Results of EAS performed in Japan using long electrodes: a multicenter retrospective survey

BACKGROUND: Electric-acoustic stimulation (EAS) has become an established treatment option for patients with high-frequency hearing loss. In Japan, all FLEX electrodes were approved for EAS in August 2023, resulting in increased use of longer electrodes. AIMS/OBJECTIVES: We investigated the impact of this approval on patient selection and electrode choice for EAS and compared hearing preservation outcomes between longer electrodes and FLEX24. MATERIALS AND METHODS: We retrospectively reviewed 68 EAS cases (80 ears) treated at 27 centers in Japan from August 2023 to October 2025 and compared the findings with those from 55 EAS cases using FLEX24 in a post-marketing survey conducted at 20 centers between 2014 and 2016. RESULTS: Preoperative hearing thresholds and age at implantation were comparable between the two surveys. Longer electrodes (FLEX26, FLEX28, or FLEX soft) were used in 68 of 80 ears (85%) in the present survey. Patients implanted with FLEX28 showed slightly poorer hearing preservation than those implanted with FLEX24; however, the difference was not statistically significant. CONCLUSIONS AND SIGNIFICANCE: Sufficient residual hearing was preserved even with longer electrodes. These findings support the increasing use of longer electrodes for EAS to provide adequate cochlear coverage while accommodating potential future deterioration in hearing.