Brachial Plexus Injury – When Shoulder and Arm Stop Working Properly

The brachial plexus is a complex network of nerves that originates in the lower cervical spine and upper thoracic spine. From there, nerve fibers branch out toward the shoulder, upper arm, forearm, and hand. This nerve network allows us to move our arms and hands, and to perceive what we touch – whether it’s warmth, pain, or even a breeze on the skin.

What is the brachial plexus?

The brachial plexus is formed from several nerve roots that emerge from the spinal cord, typically from the C5 to Th1 segments. Only the anterior (motor and sensory) parts of these roots contribute to the plexus – these carry the fibers responsible for muscle control and sensation in the arm and hand.

Depiction of the brachial plexus on the left side. Central view of the collarbone. — The brachial plexus is formed by nerve roots from the lower cervical and upper thoracic spine. In this illustration, it is shown after passing through the scalene muscles, running beneath the clavicle toward the axilla. The image shows the left side of the body, viewed from a slightly elevated angle centered on the clavicle. The nerve structures are highlighted in yellow.

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The nerve roots first unite to form three primary trunks (Trunci). Already at this level, smaller nerves branch off to supply muscles around the shoulder.

Each trunk then divides into an anterior and posterior division (Divisiones), which are functionally significant: anterior divisions mainly serve flexor muscles, while posterior divisions primarily supply extensor muscles.

From these divisions arise three secondary cords (Fasciculi), which ultimately give rise to the major nerves of the arm:

Median nerve – involved in hand and finger movements
Ulnar nerve – runs along the inner arm and supplies fine hand muscles
Radial nerve – mainly responsible for finger and wrist extension and sensation on parts of the back of the hand
Musculocutaneous nerve – important for elbow flexion
Axillary nerve – supplies the shoulder and is essential for lifting the arm sideways

These nerves enable us to move the arm, grasp objects, and sense touch or temperature changes.

What can cause brachial plexus injury?

Injuries to the brachial plexus can occur in various ways. The nerve network is particularly vulnerable to strong traction or compression of the shoulder and arm. Common causes include:

Accidents, such as motorcycle or car crashes, especially with sudden pulling of the arm upward, backward, or to the side

Depiction of a motorcycle crash causing brachial plexus injury to the left arm. — Severe traction during a motorcycle crash can lead to brachial plexus injury.

Overstretching of individual nerve branches, e.g. from a fall or impact
Birth-related trauma, such as shoulder dystocia
Tumors or inflammation compressing or displacing the nerves
Electrical injuries
Chemical injuries (e.g. due to cement or medications)
Radiation-related damage after cancer treatment

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Depending on the type of injury, only parts of the plexus may be affected – or the entire network. Clinically, we distinguish:

Upper plexus lesions (e.g. C5–C6): often affect shoulder and arm muscles
Lower plexus lesions (e.g. C8–Th1): typically affect hand muscles
Global lesions: involve the whole arm

Types of nerve damage

Stretch injury – nerve fibers are pulled but not torn
Rupture – the nerve is torn along its path
Avulsion – nerve roots are pulled out from the spinal cord
Compression – due to pressure from bone, scar tissue, or hematomas

Less common causes include:

Laceration
Electric shock
Chemical or radiation damage

Typical symptoms

Symptoms can vary greatly. Some patients experience immediate arm paralysis, others only notice tingling or weakness. Common signs include:

Muscle weakness or paralysis in the arm or hand
Numbness, tingling, or burning sensations
Nerve pain (sharp or electric)
Limited shoulder, elbow, or hand movement
Muscle wasting (atrophy) if the damage persists
A feeling of heaviness or detachment in the arm
Cold sensation or pale skin due to impaired blood flow

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Variable course of injury

The term “brachial plexus injury” is a broad description and does not refer to a single pattern. Each case is unique and must be individually assessed.

Symptoms may appear immediately or develop gradually. The outlook depends on the severity of the damage. Some nerves recover partially over time, while others may result in long-term deficits. Modern diagnostics help assess the extent and possible prognosis more precisely.

How is the diagnosis made?

A thorough clinical and technical assessment helps determine which parts of the nerve are affected and how severely.

Clinical examination

Shoulder, elbow, and wrist mobility
Differentiation between joint, muscle, or nerve-related restrictions
Muscle strength, sensation, and reflex testing
Circulatory status and visible signs (e.g. scars)

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Imaging

High-resolution nerve ultrasound

This non-invasive method allows direct visualization of nerve structures along their path – from the neck down to the hand. It can detect swellings, scarring, or compression. Even with existing implants like plates, screws, or prostheses, the nerves can often still be assessed reliably.

Illustration of an ultrasound examination from the neck to just before the fingertip. — High-resolution ultrasound allows for extended visualization of peripheral nerves – from the neck region to parts of the hand, depending on location and depth.

However, limitations exist for deeper regions under the clavicle or within the spinal canal. Therefore, MR neurography is often recommended when deeper structures or nerve root avulsions are suspected.

Muscle ultrasound – indirect assessment

Muscle ultrasound can detect secondary signs of nerve damage by assessing the muscles supplied by the affected nerve. Denervation changes – such as structural softening or muscle shrinkage – provide clues to the extent and location of nerve injury.

Muscle ultrasound: Ultrasound examination of muscles to diagnose scarring, fatty degeneration, atrophy, and muscle wasting. — Muscle ultrasound can help identify changes such as bleeding, scarring, atrophy, and fatty degeneration in muscles. It can also support follow-up examinations and assessment over time.

This method helps select suitable muscles for EMG testing and can reduce the number of needle insertions needed.

MR neurography – for deep nerve evaluation

MR neurography is the gold standard for visualizing nerve structures inside the body, especially at the nerve root level. It shows the course of nerves from the spinal cord through to the shoulder and can reveal avulsions, scarring, or masses.

MRI scanner for visualizing nerve structures and soft tissues – modern imaging for diagnosing nerve damage. — MRI delivers high-resolution images of soft tissues, whereas MR neurography is specifically designed for detailed nerve imaging and diagnosis.

Limitations include decreased clarity shortly after trauma due to bleeding or hematomas. Metallic implants may also interfere with imaging. Some changes, such as neuroma formation, become visible only over time.

X-ray and CT – for bone-related injuries

When bone injuries (e.g. fractures or dislocations) are suspected, X-ray and CT are important tools. They also help interpret nerve imaging by identifying potential bony causes of nerve compression.

Nerve function tests

Nerve conduction study (NCS / ENG)

This test measures how well electrical signals travel through a nerve. It helps assess whether a nerve is mildly or severely damaged. In lower plexus injuries, it often yields reliable results. In upper plexus injuries or root avulsions, the findings may be limited.

Interestingly, in suspected root avulsion, the sensory nerve signal may still be present while the motor response is absent. This is because the sensory nerve cell bodies remain intact outside the spinal cord – a pattern that may point to a root-level injury.

Illustration of the electrodes used for nerve conduction studies (neurography / NCS / ENG). — Nerve conduction studies (neurography) are performed using a stimulation electrode and adhesive skin electrodes.

Electromyography (EMG)

EMG records the electrical activity of specific muscles. It helps determine whether the muscle is still receiving nerve signals or has lost its connection. By testing muscles supplied by different nerves, the pattern of nerve damage can be mapped.

Close-up of the tip of a concentric needle electrode with inner and outer recording surfaces. — The tip of the concentric needle electrode contains an inner and an outer electrode that record electrical activity of individual muscle fibers within a few millimeters.

Somatosensory evoked potentials (SSEPs)

SSEPs measure how well sensory signals travel from the arm through the spinal cord to the brain. In unclear or complex cases, they can help assess whether the signal conduction along central pathways is intact. This is especially helpful in suspected root avulsions.

What can be done?

The appropriate treatment depends on the extent of nerve damage, the areas involved, and whether spontaneous recovery seems possible. The term brachial plexus injury covers a wide range of different problems – the exact nature of the injury can often be clarified through modern diagnostics.

Understanding which nerves are affected and how severely allows for tailored treatment planning.

Medical options – individualized treatment planning

Early evaluation by specialists is essential. Based on the findings, an individualized treatment plan can be developed.

Depending on the situation, conservative treatment such as physical or occupational therapy may be considered. In selected cases, surgical options may be appropriate – for example, microsurgical nerve repair, nerve transfer, or scar release (neurolysis).

Schematic illustration of a personalized treatment plan with a central symbol surrounded by medical options. — Every treatment plan should be tailored to the symptoms and needs of the individual.

Importantly, even in complex cases, structured therapy can lead to improvement. Passive observation without follow-up is often not appropriate. Careful diagnostics and individualized treatment planning are key to supporting recovery.

What you can do

Your active participation plays a crucial role in recovery. Understanding your condition and sticking to therapy recommendations are essential – especially with nerve injuries.

Exercises should ideally be done twice daily, integrated into your daily routine. Short, frequent sessions are more effective than long, infrequent ones. Physical and occupational therapy work best when combined with consistent home practice.

Cheerful yellow cartoon neuron with a bandage on its axon, symbolizing nerve healing — Even after injury, nerves may have the capacity to recover – especially with supportive treatment and monitoring.

Regular follow-up with a specialist is also important to track progress and adjust the treatment plan as needed.

Disclaimer: The information provided on this page is for general informational purposes only and does not constitute medical advice. It is not a substitute for personal consultation, examination, or treatment by a physician or other qualified healthcare professional. No guarantees of healing or cure are made. While we strive for accuracy and completeness, we cannot guarantee that all content is up to date or free from errors, and we accept no liability for any inaccuracies.