Dear Editor,

Retropalatal collapse is one of the most common findings during drug-induced sleep endoscopy (DISE). The main cause of pathological upper airway collapsibility in patients with obstructive sleep apnea (OSA) is impaired pharyngeal neuromuscular tone with increased collapsibility during sleep [1]. The most popular DISE classifications (VOTE, NOHL) define the circumferential retropalatal collapse as “concentric”. The term “concentric” commonly should refer to a collapse of 360° [2]. What we usually observe in patients with retropalatal concentric collapse is an anteroposterior collapse pattern associated with a latero-lateral (transverse) one, which gives an optical effect of a circular 360° collapse. To be classified as a 360° collapse, it should theoretically also reveal an anterior collapse of the posterior pharyngeal wall. Although video-stroboscopy exhibited the vibration of the mucosa of the posterior pharyngeal wall during snoring [3], has anyone seen or described a postero-anterior collapse at DISE? No, because this phenomenon is almost impossible under normal conditions. In fact, the posterior pharyngeal wall at the midline is firmly attached to the vertebral bodies through the connections between the buccopharyngeal fascia with the alar fascia and the posterior pharyngeal raphe [4], [5]. Those posterior fascial connections give a remarkable stability to the posterior pharyngeal wall in all sleeping position.

In conclusion, we should remember to take into consideration that when we detect and classify a concentric retropalatal collapse what we are really observing is actually a horseshoe 270° collapse.

An immediate evidence is that none of the most popular pharyngoplasty techniques addresses the posterior pharyngeal wall, but rather the collapsible soft palate and lateral pharyngeal walls.