Learning Objectives:

Introduction: The concept of cochlear implantation (CI) with hearing preservation by atraumatic soft surgery is well established. The preservation of residual hearing after conventional CI is also frequently observed. The purpose of this study was to investigate predictive factor for residual hearing preservation after atraumatic CI.

Patients: Twenty-six patients (13 adults and 13 children) included in this study were received CI with atraumatic technique using standard-length flexible electrode implant through the round window approach.

Main outcome measure: Residual hearing was defined by unaided preoperative pure-tone threshold by air conduction at the mean of frequencies 125, 250 and 500 Hz. Complete hearing preservation was defined as postoperative thresholds within 10 dB of pre-implant values, hearing loss was defined greater than 10 dB of pre-implant values. Preoperative magnetic resonance imaging (MRI) was undergone in all patients, to measure cochlear fluid using software package included in the electric medical chart system.

Result: Complete hearing preservation was achieved in 17 of 26 (65%) patients. Complete hearing preservation were observed in seven of 13(54%) adults and ten of 13 (77%) children . In the patients less than the age of 6, residual hearing preservation was significantly achieved compared to other patients(p < 0.05). The cochlear volumes were ranged between 60 and 108 mm³ in 26 patients. The mean cochlear volume was 81.7 mm³ in the group of the complete hearing preservation, 69.0 mm³ in the group of hearing loss, respectively. Cochlear volume was significantly larger in those with the complete hearing preservation than those with the hearing loss.

Conclusion: Residual hearing preservation after conventional CI was observed in patients with younger age at implantation and larger cochlear volume in the present study. Cochlear volume could be a useful tool in predictively for residual hearing preservation after conventional CI.