Conservation of low-frequency hearing in cochlear implantation

• Published in: Acta oto-laryngologica Vol. 124; no. 3; pp. 272 - 280
• Main Authors: Kiefer, Jan, Gstoettner, Wolfgang, Baumgartner, Wolfgang, Pok, Stephen Marcel, Tillein, Jochen, Ye, Qing, von Ilberg, Christoph
• Format: Journal Article
• Language: English
• Published: Stockholm Informa UK Ltd 01.03.2004; Taylor & Francis; Taylor and Francis
• Subjects: acoustic stimulation; Adult; Aged; Audiometry, Pure-Tone; Auditory Threshold; Biological and medical sciences; Child; Child, Preschool; cochlear implant; Cochlear Implantation - adverse effects; Cochlear Implantation - methods; deafness; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; electrical stimulation; Hearing Loss, Sensorineural - physiopathology; Hearing Loss, Sensorineural - surgery; hearing preservation; Humans; inner ear; Medical sciences; Middle Aged; Non tumoral diseases; Otorhinolaryngology. Stomatology; Prospective Studies; residual hearing; Treatment Outcome; Human; electrical stimulation; hearing preservation; Electrical stimulus; Auditory disorder; residual hearing; Low frequency; Inner ear; Hearing loss; acoustics stimulation; Hearing; Acoustic stimulus; Cochlea; Cochlear implant; ENT disease; deafness
• ISSN: 0001-6489; 1651-2251
• DOI: 10.1080/00016480310000755a

Objective As results with cochlear implants have continued to improve, patients with some remaining cochlear function have become eligible for cochlear implantation. Thus, preservation of acoustic hearing after implantation has gained importance. Hearing preservation can be considered a benchmark for atraumatic implantation preventing neural degeneration from loss of residual hair cells or subsequent to local trauma. In this prospective study, the possibility of preserving low-frequency hearing in cochlear implantation using a modified surgical technique has been explored. Materials and Methods In a prospective study design, 14 subjects with considerable low-frequency hearing of 2-60 dB in the frequency range 125-500 Hz but with unsatisfactory speech understanding with hearing aids of < 35% monosyllabic word understanding were implanted with a MED-EL COMBI-40+ cochlear implant. The insertion depth was intentionally limited to 19-24 mm to prevent damage to low-frequency regions of the cochlea. Pre- and postoperative pure-tone thresholds were measured. Results Hearing was conserved within 0-10 dB in 9/14 subjects and within 11-20 dB in 3/14; in 2/14 subjects hearing was completely lost in the implanted ear. Thus hearing could at least partially be conserved in 12/14 subjects (86%). Median threshold values decreased by 10, 15, 17.5 and 5 dB at 125, 250, 500 and 1000 Hz, respectively. Even high levels of hearing, e.g. 30 dB at 500 Hz, could be maintained after implantation in some subjects. Conclusions This study reports successful conservation of hearing after cochlear implantation using a modified surgical technique. Even high levels of hearing could be maintained, showing that implantation of an intracochlear electrode can be performed atraumatically with preservation of functional structures.