Developmental anatomy of the supratubal recess in temporal bones from fetuses and children

The supratubal recess (STR), located superior to the bony eustachian tube and anterior to the attic and often the site of disease, is clearly separated from the attic by the presence of a bony partition. Its anatomic development in childhood, however, remains unclear. We reviewed serial horizontal sections of fetal and children's temporal bones from the collection of the Otopathology Laboratory, University of Minnesota. Apparently, upward expansion of the bony eustachian tribe begins at a late fetal stage and continues throughout childhood, thus forming the STR. Our finding that the STR had already developed in temporal bones without pneumatization of petrous bone suggests that its formation is independent of the air-cell system. Absorption of mesenchymal tissue in the STR tends to be slower than elsewhere in the temporal bone. Surrounded solely by petrous bone, the STR seems, both developmentally and anatomically, a distinctive compartment of the middle ear.