Temporal bone findings in trisomy 13 with cyclopia.

Temporal bone findings in a fetus with trisomy 13 syndrome and cyclopia may be histopathologically characterized by the dysplasia of bony and membranous labyrinth and of the nervous system. In the left ear, there was a shortened cochlea housing a malformed Corti's organ appearing as a ribbonlike structure, an unexpected canal running obliquely through the scala tympani, a peculiar shape of the utricular macula and posterior canal crista, and a delayed ossifying process in the otic capsule. The poor development of the structures in the seventh and eighth nerves and their ganglions was observed in both ears. The type of anomaly can be classified as Mondini or Mondini-Alexander. The several anomalies might involve the organs that begin to develop during the period from five to eight gestational weeks.