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Most common in newborns, Erb’s palsy is a condition caused by damage to some of the nerves that control the shoulder and arm. These nerves are a portion of a larger bundle of nerves, called the brachial plexus, which connects the spinal cord to the shoulders, arms, and hands, providing sensation and control of movements.
Different nerves control different parts of the arm, so in one case the hand may be affected, while in another it is the shoulder. When those nerves get damaged, which in the majority of cases occurs during childbirth, movement and sensation can become impaired. 
The word palsy generally refers to muscular weakness or paralysis, where the source of the problem is an injury to some of the nerves. In the case of Erb’s palsy, the nerves affected are the ones that connect to the shoulder and upper arm. So the signs of injury will be seen in those areas, but the hand and wrist movements are expected to be normal.
The symptoms of injury in Erb’s palsy vary with the extent of the damage: the greater the injury, the more severe the symptoms. Fortunately, Erb’s palsy is usually temporary, and these are not symptoms most children will have to live with forever.
Symptoms Are Immediate
Since the damage that causes Erb’s palsy usually occurs during birth, the results are often seen immediately. This means that treatment can begin right away to give a newborn the best prognosis.
Medical caregivers should be able to see signs of the condition shortly after birth, simply by observing the infant’s movements. Even if they are not apparent just by watching the baby, standard reflex tests along with a routine physical exam will most likely uncover findings consistent with Erb’s palsy if the damage occurred during the birth process. 
Lack of Movement
One of the first signs that a doctor or new parent may detect in an infant is a lack of movement or weakness in the affected arm. Although motor control is limited in newborns, infants do move their arms around to some extent right after birth.
If one arm is moving and the other is not, it is likely a sign of Erb’s palsy. The lack of movement may be mild or severe, ranging from merely a limited range of motion at the shoulder to no movement at all.
Babies should be born with certain inherent reflexes, and a diminishment or loss of the normal reflexes in one arm may be a sign of Erb’s palsy. An easy way to test for this is to check for the Moro reflex (or startle reflex), a natural response that is present immediately after birth, which disappears by three to four months of age.
To test the Moro 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. Less movement on one side is often an indication of Erb’s palsy.
Positioning the Arm Abnormally
Another sign of Erb’s palsy, often seen in newborns, is an awkward positioning of the affected arm. The infant may hold its arm extended downward and rotated in toward its side, which does not look normal.
This abnormal positioning of the arm is readily apparent and most commonly seen in these cases, but any placement of the arm that seems unnatural could indicate Erb’s palsy.
Poor Grip Strength
Damage to the brachial plexus sometimes affects a baby’s ability to grip objects. If you place something in a baby’s hand, like your finger, it should be able to grasp it and hold on pretty tightly.
A symptom of Erb’s palsy is a grip in one hand with a noticeably weaker or no grip in the other. This is a relatively simple test and one that can quickly indicate nerve damage. 
Loss of Sensation
A newborn cannot tell you that it has no feeling in or cannot move one arm, but these are potential symptoms of Erb’s palsy. This is why it is important to find other, more noticeable symptoms so that the condition can be detected early and treated.
Symptoms of Brachial Plexus Injuries in Adults and Children
Most cases of Erb’s palsy are in seen newborns and are generally due to difficulties associated with childbirth. However, damage to any part of the brachial plexus can occur later in life from other types of injuries or accidents. Car accidents, sports injuries, and even tumors can cause damage to the brachial plexus.
Symptoms of this may include a burning sensation like an electric shock that passes down the arm, weakness or numbness in the arm, and paralysis, or pain. When the entire brachial plexus is injured, and not just the nerves involved in Erb’s palsy, the whole arm will be affected, including the wrist and hands.
Any symptoms of Erb’s palsy or brachial plexus injury should be taken seriously. Most newborns recover well from this condition, but even if other forms of treatment are not needed, physical therapy can help a baby heal faster to regain normal movement. If you see signs in your child that seem like Erb’s palsy, talk to your doctor about it right away.
- Erb's Palsy (Brachial Plexus Birth Palsy) OrthoInfoAAOS. (n.d.). American Academy of Orthopaedic Surgeons.
Retrieved from: https://orthoinfo.aaos.org/topic.cfm?topic=a00077
- 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 Palsies: Background, Pathophysiology, Epidemiology. (2019, November 9). Diseases & Conditions - Medscape Reference.
Retrieved from: https://emedicine.medscape.com/article/317057-overview
- Brachial plexus injury - Symptoms and causes. (2018, December 5). Mayo Clinic.
Retrieved from: https://www.mayoclinic.org/diseases-conditions/brachial-plexus-injury/symptoms-causes/dxc-20127374