Anomalous facial nerve canal with cochlear malformations

Area of Science:

• Otolaryngology
• Neuroradiology
• Developmental Biology

Background:

• Anteromedial migration of the first segment of the facial nerve canal is a rare anomaly.
• This migration has been previously observed in association with non-Mondini-type cochlear malformations.

Purpose of the Study:

• To investigate the association between anteromedial facial nerve canal migration and cochlear malformations.
• To characterize the types of cochlear malformations associated with this facial nerve anomaly.

Main Methods:

• Retrospective review of temporal bone CT scans from 15 patients (22 cases) with anteromedial facial nerve canal migration.
• Grading of facial nerve migration (mild/moderate or pronounced).
• Detailed analysis of cochlear morphology, including the presence and size of basilar, second, and apical turns, and comparison with 8 Mondini malformations.

Main Results:

• All 22 cases with facial nerve migration exhibited non-Mondini cochlear abnormalities.
• Associated cochlear malformations included common cavity, enlarged basal turns with absent upper turns, and small/absent upper turns.
• No anteromedial facial nerve canal migration was found in patients with Mondini-type cochlear malformations.

Conclusions:

• Anteromedial migration of the facial nerve canal is associated with specific non-Mondini cochlear malformations.
• The absence of this migration in Mondini malformations may be due to the normal size of the cochlea in these cases.
• This finding aids in understanding the complex developmental relationships within the inner ear and surrounding structures.