Brachial plexus palsy is a condition that occurs when a group of nerves around the shoulder is damaged at birth, according to MedlinePlus. The brachial plexus is the bundle of nerves that sends signals from the spinal cord to the shoulder, arm and hand.
Brachial plexus palsy is usually associated with a baby's difficult birth when the affected arm and the neck are stretched during the delivery. It can also occur in older children as the result of an accident.
Injuries to the brachial plexus can cause weakness and loss of motion in the shoulder, arm, hand and fingers on the affected side of the body.