The brachial plexus is a group of nerves that branch out from the spinal cord in the neck and travel down through the arm to the wrist and hand. Babies frequently suffer brachial plexus injuries when excessive stretching of the neck tears or overextends these nerves, according to the Mayo Clinic. In many cases, brachial plexus injuries are caused by unnecessary trauma sustained during labor or delivery.

Trauma to the brachial plexus can result in paralysis, a loss of movement, or permanent weakness in the limbs, a collection of conditions that are often referred to as neonatal brachial plexus palsies.

Brachial Plexus Injury At Birth

An injury to the brachial plexus can lead to complications both minor and severe. After minor injuries, a child’s symptoms are likely to subside within a matter of days or weeks. But serious brachial plexus injuries often result in total paralysis to the arm, while other traumas can cause a permanent loss of feeling in the upper limbs or hands.

Brachial Plexus Injury Infographic
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How Nerve Injuries Work

Together, the brachial plexus nerves control muscles in the shoulder, elbow, wrist and hand, while providing for feeling in the arm. Doctors distinguish between two basic categories of the nerves that make up the brachial plexus:

  • upper brachial plexus – these nerves originate in the vertebrae C5 and C6
  • lower brachial plexus – these nerves originate in the vertebrae C7, C8 and T1

The severity of a newborn’s injury will largely be determined by which portion of the nerve has been injured. But how the nerves become damaged is also important in outlining treatment strategies and predicting long-term consequences. In general, there are four ways that a nerve can be hurt:

  • neurapraxia – the nerve is stretched, but not torn, inside the spinal cord. Neurapraxia-type injuries are most common, and usually resolve of their own accord within a matter of months.
  • neuroma – a secondary complication of stretch-type injuries, neuroma occurs when an injured nerve attempts to heal by growing scar tissue. This can pinch the remaining healthy nerve, requiring surgical treatment.
  • rupture – when a nerve is stretched beyond its limit and tears. This form of injury generally requires medical treatment, and will not resolve on its own.
  • avulsion – when a nerve is torn from the spinal cord itself. Avulsions are the most severe form of nerve injury, and may require a nerve graft operation.

Nerve injuries, especially those affecting the brachial plexus nerves, often result in conditions that we collectively know as “palsies.” Palsy is a medical term for any one of several types of paralysis, which are usually accompanied by weakness and a loss of feeling.

Types Of Brachial Plexus Palsy

Brachial plexus injuries usually result in one of three different palsy conditions, which are distinguished by the portion of the brachial plexus that has been injured.

Erb’s Palsy: Injury To The Upper Brachial Plexus

Most children sustain injury to the upper brachial plexus nerves, and develop a condition known as Erb’s Palsy. Around 60% to 70% of all brachial plexus palsies fall into this category, which is marked by weakness in the shoulder, bicep and elbow muscles of the affected arm.

Klumpke’s Palsy: Injury To The Lower Brachial Plexus

Klumpke’s Palsy is very rare in babies. The injury involves only the lowest root nerves of the brachial plexus, those originating in the vertebrae C8 and T1. Injuries of this type usually impact muscles in the hand.

Horner’s Syndrome: Injury To The Total Brachial Plexus

Around 20% to 30% of babies with brachial plexus injuries will develop what is known as Horner’s Syndrome, in which every nerve that makes up the brachial plexus is injured in some way. In many cases, a secondary set of nerves are also damaged, which can cause more widespread symptoms, like drooping eyelids.

Brachial Plexus Injury Symptoms In Newborns

The injury type can have major implications for treatment, as well as the long-term prognosis of a brachial plexus injury. But the symptoms of a nerve injury will remain the same, no matter which type of injury has been sustained. These symptoms are usually apparent directly after birth:

  • inability to move the arm or hand
  • arm bent at the elbow and held to the body
  • impaired gripping ability on the affected side

Since brachial plexus injuries usually only affect one side of a child’s body, doctors will compare the range of motion and gripping ability between arms to make a diagnosis.

Some babies will experience pain after suffering a brachial plexus injury, the experts at Medscape report, although the level of pain will depend on the severity of nerve damage. Babies with minor injuries usually don’t experience pain. Unlike adults, who can also sustain injuries to the brachial plexus, an infant’s nerves aren’t fully developed, so discomfort doesn’t usually accompany a stretch-type injury.

Impaired Moro Reflex

An absence of the Moro reflex is another common sign of an injury to the brachial plexus nerves. Up to the ages of four or five months, all infants react unconsciously to a sudden loss of support. This reflexive response to the sense of falling or being dropped is known as the Moro reflex, and it’s characterized by a sequence of two movements. The infant will spread their arms out (abduction), and then quickly unspread their arms again (adduction). Most babies also cry while experiencing the Moro reflex.

In children who have suffered a brachial plexus injury, the Moro reflex is usually either absent or impaired in some way.

Causes Of Brachial Plexus Injury

Brachial plexus injuries are most common during long, difficult deliveries. In fact, the strain and stress of contractions alone can cause injuries to nerves in the shoulder and arm, especially when the baby becomes stuck in the birth canal. In some cases, there may be nothing a medical team can do to prevent such injuries, but that isn’t always true.

  • In a breech birth, a baby’s feet or buttocks enter the birth canal first. If the child’s arms are extended over his or her head, they can be pinched by the birth canal, leading to nerve damage in the brachial plexus.
  • In cases of shoulder dystocia, an infant’s head is able to exit the birth canal, but his or her shoulders become stuck inside the mother’s pelvis. With further straining, the nerves leading through the shoulder and down through the arm can stretch to the point of injury.
  • In a delivery by hand, a doctor can apply inappropriate, excessive force to a baby’s arm, shoulder or neck, increasing the likelihood of a brachial plexus injury. This is particularly common under emergency circumstances, when physicians sometimes choose to grab an infant’s shoulders and pull forcefully.
  • The use of birth-assistive devices, like forceps and vacuum extractors, can also increase the likelihood of a brachial plexus injury, especially when these instruments are clamped directly to a child’s shoulder during delivery.

Despite advances in obstetrics, brachial plexus injuries are still surprisingly common. While estimates vary, most researchers agree that around 1 to 2 out of every 1,000 babies born in the developed world will suffer trauma to the brachial plexus nerves, OrthoInfo reports.

In many cases, the injury is entirely preventable. According to medical publishing company Wolters Kluwer, researchers believe that brachial plexus injuries are usually “iatrogenic” in nature – caused by medical treatment itself, rather than an unavoidable pre-existing health condition. That means many brachial plexus injuries could have been avoided with appropriate medical care.

Risk Factors For Brachial Plexus Injury

Researchers have known for decades that some babies are more likely to suffer brachial plexus injuries than others. Since the first brachial plexus injury was identified in 1779, medical scientists have identified a number of factors that increase the risk of damage to the brachial plexus nerves:

  • Maternal diabetes
  • Maternal obesity
  • Underdeveloped muscles in an infant’s neck
  • Breech delivery
  • Use of forceps or vacuum extraction
  • Twin or multiple pregnancies
  • Uterine fibroids that affect how a baby is positioned inside the womb

Fetal macrosomia, which is a term that describes babies who are significantly larger than the average infant, is another well-known risk factor for brachial plexus injuries.

Shoulder Dystocia

Shoulder dystocia is likely the most common cause of these injuries, according to researchers at the Cincinnati Children’s Hospital Medical Center, increasing the risk of an injury to the brachial plexus by 100 times.

While the term “dystocia” itself only means slow or difficult labor, shoulder dystocia is a far more specific medical term. In normal deliveries, an infant’s shoulders emerge from the birth canal shortly after the head. Shoulder dystocia, on the other hand, happens when a baby’s shoulders get stuck inside the mother’s body during labor. Most definitions of shoulder dystocia define a certain delay period, between when the head and shoulders emerge, although some researchers believe that medical intervention is required to truly create a case of shoulder dystocia.

In any event, doctors intervene in cases of shoulder dystocia quite frequently, often pulling downward on a baby’s head to force their shoulders out of the birth canal. The risk for traumatic injury should be obvious, but brachial plexus injuries are most likely to occur when an infant’s neck and shoulder are pulled in opposite directions, or stretched from side-to-side.

Severe trauma can even rip the nerves out from the spinal cord, requiring surgical intervention at an extremely young age.

Brachial Plexus Injury Treatment Options

Many children will fully recover after sustaining brachial plexus injuries, and come to regain normal (or nearly normal) functioning in their affected arm.

Minor nerve damage often heals naturally, with little more than physical therapy that can be performed at home. Your doctor can teach you specific exercises that will be crucial to your child’s recovery, some of which you may need to perform daily for years. In this context, the primary goal of therapy is to prevent the infant’s shoulder from atrophying, while developing muscles in the affected arm to promote improved functioning.

Some exercises are designed to prevent the shoulder from developing improperly. Injuries to the brachial plexus can change the way your child’s joints grow over time. Many families go in for routine diagnostic tests to monitor their child’s shoulder development over time.

Surgical Intervention

More severe injuries often require surgery, although surgeons usually wait at least three months before recommending an operation.

In most operations, the initial goal is to remove any scar tissue that has grown around the damaged nerve, which can pinch the nerve and block its contact with the muscle that it’s supposed to control. Removing this scar tissue allows the nerve more room to heal, while improving the nerve’s ability to conduct electrical signals.

Sometimes, removing the scar tissue is enough. But in other cases, the affected nerve still isn’t able to transmit electricity properly. In this case, a nerve graft may be the best option. In this procedure, surgeons remove the damaged portion of the brachial plexus and replace it with healthy nerves taken from a less-used body part, usually the back of a child’s calf. While this reduces feeling in the calf, it shouldn’t affect movement.