Erb’s palsy is caused by damage to nerves of the brachial plexus. This is the underlying cause, but what leads to that damage is more varied. Damage to the nerves that run from the spinal cord, through the bones of the neck to the shoulder and finally down the arm, leads to various degrees of weakness, paralysis, and loss of sensation. The effects can be seen in any part of the arm depending on which nerves were damaged. The overwhelming cause of this damage is related to how a child is born.
Damage During Child Birth
The number one cause of Erb’s palsy is damage to the nerves that occurs during child birth. There are various ways in which this can happen, but essentially the damage occurs when the head and arm or shoulder are stretched apart from each other. The nerves run from the spine, to the neck, and then to the shoulder and down the arm, so pulling or stretching the body in this way also stretches the nerves.
Mild stretching can stress the nerves out, which is considered minor damage that heals naturally or with a little bit of physical therapy. More stretching can damage the nerves more severely. They can actually become torn, or in the worst cases, ripped right out of the spinal column. Various conditions of child birth can lead to the stretching that causes mild to severe damage.
Manipulating the Baby During Child Birth
There are many different factors that can lead to nerve damage during child birth, but ultimately all lead to the doctor or other medical professional manipulating the baby in such a way that the brachial plexus nerves get stretched and damaged. For instance the head and neck of the baby may get pulled to the side as the shoulders are pulled out of the birth canal. Another possibility is that the baby’s head gets pulled while the shoulders are still in the birth canal. The way that the person delivering the baby uses instruments can cause stretching in the nerves.
High Birth Weight
When an infant is abnormally large, it is a struggle to get it through the birth canal. This can lead to the head, shoulder, or arm being pulled or tugged in such a way that the nerves get damaged. If a child is abnormally large, it can usually be detected in the last few weeks of pregnancy. At that point a doctor must decide if a Cesarean section should be done to avoid a difficult birth that can lead to Erb’s palsy among other complications.
A breech birth is another factor that increases the risk of Erb’s palsy. This is a birth in which the baby’s buttocks or feet emerge through the birth canal first. A normal birth is when the head comes out first. Erb’s palsy is just one risk of a breech birth, with others being more serious. Erb’s palsy can occur because as the doctor pulls the baby’s feet out first, the arms necessarily go over the head. This can put stress on the brachial plexus and cause damage. As with a high birth weight, a breech position is often detected in advance of labor and may lead to a Cesarean section.
Erb’s Palsy During Cesarean Section
A Cesarean section, the surgical delivery of the baby through an incision in the abdomen, is usually done to avoid high-risk births. If a delivery is expected to be long, to be breech, or to have other important risk factors, a doctor may decide to perform a Cesarean section. Erb’s palsy is generally not a risk of having this procedure done, but in very rare cases it happens. Only about one percent of cases of Erb’s palsy occur during Cesarean section births.
Erb’s Palsy at Any Age
Erb’s palsy is overwhelmingly a condition of child birth and infancy, but it is possible to sustain injuries to the brachial plexus at any age. Any kind of accident, violence, or other injury that stretches those nerves can cause enough damage to trigger Erb’s palsy. Some of the more common ways someone might injure the brachial plexus include contact in sports like football, trauma from car accidents, bullet wounds, or falls, and tumors putting pressure on the nerves.
Whatever the cause of Erb’s palsy, for infants especially, the damage is usually short-lived. The nerves are often able to heal naturally, given enough time and most babies will grow into healthy children with no lasting effects. For those that have more severe damage, the effects may be permanent, but aren’t usually severe.