Congenital occlusion of the choana is a comparatively rare developmental anomaly, approximately only 160 cases having been reported since 1830. Only six cases have been seen in the Section on Rhinology of the Mayo Clinic since 1907, and in only one of these cases was the occlusion bilateral.
It is surprising to note that all the patients were in fairly good health, inability to breathe properly through the nose apparently not having been a serious handicap to their normal development. There was no history indicating any hereditary tendency toward development of the condition, and there were no other apparent deformities or asymmetries. None of the patients seen at the clinic had any disease of the ears. Removal of the obstruction in each case restored normal function.
The olfactory epithelium arises in embryos of about 4 mm. as paired ectodermal thickenings, olfactory placodes, on the ventrolateral sides of the head.