Diaphragmatic elevation due to phrenic nerve paralysis is an acquired lesion. Disorders of the phrenic nerve are classified as posttraumatic, infectious, neoplastic, neuromuscular, or idiopathic. Trauma occurs most commonly after surgery for congenital cardiovascular disorders. Herpes zoster, influenza, and subphrenic abscess are infectious causes. Poliomyelitis is a neurogenic cause. Neoplastic involvement of the phrenic nerve is often secondary to mediastinal tumors and bronchogenic carcinoma with mediastinal involvement.