ACEMg-mediated hearing preservation in cochlear implant patients receiving different electrode lengths (PROHEARING): study protocol for a randomized controlled trial.

BACKGROUND: The indications for a cochlear implant (CI) have been extended to include patients with some residual hearing. Shorter and thinner atraumatic electrodes have been designed to preserve the residual hearing in the implanted ear. However, the insertion of the electrode array into the cochlea, with potential mechanical trauma and the presence of this foreign body inside the cochlea, may lead to free radical formation and reduced blood perfusion of the cochlea which can result in the loss of residual hearing. METHODS/DESIGN: In this single-center, randomized, placebo-controlled, double-blind phase II clinical trial the effect of free radical scavengers and a vasodilator on the residual hearing of 140 CI patients will be evaluated. The formulation is composed of ß-carotene (vitamin A), ascorbic acid (vitamin C), dl-α-tocopherol acetate (vitamin E) and the vasodilator magnesium (Mg), or ACEMg. Medication is administered twice daily per os for approximately 3 months. The primary measure is based upon the reduction in postoperative low-frequency air-conducted pure-tone thresholds compared to preoperative thresholds in ACEMg-treated patients compared to those of a placebo group. Additionally, the effect of different electrode lengths (20, 24 and 28 mm) is analyzed. Study visits are scheduled 2 days before surgery, at first fitting, which is the adjustment and start of stimulation via CI 4 weeks after surgery and 3, 6, 9 and 12 months after first fitting. The primary endpoint is the air-conduction hearing loss at 500 Hz 3 months after first fitting. Additionally, speech recognition tests, hearing aid benefit in the implanted ear and electrophysiological measurements of implant function are assessed. Since this is a blinded clinical trial and recruitment is still ongoing, data continue to accrue and we cannot yet analyze the outcome of the ACEMg treatment. DISCUSSION: There is an unfulfilled need for new strategies to preserve acoustic hearing in CI patients. This study will provide first-in-man data on ACEMg-mediated protection of residual hearing in CI patients. Performing all surgeries and patient follow-up at one study site improves consistency in diagnosis and therapy and less variability in surgery, audiological test techniques and fitting. This approach will allow investigation of the influence of ACEMg on residual hearing in CI patients. TRIAL REGISTRATION: The German Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM) application number 4039192, was registered on 6 December 2013 with protocol amendment version 3.0 from 19 August 2014. EudraCT number: 2012-005002-22 .

The Impact of Electrode Array Length on Hearing Preservation in Cochlear Implantation.

OBJECTIVE: The aim of the study was to determine the degree of hearing preservation (HP) and its relation to electrode array length after cochlear implantation using different thin flexible electrode arrays (TFEA). STUDY DESIGN: Retrospective analysis. INTERVENTION: One hundred twenty adult patients with preoperative residual hearing received a cochlear implant with a TFEA: 46 received a TFEA20, 34 a TFEA24, and 40 a TFEA28 mm. MAIN OUTCOME MEASURES: Pure-tone audiometry (125-1500 Hz) was performed preoperatively, at initial fitting, and at 3, 6, and 12 months postoperatively. Median hearing loss (HL) was determined for each of the three array groups. The pre- to postoperative pure-tone average difference was scaled into three groups (≤15 dB, >15 to ≤30 dB, >30 dB) for array group. RESULTS: At initial fitting, median HL of 17.5 dB (TFEA20), 20 dB (TFEA24), and 24 dB (TFEA28) was observed. At 12 months, medial HL of 15 dB (TFEA20), 19.4 dB (TFEA24), and 32.5 dB (TFEA28) was observed. At initial fitting, a HL of ≤15 dB was achieved in 45.6% TFEA20 subjects, 29.4% TFEA24 subjects, and 15.0% TFEA28 subjects; compared with 48.8% TFEA20 subjects, 50.0% TFEA24 subjects, and 15.8% TFEA28 subjects at 12 months. CONCLUSION: HP is possible in the majority of subjects who are implanted with a TFEA20, 24, or 28. Using shorter arrays led to greater HP and lower median HL.

A comparison of conventional and in-situ audiometry on participants with varying levels of sensorineural hearing loss.

BACKGROUND: In-situ audiometry is a hearing aid feature that enables the measurement of hearing threshold levels through the hearing instrument using the built-in sound generator and the hearing aid receiver. This feature can be used in hearing aid fittings instead of conventional pure-tone audiometry (PTA), particularly in places where no standard audiometric equipment is available. Differences between conventional and in-situ thresholds are described and discussed for some particular hearing aids. No previous investigation has measured and compared these differences for a number of current hearing aid models by various manufacturers across a wide range of hearing losses. PURPOSE: The purpose of this study was to perform a model-based comparison of conventionally and in-situ measured hearing thresholds. Data were collected for a range of hearing aid devices to study and generalize the effects that may occur under clinical conditions. RESEARCH DESIGN: Research design was an experimental and regression study. STUDY SAMPLE: A total of 30 adults with sensorineural hearing loss served as test persons. They were assigned to three subgroups of 10 subjects with mild (M), moderate to severe (MS), and severe (S) sensorineural hearing loss. INTERVENTION: All 30 test persons underwent both conventional PTA and in-situ audiometry with four hearing aid models by various manufacturers. DATA COLLECTION AND ANALYSIS: The differences between conventionally and in-situ measured hearing threshold levels were calculated and evaluated by an exploratory data analysis followed by a sophisticated statistical modeling process. RESULTS: At 500 and 1500 Hz, almost all threshold differences (conventional PTA minus in-situ data) were negative, i.e., in the low to mid frequencies, hearing loss was overestimated by most devices relative to PTA. At 4000 Hz, the majority of differences (7 of 12) were positive, i.e., in the frequency range above 1500 Hz, hearing loss was frequently underestimated. As hearing loss increased (M→MS→S), the effect of the underestimation decreased. At 500 and 1500 Hz, Resound devices showed the smallest threshold deviations, followed by Phonak, Starkey, and Oticon instruments. At 4000 Hz, this observed pattern partly disappeared and Starkey and Oticon devices showed a reversed effect with increasing hearing loss (M→MS→S). Because of high standard errors for the estimates, only a few explicit rankings of the devices could be established based on significant threshold differences (5% level). CONCLUSIONS: Differences between conventional PTA and in-situ threshold levels may be attributed to (1) frequency, (2) device/hearing loss, and (3) calibration/manufacturer effects. Frequency effects primarily resulting in an overestimation of hearing loss by in-situ audiometry in the low and mid frequencies are mainly due to sound drain-off through vents and leaks. Device/hearing loss effects may be due to leakage as well as boundary effects because in-situ audiometry is confined to a limited measurement range. Finally, different calibration approaches may result in different offset levels between PTA and in-situ audiometry calibration. In some cases, the observed threshold differences of up to 10-15 dB may translate to varied hearing aid fittings for the same user depending on how hearing threshold levels were measured.