Cross-sectional Imaging Anatomy and Pathologic Conditions Affecting Thoracic Nerves.

While in many cases they are not directly visualized, awareness of the thoracic nerves and their courses at cross-sectional imaging is important for radiologists. An understanding of the normal function of each nerve is important, as many patients present with neurologic signs and symptoms that can be used to reinforce search patterns for disease and detection of supportive radiologic abnormalities. In the case of primary neoplasms, understanding the expected presence of a nerve in the location of a mass can enhance and improve the accuracy of differential diagnoses. Even in the absence of neurologic symptoms, secondary involvement of these structures by malignancy or close proximity to other intrathoracic disease can prompt significant alterations in oncologic or surgical management. The major components of the thoracic nervous system with which the thoracic radiologist must be familiar are the phrenic, vagus, recurrent laryngeal, intercostal, and long thoracic nerves in addition to the sympathetic chain and brachial plexus. The anatomic structure and course of each component are described including its major functions. Major clinical signs and symptoms attributable to nerve dysfunction or disease are reviewed as well as any associated radiologic signs. Emphasis is placed on primary and secondary malignant involvement of the nerves and iatrogenic and traumatic injuries. Online supplemental material is available for this article. ^© RSNA, 2016.