Safety of hearing devices attached to the tympanic membrane depends on applied forces and resulting movements of the ossicles when pulling off the device. A robotized temporal bone measurement setup was designed to apply and measure defined pull-off forces and as well as the corresponding displacements of the round-window membrane via Laser-Doppler-vibrometry. Here, we investigate in five temporal bones the pull-off dynamics of the Vibrosonic Hearing Contact Lens® the silicone membrane of which being formed to match the tympanic-membrane shape of individual temporal bones. The devices were pulled off with a linear stage actuator in a defined manner. We here show that the time courses of stapes displacement and pull-off force follow a consistent characteristic. Mean geometrical maximum stapes displacements were determined to be 5.4 µm ± 6.9 dB, and the geometrical mean maximum force 0.14 N ± 3.8 dB. The acoustical middle-ear transfer function of the temporal bones, expressed as stapes head displacement vs. ear-canal sound pressure, did not change significantly over up to 7 repeated pull-off procedures, as assessed by a low-frequency displacement average. Based on these results, the detachment of the hearing contact lens appears to be tolerable.

Distortion-product otoacoustic emission (DPOAE) level maps provide a three-dimensional, frequency-specific representation of cochlear nonlinearities and offer an objective tool to estimate conductive hearing loss (CHL). While previous experimental studies have simulated or transiently induced conductive loss in normal-hearing (NH) ears, this study presents the estimation of the air-bone gap (ABG) based on pulsed DPOAE level maps in patients with pathologic minor-to-moderate CHL or mixed hearing loss. Using an adaptive measurement algorithm, DPOAE level maps were recorded in nine CHL patients and compared with maps from 15 NH controls and five patients with sensorineural hearing loss (SNHL). We evaluated two DPOAE-based metrics: (1) the shift of the optimal L1-L2 stimulus path, and (2) the slope of the semilogarithmic DPOAE growth function. In CHL ears, DPOAE growth slopes decreased and level maps shifted to higher L1, consistent with reverse and forward transmission losses of the middle ear. These features were clearly different in SNHL, enabling differentiation between conductive and cochlear components. Both metrics significantly correlated with the measured ABG, and their average yielded the most accurate ABG estimate. Furthermore, estimated DPOAE thresholds (EDPT) closely tracked behavioral thresholds across groups. DPOAE level maps provide a foundation for separating conductive and sensorineural components objectively. The results support the hypothesis that the slope of the semilogarithmically scaled DPOAE input-output function reflects the CHL and suggests potential utility as an adjunctive tool for diagnosing suspected otosclerosis and for monitoring this pathology.

Distortion-product otoacoustic emissions (DPOAE) are intermodulation products stimulated by two tones and reflect the nonlinear mechanical processing within the inner ear by the so-called cochlear amplifier. Therefore, they are interpreted as a diagnostic measure of its functional state. Due to their small amplitudes and the correspondingly long averaging time, current clinical systems measure one DPOAE amplitude at approximately seven fixed frequencies, representing a one-dimensional (1D) scan. More advanced systems record input-output functions of the distortion product amplitudes, where both tones are varied in a predefined ratio, resulting in a two-dimensional (2D) scan. A three-dimensional (3D) scan, where both stimulus tones are varied independently, yields more detailed information about the cochlea, but at the cost of longer measurement times. In this study, we introduce an adaptive measurement method, that autonomously collects more DPOAE data with sufficient signal-to-noise ratio (SNR) and leads more often to the identification of the so-called “individually optimal stimulus level path” than the previously used static method, which uses predefined fixed stimulus levels. In six ears of three subjects, the adaptive method detected 23% more valid DPOAE data. A bivariate histogram of area and density of DPOAE amplitudes for the optimal path samples shows that the adaptive method balances these competing goals more effectively. This results in higher-quality DPOAE level maps. Thus, the adaptive method has proven to be a time-efficient approach to characterize cochlear function more comprehensively.

Distortion-product otoacoustic emissions (DPOAEs) are widely used to assess cochlear function, but their diagnostic value is limited by interference between DPOAE components, dependence on optimal stimulus levels, middle-ear transmission, and variability due to ear-canal acoustics. Pulsed DPOAE level maps (LMs), which allow the derivation of estimated distortion-product thresholds (L2,EDPT), address some of these limitations. However, their reliability may still be compromised by standing-wave phenomena and calibration errors. In this study, we systematically compared four calibration methods-standard sound-pressure level (SPL), forward pressure level (FPL), integrated pressure level (IPL), and the combined methods of IPL and emitted pressure level (EPL), denoted as IPL+EPL-on LMs in eleven subjects across two sessions with intentionally varied probe insertion depths. Both FPL and IPL significantly reduced the intersession variability of LM-parameters compared with SPL, while IPL performed consistently better. The IPL+EPL calibration demonstrated additional benefits in reducing standing-wave effects on DPOAE and derived quantities. The analysis of three parameters describing the dependence of DPOAE on the two primary levels L2 and L1, confirmed that calibration-dependent changes in LM parameters could be interpreted as conduction loss (or gain) specifically for the frequencies f1, f2, and fDP. Advanced calibration methods, particularly IPL, substantially improve the reliability of LMs and enhance their potential for clinical audiometric applications.

Abstract Since young adults hear sounds up to 20 kHz, the loss of extended high-frequency hearing ( EHF ; above 8 kHz) is a hallmark of age-related hearing loss, often progressing from early lifetime. However, this deficit frequently goes undetected because routine clinical hearing tests and most hearing aids are currently limited mostly up to 8 kHz. EHF hearing has been linked to deficits in speech perception in noise and to self-reported hearing. However, it remains elusive how EHF hearing influences speech intelligibility. Here we recorded neuromagnetic brain responses using magnetoencephalography (MEG) within a frequency-tagging speech paradigm designed to probe hierarchical levels of attention and memory-dependent speech processing and recognition. Auditory evoked cortical magnetic field (AEF) responses were significantly reduced in both left and right brain hemispheres in individuals with impaired EHF hearing compared to those subjects with rather preserved EHF hearing. A gradual reinforcement of left-hemispheric AEF seen over age was not observed in young adults (19-29 y) with preserved EHF hearing. This was linked to stronger auditory brainstem responses (ABR), reflecting better neural synchronized auditory responses at stimulus onset. The reinforced left hemispheric dominance in young adults with impaired EHF hearing, in contrast, was linked to lower ABRs. Our findings suggest that sound energy above 8 kHz contributes through its impact on stimulus-onset synchrony to phase locking of oscillations in the auditory cortex to intelligible speech. Together, the results highlight the need to reconsider the neglect of EHF hearing in both audiological assessment and hearing aid design. Significance We show here that deficits in extended high-frequency (EHF) hearing, up to now neglected in routine clinical audiometry and hearing aid technology, lead to reduced cortical evoked auditory field (AEF) response amplitudes to attended and unattended speech, even at a young age. A gradual increase in reinforced left-hemispheric AEF responses during attended speech does not occur in young people with good EHF hearing; this is linked to better synchronization of neural responses at the onset of sound. This suggests a crucial role of sounds containing energy above 8kHz in minimizing the need for cognitive resources during active listening. Collectively, our results challenge current clinical practices and underscore the need to incorporate EHF hearing into audiological assessment and hearing aid design.

To assess system properties of the human auditory system, such as cochlear gain, frequency selectivity, and their dependence on frequency and level, it is essential to examine the interrelation of various readouts. By measuring and analyzing otoacoustic emission (OAE) and auditory brainstem response (ABR) latencies, among others, predictions of cochlear models and applicability of properties such as the minimum-phase principle, level dependence of latencies, or related changes of the gain of a presumed positive-feedback mechanism can be investigated. Here, we present measurements of the latency of the nonlinear-distortion component of pulsed distortion-product otoacoustic emissions (DPOAE) ( f_2 = 1–14 kHz, L_2 = 25–85 dB SPL) in 20 ears (12 female, 8 male). This yields a direct estimate of intracochlear traveling-wave build-up by recording the time elapsed between the f_2 primary stimulus and the distortion-product pulse response. Thus, this technique does not require deriving latency from phase gradients of the coherent-reflection component of different frequencies, as is done using swept-tone DPOAE or SFOAE. At low stimulus levels ( L_2 = 35 dB), DPOAE latency was 13 ms at f_2 = 1 kHz, exponentially to 2 ms at f_2 = 12–14 kHz. In periods of the corresponding frequency, this rose from ≈ 13 periods at 1 kHz to ≥ 25 periods above 6 kHz. Between 3 and 6 kHz, latency showed a steeper rise, departing from a pure exponential relation. Level dependence of latencies varied among subjects, with changes ranging from –2 to –12 ≈ 0.3 dB/dB. A transition region between 3 and 6 kHz shows scaling in some ears approaching 1 dB/dB, violating local scaling symmetry. Although comparison with ABR literature reveals some unresolved discrepancies, latencies of pulsed DPOAE allow a way to estimate cochlear tuning properties.

To date, there is no consensus on how to standardize the assessment of ototoxicity in serial measurements. For the diagnosis of damage to the cochlear amplifier, measurement methods are required that have the highest possible test-retest reliability and validity for detecting persistent damage. Estimated distortion-product thresholds (LEDPT) based on short-pulse distortion-product otoacoustic emission (DPOAE) level maps use individually optimal DPOAE stimulus levels and allow reliable quantitative estimation of cochlea-related hearing loss. Hearing thresholds were estimated objectively using LEDPT and subjectively using modified Békésy tracking audiometry (LTA). Recordings were performed seven times within three months at 14 frequencies (f2 = 1–14 kHz) in 20 ears (PTA4(0.5–4 kHz) < 20 dB HL). Reconstruction of the DPOAE growth behavior as a function of the stimulus levels L1, L2 was performed on the basis of 21 DPOAE amplitudes. A numerical fit of a nonlinear mathematical function to the three-dimensional DPOAE growth function yielded LEDPT for each stimulus frequency. For the combined analysis, probability distributions of hearing thresholds (LTA, LEDPT), DPOAE levels (LDP), and combinations thereof were determined. LTA and LEDPT each exhibited a test-retest reliability with a median of absolute differences (AD) of 3.2 dB and 3.3 dB, respectively. Combining LEDPT, LDP, and LTA into a single parameter yielded a significantly smaller median AD of 2.0 dB. It is expected that an analysis paradigm based on a combination of LEDPT, suprathreshold LDP, and fine-structure-reduced LTA would achieve higher test performance (sensitivity and specificity), allowing reliable detection of pathological or regenerative changes in the outer hair cells.

Hintergrund Man geht zur Zeit davon aus das Sprachdiskriminationsstörungen im Alter mit einer Cochlea-Synaptopathie, nicht aber primär mit dem Verlust von äußeren Haarzellen einhergeht. Für die Entwicklung wirksamer therapeutischer Interventionen von Sprachstörungen, ist es von entscheidender Bedeutung, den Mechanismus von Sprachkodierung und Sprachdiskrimination zu verstehen.

Nach wie vor sind die neuronalen Grundlagen von Tinnitus nicht vollständig aufgeklärt, was die Entwicklung von kausalen Therapien verzögert. Ziel der vorliegenden Studie war die Identifikation objektiver Merkmale von Tinnitus ohne (T) oder mit gleichzeitiger Hyperakusis (TH). Zu diesem Zweck führten wir Elektroenzephalographie (EEG) und funktionelle Nahinfrarotspektroskopie (fNIRS) durch, während die Probanden eine auditive Unterscheidungsaufgabe innerhalb ihrer Tinnitusfrequenz und einer Referenzfrequenz durchführten mussten sowie funktionelle MRT Untersuchung (resting-state-fMRI-based functional connectivity (rs-fMRI-bfc)). Die T-Gruppe wies eine verlängerte Latenzzeit der Hirnstammaudiometrie (ABR) und verringerte ABR-V-Amplituden auf, was mit einer geringeren rs-fMRI-bfc zwischen aufsteigenden auditorischen Nuclei und primären auditorischen Kortex verbunden war, wie in früheren Studien beobachtet. Bei den T-Probanden waren diese Merkmale mit erhöhten spontanen und reduzierten evozierten Gamma-Oszillationen und mit reduzierten Desoxy-Hb-Konzentrationen als Reaktion auf Stimulationen mit niedrigeren Frequenzen im temporalen Kortex (Brodmann-Areal (BA) 41, 42, 22) verbunden, was auf weniger synchrone auditorische Reaktionen während der aktiven auditorischen Unterscheidung von Referenzfrequenzen hindeutet. Im Gegensatz dazu waren in der TH-Gruppe die Gamma-Oszillationen und hämodynamischen Reaktionen in den temporoparietalen Regionen während der aktiven Unterscheidung der Tinnitus-Frequenzen umgekehrt. Zusammenfassend konnten wir zeigen, dass sich Tinnitus ohne und mit Hyperakusis mittels der verwendeten EEG- und fNIRS Paradigmen unterscheiden lassen, was eine präzisere Subklassifizierung von Tinnitus und zukünftige verbesserte Behandlungsansätze ermöglichen könnte.

The ongoing controversies about the neural basis of tinnitus, whether linked with central neural gain or not, may hamper efforts to develop therapies. We asked to what extent measurable audiometric characteristics of tinnitus without (T) or with co-occurrence of hyperacusis (TH) are distinguishable on the level of cortical responses. To accomplish this, electroencephalography (EEG) and concurrent functional near-infrared spectroscopy (fNIRS) were measured while patients performed an attentionally demanding auditory discrimination task using stimuli within the individual tinnitus frequency (fTin) and a reference frequency (fRef). Resting-state-fMRI-based functional connectivity (rs-fMRI-bfc) in ascending auditory nuclei (AAN), the primary auditory cortex (AC-I), and four other regions relevant for directing attention or regulating distress in temporal, parietal, and prefrontal cortex was compiled and compared to EEG and concurrent fNIRS activity in the same brain areas. We observed no group differences in pure-tone audiometry (PTA) between 10 and 16 kHz. However, the PTA threshold around the tinnitus pitch was positively correlated with the self-rated tinnitus loudness and also correlated with distress in T-groups, while TH experienced their tinnitus loudness at minimal loudness levels already with maximal suffering scores. The T-group exhibited prolonged auditory brain stem (ABR) wave I latency and reduced ABR wave V amplitudes (indicating reduced neural synchrony in the brainstem), which were associated with lower rs-fMRI-bfc between AAN and the AC-I, as observed in previous studies. In T-subjects, these features were linked with elevated spontaneous and reduced evoked gamma oscillations and with reduced deoxygenated hemoglobin (deoxy-Hb) concentrations in response to stimulation with lower frequencies in temporal cortex (Brodmann area (BA) 41, 42, 22), implying less synchronous auditory responses during active auditory discrimination of reference frequencies. In contrast, in the TH-group gamma oscillations and hemodynamic responses in temporoparietal regions were reversed during active discrimination of tinnitus frequencies. Our findings suggest that T and TH differ in auditory discrimination and memory-dependent directed attention during active discrimination at either tinnitus or reference frequencies, offering a test paradigm that may allow for more precise sub-classification of tinnitus and future improved treatment approaches.

Background Cochlear synaptopathy has been shown to precede hair cell loss and threshold shift over age. Cochlear synaptopathy is assumed to alter auditory information processing, whether accompanied by threshold elevations or not, and is a predicted contributor to speech-in-noise difficulties. It is crucial to understand the impact of cochlear synaptopathy on speech coding to develop effective therapeutic interventions.

The neuronal basis of tinnitus is still not fully understood, which delays the development of causal therapies. The aim of the present study was to identify objective characteristics of tinnitus without (T) or with concomitant hyperacusis (TH). For this purpose, we performed electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) while subjects had to perform an auditory discrimination task within their tinnitus frequency and a reference frequency as well as functional MRI examination (resting-state fMRI-based functional connectivity (rs-fMRI-bfc)). The T group showed prolonged brainstem audiometry (ABR) latency and decreased ABR-V amplitudes, which was associated with lower rs-fMRI-bfc between ascending auditory nuclei and primary auditory cortex, as observed in previous studies. In the T subjects, these features were associated with increased spontaneous and reduced evoked gamma oscillations and with reduced deoxy-Hb concentrations in response to lower frequency stimuli in temporal cortex (Brodmann area (BA) 41, 42, 22), suggesting less synchronous auditory responses during active auditory discrimination of reference frequencies. In contrast, in the TH group, gamma oscillations and hemodynamic responses in the temporoparietal regions were reversed during active discrimination of tinnitus frequencies. In conclusion, we were able to show that tinnitus without and with hyperacusis can be distinguished by the EEG and fNIRS paradigms used, which may allow a more precise subclassification of tinnitus and future improved treatment approaches.

Zusammenfassung Hintergrund Hörgeschädigte Menschen mit asymmetrischem Hörverlust und einseitiger Indikation für ein Cochleaimplantat (CI) profitieren in aller Regel deutlich von einer bimodalen Hörversorgung. Der Einfluss dieser Versorgungsart auf das Sprachverstehen (SV) im zeitlichen Verlauf ist bislang nicht hinreichend untersucht. Die vorliegende Studie untersucht den Einfluss einer bimodalen Versorgung auf das SV postlingual ertaubter, bimodal versorgter CI-Träger:innen nach einer Tragedauer von mindestens 36 Monaten und analysiert dabei mögliche Einflussfaktoren. Methode Es wurden 54 bimodal versorgte lautsprachkompetente CI-Träger:innen mit einer CI-Erfahrung von mindestens 36 Monaten in diese retrospektive Längsschnittstudie eingeschlossen. Audiometrische Daten von diesen CI-Träger:innen wurden im zeitlichen Verlauf verglichen. Ergebnisse Die Veränderung der Ergebnisse im Freiburger Einsilbertest (FBE) im Verlauf der 36 Monate war für die Ertaubungsgruppe < 10 Jahre sowohl für den Pegel 65 dB „sound pressure level“ (SPL) als auch für 80 dB SPL signifikant und für die Ertaubungsgruppe ≥ 10 Jahre für 65 dB SPL signifikant ( p < 5 %). Beim Oldenburger Satztest (OlSa) ergab sich für die Konfigurationen S 0 , S 0 N 0 und S 0 N CI eine hochsignifikante Veränderung ( p < 0,1 %). und für S 0 N HG (HG: Hörgerät) eine sehr signifikante Veränderung ( p < 1 %). Das Alter bei Versorgung als möglicher Einflussfaktor konnte durch den FBE nicht bestätigt werden. Die Ertaubungsdauer stellte dagegen einen negativen Einflussfaktor für das SV mit dem CI dar, wobei eine längere Ertaubungsdauer mit schlechteren Ergebnissen beim FBE assoziiert ist. Der Grad der Schwerhörigkeit des mit HG versorgten Ohrs beeinflusste das SV nicht. Im Median betrug der bimodale Nutzen (Differenz aus dem SV mit bimodaler Versorgung gegenüber einseitiger HG-Versorgung beim FBE für 65 dB SPL) über die gesamte Untersuchungszeit 10 %. Für im Median 79 % der Versuchspersonen war der bimodale Nutzen über den gesamten Zeitverlauf von 36 Monaten nachweisbar. Schlussfolgerung Im zeitlichen Verlauf verbessert sich das SV mit dem CI der bimodalen Versuchspersonen signifikant. Die untersuchten Einflussfaktoren (Alter, Ertaubungsdauer und Grad der Schwerhörigkeit des Gegenohrs) unterstützen die leitliniengerechte Indikationsstellung einer bimodalen Versorgung in Deutschland – unabhängig von Alter, Ertaubungsdauer und Hörfähigkeit des Gegenohrs – eine Cochleaimplantation durchzuführen.

Background: To date, there is no consensus on how to standardize the assessment of ototoxicity in serial measurements. For the diagnosis of damage to the cochlear amplifier, measurement methods are required that have the highest possible test-retest reliability and validity for detecting persistent damage. Estimated distortion-product thresholds (L-EDPT) based on short-pulse distortion-product otoacoustic emission (DPOAE) level maps use individually optimal DPOAE stimulus levels and allow reliable quantitative estimation of cochlea-related hearing loss. Materials and methods: Hearing thresholds were estimated objectively using L-EDPT and subjectively using modified B & eacute;k & eacute;sy tracking audiometry (L-TA). Recordings were performed seven times within three months at 14 frequencies (f(2) = 1-14 kHz) in 20 ears (PTA(4)((0.5-4) (kHz)) < 20 dB HL). Reconstruction of the DPOAE growth behavior as a function of the stimulus levels L-1, L-2 was performed on the basis of 21 DPOAE amplitudes. A numerical fit of a nonlinear mathematical function to the three-dimensional DPOAE growth function yielded L-EDPT for each stimulus frequency. For the combined analysis, probability distributions of hearing thresholds (L-TA, L-EDPT), DPOAE levels (L-DP), and combinations thereof were determined. Results: L-TA and L-EDPT each exhibited a test-retest reliability with a median of absolute differences (AD) of 3.2 dB and 3.3 dB, respectively. Combining L-EDPT, L-DP, and L-TA into a single parameter yielded a significantly smaller median AD of 2.0 dB. Conclusion: It is expected that an analysis paradigm based on a combination of L-EDPT, suprathreshold L-DP, and fine-structure-reduced L-TA would achieve higher test performance (sensitivity and specificity), allowing reliable detection of pathological or regenerative changes in the outer hair cells.

Background: It is assumed that speech comprehension deficits in background noise are caused by age-related or acquired hearing loss. Methods: We examined young, middle-aged, and older individuals with and without hearing threshold loss using pure-tone (PT) audiometry, short-pulsed distortion-product otoacoustic emissions (pDPOAEs), auditory brainstem responses (ABRs), auditory steady-state responses (ASSRs), speech comprehension (OLSA), and syllable discrimination in quiet and noise. Results: A noticeable decline of hearing sensitivity in extended high-frequency regions and its influence on low-frequency-induced ABRs was striking. When testing for differences in OLSA thresholds normalized for PT thresholds (PTTs), marked differences in speech comprehension ability exist not only in noise, but also in quiet, and they exist throughout the whole age range investigated. Listeners with poor speech comprehension in quiet exhibited a relatively lower pDPOAE and, thus, cochlear amplifier performance independent of PTT, smaller and delayed ABRs, and lower performance in vowel-phoneme discrimination below phase-locking limits (/o/-/u/). When OLSA was tested in noise, listeners with poor speech comprehension independent of PTT had larger pDPOAEs and, thus, cochlear amplifier performance, larger ASSR amplitudes, and higher uncomfortable loudness levels, all linked with lower performance of vowel-phoneme discrimination above the phase-locking limit (/i/-/y/). Conslusions: This study indicates that listening in noise in humans has a sizable disadvantage in envelope coding when basilar-membrane compression is compromised. Clearly, and in contrast to previous assumptions, both good and poor speech comprehension can exist independently of differences in PTTs and age, a phenomenon that urgently requires improved techniques to diagnose sound processing at stimulus onset in the clinical routine.

Bisher gibt es keinen Konsens darüber, wie Ototoxizität in Verlaufsmessungen standardisiert zu erfassen ist. Für die Diagnostik von Schädigungen des cochleären Verstärkers sind Messverfahren notwendig, die eine möglichst hohe Test-Retest-Zuverlässigkeit und eine hohe Aussagekraft hinsichtlich persistierender Schädigungen aufweisen. Hörschwellenschätzungen auf der Grundlage von Kurzpuls-DPOAE-Pegelkarten („estimated distortion-product thresholds“, LEDPT) berücksichtigen individuell optimale DPOAE-Anregungspegel und erlauben eine zuverlässige quantitative Schätzung des cochleär bedingten Hörverlusts. Hörschwellen wurden mithilfe von LEDPT objektiv geschätzt und mit einer modifizierten Békésy-Tracking-Audiometrie (LTA) subjektiv erfasst. Die Messungen wurden siebenmal innerhalb von drei Monaten bei 14 Frequenzen (f2 = 1–14 kHz) in 20 Ohren (PTA4 (0,5–4 kHz) < 20 dB HL) durchgeführt. Die Rekonstruktion des DPOAE-Wachstumsverhaltens in Abhängigkeit von den Anregungspegeln L1,L2 erfolgte auf der Grundlage von 21 DPOAE-Amplituden und ermöglichte mithilfe einer numerischen Anpassung einer nichtlinearen mathematischen Funktion die Berechnung eines LEDPT für jede Anregungsfrequenz. Für die gleichzeitige kombinierte Betrachtung wurden Verteilungen der Hörschwellen (LTA, LEDPT), der DPOAE-Pegel (LDP) und Kombinationen davon ermittelt. Einzeln betrachtet wiesen LTA und LEDPT jeweils eine Test-Retest-Zuverlässigkeit mit einem Median der absoluten Differenzen (AD) von 3,2 dB bzw. 3,3 dB auf, der sich durch Anwendung eines kombinierten Analyseparadigmas aus LEDPT, LDP und LTA auf 2,0 dB signifikant reduzieren ließ. Es ist zu erwarten, dass ein auf einer Kombination von LEDPT, überschwelligen LDP, und feinstrukturreduzierter LTA basierendes Analyseparadigma eine höhere Güte (Sensitivität und Spezifität) des Tests erzielt, um pathologische oder auch regenerative Veränderungen der äußeren Haarsinneszellen zuverlässig zu detektieren.

Background: Hearing-impaired persons with asymmetric hearing loss and a unilateral indication for a cochlear implant (CI) generally benefit from a bimodal hearing solution. The influence of bimodal fitting on speech comprehension (SC) over time has not yet been sufficiently investigated. The present study examines the influence of bimodal fitting on SC in bimodally fitted CI users with postlingual deafness at least 36 months after implantation and analyzes possible influencing factors. Methods: Included in this retrospective longitudinal study were 54 bimodally fitted speech-competent CI users with at least 36 months of CI experience. Audiometric data of these CI users at predefined timepoints were compared. Results: The change in the results of the Freiburg monosyllabic test (FT) over 36 months was significant (p < 5%) for the deafness group at <10 years for both the 65 dB sound pressure level (SPL) and at 80 dB SPL and also significant for the deafness group >= 10 years for 65 dB SPL. In the Oldenburg sentence test (OlSa) there was a highly significant change (p < 0.1%) for S-0, S0N0, and S0NCI configurations and a very significant change (p < 1%) for S0NHA (HA: hearing aid). Age at implantation as a possible influencing factor could not be confirmed in the FT. In contrast, the duration of deafness was a negative influencing factor for SC with CI in the FT, whereas a longer duration of deafness was associated with worse results in the FT. The degree of hearing loss in the ear fitted with an HA did not influence SC. The median bimodal benefit (here: difference in SC with bimodal fitting compared to unilateral HA fitting for FT at 65 dB SPL) was 10% over the total study period. For a median of 79% of the test subjects, the bimodal benefit was found over the entire period of 36 months. Conclusion: Over time, SC improves significantly with a CI for the bimodal test subjects. The investigated influencing factors (age, duration of deafness, and degree of hearing loss in the contralateral ear) support the indication for bimodal provision in accordance with the guideline in Germany for cochlear implantation-regardless of age, duration of deafness, and hearing ability of the contralateral ear.

Zusammenfassung Hintergrund Bisher gibt es keinen Konsens darüber, wie Ototoxizität in Verlaufsmessungen standardisiert zu erfassen ist. Für die Diagnostik von Schädigungen des cochleären Verstärkers sind Messverfahren notwendig, die eine möglichst hohe Test-Retest-Zuverlässigkeit und eine hohe Aussagekraft hinsichtlich persistierender Schädigungen aufweisen. Hörschwellenschätzungen auf der Grundlage von Kurzpuls-DPOAE-Pegelkarten („estimated distortion-product thresholds“, L EDPT ) berücksichtigen individuell optimale DPOAE-Anregungspegel und erlauben eine zuverlässige quantitative Schätzung des cochleär bedingten Hörverlusts. Methodik Hörschwellen wurden mithilfe von L EDPT objektiv geschätzt und mit einer modifizierten Békésy-Tracking-Audiometrie ( L TA ) subjektiv erfasst. Die Messungen wurden siebenmal innerhalb von drei Monaten bei 14 Frequenzen ( f 2 = 1–14 kHz) in 20 Ohren (PTA 4 (0,5–4 kHz) < 20 dB HL) durchgeführt. Die Rekonstruktion des DPOAE-Wachstumsverhaltens in Abhängigkeit von den Anregungspegeln L 1 , L 2 erfolgte auf der Grundlage von 21 DPOAE-Amplituden und ermöglichte mithilfe einer numerischen Anpassung einer nichtlinearen mathematischen Funktion die Berechnung eines L EDPT für jede Anregungsfrequenz. Für die gleichzeitige kombinierte Betrachtung wurden Verteilungen der Hörschwellen ( L TA , L EDPT ), der DPOAE-Pegel ( L DP ) und Kombinationen davon ermittelt. Ergebnisse Einzeln betrachtet wiesen L TA und L EDPT jeweils eine Test-Retest-Zuverlässigkeit mit einem Median der absoluten Differenzen (AD) von 3,2 dB bzw. 3,3 dB auf, der sich durch Anwendung eines kombinierten Analyseparadigmas aus L EDPT , L DP und L TA auf 2,0 dB signifikant reduzieren ließ. Schlussfolgerung Es ist zu erwarten, dass ein auf einer Kombination von L EDPT , überschwelligen L DP , und feinstrukturreduzierter L TA basierendes Analyseparadigma eine höhere Güte (Sensitivität und Spezifität) des Tests erzielt, um pathologische oder auch regenerative Veränderungen der äußeren Haarsinneszellen zuverlässig zu detektieren.

Distortion-product otoacoustic emissions (DPOAEs) are sound signals in the ear canal arising from nonlinear amplification of hydrodynamic oscillations in the cochlea. The analysis of the growth behavior of DPOAE pressure as function of stimulus level offers a quantitative assessment of the mechanical state of the cochlea. However, middle-ear dysfunction directly influences DPOAEs and their diagnostic accuracy. The present work simulates the impact of middle-ear dysfunction on DPOAEs using a hydrodynamic model of the human cochlea coupled to a middle-ear model for five frequencies from f2=1 to 4 kHz. DPOAEs in the ear canal are simulated by simultaneously solving the equations of motion representing the dynamics of the middle-ear and cochlea models in the time domain. Increasing the damping and stiffness of the annular ligament in the middle-ear model introduces conductive hearing loss (CHL) of various degrees. The changes in estimated distortion-product thresholds (EDPTs) and slopes of input-output (I/O) functions derived from the simulated DPOAE growth behavior are compared to changes in the middle-ear transfer functions (METFs). Pooled over all frequencies and degrees of CHL, the relative change of the METF amplitude at f2 exhibits a linear dependency on the relative change of EDPT level while the relative change of the METF amplitude at the distortion-product frequency fDP is linearly related to the relative change of the slope. The statistically significant linear relationships of the relative changes in EDPT level and slope of the I/O functions with relative changes in the METF amplitude indicate that conductive hearing loss can be objectively quantified from the DPOAE growth behavior.

The slowing and reduction of auditory responses in the brain are recognized side effects of increased pure tone thresholds, impaired speech recognition, and aging. However, it remains controversial whether central slowing is primarily linked to brain processes as atrophy, or is also associated with the slowing of temporal neural processing from the periphery. Here we analyzed electroencephalogram (EEG) responses that most likely reflect medial geniculate body (MGB) responses to passive listening of phonemes in 80 subjects ranging in age from 18 to 76 years, in whom the peripheral auditory responses had been analyzed in detail (Schirmer et al., 2024). We observed that passive listening to vowels and phonemes, specifically designed to rely on either temporal fine structure (TFS) for frequencies below the phase locking limit (<1500 Hz), or on the temporal envelope (TENV) for frequencies above phase locking limit, entrained lower or higher neural EEG responses. While previous views predict speech content, particular in noise to be encoded through TENV, here a decreasing phoneme-induced EEG amplitude over age in response to phonemes relying on TENV coding could also be linked to poorer speech-recognition thresholds in quiet. In addition, increased phoneme-evoked EEG delay could be correlated with elevated extended high-frequency threshold (EHF) for phoneme changes that relied on TFS and TENV coding. This may suggest a role of pure-tone threshold averages (PTA) of EHF for TENV and TFS beyond sound localization that is reflected in likely MGB delays. When speech recognition thresholds were normalized for pure-tone thresholds, however, the EEG amplitudes remained insignificant, and thereby became independent of age. Under these conditions, poor speech recognition in quiet was found together with a delay in EEG response for phonemes that relied on TFS coding, while poor speech recognition in ipsilateral noise was observed as a trend of shortened EEG delays for phonemes that relied on TENV coding. Based on previous analyses performed in these same subjects, elevated thresholds in extended high-frequency regions were linked to cochlear synaptopathy and auditory brainstem delays. Also, independent of hearing loss, poor speech-performing groups in quiet or with ipsilateral noise during TFS or TENV coding could be linked to lower or better outer hair cell performance and delayed or steeper auditory nerve responses at stimulus onset. The amplitude and latency of MGB responses to phonemes requiring TFS or TENV coding, dependent or independent of hearing loss, may thus be a new predictor of poor speech recognition in quiet and ipsilateral noise that links deficits in synchronicity at stimulus onset to neocortical activity. Amplitudes and delays of speech EEG responses to syllables should be reconsidered for future hearing-aid studies.