Investigation of a circannual rhythm in nasopharyngeal airway patency in children.

We have studied nasopharyngeal adenoids on standardized cephalometric radiograms of 25 children in each season. While individual subjects showed changes ranging from 1-17% throughout the year, a synchronized circannual rhythm could be described for the girls only. Similar changes were observed in boys, although a synchronized group rhythm could not be ascertained. No clear explanation for this apparent sexual dimorphism is known at this time, but different hormonal influences are likely. Evaluation of the nasopharyngeal airway (NPA) patency is thus affected by the season in which a cephalogram is taken. It should be noted that due to the described circannual rhythmicity, a single determination of the adenoid masses may be an insufficient and misleading indicator of the NPA obstruction. Etiology and clinical significance of these rhythmic changes need to be explored further.