Congenital atresia of the postnasal orifices is due to the failure to disappear of normally occurring embryonic structures. The theories of its formation ascribe it to (a) the persistence of the bucconasal membrane, (b) the persistence of the buccopharyngeal membrane or (c) the overgrowth of the horizontal and vertical processes of the maxillas.
Schaeffer1 described the formation and the disappearance of the bucconasal membrane as follows:
Thirty-five (35) day embryos show that the nasal pits have deepened sufficiently to partake of the nature of cleft-like fossae. . . . The fossae communicate freely with the exterior by means of the nares (anterior nares) but in the absence of choanae (posterior nares) end blindly at their dorsal and inferior termination. . . . The dorsal growth or extension of the blind, pouch-like primitive nasal fossae meets the ectoderm of the oral fossa. One now finds in these positions the bucconasal membranes composed of two layers
MORGENSTERN DJ. CONGENITAL ATRESIA OF THE POSTNASAL ORIFICES: A SIMPLE, EFFECTIVE OFFICE TECHNIC FOR TREATMENT BY ELECTROCOAGULATION. Arch Otolaryngol. 1940;31(4):653–662. doi:10.1001/archotol.1940.00660010658007
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