Nerves are small bundles of fibers that send and receive messages between the brain and the body. The brachial plexus is a set of these nerves that controls the shoulder, wrist, hand, and elbow muscles. It also provides feeling in the arm. It starts from the neck and extends down the arms.
The brachial plexus can become damaged, causing the nerves that usually send signals from the brain to the shoulders, wrists, hands, or elbows, to stop working. These muscles can then become weak, and can even cause a child to lose feeling or movement. When this happens, it’s called brachial plexus palsy.