목적: In patients with enlarged vestibular aqueduct (EVA), deterioration of residual hearing is common after cochlear implantation due to accompanying cochlear malformation and perilymph leakage during cochleostomy. The purpose of this study is to investigate if cochlear implantation in the patients with EVA via round approach could achieve preservation of residual hearing, and to evaluate their speech reception with electroacoustic stimulation (EAS). 방법:This is a retrospective chart review of 6 patients with bilateral EVA, who had bi-allelic pendrin mutations. They consisted of 4 female and 2 male, and the mean age was 10.4-years old (range 4-16). In all patients, cochlear implantation was performed using round window approach without bony drilling. Audiological results were compared before and after implantation. With EAS mode, Korean HINT was also conducted. 결과:Preoperative pure-tone average was 91.39dB, and postoperative pure-tone average was 105.55dB. Hearing deterioration after implantation was 14dB in average (range 3.33-26.66). Among them, 3 patients show hearing loss less than 10dB after implantation. Hearing deterioration in low tone was 17.5dB (7.5-40). On Korean HINT, reception threshold for speech was at Quiet background was 50.47dB (43.9-53.8). The average signal to noise ratio (SNR) was 9.9 at Noise Front condition, 6.87 at Noise Right, and 9.29 at Noise Left, respectively. The Composite SNR was 9.02. 결론: Preservation of residual hearing could be achieved after cochlear implantation in the patients with EVA via round approach. They exhibited improvement of speech reception in both quiet and noise condition with the help of EAS. For successful preservation of residual hearing, application of newly-developed soft electrode and meticulous surgical technique should be considered.