Nerve: Brachial plexus
The right brachial plexus with its short branches, viewed from in front.
Latin	plexus brachialis
Gray's	subject #210 930
Innervates	Sensory and motor innervation to the upper limb
From	C5, C6, C7, C8, T1
MeSH	Brachial+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 (C5-C8, T1). It proceeds through the neck, the axilla (armpit region), and into the arm. It is a network of nerves passing through the cervico-axillary canal to reach axilla and supplies brachium (upper arm), antebrachium (forearm) and hand.

Function [edit]

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 (CN XI) and an area of skin near the axilla innervated by the intercostobrachial nerve.

Lesions can lead to severe functional impairment.^[1]

Anatomy [edit]

The brachial plexus is divided into Roots, Trunks, Divisions, Cords, and Branches. There are five "terminal" branches and numerous other "pre-terminal" or "collateral" branches that leave the plexus at various points along its length.

Root [edit]

The five roots are the five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck. The brachial plexus emerges at five different leveles; C5, C6, C7, C8, and T1.

Trunk [edit]

These roots merge to form three trunks:

• "superior" or "upper" (C5-C6)
• "middle" (C7)
• "inferior" or "lower" (C8, T1)

Division [edit]

Each trunk then splits in two, to form six divisions:

• anterior divisions of the upper, middle, and lower trunks
• posterior divisions of the upper, middle, and lower trunks

Cord [edit]

These six divisions will regroup to become the three cords. The cords are named by their position with respect to the axillary artery.

• The posterior cord is formed from the three posterior divisions of the trunks (C5-C8,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 anterior division of the lower trunk (C8,T1)

Branches [edit]

The branches are listed below. Most branch from the cords, but a few branch (indicated in italics) directly from earlier structures. The five on the left are considered "terminal branches".

Diagram [edit]

Anatomical illustration of the brachial plexus with areas of roots, trunks, divisions and cords marked. Clicking on names of branches will link to their Wikipedia entry.

Diagrammatic representation of the brachial plexus using colour to illustrate the contributions of each nerve root to the branches

The brachial plexus, including all branches of the C5-T1 ventral primary rami. Includes mnemonics for learning the plexus' connections and branches.

Specific branches [edit]

Bold indicates primary spinal root component of nerve. Italics indicate spinal roots that frequently, but not always, contribute to the nerve.

Some mnemonics for remembering the branches:

• Posterior cord branches
  • STAR - subscapular (upper and lower), thoracodorsal, axillary, radial
  • RATS- Radial nerve, Axillary nerve, Thoracodorsal nerve, Subscapular (Upper & Lower)nerve.
  • ULTRA - upper subscapular, lower subscapular, thoracodorsal, radial, axillary
  • ULNAR- Upper subscapular nerve, Lower subscapular nerve,Nerve to lattissimus dorsi, Axillary nerve, Radial nerve.
• Lateral Cord Branches
  • LLM "Lucy Loves Me" - lateral pectoral, lateral root of the median nerve, musculocutaneous
  • Love Me Latha (LML) - Lateral pectoral nerve, Musculocutaneous nerve, Lateral root of Median Nerve.
• Medial Cord Branches
  • MMMUM "Most Medical Men Use Morphine" - medial pectoral, medial cutaneous nerve of arm, medial cutaneous nerve of forearm, ulnar, medial root of the median nerve
  • Union of 4 Medials - Ulnar nerve, Medial cutaneous nerve of arm, Medial cutaneous nerve of forearm, Medial pectoral nerve, Medial root of Median Nerve.
• 5 main nerves of brachial plexus, in order laterally to medially
  • "My Aunty Raped My Uncle" - Musculocutaneous, axillary, radial, median, ulnar

Injuries [edit]

Injuries to the brachial plexus affect cutaneous sensations and movements in the upper limb. They can be caused by stretching, diseases, and wounds to the lateral cervical region (posterior triangle) of the neck or the axilla. Depending on the location of the injury, the signs and symptoms can range from complete paralysis to anesthesia. Testing the patient's ability to perform movements and comparing it to their normal side is a method to assess the degree of paralysis. A common brachial plexus injury is from a hard landing where the shoulder widely separates from the neck (such as in the case of motorcycle accidents or falling from a tree). These stretches can cause ruptures to the superior portions of the brachial plexus or avulse the roots from the spinal cord. Upper brachial plexus injuries are frequent in newborns when excessive stretching of the neck occurs during delivery. Studies have shown a relationship between birth weight and brachial plexus injuries; however, the number of cesarean deliveries necessary to prevent a single injury is high at most birth weights.^[3] For the upper brachial plexus injuries, paralysis occurs in those muscles supplied by C5 and C6 like the deltoid, biceps, brachialis, and brachioradialis. A loss of sensation in the lateral aspect of the upper limb is also common with such injuries. An inferior brachial plexus injury is far less common, but can occur when a person grasps something to break a fall or a baby's upper limb is pulled excessively during delivery. In this case, the short muscles of the hand would be affected and cause the inability to form a full fist position.^[4]

Acute brachial plexus neuritis is a neurological disorder that is characterized by the onset of severe pain in the shoulder region. Additionally, the compression of cords can cause pain radiating down the arm, numbness, paresthesia, erythema, and weakness of the hands. This kind of injury is common for people who have prolonged hyperabduction of the arm when they are performing tasks above their head.

Prevention [edit]

Definition [edit]

plexus injuries can be defined as an injury which affects the nerves which send signals from the spine to your shoulder. This can be caused by the shoulder being pushed down and the head being pulled up which causes the nerves to be stretched or torn. Injuries associated with [1] commonly effect the brachial plexus nerves rather than other peripheral nerve groups.^[5] Due to the brachial plexus nerves being very sensitive to position, there are very limited ways of preventing such injuries. The most common victims of brachial plexus injuries consist of victims of motor vehicle accidents and newborns.

Motorcycle accidents [edit]

Motorcyclists who are involved accidents are very susceptible to brachial plexus injuries due to the nature of the collision. “Brachial plexus injuries were identified in 54 of 4538 patients presenting to a regional trauma facility… Motor vehicle accidents were the most frequent cause overall.” ^[6]

Many of these patients were forced to undergo reconstructive surgery. During therapy, the position of the brachial plexus became very important in order to avoid further damage. “The risk can be reduced by thorough release of the tissues from the inferior surface of the clavicle before mobilization of the fracture fragments.” ^[7] By wearing protective gear, like a helmet, a motorcyclist can help prevent nerve damage after collisions.

In this photo, the subject is performing an example of a motorcyclist colliding with the floor at an angle which may damage the brachial plexus nerves. One can see from the photo, the head and the shoulder are extremely separated which may cause the nerves in the between area to become stretched and maybe even torn. Wearing protective gear can help prevent nerve damage by providing extra support on the opposite side of the head which prevents over stretching of the neck.

Injuries During Birth [edit]

Brachial Plexus injuries also become an issue during the delivery of newborns. “…there were 80 brachial plexus injuries identified, for an incidence of 1.03 per 1000 live birth.” ^[8] Nerve damage has been connected to birth weight with larger newborns being more susceptible to the injury but it also has to do with the delivery methods. Although very hard to prevent during live birth, doctors must be able to deliver a newborn with precise and gentle movements in order to decrease chances of injuring the child.

Additional images [edit]

Mind map showing branches of brachial plexus

See also [edit]

• Brachial plexus injury
• Anesthesia of the brachial plexus (concerning nerve blocks for surgical procedures)

References [edit]

Dissection videos [edit]

• Learn to draw brachial plexus - Medchrome
• Video of the dissected axilla and Brachial Plexus

External links [edit]

Wikimedia Commons has media related to: Brachial plexus

• Brachial Plexus and its injury
• lesson3brachialplexus at The Anatomy Lesson by Wesley Norman (Georgetown University)
• Tutorial at Newcastle University
• Blog about Brachial Plexus Injury
• Brachial Plexus Injury/Illustration, Cincinnati Children's Hospital Medical Center
• Learn the Brachial Plexus in Five Minutes or Less by Daniel S. Romm, M.D. and Dennis A. Chu Chu, M.D. [2]
• Brachial Plexus Injury/Illustration, Cincinnati Children's Hospital Medical Center