Radiological classification of the mastoid portion of the facial nerve: impact on the surgical accessibility of the round window in cochlear implantation.

BACKGROUND

Mastoid portion of the facial nerve plays an important role in the round window approach of cochlear implantation.

OBJECTIVES

This study aimed to predict the anterior displacement of the mastoid portion of the facial nerve in the preoperative HRCT coronal cuts. We also aimed to detect the implication of anterior displacement of MPFN on the R.W. accessibility through the posterior tympanotomy during cochlear implantation.

MATERIALS AND

METHODS

It was a retrospective observational cohort study in tertiary referral hospitals. We included 246 pediatric patients who underwent cochlear implantation due to bilateral severe to profound SNHL through a posterior tympanotomy approach.

RESULTS

Type I MPFN was present in 84 cases, type II MPFN was present in 149 patients, and type III MPFN was present in 13 cases. R.W. was inaccessible in 3 cases with MPFN type II and in 11 subjects with MPFN type III. There was a statistically significant difference regarding the R.W. accessibility between the three types of MPFN (p-value <.05). There was a strong statistically significant correlation between R.W. accessibility and the radiological type of the MPFN.

CONCLUSION

Mandour radiological classification of the mastoid portion of the facial nerve in the preoperative HRCT coronal offers an easily applicable method to detect the anterior displacement of the facial nerve by using easy and well-known landmarks. This classification can also predict R.W. accessibility through posterior tympanotomy during cochlear implantation with 97.97% accuracy.