Brachialis: Definition, Anatomy, Associated Injuries and their Causes, Symptoms and Treatments

It refers to the arm or everything related to this part of the body.

The brachial plexus is a network of intertwined nerves that control movement and sensation in the arm and hand.

A traumatic brachial plexus injury involves sudden damage to these nerves and can cause weakness, loss of sensation, or loss of movement in the shoulder, arm, or hand.

The brachial plexus begins at the neck and crosses the upper chest to the armpit. Injury to this network of nerves often occurs when the arm is forcibly pulled or stretched.

Mild brachial plexus injuries can heal without treatment. More serious injuries may require surgery to regain function of the arm or hand.


The brachial plexus is made up of five nerves that originate in the spinal cord of the neck. The plexus connects these five nerves with the nerves that provide sensation to the skin and allow movement in the muscles of the arm and hand. There is a brachial plexus on each side of the body.

Each of the five nerves in the brachial plexus has a specific function, such as driving muscles or carrying sensory information from the hand to the brain.

Because each nerve has a function, the location of the nerve injury within the plexus is important in predicting outcomes and in planning treatment.

The brachial plexus has five anatomical sections, and brachial plexus injuries can occur in one or more of these areas.

Causes of brachial plexus injuries

Most traumatic brachial plexus injuries occur when the arm is pulled or stretched forcibly. Many events can cause injuries, such as falls, motor vehicle collisions, stab or firearm injuries, and most commonly motorcycle collisions.

It is not known exactly how many brachial plexus injuries occur each year, but the number appears to be growing around the world.

Increased participation in high-energy sports and higher survival rates from high-speed motor vehicle collisions may be factors in the increasing number of these injuries.


Brachial plexus injuries vary greatly in severity, depending on the type of injury and the amount of force placed on the plexus. The same patient can injure several different brachial plexus nerves in varying severity.

  • Avulsion : In this more serious brachial plexus injury, the nerve root has been torn away from the spinal cord. These types of injuries may not be repairable with surgery.
  • Stretching (Neuropraxia) : When the nerve is slightly stretched, it may heal on its own or require simple, non-surgical treatment methods to return to normal function.
  • Rupture: a stronger stretch on the nerve can cause it to tear partially or completely. These types of injuries can sometimes be repaired with surgery.

Upper trunk paralysis injury

Upper trunk paralysis occurs when the angle between the shoulder and the neck is forcibly widened, such as when a fall forces the shoulder down and the head to the opposite side.

Patients with upper trunk palsy cannot use the shoulder to lift the arm out of the body, have arm weakness, and cannot flex the arm at the elbow. There may be loss of sensation in the shoulder, outside of the arm, and thumb.

A severe upper trunk injury can paralyze the shoulder muscles (deltoid muscle and rotator cuff), as well as the upper arm muscle (biceps).

Lower trunk paralysis injury

Lower trunk paralysis occurs when the angle between the arm and the chest wall is forcibly widened. This can damage the lower nerves and lower trunks.

Patients with lower trunk paralysis will normally maintain strength in the shoulder and elbow, but lose hand function. Over time, this will cause the fingers to contract into a claw position, and the patient will not be able to perform fine motor tasks.

Patients also often have hand numbness in at least the ring finger and the little finger.

Panplexus paralysis injury

Panplexus palsy can occur if the force of the injury is extreme. In panplexus palsy, all levels of the nerves and the trunk are damaged. This results in complete paralysis of the arm and hand, which is often referred to as a “flail limb.”

Bullet wounds

Brachial plexus injuries caused by a gunshot wound do not usually seriously damage the nerve.

The severity of the injury will depend on the caliber, speed, and angle of entry of the bullet. Low velocity bullets typically damage nerves by hitting them directly.

High velocity bullets can injure nerves by direct impact (bruising) or, more commonly, by shock waves that stretch the nerve.

A stretching and bruising injury to the nerves will often heal on its own. Gunshot wounds can also cause artery or vein injuries that require immediate or delayed repair.

Penetrating wounds

A brachial plexus injury caused by a penetrating injury, such as a knife wound (laceration), can damage or cut the nerve. This type of nerve injury will usually not heal on its own, prompting more immediate treatment.

Additional injuries

Because brachial plexus injuries are generally caused by high-energy and forceful events, many patients have additional injuries.

These may include artery or vein injuries, shoulder or arm fractures, rib fractures, a collapsed lung, bleeding into the lungs or chest cavity, spinal fractures, spinal cord injury, and traumatic brain injury. .


Symptoms vary depending on the type and location of the brachial plexus injury, as well as whether the patient suffered other injuries.

The most common symptoms of brachial plexus injury include:

  • Weakness or numbness
  • Loss of sensation.
  • Loss of movement (paralysis).
  • Pain.

The pain from brachial plexus injuries is the result of an injury to the spinal cord where nerve roots detach from the cord. This pain is neuropathic in nature and can be very difficult to treat. The pain can last a long time.

Brachial plexus injuries that occur at the level of the spinal cord often cause more pain than more distant spinal cord injuries. Also, injuries closer to the spinal cord can cause burning numbness, which is called paresthesias or dysesthesias.

Medical exam

Patients with brachial plexus injuries should be evaluated and treated within an appropriate time frame, usually within 6 to 7 months after injury. The longer a muscle is without nerve input, the less likely the muscle is to function normally in the future.

This is true even if the muscle eventually regains its nerve signals.

The exact time to seek treatment depends on the type of injury and its location.

Physical exam

If your doctor suspects a brachial plexus injury, he or she will perform a comprehensive exam to diagnose the injury and determine if there are any associated injuries.

He or she will examine all the nerve groups controlled by the brachial plexus to identify the specific location of the nerve injury and its severity.

The pattern by which the brachial plexus nerves control various muscles in the arm and hand will help your doctor identify potential sites of nerve injury. Your doctor will examine all the nerve groups controlled by the brachial plexus.

Also, some patients show specific signs that help determine the location of the nerve injury:

Narrowing of the pupils, drooping eyelid, and lack of ability to sweat (Horner syndrome) is a sign that the injury is close to the spinal cord.

A stabbing pain like a nerve when the doctor touches the affected nerves (Tinel’s sign) suggests an injury beyond the spinal cord. Over time, if the location of the Tinel sign moves down the arm toward the hand, it is a sign that the injury is healing.

During the physical exam, your doctor will also evaluate your arm and shoulder for stability and range of motion.

Imaging tests

X-rays: This imaging test creates sharp images of dense structures, such as bones. X-rays of the neck, chest, shoulder, and arm are taken to rule out associated fractures.

Chest x-rays are obtained to look for rib fractures or lung injury.

If you are unable to take a deep, deep breath during the chest X-ray, your doctor may consider lung function testing with the help of a pulmonologist to rule out damage to the nerves that control deep breathing.

Nerve conduction studies: Nerve conduction studies measure the signals that travel in the nerves in your arm and hand.

Computed Tomography (CT): This test is considered the most reliable test for detecting avulsion injuries of the spinal nerve.

A dye is injected around the spinal cord in the neck to show the lesion more clearly on the CT image.

CT is usually done at least 3 to 4 weeks after the injury to allow any possible blood clots in the nerve root area to dissolve.

Some centers may also use magnetic resonance imaging (MRI) instead of, or in addition to, a CT scan.

Electrodiagnostic studies: These tests measure nerve conduction and muscle signals. They are important assessment tools because they can confirm the diagnosis, locate the nerve injury, characterize its severity, and assess the rate of nerve recovery.

An initial electrodiagnostic exam is done 3 to 4 weeks after the injury. This allows any nerve degeneration that may occur to become detectable.

Electrodiagnostic studies are repeated 2 to 3 months after the initial study and then repeatedly over time to assess whether the nerves are recovering.


Non-surgical treatment

Many brachial plexus injuries will heal spontaneously without surgery over a period of weeks to months, especially if they are mild.

Nerve injuries that heal on their own tend to have better functional outcomes. If your doctor believes that the injury has good potential for recovery without surgery, he or she may delay the procedures and simply control your injury.

The nerve healing process itself takes time, and your doctor may recommend physical therapy to prevent joint and muscle stiffness.

Surgical treatment

Surgical treatment is generally recommended when the nerves do not heal on their own or do not heal enough to restore necessary function to the arm and hand.

It is important to note that, depending on the severity of the injury, even surgery may not be able to return the arm or hand to pre-injury skills.


Recovery: During your discussion with your doctor, it will be important to set realistic goals and expectations for surgical treatment. Nerves heal slowly.

The recovery period after surgery is often long and requires a strong commitment to a comprehensive rehabilitation program to restore physical capabilities. This is something that should be taken into account when making the decision to proceed with surgery.

Candidates for surgery : Although brachial plexus surgery can help restore function in many patients, there are some factors that prevent a patient from being a candidate for surgery, most importantly, unrealistic expectations.

Other factors include:

  • Joint stiffness and contractures.
  • Advanced age.
  • Additional medical conditions or injuries.
  • Traumatic brain injury.
  • Spinal cord injury.

Your doctor will discuss with you if you are a candidate for surgery.

Complications: Surgical treatment may not restore desired movement or the surgical wound may become infected. Both results could require additional surgery.

Additionally, patients with pre-existing medical problems have additional potential risks related to any large reconstructive surgery, including chronic pain, blood clots, heart attacks, strokes, and even death.

Surgical procedures

Various surgical techniques are used to treat nerve injuries, depending on the type of injury and the time that has elapsed since the injury.

In most procedures, an incision is made near the neck above the collarbone. If the injury extends down the brachial plexus, another incision may be needed in the front of the shoulder.

To repair or reconnect nerves, surgeons often use high-powered microscopes and small specialized instruments.

Nerve repair: In this procedure, the surgeon reattaches the two ragged edges of a severed nerve. Nerve repair is usually done immediately for acute lacerations of the nerves, as in a knife wound.

Nerve graft: Nerve graft is a procedure in which a healthy nerve taken from another part of the body is sewn between the two ends of a lacerated nerve.

The transplanted nerve acts as a scaffold to support the injured ends as they regenerate and grow back together.

Nerve grafting can only be done if there is a functioning nerve stump in the spinal cord to conduct a nerve signal.

The goal is for the transplanted nerve to guide nerve regeneration and ultimately restore nerve signals to feed paralyzed muscles.

Nerve Transfer : A nerve transfer procedure is used when there are no functioning nerve stumps in the neck to which nerve grafts can connect.

In this procedure, a healthy donor nerve is cut and reconnected to the injured nerve to provide a signal to a paralyzed muscle. In many cases, the healthy nerve is connected closer to the affected muscle.

In other cases, the healthy nerve is connected to the damaged nerve within the brachial plexus.

Tendon and muscle transfers : Patients who delay the first doctor visit for more than 12 months after injury tend to have poor results with surgery to rebuild the nerves.

These patients are best managed with surgery that focuses on reconstruction of the tendon (tendon transfer) or muscle (free-functioning muscle transfer).

A tendon transfer is a type of surgery in which the tendon of a functioning muscle is cut and sewn into a non-functioning muscle tendon to restore a specific movement or motor function.

In a free-running muscle transfer, a muscle from one part of the body is moved to the injured area, along with its tendon, artery, vein, and nerve. Each of these structures is connected to corresponding structures in the injured area to restore movement or motor function.

Recovery and rehabilitation

Because nerve regeneration occurs slowly at a rate of approximately 1mm / day, recovery from a brachial plexus injury takes time, and patients may not experience results for several months.

A positive mindset and the support of family, friends, and healthcare professionals are important to recovery and rehabilitation.

During this recovery process, occupational therapists teach patients how to use the unaffected arm for daily activities such as eating and personal hygiene.

Physical therapy of the shoulder, elbow, wrist, and fingers involves specific exercises to prevent stiffness, contractures, or muscle atrophy.

A physical therapist may also recommend assistive devices such as splints or support braces to help support a flaccid arm and joints.

Compression gloves and sleeves can be used to prevent swelling in the affected arm, which can lead to joint pain and contractures.

Pain can be controlled with medications, therapy, and assistive devices.

Additionally, patients will require healthy coping skills to make adjustments in their lives, both in terms of employment and daily activities, in anticipation of a less functional arm and / or hand.

Future developments

Although brachial plexus injuries can be devastating and difficult to manage, a team approach to treatment has achieved significant improvements in patient function.

Although current technology cannot return patients with a flail limb to their pre-injury state, restoring some functions of the arm is a major improvement.

Future developments in the treatment of these injuries include new techniques to repair or transfer nerves, as well as new drugs or materials to help promote and stimulate healthy nerve regeneration.