[Reduction in transparency of the airway tracheogram, a sign of upper mediastinal pathology].

Some cases of mediastinal pathology in which the only pathological pattern was a "dimness" of the tracheal transparency are described. This sign is not described in previous reports and is described as a short break in the aerial tracheogram as seen on the frontal roentgenograph. This sign is produced by an increase in the structures outside the trachea or by a decrease in the air column inside the trachea. Conventional and CT anatomic findings which account for the sign are discussed. A short review of the "normal" causes of tracheal dimness is presented. This sign may be useful especially in emergency radiology, since it provides additional information to a simple routine chest roentgenograph.