Comparison of ABR and ASSR using narrow-band-chirp-stimuli in children with cochlear malformation and/or cochlear nerve hypoplasia suffering from severe/profound hearing loss.

OBJECTIVES: In pediatric audiology, objective techniques for hearing threshold estimation in infants and children with profound or severe hearing loss play a key role. Auditory brainstem responses (ABR) and auditory steady-state responses (ASSR) are available for frequency-dependent hearing threshold estimations and both techniques show strong correlations but sometimes with considerable differences. The aim of the study was to compare hearing threshold estimations in children with and without cochlear and cochlear nerve malformations. METHODS: Two groups with profound or severe hearing loss were retrospectively compared. In 20 ears (15 children) with malformation of the inner ear and/or cochlear nerve hypoplasia and a control group of 20 ears (11 children) without malformation, ABR were measured with the Interacoustics Eclipse EP25 ABR system® (Denmark) with narrow-band CE-chirps® at 500, 1000, 2000 and 4000 Hz and compared to ASSR at the same center frequencies under similar conditions. RESULTS: ABR and ASSR correlated significantly in both groups (r = 0.413 in malformation group, r = 0.82 in control group). The malformation group showed a significantly lower percentage of "equal" hearing threshold estimations than the control group. In detail, patients with isolated cochlear malformation did not differ significantly from the control group, whereas patients with cochlear nerve hypoplasia showed significantly greater differences. CONCLUSION: ABR and ASSR should be used jointly in the diagnostic approach in children with suspected profound or severe hearing loss. A great difference in hearing threshold estimation between these techniques could hint at the involvement of cochlear nerve or cochlear nerve hypoplasia itself.

A psychoacoustic application for the adjustment of electrical hearing thresholds in cochlear implant patients.

OBJECTIVE: Fitting cochlear implants, especially the precise determination of electrical hearing thresholds, is a time-consuming and complex task for patients as well as audiologists. Aim of the study was to develop a method that enables cochlear implant (CI) patients to determine their electrical hearing thresholds precisely and independently. Applicability and impact of this method on speech perception in noise at soft speech levels were evaluated. METHOD: An adaptive psychoacoustic procedure for precise hearing threshold determination (precT) was implemented using MatLab (MathWorks) and a graphical user interface was created. Sound signals were calibrated with a CIC4-Implant-Decoder. Study design: A prospective study including 15 experienced adult cochlear implant users was conducted. Electrical hearing thresholds were determined using the automated precT procedure (auto-precT). Speech perception in noise at 50 dB SPL presentation levels was measured for three conditions: (P1) T-levels kept at the previously established T-levels; (P2) T-levels set to the hearing thresholds determined using auto-precT application; (P3) T-levels set 10 cu below the values determined with auto-precT. RESULTS: All subjects were able to perform the auto-precT application independently. T-levels were altered on average by an absolute value of 10.5 cu using auto-precT. Median speech reception thresholds were significantly improved from 2.5 dB SNR (P1) to 1.6 dB SNR (P2, p = 0.02). Speech perception was lowest using the globally lowered T-levels, median 2.9 dB SNR (P3, not significant compared to P1 and P2). CONCLUSION: The applicability of the developed auto-precT application was confirmed in the present clinical study. Patients benefited from adjusting previously established T-levels to the threshold levels determined by the auto-precT application. The integration of the application in the clinical fitting routine as well as a remote fitting software approach is recommended. Furthermore, future possibilities of auto-precT include the implementation of the application on tablets or smart phones.

Masking release with changing fundamental frequency: Electric acoustic stimulation resembles normal hearing subjects.

It has been shown that patients with electric acoustic stimulation (EAS) perform better in noisy environments than patients with a cochlear implant (CI). One reason for this could be the preserved access to acoustic low-frequency cues including the fundamental frequency (F0). Therefore, our primary aim was to investigate whether users of EAS experience a release from masking with increasing F0 difference between target talker and masking talker. The study comprised 29 patients and consisted of three groups of subjects: EAS users, CI users and normal-hearing listeners (NH). All CI and EAS users were implanted with a MED-EL cochlear implant and had at least 12 months of experience with the implant. Speech perception was assessed with the Oldenburg sentence test (OlSa) using one sentence from the test corpus as speech masker. The F0 in this masking sentence was shifted upwards by 4, 8, or 12 semitones. For each of these masker conditions the speech reception threshold (SRT) was assessed by adaptively varying the masker level while presenting the target sentences at a fixed level. A statistically significant improvement in speech perception was found for increasing difference in F0 between target sentence and masker sentence in EAS users (p = 0.038) and in NH listeners (p = 0.003). In CI users (classic CI or EAS users with electrical stimulation only) speech perception was independent from differences in F0 between target and masker. A release from masking with increasing difference in F0 between target and masking speech was only observed in listeners and configurations in which the low-frequency region was presented acoustically. Thus, the speech information contained in the low frequencies seems to be crucial for allowing listeners to separate multiple sources. By combining acoustic and electric information, EAS users even manage tasks as complicated as segregating the audio streams from multiple talkers. Preserving the natural code, like fine-structure cues in the low-frequency region, seems to be crucial to provide CI users with the best benefit.

Long-term Hearing Preservation Outcomes After Cochlear Implantation for Electric-Acoustic Stimulation.

OBJECTIVE: This study reviewed outcomes of hearing preservation (HP) surgery in a cochlear implant patient population, with clinical follow-up results up to 11 years after implantation. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral university hospital. PATIENTS: Ninety six patients (103 ears) with partial deafness who underwent HP surgery at the University Hospital Frankfurt since 1999 were included. Electrode carriers were Cochlear Slim Straight, MED-EL Standard, Medium, Flex, and Flex. INTERVENTION: Cochlear implantation using the HP surgery technique with either the cochleostomy or round window approach. MAIN OUTCOME MEASURES: Pure-tone averages for low frequencies (125 Hz, 250 Hz, 500 Hz, PTAlow) and speech perception scores of the Freiburg monosyllable and number tests in quiet. PTAlow shifts were used to evaluate HP as complete for ≤10 dB, partial between 10 and 30 dB, and minimal for ≥30 dB. Time intervals were: preoperative, postoperative, after 12 months, and long-term (>24 months, mean 51.4 months, range 2-11 years). Impacts of electrode design and surgical approach were analyzed. RESULTS: Postoperatively (n = 103), HP was complete in 32 (31.1%), partial in 49 (47.6%), minimal in 14 (13.6%), and loss of hearing occurred in 8 cases (7.8%). After 12 months (n = 81), HP was complete in 22 (27.2%), partial in 33 (40.7%), minimal in 11 (13.6%), and loss of hearing occurred in 7 additional cases. For long-term outcomes (n = 62) HP was complete in 7 (11.3%), partial in 24 (38.7%), minimal in 9 (14.5%), and loss of hearing occurred in 7 additional cases (total 22/103, 21.4%). Cases with residual hearing who could utilize acoustic amplification (i.e., PTAlow < 80 dB HL) were 82/95 (85.3%) postoperatively, 58/66 (87.9%) after 12 months, and 38/40 (95.0%) for long-term outcomes. CONCLUSIONS: Long-term HP is feasible in a subset of patients. Patients with sufficient long-term residual hearing had the prerequisite to benefit from additional acoustic stimulation. No correlation of total hearing loss with etiology, electrode design, or surgical approach was evident. Apart from individual effects of structural damage or inflammation, genetic factors are suggested to influence HP. Cases with total hearing loss still demonstrated successful speech perception in long-term monosyllable recognition scores.

Towards a Unified Testing Framework for Single-Sided Deafness Studies: A Consensus Paper.

BACKGROUND: While hearing aids for a contralateral routing of signals (CROS-HA) and bone conduction devices have been the traditional treatment for single-sided deafness (SSD) and asymmetric hearing loss (AHL), in recent years, cochlear implants (CIs) have increasingly become a viable treatment choice, particularly in countries where regulatory approval and reimbursement schemes are in place. Part of the reason for this shift is that the CI is the only device capable of restoring bilateral input to the auditory system and hence of possibly reinstating binaural hearing. Although several studies have independently shown that the CI is a safe and effective treatment for SSD and AHL, clinical outcome measures in those studies and across CI centers vary greatly. Only with a consistent use of defined and agreed-upon outcome measures across centers can high-level evidence be generated to assess the safety and efficacy of CIs and alternative treatments in recipients with SSD and AHL. METHODS: This paper presents a comparative study design and minimum outcome measures for the assessment of current treatment options in patients with SSD/AHL. The protocol was developed, discussed, and eventually agreed upon by expert panels that convened at the 2015 APSCI conference in Beijing, China, and at the CI 2016 conference in Toronto, Canada. RESULTS: A longitudinal study design comparing CROS-HA, BCD, and CI treatments is proposed. The recommended outcome measures include (1) speech in noise testing, using the same set of 3 spatial configurations to compare binaural benefits such as summation, squelch, and head shadow across devices; (2) localization testing, using stimuli that rove in both level and spectral content; (3) questionnaires to collect quality of life measures and the frequency of device use; and (4) questionnaires for assessing the impact of tinnitus before and after treatment, if applicable. CONCLUSION: A protocol for the assessment of treatment options and outcomes in recipients with SSD and AHL is presented. The proposed set of minimum outcome measures aims at harmonizing assessment methods across centers and thus at generating a growing body of high-level evidence for those treatment options.

Impact of a moving noise masker on speech perception in cochlear implant users.

OBJECTIVES: Previous studies investigating speech perception in noise have typically been conducted with static masker positions. The aim of this study was to investigate the effect of spatial separation of source and masker (spatial release from masking, SRM) in a moving masker setup and to evaluate the impact of adaptive beamforming in comparison with fixed directional microphones in cochlear implant (CI) users. DESIGN: Speech reception thresholds (SRT) were measured in S0N0 and in a moving masker setup (S0Nmove) in 12 normal hearing participants and 14 CI users (7 subjects bilateral, 7 bimodal with a hearing aid in the contralateral ear). Speech processor settings were a moderately directional microphone, a fixed beamformer, or an adaptive beamformer. The moving noise source was generated by means of wave field synthesis and was smoothly moved in a shape of a half-circle from one ear to the contralateral ear. Noise was presented in either of two conditions: continuous or modulated. RESULTS: SRTs in the S0Nmove setup were significantly improved compared to the S0N0 setup for both the normal hearing control group and the bilateral group in continuous noise, and for the control group in modulated noise. There was no effect of subject group. A significant effect of directional sensitivity was found in the S0Nmove setup. In the bilateral group, the adaptive beamformer achieved lower SRTs than the fixed beamformer setting. Adaptive beamforming improved SRT in both CI user groups substantially by about 3 dB (bimodal group) and 8 dB (bilateral group) depending on masker type. CONCLUSIONS: CI users showed SRM that was comparable to normal hearing subjects. In listening situations of everyday life with spatial separation of source and masker, directional microphones significantly improved speech perception with individual improvements of up to 15 dB SNR. Users of bilateral speech processors with both directional microphones obtained the highest benefit.

Speech perception with combined electric-acoustic stimulation and bilateral cochlear implants in a multisource noise field.

OBJECTIVE: The aim of the study was to measure and compare speech perception in users of electric-acoustic stimulation (EAS) supported by a hearing aid in the unimplanted ear and in bilateral cochlear implant (CI) users under different noise and sound field conditions. Gap listening was assessed by comparing performance in unmodulated and modulated Comité Consultatif International Téléphonique et Télégraphique (CCITT) noise conditions, and binaural interaction was investigated by comparing single source and multisource sound fields. METHODS: Speech perception in noise was measured using a closed-set sentence test (Oldenburg Sentence Test, OLSA) in a multisource noise field (MSNF) consisting of a four-loudspeaker array with independent noise sources and a single source in frontal position (S0N0). Speech simulating noise (Fastl-noise), CCITT-noise (continuous), and OLSA-noise (pseudo continuous) served as noise sources with different temporal patterns. Speech tests were performed in two groups of subjects who were using either EAS (n = 12) or bilateral CIs (n = 10). All subjects in the EAS group were fitted with a high-power hearing aid in the opposite ear (bimodal EAS). The average group score on monosyllable in quiet was 68.8% (EAS) and 80.5% (bilateral CI). A group of 22 listeners with normal hearing served as controls to compare and evaluate potential gap listening effects in implanted patients. RESULTS: Average speech reception thresholds in the EAS group were significantly lower than those for the bilateral CI group in all test conditions (CCITT 6.1 dB, p = 0.001; Fastl-noise 5.4 dB, p < 0.01; Oldenburg-(OL)-noise 1.6 dB, p < 0.05). Bilateral CI and EAS user groups showed a significant improvement of 4.3 dB (p = 0.004) and 5.4 dB (p = 0.002) between S0N0 and MSNF sound field conditions respectively, which signifies advantages caused by bilateral interaction in both groups. Performance in the control group showed a significant gap listening effect with a difference of 6.5 dB between modulated and unmodulated noise in S0N0, and a difference of 3.0 dB in MSNF. The ability to "glimpse" into short temporal masker gaps was absent in both groups of implanted subjects. CONCLUSIONS: Combined EAS in one ear supported by a hearing aid on the contralateral ear provided significantly improved speech perception compared with bilateral cochlear implantation. Although the scores for monosyllable words in quiet were higher in the bilateral CI group, the EAS group performed better in different noise and sound field conditions. Furthermore, the results indicated that binaural interaction between EAS in one ear and residual acoustic hearing in the opposite ear enhances speech perception in complex noise situations. Both bilateral CI and bimodal EAS users did not benefit from short temporal masker gaps, therefore the better performance of the EAS group in modulated noise conditions could be explained by the improved transmission of fundamental frequency cues in the lower-frequency region of acoustic hearing, which might foster the grouping of auditory objects.

Pitch matching psychometrics in electric acoustic stimulation.

OBJECTIVE: Combined electric-acoustic stimulation (EAS) is a therapeutic option for patients with severe to profound mid- and high-frequency hearing loss while low-frequency hearing is mostly unaffected. The present study investigates bimodal pitch matching in EAS users as a function of the angular placement of electrodes. Results are compared with data obtained from previous pitch matching studies. Knowledge of electric and acoustic pitch mapping may be important for effective fitting to control the frequency range of acoustic and electric processing. DESIGN: Pitch adjustment experiments were conducted in eight subjects with residual hearing in the opposite ear as well as in the implanted ear. Four subjects received a standard 31.5-mm electrode array and four subjects received the shorter, more flexible 24-mm FLEX electrode array (PULSARCI100 or SONATATI100 stimulator, MED-EL, Innsbruck, Austria). The subjects' task was to listen to single-electrode stimuli presented at a fixed rate (800 pulses per second) via the cochlear implant and to adjust the frequency of the acoustic stimulus until the perceived pitch matched the perception of the electrically conveyed stimulus. Two to four of the most apical electrodes were tested depending on the range of the individual's residual hearing. Postoperative x rays (modified Stenver's view) were analyzed to compare individual pitch matching data in terms of the electrode arrays' insertion angle. RESULTS: The average mean frequency match for the most apical electrode 1 in EAS subjects implanted with the FLEX array was 583 Hz, while for the two subjects with a deep insertion of the 31.5-mm standard electrode array, the matches were 128 and 223 Hz. Because the residual hearing in the EAS subgroup was rather limited in the high-frequency range, a limited number of basal electrodes were assessed to determine the slope of the electric place/pitch function. A considerable variation in terms of the individual pitch function was observed. The slope of the pitch function varied to a large extent among subjects. The differences between contra- and ipsilateral adjustments were very small (mean average 14 Hz) and within the range of the variance (average SD 124 Hz). CONCLUSIONS: The application of a pitch matching procedure to assess the electric/acoustic crossover frequency is feasible. In the present study, ipsi- and contralateral pitch matches made by EAS patients were nearly equal; therefore, a severe alteration in the excitation pattern of the basilar membrane in the implanted ear can be ruled out.

Cochlear reimplantation after surgery for electric-acoustic stimulation.

BACKGROUND/AIMS: Combined electric-acoustic stimulation (EAS) of the auditory system usually results in better speech understanding than electric stimulation only, assuming low-frequency hearing can be preserved. Treatment options and outcomes for 4 subjects experiencing compromised hearing after EAS surgery are discussed. METHODS: Each subject underwent revision surgery to replace the original 21-mm electrode arrays used in EAS surgery with cochlear implants (CIs) with 31-mm arrays. Our aims were: (1) to investigate whether deeper insertion is possible, and (2) to evaluate the influence of electrode insertion angle by comparing speech perception scores before and after revision surgery. RESULTS: Deeper insertion was feasible in all subjects. Speech understanding scores after reimplantation were comparable to those seen after the first intervention. CONCLUSION: A 360-degree insertion under EAS conditions provides sufficient speech understanding, even in cases of additional hearing loss. Reimplantation with a longer electrode array is feasible in former EAS patients.