The brachial plexus is a network of nerves that sends signals from the spine to the shoulder, arm, and hand. Damage to the brachial plexus can cause symptoms such as
A limp or paralyzed arm
Lack of muscle control in the arm, hand, or wrist
Lack of feeling or sensation in the arm or hand
Brachial plexus injuries can happen because of shoulder trauma, tumors, or inflammation. Sometimes they happen during childbirth when a baby's shoulders become stuck during delivery and the nerves stretch or tear.
Some brachial plexus injuries may heal without treatment. Many children who are injured during birth improve or recover by 3 to 4 months of age. Treatment includes physical therapy and, in some cases, surgery.
NIH: National Institute of Neurological Disorders and Stroke