Objective: To determine the incidence and location of dehiscence of the facial nerve in patients with cholesteatoma.
Study design: Prospective case series.
Setting: Tertiary referral centers.
Patients: Charts and operative details from 1,372 consecutive chronic ear cases performed by a single surgeon were reviewed for anatomic details regarding the facial nerve. The study group was limited to the 416 ears in which cholesteatoma was confirmed at the time of surgery.
Main outcome measures: Facial nerve dehiscence was graded as present or absent for both the tympanic and mastoid segments; the location of dehiscence in the tympanic segment was further characterized in regard to its relationship to the oval window and cochleariform process. Adherence of cholesteatoma to any area of dehiscence was also noted as was the presence of any coexisting inner ear fistula.
Results: Dehiscence of the tympanic segment was present in 18.8% (78 of 416) of ears in the study group. There were five cases of mastoid dehiscence. Approximately 80% of nerves that were dehiscent involved the area just superior to the oval window, and 12% involved the nerve anterior to the cochleariform process. Adults in the study were more likely to have dehiscence than those 18 years and younger (p = 0.0003, chitest), and inner ear fistula was also more common in those with dehiscence (p = 0.0118, chitest). Case studies of cholesteatoma adherent to the facial nerve are reviewed.
Conclusion: This study represents the largest group of patients evaluated to date for dehiscence of the facial nerve in the setting of cholesteatoma. Dehiscence is common, especially in patients with cholesteatoma, and the careful surgeon can avoid damage to the facial nerve through understanding of this anatomic variation.