Temporal Bone Histopathological Findings in Trisomy 13 Syndrome

The histopathological findings of 14 temporal bones of infants with trisomy 13 syndrome are reported. The temporal bones were removed and then decalcified. The most primitive anomalies in the structures of the inner and middle ears in the present series are those of the semicircular canals, particularly of the horizontal canals; flattened horizontal canal cristae; absence or opening of the utricular endolymphatic valve; small facial nerve and obtuse angle of the geniculate ganglion area of the facial nerve. Each ear demonstrated more than one of these anomalies. The anomalies have features similar to those found in the structures of the normal six to ten weeks fetus. Many other anomalies such as the straight and shortened course of the endolymphatic duct and sac ending blindly in the otic capsule, shortening of cochlear length, wide cochlear aqueduct, bulky or thick stapes resembling the fetal form, malleus and incus containing large bone marrow cavities, absence of the pyramidal eminence, absence of the antrum, etc., seen in these cases, are similar to features of later fetal life. Most of the anomalies found in the inner and middle ears of these cases appear to be the result of poor development of the structures for reasons which are not now clear. Some abnormal inner ear findings which seem unrelated to poor development, such as endolymphatic hydrops in the cochlea, were also present in a few cases. Except for partial saccular dysplasia in 3 ears, all cases demonstrated well developed vestibular and cochlear end organs, even though there were macroscopic anomalies of the membranous labyrinth. These anomalies did not seem to correspond entirely with anomalies previously described such as: complete failure of the development of the inner ear (Michel type); incomplete development of bony and membranous labyrinth (Mundini type); incomplete development of membranous labyrinth (Bing Siebenman type); membranous cochleo saccular aplasia (Scheibe type); and membranous cochlear aplasia (Alexander type). In addition to these anomalies, middle ear infection was found in all cases. The possibility of such infection being secondary to upper respiratory infection in the presence of the cleft palate is mentioned.