Temporal bone histopathology in trisomy 18 syndrome: a report of two cases.

Temporal bone histopathological findings of two patients with trisomy 18 syndrome are described. Many of the abnormalities previously described were seen in the present cases; namely, atresia of the external auditory canal, aberrant course of the tensor tympani muscle, malformed stapes, aberrant course of the facial nerve with an obtuse angulation at the first genu and displacement of geniculate ganglion cells into the internal auditory canal, shortened cochlea with decreased spiral ganglion cell population, and vestibular anomalies, such as bony and membranous blockage of the superior semicircular canal. Moreover, an extremely underdeveloped malleus and incus continuous with a persistent Meckel's cartilage were observed.