Brachial Plexus Injury Causes

Infant brachial plexus injuries occur when the brachial plexus–a network of nerves that run throughout the spine, neck, and arms–is damaged. There are a few causes for these types of injuries, but in most instances, they occur during a prolonged and/or difficult labor and delivery.

Types of Brachial Plexus Injuries

The network of nerves that makes up the brachial plexus is located in the neck. It consists of a series of nerve roots that end up divided into peripheral nerves. These nerves control movement and sensation to the shoulders, arms, lower arms, hands, and some portions of the chest and back.

According to the National Institutes of Health (NIH), a newborn baby’s brachial plexus can be injured during the passage through the birth canal, especially in a difficult delivery. When this type of injury occurs, the nerves suffer damage. The severity of the damage and its lasting effects depends on what caused the injury, the location of the injury, and what type of nerve damage was done.

Per the University of California, Los Angeles (UCLA) School of Medicine, there are four types of lesions and injuries that can damage the brachial plexus. Each of these has its unique symptoms and forms of diagnosis. The four types are:

  • Upper plexus lesions
  • Posterior cord lesions
  • Lower plexus lesions
  • Complete brachial plexus injury

There are also four types of specific injuries to the nerves in the brachial plexus. The most common injury is neuropraxia, in which the nerves are compressed or stretched. Neuromas are tumors that form on nerves that were torn, healed, but now have scar tissue. This scar tissue puts pressure on the nerves and blocks neuroelectrical signals from the spinal cord. Ruptures occur when the nerve is torn but not at the spine. Avulsion, the most severe injury, occurs when the nerve is torn from the spinal cord.

Most, but not all, brachial plexus injuries can be treated either through physical therapy or surgery. In cases where ruptures or avulsion occur, the damage to the nerves and affected area is permanent unless surgical intervention is done quickly.

Risk Factors for Brachial Plexus Injuries

According to NIH, there are several risk factors for obstetric brachial plexus injuries. The chances for brachial plexus palsy increase if:

  • The infant is born during a breech delivery
  • The baby is larger than normal, especially in cases where the mother is diabetic
  • Maternal obesity and/or gestational diabetes

According to the Miami Children’s Hospital pediatric neurosurgery specialists, there are instances where other factors may trigger neonatal brachial plexus injuries. Trauma to either the mother or unborn baby before delivery is a likely factor in cases of brachial plexus injuries. In addition, amniotic bands in the neck and shoulder nerve distributions may cause brachial plexus palsy.

Common Causes of Brachial Plexus Injuries

When the aforementioned risk factors happen during birth, the risk for a brachial plexus injury heightens as the labor and delivery of the baby becomes more stressful. The most common reasons brachial injuries occur include:

Improper Use of Birth-Assisting Tools

Birth-assisting tools such as forceps and a vacuum-extraction tool may be used when the baby is lodged in the mother’s pelvic bone and/or is having a difficult time moving through the birth canal normally. However,  improper force and failure to use birth-assisting tools correctly can lead to tears, scratches, and lacerations that can damage any area of the brachial plexus.

Excessive Pulling

Even when birth-assisting tools are not used, doctors may pull excessively and improperly with their own hands when attempting to deliver an infant. Although this may seem necessary in order to delivery the baby and ensure there is no oxygen deprivation, it can also lead to an array brachial plexus injuries.

Although brachial plexus injuries have been primarily associated with breech deliveries, they can also happen during head-first deliveries, especially if there is excessive pulling and force on the shoulders after the baby’s head has been delivered. Known as shoulder dystocia, this often happens when the infant is too big to pass through the birth canal without difficulties.

Prolonged Contractions During Labor and Delivery

During a stressful labor and delivery, the mother’s contractions may place undue pressure on the infant’s head and shoulders, especially if the baby is stuck in the mother’s pelvic area. These can lead to a host of medical problems, including stretching and damaging the infant’s brachial plexus nerves.