The location of the mastoid portion of the facial nerve in patients with congenital aural atresia.

In order to investigate the location of the mastoid portion of the facial nerve in patients with congenital aural atresia and to assess its effect on the round window middle ear implant (MEI) transducer implantation approach, 70 patients with unilateral congenital aural atresia were examined by computer tomography (CT). The patients were divided into two groups based on their ages: 44 patients in Group A (2-12 years) and 26 patients in Group B (13-29 years). CT scans were reviewed for each patient. Based on the CT findings, the mastoid portion of the facial nerve's spatial configuration with respect to the oval and round windows was qualitatively recorded. Additionally, the exact location of the facial nerve was measured quantitatively. The results suggested that of the 70 deformed ears, 57 had facial nerves located at the round window, six at the oval window, and seven at the normal site. Of the 70 normal opposite ears, 63 had facial nerves located at the normal site, and the other seven had facial nerves located at the round window. Based on the quantitative measurements, the mastoid portion of the facial nerve was more anteriorly positioned in the deformed ears: 3.44-6.09 mm more anteriorly located in Group A and 4.35-7.41 mm more anteriorly located in Group B. In conclusion, in patients with congenital aural atresia, the dislocation of the facial nerve could have significant effects on the surgical approach to round window MEI transducer implantation.