Round window membrane visibility related to success of hearing preservation in cochlear implantation

Abstract

OBJECTIVES: This study was designed to evaluate the relationship between the degree of round window membrane (RWM) exposure and hearing outcome. MATERIALS AND METHODS: Forty-six ears with cochlear implantation (CI) were enrolled. The degree of RWM exposure was divided into Grade I (<25%), Grade II (25-50%), and Grade III (>50%). The hearing outcomes were evaluated at 1.5 and 12 months postoperatively. RESULTS: Twenty-seven ears were Grade I, 13 were Grade II, and 6 were Grade III. RW approach was used in all ears of Grades II and III and 20 ears of Grade I and cochleostomy was used in 7 ears of Grade I. The pattern of bony overhang was multidirectional in 41 ears. Threshold shift significantly decreased proportional to the increase of RWM exposure after CI. The mean RWM exposure was 32.1 +/- 24.4% in ears with more than partial preservation (n = 17), and 13.3 +/- 11.7% in the other ears (n = 6) at 12 months post-CI (p = .061). Age at CI differed significantly between ears that had more than partial preservation and the other ears at 1.5 months post-CI. CONCLUSIONS AND SIGNIFICANCE: Degree of RWM exposure and age at CI might be factors predicting hearing outcome after CI using the RW approach.