Key Points

• Comprehensive knowledge of phrenic nerve anatomy is essential to avoid injury.
• First-degree injury (neurapraxia) and second-degree injury (axonotmesis) will resolve in weeks to months; however, more severe injury (third to fifth degree) will not heal.
• Although it is theoretically possible to repair a transected phrenic nerve, this is uncommonly reported.
• Diaphragmatic plication and nerve transfers may be necessary for treatment of respiratory compromise after phrenic injury.