What causes Cervicothoracic sign in superior mediastinum on chest radiography?
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Answer:
Upper mediastinal opacity with well-defined superior border extending above the clavicles indicates a posterior mediastinal lesion (Cervicothoracic sign positive for posterior), commonly due to neurogenic tumors, foregut duplication cysts, or aneurysms; if the superior border is obscured or ends at or below the clavicles, it indicates an anterior mediastinal lesion such as thymoma, teratoma, thyroid mass, or cystic hygroma. This finding is best appreciated on chest radiography of the superior mediastinum.
Why is it called so?
Named Cervicothoracic sign due to its reliance on the anatomical transition at the cervicothoracic junction (thoracic inlet), where posterior mediastinal structures can extend into the cervical region while anterior ones are limited by the clavicles.
Pathophysiology
The posterior lung apex extends superiorly beyond the clavicles because of the obliquity of the thoracic inlet (bounded by the manubrium anteriorly, first ribs laterally, and T1 posteriorly). This allows posterior mediastinal masses to be surrounded by aerated lung that outlines their cephalic border sharply above the clavicles; anterior masses contact neck soft tissues at or below the clavicles, obscuring their superior margin as a variation of the silhouette sign.
Alternative names: None
Other associated named signs: Silhouette sign
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