Segmental paralysis of phrenic nerve

The brachial plexus is a network (plexus) of nerves (formed by the anterior rami of the lower four cervical nerves and first thoracic nerve (C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in the neck, over the first rib, and into the armpit. [Source: Wikipedia ]