Selection of cochlear electrode array implantation lengths and outcomes in patients with bilateral sensorineural hearing loss

Abstract

Objective: To perform a comprehensive comparison on the therapeutic effects of unilateral 31.5 mm and 28 mm cochlear implantation (CI) on the post-operative hearing rehabilitation outcomes, including hearing threshold, speech recognition and quality of life, in patients with bilateral sensorineural hearing loss. Methods: A total of 26 patients [12 males, 14 females, aged 19-71 (43±16) years] diagnosed with bilateral severe-to-profound sensorineural hearing loss at Peking Union Medical College Hospital from April 2018 to August 2019 were included. Patients underwent temporal bone high resolution CT (HRCT), based on which the electrode lengths were calculated using OTOPLAN. Eleven and fifteen ears were implanted with MED-EL Flex 31.5 mm and Flex 28 mm electrode arrays respectively, via round window approach under minimally invasive surgery. The patients were followed up regularly for up to 2 years. At each follow-up, aided hearing threshold, speech recognition in quiet and noise, and Nijmegen Cochlear Implantation Questionnaire (NICQ) scores were evaluated and compared. Results: Post-operative hearing thresholds were (46.5±3.4) dB and (48.5±2.2) dB in patients implanted with MED-EL Flex 31.5 mm and Flex 28 mm electrode arrays, respectively, with no statistically significant difference (P=0.074). Both hearing thresholds and speech recognition demonstrated significant post-operative improvement compared with pre-operative results. Hearing thresholds after 1-year post-operation were (32.1±1.2) dB and (32.5±0.9) dB, respectively (P=0.355). Patients implanted with Flex 31.5 mm electrode scored significantly higher at speech recognition under 65 dB sound pressure level (SPL) at most of the follow-ups (All P<0.05). Speech recognition in noise (S/N=10 dB) was also improved in patients implanted with Flex 31.5 mm electrode. All sub-divisions of the NICQ demonstrated significant post-operative improvement, and no significant difference between the 2 groups was observed apart from the"self-confidence"sub-division. Conclusions: Selection of MED-EL Flex 31.5 mm and 28 mm implantation based on pre-operative OTOPLAN evaluation can both bring significant improvements to patients' hearing and quality of life. Flex 31.5 mm electrode can potentially provide better speech recognition within a certain period after surgery.