“Partial Luftsichel Sign”
Frontal CXR in a Patient with Central Carcinoid Tumor Obstruction of the Lingular Airways and Lingular Atelectasis with Correlative Sagittal CT to Explain the Findings in the Left Apex
The word Luftsichel is German for “air crescent.” The finding is seen in the setting of left upper lobe collapse. Due to the absence of a minor fissure on the left, as the left upper lobe collapses, the major fissure assumes a vertical position roughly parallel to the anterior chest wall.4 As volume loss progresses, the fissure continues to migrate more anteriorly and medially until the atelectatic lobe is contiguous with the left heart border, effectively obliterating its contour on the frontal radiograph (Figs. 17A–C). With movement of the apical upper lobe segment anteromedially, the superior segment of the left lower lobe hyperinflates and fills the vacated apical space.4,52 Occasionally this segment will insinuate itself between the aortic arch and the collapsed left upper lobe creating a sharp outline, or periaortic lucency, described as the Luftsichel.3,4,52