Morphological classification of crista fenestra of round window corridor during pediatric cochlear implantation

Objectives: This study aimed to document the observation of the Crista Fenestra's morphological types (CF) of the round window and to detect its impact during cochlear implant operation.

Study design: A prospective descriptive cohort study.

Settings: We conducted this study at tertiary referral institutions in Egypt.

Patients: This study included 140 children who underwent cochlear implantation.

Intervention: We observed the CF's morphological type during the operation according to (Baki-Elzayat) novel classification of CF anatomy, and the need for drilling in each CI operation.

Main outcome measures: CF has two main types. Type A, in which CF was present at the same level of round window membrane and attached to it. Type B, in which CF was medial to the Round window membrane.

Results: Type (A) CF was detected in 125 cases (89.28%), while 25 cases (10.71%) showed type (B) CF. Drilling was needed in 10 cases (7.14%), including CF types A.3 and B2. Drilling was not needed in 130 cases (92.85%), including CF type A.1, A.2, and B.1. There was a statistically significant difference in the need for drilling (P-value <0.001).

Conclusions: According to this prospective study, CF had complicated anatomy. Baki-Elzayat classified the CF into two main types. In type A, CF was at the same level of RWM and attached to it. In type B, CF was medial to RWM. We recommended drilling for partial removal of massive CF types (A.3 and B.2) for atraumatic safe insertion of the electrode without deflection. This classification can offer an easy language system for CI surgeons to describe and register CF during their operations and in the surgical files.