The brachial plexus is a network of nerves located in the neck and upper back that supplies the arms and hands. It is formed by the merging of the lower cervical and upper thoracic spinal nerves, specifically from C5 to T1. This complex system of nerves controls muscle movements and sensations in the shoulder, arm, and hand. Injuries to the brachial plexus can lead to weakness, numbness, or paralysis in the affected arm. Such injuries may occur due to trauma, stretching, or compression of the nerves. Treatment options vary and may include physical therapy, medication, or, in severe cases, surgery to repair damaged nerves.