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Brachial plexus injuries are caused by damage to the nerves that control the arms, wrists, and hands. This type of damage can occur in anyone of any age after an accident or traumatic injury, but the most common cause is childbirth. Infants born with brachial plexus injuries are usually able to recover within a few months and have no lasting effects.
Some infants, however, are born with serious injuries to the brachial plexus and will have more severe symptoms. They are likely to retain some degree of dysfunction of the affected areas for the rest of their lives. Treatments are available, but with severe disabilities, symptoms may persist. Even so, most people with this injury can live a normal and full life.
How Brachial Plexus Injuries Occur
The brachial plexus is a bundle of five major nerves that originate in the spinal cord, run through the neck, and then attach to smaller nerves in the arm. These nerves are responsible for providing function to various parts of the arms, wrists, and hands, allowing for control of all muscle movement and sensation in those areas. 
If an injury causes damage to the nerves, all sensation and movement may be interrupted. In a child or adult, this can happen because of some kind of traumatic injury that stretches the nerves. It can occur during contact sports, due to a fall, in a collision, or as a result of a gunshot wound, to name a few possible causes.
Infants may be born with some degree of brachial plexus injury because the head, shoulder, and neck were stretched during the descent through the birth canal. This may happen if the person delivering the baby pulls forcibly on the arm or shoulder while the head is still in the birth canal.
It can also occur during a breech birth in which the baby’s arms are lifted above the head, and from pulling on the lower body, stretching out the neck. Breech births, births of larger-than-average size babies, and long and difficult labors all bring a greater risk of brachial plexus injury.
Location of Symptoms
Where the symptoms of brachial plexus injury occur depends on which nerves in the bundle are damaged. Erb’s palsy refers to damage to the nerves that control the upper arm. In this case, the affected person will experience numbness, tingling, weakness or paralysis in the muscles of the upper arm from the shoulder to the elbow, but may have perfectly normal sensation and movement from the elbow down to the fingers.
Damage to the nerves that control the lower arm is called Klumpke’s paralysis or palsy. This causes symptoms anywhere between the elbow and down through the fingers. If all five nerves of the brachial plexus are damaged, the symptoms will affect the entire arm. This is called a global palsy.
Symptoms of Mild Injury
A mild brachial plexus injury may feel like a shock or burning feeling running down the affected arm. This is usually followed by a sensation of numbness and weakness in the area. It can occur anywhere in the arm, from the shoulder to the fingers.
In mild cases, these symptoms usually resolve on their own in about a week (for both children and adults). For infants that are injured during the birth process, it generally takes about three to six months to heal and may require physical and occupational therapy.
Symptoms of Moderate to Severe Injuries
A more severe injury to the brachial plexus will cause significant weakness, and in the more severe cases, complete paralysis of one or more muscles in the arm. There may even be paralysis of the entire arm, from shoulder to fingertips, if all the nerves of the brachial plexus have been badly damaged. There may also be severe pain or a complete loss of sensation due to the trauma in these more serious injuries.
Symptoms in a Newborn
Symptoms of brachial plexus injuries are similar no matter the age of the affected person, but an infant cannot tell you if they feel numb or cannot move its arm. The symptoms of this kind of injury in a newborn must be detected by a medical professional or the parents so that it can be properly assessed and treated. 
Signs to look for include a weaker grip in one hand as compared to the other, movement in one arm, but less in the other, and an arm that is rotated toward and held against the body.
Another sign is that the Moro reflex is diminished or absent on one side. Infants have a natural reflex from birth, which usually disappears by about three or four months of age. To test this reflex, the baby is placed on its back.
The arms are gently lifted and then let go together. This gives the feeling of falling, and the baby should appear startled during this maneuver, extending the arms outward first, then to the front, and finally back again to the sides. This predictable movement is called the Moro reflex, and it should be symmetrical. Diminished or absent movement on one side is often an indication of brachial plexus injury. 
A rare complication of brachial plexus damage is called Horner’s syndrome. These symptoms in this condition include pupil constriction in one eye, drooping of one eyelid, and an inability to sweat on one half of the face. These are rare symptoms, but they are caused by damage to nerves in the part of the brachial plexus that includes nerves going to the face and eyes.
The outlook for a brachial plexus injury depends on the severity of the damage to the nerves. For most infants, the impairment is only mild and will heal within three to six months of birth. In these cases, the child should not experience any symptoms once the nerves have healed. For more severe injuries, including those in which the nerves are torn, more treatment may be needed, including surgery to repair damaged nerves.
- Neonatal brachial plexus injuries: An integrated approach. (2019, January 25). Mayo Clinic - Mayo Clinic.
Retrieved from: https://www.mayoclinic.org/medical-professionals/neurology-neurosurgery/news/neonatal-brachial-plexus-injuries-an-integrated-approach/mac-20451969
- Brachial plexus injury in newborns: MedlinePlus Medical Encyclopedia. (n.d.). MedlinePlus - Health Information from the National Library of Medicine.
Retrieved from: https://medlineplus.gov/ency/article/001395.htm
- Neonatal Brachial Plexus Injury. (2019, September 1). American Academy of Pediatrics.
Retrieved from: https://pedsinreview.aappublications.org/content/40/9/494