingling feeling in the thumb, index, middle and ring fingers. This can be due to fluid retention or swelling (during ...

LifeNews.com

LifeNews.com
Wed, 27 Apr 2016 09:07:30 -0700

This is the proof of concept study with multi-modality approach (using intra-thecal bioactive peptides, stem cells, laser and transcranial IV laser and Median Nerve stimulation as adjuvants) in cases of brain death due to traumatic brain injury having ...

KSL.com

KSL.com
Mon, 25 Apr 2016 13:11:35 -0700

These symptoms cause increased pressure on the median nerve, cutting off blood flow. CTS is extremely painful and often debilitating. For serious cases, a true solution comes in the form of endoscopic surgery. Below are some common questions about ...

Ithaca Journal

Ithaca Journal
Thu, 21 Apr 2016 09:34:19 -0700

The treatment reduces swelling that pinches the median nerve that runs through a small space in your wrist called the carpal tunnel. The pinched median nerve most often causes numbness and tingling, rather than pain. Those symptoms usually appear in ...

Miami Herald

Miami Herald
Fri, 22 Apr 2016 13:15:00 -0700

We all have aches and pains. But as we age, our joints, tendons or ligaments can get sore, stiff or injured. We spoke to three orthopedic doctors — Dr. Alejandro Badia of OrthoNow, Dr. Clifton Page, sports medicine physician with UHeath - University ...

Daily Mail

Daily Mail
Fri, 22 Apr 2016 05:06:56 -0700

They will use techniques involving peptides, lasers, stem cells and median nerve stimulation to try and bring about the reversal of brain death, whilst monitoring the patients using MRI scans. 'We hope to see results within the first two to three ...
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