Brachial Plexus Causes

Fact Checked

Brachial plexus injuries can happen to anyone at any age caused by physical trauma or an accident. In infants, this type of injury is caused by difficulties or complications during childbirth. The brachial plexus is the bundle of nerves that controls the arms, and when damaged, the affected areas may lose sensation and even movement.[1]

Brachial Plexus Damage

The brachial plexus nerves are attached at one end to the spinal cord and at the other end to smaller nerves in the arms. They run through the neck, so if the neck gets pulled too much by stretching the head and shoulder in opposite directions, these nerves can be injured.

Damage may range from mild stretching to small and large tears and, in the worst cases, complete separation of the nerves from the spinal cord.

Each of the five nerves of the brachial plexus control different parts of the arm, so the signs of injury will correlate with the particular nerves that have been damaged.

The extent of injury dictates the severity of symptoms. Possible symptoms include:

• Numbness
• Weakness
• Loss of sensation
• Paralysis

Most infants with brachial plexus injury heal naturally with time. Those with more severe injuries need some physical therapy, and a few will need surgery to repair more significant dysfunction. Some end up with lifelong disabilities.

Large Size at Birth

One of the potential causes and risk factors for brachial plexus injury is a large size at birth. This can lead to a difficult delivery if the neck gets stretched too far during the birth process.

The medical term for a large fetus is large for gestational age and is considered any baby with a birth weight greater than the 90th percentile.[2] The average weight for a baby at birth is seven pounds.

A woman’s doctor should estimate birth weight as the pregnancy proceeds. It is not an exact science, but various measurements can lead to a relatively accurate estimation of how big the infant will be at birth.

This helps a doctor decide if a woman will need to have a cesarean section to avoid complications such as an injury to the brachial plexus.

Difficult or Obstructed Labor

Another risk factor for brachial plexus injury is complex or prolonged labor due to any cause. This may be from an obstructed birth or simply from mistakes made by the delivery team, including excessive pulling or misuse of instruments.

Normal delivery is when the head comes out first, but sometimes the shoulder gets stuck after the head emerges. This is called shoulder dystocia, and it is one of the most common causes of brachial plexus injury.

The damage occurs as the baby is being pulled. The pressure can stretch the brachial plexus nerve bundle to the point of injury. Up to 15 percent of infants born with this complication will have injuries to the brachial plexus.

Breech Birth

A breech birth is not an ideal way for a baby to be born. A baby should come out head first, but when the buttocks emerge first from the birth canal, it’s called a breech birth. A breech birth can lead to complications.

As the infant is proceeding out from the birth canal in this direction, the arms are pulled above the head.[3] This makes it more difficult to get the entire body out, and the pressure applied can cause stretching of the brachial plexus nerves.

As with a large fetus, a doctor should recognize the risk of breech birth and determine if a cesarean section (c-section) delivery would be a safer option for the mother and baby.

Mishandling During Birth

Doctors and other caregivers are better trained in delivering babies than ever before, but they can still make mistakes. Those mistakes can lead to birth injuries, including brachial plexus damage.

Whether the birth is normal or difficult, the person delivering the baby may pull too hard on an arm or shoulder and stretch out the baby’s neck. It’s also possible to use instruments, such as forceps or vacuum, inappropriately and cause damage to the nerves.

Other Brachial Plexus Injuries

Birth-related brachial plexus injuries are the most common cause of associated palsies, but they can also result from trauma and injury in adults and children.

A fall, an automobile collision, a bullet wound, and even playing contact sports can all lead to the kind of stretching or other trauma that damages the brachial plexus.

Prognosis

For most infants with this type of injury, regardless of the cause, the outlook is good. They will heal and completely recover with time. In some cases, however, the damage is too great to heal naturally and may require surgery to fix.

Surgery cannot always correct all of the dysfunction, however, and in rare cases, a child may live with the signs of brachial plexus injury for the rest of their lives.

If your child is born with weakness or paralysis in an arm, talk to your doctor about diagnosing a brachial plexus injury. Talk to a birth injury lawyer if you believe it resulted from negligence.