Brachial plexus injury

What is a brachial plexus injury?

The brachial plexus is a network of nerves that runs from your spinal cord in the neck, under the collarbone, and into the shoulder, arm and hand, carrying the signals that control movement and feeling there. A brachial plexus injury is damage to these nerves, ranging from a mild, temporary stretch to a complete, permanent tear, and can leave part or all of the arm weak, numb or paralysed.

What are the symptoms of a brachial plexus injury?

Symptoms can include:

• a limp or paralysed arm
• weakness or lack of muscle control in the arm, hand or wrist
• reduced or absent feeling in the arm or hand
• sudden stinging or burning pain in the shoulder or arm.

The pattern of symptoms depends on which part of the plexus is affected. An upper plexus injury typically pulls the arm inward and rotates it in towards the body, with the elbow straightened, sometimes described as a 'waiter's tip' position. A lower plexus injury more often affects the wrist and hand specifically, sometimes causing a clawed appearance, since the small muscles of the hand are affected while the wrist itself can still extend. A complete injury affects movement and sensation throughout the whole arm.

Severe, burning pain in an otherwise numb limb can be a sign of a more serious injury. A drooping eyelid, a smaller pupil, or reduced sweating on the same side of the face can also develop a few days after a severe injury and points towards the nerve having been torn away from the spinal cord itself.

What causes a brachial plexus injury, and who's at risk?

Brachial plexus injuries are typically caused by trauma, tumours, inflammation, pressure, sports injuries, or the nerves being stretched too far; some happen to babies during birth.

In adults, the most common cause by far is a traction (stretching) injury, usually from a road traffic accident, particularly involving motorcyclists. Other causes include falls, direct blows to the shoulder or neck, penetrating injuries such as knife or gunshot wounds, and, less commonly, tumours, radiation, or an inherited extra rib in the neck (a cervical rib).

The direction of the force involved affects which part of the plexus is hurt: a shoulder forced downward tends to injure the upper plexus, while the arm being forced upward or outward, such as grabbing onto something while falling, tends to injure the lower plexus. Milder, usually temporary versions of this injury, sometimes called 'burners' or 'stingers', can happen in contact sports.

Some brachial plexus injuries happen to babies during birth, if the baby's shoulder becomes stuck (impacted) during a difficult delivery, stretching or tearing the nerves.

A rare condition called Parsonage-Turner syndrome causes inflammation of the brachial plexus without any obvious injury, but can still cause disabling symptoms.

Are there different types of brachial plexus injury?

Injuries are classified by how badly the nerve itself is damaged:

• neurapraxia (stretch): the mildest form, where nerve fibres temporarily stop working but usually recover on their own, fairly quickly and without surgery
• stretched but intact: the nerve is damaged but not torn apart; it may recover to varying degrees on its own over months, and may not need surgery
• rupture: the nerve has been stretched to breaking point and has snapped, similar to an overstretched elastic band; this needs surgery to heal
• avulsion: the most severe type, where the nerve is torn away from the spinal cord itself and can't be rejoined there; some function is permanently lost, though nerves can sometimes be rerouted from elsewhere during surgery to restore some movement. A partial (incomplete) form also exists, leaving some potential for gradual recovery.

Injuries are also described by which part of the plexus is affected:

• an upper plexus injury (Erb's palsy) is the most common pattern and generally has the best outlook
• a lower plexus injury (Klumpke's palsy) is rarer and tends to be more severe
• a total injury, affecting the whole plexus, has the least favourable outlook.

Injuries below the collarbone tend to do better than those above it.

How is a brachial plexus injury diagnosed?

A specialist will assess the movement, strength and sensation in your arm, and check the pulses in your arm to rule out any associated damage to the blood vessels running alongside the nerves. Depending on what's suspected, you may also have:

• nerve conduction studies, which assess how well electrical signals travel along your nerves
• an MRI scan, using magnets and radio waves to build detailed images of the area
• a CT scan, using X-rays, sometimes combined with a special dye study (myelogram) that is considered the most reliable way to pinpoint damage at the point where the nerve leaves the spinal cord; this is usually done a few weeks after the injury, once the initial swelling has settled
• an X-ray, which can show rib fractures suggesting plexus damage, or signs that your diaphragm isn't moving normally, which can point to a higher-level injury
• electromyography (EMG), which tests muscle activity and is usually carried out a few weeks after the injury, once enough time has passed for changes to show up clearly.

How is a brachial plexus injury treated?

Treatment depends on how the injury is classified and how badly the nerves are damaged.

• Mild injuries (neurapraxia, or nerves that are stretched but intact) are usually monitored in outpatient clinics, since meaningful recovery is expected without surgery, though it can take months.
• More severe injuries (rupture or avulsion) are usually treated with surgical exploration and repair.

Timing varies by situation:

• some injuries, such as an open wound or a suspected clean cut to the nerve, or associated damage to major blood vessels, need surgical exploration within about a week
• injuries affecting most or all of the plexus, from a high-force injury, are often explored within 3 to 6 weeks
• other injuries may be managed with surgery delayed 3 to 6 months, once it's clearer which nerves are likely to recover by themselves.

Surgical repair techniques include:

• nerve grafting, where the damaged section of nerve is removed and bridged using a length of nerve taken from elsewhere in the body, often a sensory nerve from the back of the leg, which then needs to regrow across the repair
• nerve transfer, where a working but less critical nerve is rerouted to power a more important muscle that has lost its own nerve supply
• muscle or tendon transfer, where a working muscle or tendon is repositioned to take over a lost function, generally considered when nerve recovery isn't expected.

After surgery, your arm is typically strapped to your side or placed in a sling and kept still for about 4 weeks to protect the repair, with a hospital stay of only a few days in most cases. Follow-up typically includes a wound check around a week after surgery, removal of the strapping with the start of guided physiotherapy exercises at around 4 weeks, and a fuller review with the wider team at around 3 months, when the possibility of further surgery may be discussed if needed.

Because nerves regrow slowly, at roughly 1mm a day, recovery is a lengthy process; a repaired plexus can take up to around 3 years to reach its final result, and complete recovery isn't guaranteed, since it depends on every individual microscopic nerve fibre successfully reconnecting.

Physiotherapy and occupational therapy play a central role throughout, whether or not surgery is needed, helping you retrain movement as the nerves recover and preventing stiffness in the meantime.

Pain-relief medicines and assistive devices, such as splints or braces, may also help. In babies, some injuries improve without any treatment by 3 to 4 months of age, and most children regain some function with physiotherapy and occupational therapy.

A brachial plexus injury can have a considerable emotional impact, and specialist psychological support is often built into treatment teams for exactly this reason. It's worth asking what support is available to you if you're finding the physical or emotional side of recovery difficult.

When should you see a doctor?

Most brachial plexus injuries happen alongside significant trauma, such as a road traffic accident or a bad fall, and will be assessed as part of emergency care. Seek immediate medical attention after any injury to the shoulder, neck or arm if you notice sudden weakness, numbness or loss of movement in the arm or hand, or severe pain, since prompt assessment matters and some injury patterns benefit from very early surgical review.

If you or your child have ongoing numbness, weakness or reduced movement in an arm following any injury, including a seemingly minor one such as a sports collision, it's worth having this checked rather than assuming it will settle by itself. For parents, if a newborn isn't moving one arm normally after a difficult birth, this should be assessed promptly.