Erb’s Palsy is a type of brachial plexus birth injury that causes paralysis of the baby’s arm. An Erb’s Palsy injury typically occurs when the nerves at C5-C6 are severed. As a birth injury, Erb’s Palsy is often caused by the doctor or nurse putting too much downward force on the upper arm and shoulder. This excessive force damages the brachial plexus (a group of nerves). Since these particular nerves control the movement of the arm, when they are damaged it results in paralysis of that arm.