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Brachial plexus

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Nerve: Brachial plexus
Gray808
The right brachial plexus with its short branches, viewed from in front.
[[Image:|250px|center|]]
Latin plexus brachialis
Gray's subject #210 930
Innervates
From C1-C8, T1
To
MeSH A08.800.800.720.050

The brachial plexus is an arrangement of nerve fibres (a plexus) running from the spine (vertebrae C5-T1), through the neck, the axilla (armpit region), and into the arm.

Function

The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve and an area of skin near the axilla innervated by the intercostobrachialis nerve.

Therefore, lesions of the plexus can lead to severe functional impairment.

Anatomy

Path

One can remember the order of brachial plexus elements by way of the mnemonic, "Randy Travis Drinks Cold Beer" - Roots, Trunks, Divisions, Cords, Branches[1]

  • These roots merge to form three trunks:
    • "superior"[2] or "upper" (C5-C6)
    • "middle"[3] (C7)
    • "inferior"[4] or "lower" (C8-T1)
  • Each trunk then splits in two, to form six divisions:
    • anterior division[5] of the superior, middle, and inferior trunks
    • posterior division[6] of the superior, middle, and inferior trunks
  • These six divisions will regroup to become the three cords. The cords are named by their position in respect to the axillary artery.
    • The posterior cord is formed from the three posterior divisions of the trunks (C5-T1)
    • The lateral cord is the anterior divisions from the upper and middle trunks (C5-C7)
    • The medial cord is simply a continuation of the lower trunk (C8-T1)
  • The branches are listed below. Most branch off of the cords, but a few branch (indicated in italics) directly off of earlier structures. The five in bold are considered "terminal branches".

Specific branches

From Nerve Roots Muscles Cutaneous
roots dorsal scapular nerve C5 rhomboid muscles and levator scapulae -
roots long thoracic nerve C5, C6, C7 serratus anterior -
superior trunk nerve to the subclavius C5, C6 subclavius muscle -
superior trunk suprascapular nerve C5, C6 supraspinatus and infraspinatus -
lateral cord lateral pectoral nerve C5, C6, C7 pectoralis major and pectoralis minor (by communicating with the medial pectoral nerve) -
lateral cord musculocutaneous nerve C5, C6, C7 coracobrachialis, brachialis and biceps brachii becomes the lateral cutaneous nerve of the forearm
lateral cord lateral root of the median nerve C5, C6, C7 fibres to the median nerve -
posterior cord upper subscapular nerve C5, C6 subscapularis (upper part) -
posterior cord thoracodorsal nerve C6, C7, C8 latissimus dorsi -
posterior cord lower subscapular nerve C5, C6 lower part of subscapularis and teres major -
posterior cord axillary nerve C5, C6 anterior branch: deltoid and a small area of overlying skin
posterior branch: teres minor and deltoid muscles
posterior branch becomes upper lateral cutaneous nerve of the arm
posterior cord radial nerve C5, C6, C7, C8, T1 triceps brachii, anconeus, the extensor muscles of the forearm, and brachioradialis skin of the posterior arm as the posterior cutaneous nerve of the arm
medial cord medial pectoral nerve C8, T1 pectoralis major and pectoralis minor -
medial cord medial root of the median nerve C8, T1 fibres to the median nerve portions of hand not served by ulnar or radial
medial cord medial cutaneous nerve of the arm C8, T1 - front and medial skin of the arm
medial cord medial cutaneous nerve of the forearm C8, T1 - medial skin of the forearm
medial cord ulnar nerve C8, T1 flexor carpi ulnaris, the medial 2 bellies of flexor digitorum profundus, most of the small muscles of the hand the skin of the medial side of the hand and medial one and a half fingers on the palmar side and medial two and a half fingers on the dorsal side

 

Diagram

Brachial plexus

Injuries

Brachial plexus lesions are classified as traumautic or obstetric. These typically result from excessive stretching and avulsion injury. Traumatic injuries are often caused by high-velocity motor vehicle accidents, especially in motorcyclists. Injury from a direct blow to the lateral side of the scapula is also possible.

Most commonly, forceps delivery or falling on the neck at an angle causes upper plexus lesions (Erb's Palsy). This type of injury produces a very characteristic sign called Waiter's tip deformity due to loss of the lateral rotators of the shoulder, arm flexors, and hand extensor muscles.

Much less frequently, sudden upward pulling on an abducted arm (as when someone breaks a fall by grasping a tree branch) produces a lower plexus injury. This results in the sign known as clawed hand due to loss of function of the ulnar nerve and the intrinsic muscles of the hand it supplies.

The cardinal signs of brachial plexus avulsion are:

In most cases the nerve roots are stretched or torn from their origin, since the meningeal coverings of the nerve roots are thinner than the sheaths enclosing the peripheral nerves. The epineurium of the peripheral nerve is contiguous with the dural mater, providing extra support to the peripheral nerves. In cases where the nerve roots have been torn, recovery is unlikely without invasive experimental surgical techniques [How to reference and link to summary or text].

The diagnosis may be confirmed by an EMG examination in 5-7 days. The evidence of denervation will be evident. If there is no nerve conduction 72 hours after the injury, then avulsion is most likely.

Additional images


Brachial Plexus Palsy, also referred to as Erb's Palsy, is a condition that affects the nerves that control the muscles in the arm and hand.Possible Symptoms:-a limp or paralyzed arm-lack of muscle control in the arm-a decrease of sensation in the arm or handTypes of Brachial Plexus InjuriesThe injury may involve one or more nerves of the brachial plexus. The Brachial Plexus is located on the right and left side of your neck, between the neck and shoulder area.It is a group of nerves that run from the spinal cord through the arm to the wrist and hand.

Q. What is a Brachial Plexus Injury?

A. A brachial plexus injury is an injury to the nerves that supply the muscles of the arm. Injury to nerves of the brachial plexus can result in complete to partial paralysis to the shoulder, upper arm, elbow, forearm, wrist, hand, or fingers.


Q. Are there various degrees of severity with a Brachial Plexus Injury?

A. There are four basic types of nerve injuries. Some people only have one type while others have a combination of two or more types. � Avulsion- the nerve is detached from the spinal cord. � Rupture- the nerve is separated from itself, but not at the juncture of the nerve and the spinal cord. There may be one or more ruptures in a single nerve. � Praxis or Traction- the nerve is typically overstretched and damaged, but not detached from itself or the spinal cord. � Neuroma- scar tissue has surrounded the injured nerve and excessive pressure is now placed on the nerve. Therefore, the nerve has trouble getting all the signals to the muscle to be able to perform a movement.


Q. How do Brachial Plexus Injuries occur?

A. Brachial plexus injuries occur when there is excessive stretching, tearing, or other trauma to the brachial plexus network. Injuries can be sustained during delivery of a baby. This is known as Obstetrical Brachial Plexus. Traumatic Brachial Plexus is seen when injuries are sustained secondary to vehicular accidents such as automobiles, motorcycles, or boats, sports injuries particularly football, gunshot wounds, or surgeries. Traumatic BPI's have also been noted with animal bites or puncture wounds.


Q. What are some symptoms associated with Brachial Plexus Injuries?

A. There are several degrees of symptoms that can be seen with BPI. Here are some of the most typical examples: � Limited active range of motion of the entire arm or any part of the arm. � Sensation changes in the involved arm. � Weakness of specific muscle groups. � Poor ability to perform typical midline activities. � Poor ability to weight bear through the arm. � Neglect of the affected arm. � Posturing of the arm in atypical positions. � Developmental Delay � Torticollis- a shortened muscle of the neck, so the head tilts to one side.


Q. How often do obstetrical brachial plexus injuries occur?

A. The current research suggests that brachial plexus injuries are seen 1-3 in every 1000 live births.


Q. What are the treatments?

A. Treatments include but are not limited to the following: Physical therapy, occupational therapy, aquatic therapy, surgical interventions, splinting, casting, electrical stimulation.


Q. When should I initiate treatments?

A. It is essential that a person suffering from a brachial plexus injury initiate treatments as soon as possible. Typically, a person suffering from an obstetrical brachial plexus injury sees a physical therapist or occupational therapist in the first two weeks of life. The goal of the therapist is to assist the family in Range of motion exercises, assess for muscle contractions even when movement is not seen, address positioning, make adaptive equipment, reduce the infant's tendencies toward neglect, and avoid atypical movement patterns, avoid tightening of muscles, and assist with weight bearing activities even in the newborn stage.

See also

References

  1. Mnemonic at medicalmnemonics.com 18 2741
  2. Dorlands/Elsevier t_20/12826113
  3. Dorlands/Elsevier t_20/12826075
  4. Dorlands/Elsevier t_20/12826025
  5. Dorlands/Elsevier d_26/12310223
  6. Dorlands/Elsevier d_26/12310244

External links


Spinal cord

epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, pia mater, denticulate ligaments, conus medullaris, cauda equina, filum terminale, cervical enlargement, lumbar enlargement, anterior median fissure, dorsal root, dorsal root ganglion, dorsal ramus, ventral root, ventral ramus, sympathetic trunk, gray ramus communicans, white ramus communicans

grey matter: central canal, substantia gelatinosa of Rolando, reticular formation, substantia gelatinosa centralis, interneuron, anterior horn, lateral horn, posterior horn (column of Clarke, dorsal spinocerebellar tract)

white matter: anterior funiculus: descending (anterior corticospinal tract, vestibulospinal fasciculus, tectospinal tract), ascending (anterior spinothalamic tract, anterior proper fasciculus)

lateral funiculus: descending (lateral corticospinal tract, rubrospinal tract, olivospinal tract), ascending dorsal spinocerebellar tract, ventral spinocerebellar tract, spinothalamic tract, lateral spinothalamic tract, anterior spinothalamic tract, spinotectal tract, posterolateral tract, lateral proper fasciculus, medial longitudinal fasciculus

posterior funiculus: fasciculus gracilis, fasciculus cuneatus, posterior proper fasciculus


{{enWP|Brachial plexus

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