High-frequency Cochlear Nerve Deficit Region: Relationship With Deaf Duration and Cochlear Implantation Performance in Postlingual Deaf Adults

Abstract

Objective: To analyze the changes of cochlear nerve diameter and the presence of a cochlear nerve deficit at a high-frequency region and investigate their effects on cochlear implant (CI) performance in postlingual deaf adults. Study Design: Retrospective. Setting: Tertiary care academic center. Patients: Eighty-three postlingual deaf adults with no labyrinthine anomalies or cognitive deficits who received a CI with perimodiolar electrodes from a single manufacturer. Main Outcomes and Measures: We evaluated the changes of cochlear nerve diameter and the presence of a "tail sign," defined as identifiable nerve fibers originating from the far basal turn of the cochlea, which represents the presence of cochlear nerve at a high-frequency region in magnetic resonance imaging, on monosyllabic word recognition scores. Results: The cochlear nerve diameter showed a positive correlation with word recognition scores (maximum diameter, R-2 = 0.26, p < 0.01; minimum diameter, R-2 = 0.26, p < 0.01), but a negative correlation with deaf duration. Recipients with a positive tail sign performed better (73 +/- 19%) than those without (45 +/- 24%, p < 0.01). A positive tail sign was more commonly found in good performers (52 of 62, 84%) than in poor performers (5 of 21, 24%, p < 0.01). Conclusions: Favorable outcomes could be anticipated in postlingual deaf adults with a large cochlear nerve diameter and positive tail sign. A presence of cochlear nerve at a high-frequency region may be an imaging marker for predicting good CI performance.