The brachial plexus passes from the neck to the axilla and supplies the upper limb. It is formed from the ventral rami of the 5th to 8th cervical nerves and the ascending part of the ventral ramus of the 1st thoracic nerve. Branches from the 4th cervical and the 2nd thoracic ventral ramus may contribute.

 

Compression of the medial, lateral and posterior cords of the brachial plexus can occur between the first rib and clavicle (known as thoracic outlet) and below pectoralis minor 

 

 

The right brachial plexus with its short branches, viewed from in front.

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

 

Description

Path

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.

 

The five Roots are the five anterior rami of the lower four cervical and first thoracic nerve roots (C5-C8, T1) after they have given off their segmental supply to the muscles of the neck. These Roots merge to form three Trunks:

Upper Trunk (C5-C6)

Middle Trunk (C7)

Lower Trunk (C8, T1)

Each Trunk then splits into anterior and posterior divisions, to form six Divisions. The anterior/ posterior divisions innervate flexor groups versus extensor groups:

anterior divisions of the upper, middle, and lower trunks

posterior divisions of the upper, middle, and lower trunks

These six Divisions will regroup to become the three Cords. The Cords are named by their position 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)

 

Anatomical illustration of the brachial plexus with areas of roots, trunks, divisions, and cords marked.

Specific Branches

The branches are listed below. They mostly branch from the cords, but some originate from earlier structures.

 

From NerveRoots

rootsDorsal scapular nerveC4, C5Rhomboid muscles and Levator scapulae-

rootsLong thoracic nerveC5, C6, C7Serratus anterior-

upper trunkNerve to the subclaviusC5, C6Subclavius muscle-

upper trunkSuprascapular nerveC5, C6Supraspinatus and Infraspinatus-

lateral cordLateral pectoral nerveC5, C6, C7Pectoralis major and Pectoralis minor (by communicating with the Medial pectoral nerve)-

lateral cordMusculocutaneous nerveC5, C6, C7Coracobrachialis, Brachialis and Biceps brachiibecomes the Lateral cutaneous nerve of the forearm

lateral cordlateral root of the Median nerveC6, C7fibres to the median nerve-

posterior cordUpper subscapular nerveC5, C6Subscapularis (upper part)-

posterior cordThoracodorsal nerve (middle subscapular nerve)C6, C7, C8Latissimus dorsi-

posterior cordLower subscapular nerveC5, C6subscapularis (lower part ) and Teres major-

posterior cordAxillary nerveC5, C6anterior branch: deltoid and a small area of overlying skin posterior branch: Teres minor and deltoid musclesposterior branch becomes Upper lateral cutaneous nerve of the arm

posterior cordRadial nerveC5, C6, C7, C8, T1Triceps brachii, Supinator, Anconeus, the extensor muscles of the Forearm, and Brachioradialisskin of the posterior arm as the Posterior cutaneous nerve of the arm

medial cordMedial pectoral nerveC8, T1Pectoralis major and Pectoralis minor-

medial cordmedial root of the Median nerveC8, T1fibres to the median nerveportions of hand not served by ulnar or radial

medial cordMedial cutaneous nerve of the armC8, T1-front and medial skin of the Arm

medial cordMedial cutaneous nerve of the forearmC8, T1-medial skin of the forearm

medial cord, Ulnar nerveC8, T1Flexor carpi ulnaris, the medial two bellies of Flexor digitorum profundus, the intrinsic hand muscles except the Thenar muscles and the two most lateral lumbricalsthe 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.

 

Injuries

Injury to the brachial plexus can be very problematic because the nerves branching off of the plexus provide innervation to the upper extremity. Clinical signs and symptoms vary with which area of the plexus is involved, and generally result in paralysis or anesthesia.

 

Symptoms can range from transient nerve dysfunction to complete upper extremity weakness. Because of the anatomical variants[5] of the brachial plexus these injuries can be a challenge to diagnose.

 

Mechanism of Injury

The main causes of brachial plexus palsies are traction, due to extreme movements, and heavy impact. 

 

Brachial plexus injury can occur in a variety of ways and can occur as a result of shoulder trauma, tumours, or inflammation. The rare Parsonage-Turner Syndromec brachial plexus inflammation without obvious injury, but with nevertheless disabling symptoms. But in general, brachial plexus lesions can be classified as either traumatic or obstetric.

 

Obstetric injuries may occur from a mechanical injury involving shoulder dystocia during a difficult childbirth. During birth, excessive stretching of the neck or pulling the upper extremity can result in an upper brachial plexus injury or inferior trunk, respectively. The incidence of brachial plexus injury is approximately 1 in 1,000 live births.

Traumatic injury may arise from penetrating or sports-related injuries, falls, work-related injuries, radiation therapy and iatrogenic causes (i.e. first rib resection, shoulder surgery, brachial plexus block).

However the most common mechanism of injury is a traction injury due to the forceful separation of the neck from the shoulder.

Common associated injuries can include fractures of the proximal humerus, clavicle, scapula, cervical spine and upper limb vascular injuries. Management of these injuries may complicate the picture when diagnosing brachial plexus injury but can also guide in determining the mechanism of injury.

 

 

Classification of Injury

There are many classification systems for brachial plexus injuries, they can be divided into three types:

 

An upper brachial plexus lesion, which occurs from excessive lateral neck flexion away from the shoulder. Most commonly, forceps delivery or falling on the neck at an angle causes upper plexus lesions leading to 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.

Less frequently, the whole brachial plexus lesion occurs.

Most infrequently, sudden upward pulling on an abducted arm (as when someone breaks a fall by grasping a tree branch) produces a lower brachial plexus lesion, in which the eighth cervical (C8) and first thoracic (T1) nerves are injured either before or after they have joined to form the lower trunk. The subsequent paralysis affects the intrinsic muscles of the hand and the flexors of the wrist and fingers.This results in a form of paralysis known as Klumpke's Paralysis.

However, a commonly used one is Leffert's classification system which is based on etiology and level of injury:

 

I Open (usually from stabbing)

II Closed (usually from a motorcycle accident)

IIa Supraclavicular (preganglionic or postganglionic)

IIb Infraclavicular

IIc Combined

III Radiation-induced

IV Obstetric

IVa Erb's (upper root)

IVb Klumpke (lower root)

IVc Mixed

Signs and Symptoms

Nerve damage causes a multifaceted clinical picture consisting of sensorimotor disturbances (pain, muscle atrophy, muscle weakness, secondary deformities) as well as the reorganisation of the Central Nervous System that may be associated with upper limb underuse.

 

Pain is most common, in particular, those affecting the preganglionic fibres. Often described as crushing with intermittent severe attacks shooting down the arm.

Paralysis and anaesthesiain affected extremity.

Bizarre sensations, hyperalgesia, dysesthesia, and allodynia.

Myoclonic jerks in the affected extremity.

Ipsilateral Horners Syndromewith T1 injury.

Investigations

Xray of the shoulder area and cervical spine to determine if any boney abnormalities are causing the lesion.

MRI will help to visualise causative pathology such as tumors, neuritis, radiation injury.

EMG and NCS help to confirm a diagnosis, localise the lesion and determine the degree of axonal loss. These tests are the most useful tests to determine localisation of the plexopathy, especially, the sensory nerve conduction studies (SCSs) because sensory nerve action potential amplitude will decrease in plexopathies due to Wallerian degeneration of the postganglionic sensory fibers.

Histamine test to differentiate between pre and postganglionic lesion.

Management

brachial plexus injury may result in severe and chronic impairments in both adults and children, thus requiring early and long-lasting treatment. 

 

Medical Management

The main aspect of medical management is pain control. Often treated in a similar way to neuropathic pain with NSAID, tricyclic antidepressants, anticonvulsants, and oral or transdermal opioids.

Psychological Management

Psychological problems and a lack of cooperation by the patient may limit rehabilitation effects and increase disability.

Physiotherapy Management

See also Brachial Pluxus Injury for Physiotherapy Management

 

The aim is to maintain the range of motion of the extremity, to strengthen the remaining functional muscles, to protect the denervated dermatomes, and to manage pain.

 

Pain control - acupuncture, TENS

Maintaining ROM - passive movements,exercise therapy, splinting, positioning

Strengthen affected muscles - biofeedback, exercise therapy

Managing chronic oedema - compression garments, advice, massage therapy

Intervention Management

Continuous brachial plexus block

Transcutaneous nerve stimulation

Dorsal route entry zone (DREZ) ablation or implantable dorsal route stimulators.

Surgical techniques include neurolysis, nerve grafting, and nerve transfer. Intercostal nerves are commonly used to reinnervate muscles after a brachial plexus injury with avulsion of spinal nerve roots.

Brachial Plexus Block

A brachial plexus block allows a surgeon to operate on an upper extremity without the use of a general anesthetic, when combined with a tourniquet.

 

The location of the injection is between the posterior border of the sternocleidomastoid and the clavicle. The axillary sheath surrounds the axillary vein, axillary artery, and three cords of the brachial plexus. When the injection takes effect, the muscles and skin innervated by the cords found in the sheath are anesthetized. 

 

Other Information

Some mnemonics for remembering the branches:

 

Posterior Cord Branches

STAR - subscapular (upper and lower), thoracodorsal, axillary, radial

ULTRA - upper subscapular, lower subscapular, thoracodorsal, radial, axillary

Lateral Cord Branches

LLM "Lucy Loves Me" - the lateral pectoral, lateral root of the median nerve, musculocutaneous

Medial Cord Branches

MMMUM "Most Medical Men Use Morphine" - medial pectoral, medial cutaneous nerve of arm, medial cutaneous nerve of forearm, ulnar, the medial root of the median nerve.


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Klumpke paralysis is a neuropathy of the lower brachial plexus which may be resulted from a difficult delivery.

Usually the eighth cervical and first thoracic nerves are injured either before or after they have joined to form the lower trunk. This injury can cause a stretching (neuropraxia,), tearing (called “avulsion” when the tear is at the spine, and “rupture” when it is not), or scarring (neuroma) of the brachial plexus nerves. Most infants with Klumpke paralysis have the more mild form of injury (neuropraxia) and often recover within 6 months. 

The main mechanism of injury is hyper-abduction traction and depending on the intensity, cause signs and symptoms consistent with a neurological insult.

According to the the National Institute of Neural Disorders and Stroke (NINDS), there are four types of brachial plexus injuries that cause Klumpke’s :

Avulsion, in which the nerve is severed from the spine.

Rupture, in which tearing of the nerve occurs but not at the spine.

Neuroma, in which the injured nerve has healed but can’t transmit nervous signals to the arm or hand muscles because scar tissue has formed and puts pressure on it.

Neuropraxia or stretching, in which the nerve has suffered damage but is not torn.

Causes

Risk factors for Klumpke Paralysis are:

large birth weight babies,

maternal diabetes, 

multiparity,

difficult presentation,

shoulder dystocia,

forceps or vaccuum delivery,

breech position,

prolonged labor,

previous child with obstetric palsy,

intrauterine torticollis.

Less common includes tumors (neuromas, rhabdoid tumors), intrauterine compression, hemangioma and exostosis of the first rib in the child.

Signs and Symptoms

Signs and symptoms:

- “Claw hand” is a classic presentation seen where the forearm is supinated and the wrist and fingers are flexed.

Other signs and Symptoms include:

weakness and loss of movement of the arm and hand. Some babies experience drooping of the eyelid on the opposite side of the face as well. This symptom may also be referred to as Horner's syndrome. 

decrease of sensation along the medial aspect of the distal upper extremity along the C8 and T1 dermatome.

myotome findings that can range from decreasing muscular strength to muscular atrophy and positional deformity.

Reflexes in the affected roots are absent.

associated injuries clavicular and humerus fractures, torticollis, cephalohematoma, and facial nerve palsy.

- An infant with a nerve injury to the lower plexus (C8-T1) holds the arm supinated, with the elbow bent and the wrist extended.

Differential Diagnosis

Erb's palsy; this injury affects the upper brachial plexus which will usually result in dermatome and myotome finds along the C5-C6 path,

Distal nerve entrapment of the ulnar nerve at either the medial epicondyle of Guyon's tunnel- produces similar neurological findings as the more proximal Klumpke's. But there is no involvement of innervation proximal to the lesion, for example, pectoralis major involvement with true ulnar nerve entrapment.

Thoracic outlet syndrome : TOS is a compression injury to the brachial plexus from a rudimentary rib, first rib, or the clavicle on the ipsilateral side, this could be post-traumatic, postural driven, and or genetic.It affects more than C8- T1 roots.

Apical lung tumor

Neurofibroma

Disc herniation

Shoulder impingement

Clavicular or vertebral fracture

Other

Management

Treatment of Klumpke’s injury in babies and children is heavily dependent on the severity and the classification of the injury.

The affected arm may be immobilized across the body for 7 to 10 days. For mild cases, gentle massage of the arm and range-of-motion exercises may be recommended.

For torn nerves (avulsion and rupture injuries), symptoms may improve with surgery.   

Surgical Options:

1. Surgery on the nerves (e.g., nerve grafts and neuroma excision).

2.Tendon transfers to help the muscles that are affected by nerve damage work better.

3.Muscle transfer, in which a less important muscle or tendon is removed from another part of the body and attached to the injured arm if the muscles there deteriorate

Physiotherapy Management

Physical therapy assists in keeping the muscles and joints’ range of motion normal. Physical therapy also keeps muscles and joints to work properly and prevents stiffness in joints such as the shoulder, elbow, or wrist. 

Physiotherapy majorly focuses on :

improving flexibility,

range of motion,

strength, and

dexterity

Pain control

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