The brachial plexus is a network of nerves that conducts signals from the spine to the shoulder, arm, and hand. Brachial plexus injuries are caused by damage to those nerves.
Symptoms may include
Brachial plexus injuries can occur as a result 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