Alteration of the relative vibration of the round window membrane after implantation of a direct acoustic cochlear implant.

Objective: Subjects implanted with a Direct Acoustic Cochlear Implant (DACI) show improvements in their bone conduction (BC) thresholds after surgery. We hypothesised that a new pathway for BC sound is created via the DACI. The aim of this study was to investigate the contribution of this pathway to the cochlear response via measurements of the promontory and round window membrane (RWM) velocities while stimulating with a conventional bone conductor.Design: This study was a cadaver head study with a repeated measures study design.Study Sample: Eight ears of five fresh-frozen cadaveric whole heads were investigated in this trial.Results: After DACI implantation the promontory and RWM velocities did not change significantly in the frequency range 0.5-2 kHz when the DACI was switched off.Conclusions: No significant changes in the relative vibration magnitude of the RWM after DACI implantation were observed. The improvements in BC thresholds seen in patients implanted with a DACI very likely have their origin in the changed impedance at the oval window after DACI surgery leading to a more efficient contribution from the inner ear components to BC sound.

Subclinical conductive hearing loss significantly reduces otoacoustic emission amplitude: Implications for test performance.

OBJECTIVES: Distortion product otoacoustic emissions (DPOAEs) are a time-efficient, non-invasive means of assessing the integrity of active inner ear mechanics. Unfortunately, the presence of even relatively minor conductive hearing loss (CHL) has been suggested to reduce the clinical utility of DPOAEs significantly. The primary aims of this study were to systematically evaluate the impact of CHL on DPOAE amplitude and to determine if ear-specific primary tone level manipulations can be used to mitigate CHL impact and recover DPOAE measurability. METHODS: For 30 young adults (57 ears) with normal hearing, DPOAEs were obtained for f2 = 1-6 kHz. Observed DPOAE amplitudes were used to generate ear- and frequency-specific models with the primary tone levels, L1 and L2, as inputs and predicted DPOAE amplitude, LDP, as output. These models were then used to simulate the effect of CHL (0-15 dB), as well as L1 manipulations (0-15 dB), on DPOAE measurability. RESULTS: Mean LDP for every CHL condition was significantly different from that for all other conditions (p = <.001), with a mean LDP attenuation of 8.7 dB for every 5 dB increase in CHL. Mean DPOAE measurability in response to a standard clinical stimulation paradigm of L1/L2 = 65/55 (dB SPL) was determined to be 99%, 84%, 37%, and 9% in the presence of 0, 5, 10, and 15 dB CHL, respectively. In the presence of 10 dB CHL, altering L1 resulted in an approximately 25% increase in DPOAE responses. CONCLUSION: Subclinical CHL loss is sufficient to significantly impair DPOAE measurability in a meaningful proportion of otherwise healthy ears. However, through strategic alteration of primary tone levels, the clinician can mitigate CHL impact and at least partially recover DPOAE measurability.

Different prognoses in patients with profound sudden sensorineural hearing loss.

Background: Inner ear hemorrhage is increasingly recognized as a cochlear lesion that can cause profound sudden sensorineural hearing loss (SSNHL). Objectives: To investigate changes of cochlear and vestibular function and to compare therapeutic recovery from profound SSNHL induced by different etiologies. Material and methods: Eighty patients with profound SSNHL (≥90 dB) were divided into an inner ear hemorrhage group and a non-inner ear hemorrhage group by MRI. Statistical analysis was performed to compare the therapeutic effects from vertigo and hearing loss and the outcomes of follow-up in the two groups. Results: There were significant differences between the two groups in terms of the overall 14-day therapeutic response rate (20 vs. 48%), the incidence of imbalance (26.7 vs. 6%), the incidence of semicircular canal dysfunction on the affected side (60 vs. 20%), the incidence of abnormal C-VEMP and O-VEMP on the affected side (63.3 vs. 38%; and 60 vs. 30%, respectively), the average hearing threshold (74.2 ± 10.7 vs. 53.6 ± 11.4 dB), and the word recognition score (65.5 ± 21.7 vs. 83.5 ± 24.5%) at a 12-month follow-up. Conclusions and significance: A higher percentage of patients with profound SSNHL induced by inner ear hemorrhage were associated with vertigo and had a poor prognosis.

The Clinical Benefit of Device Therapy for Meniere's Disease in Adults: Systematic Review and Meta-Analysis.

OBJECTIVES: This study aimed to assess the clinical benefit of device therapy on controlling the symptoms of Meniere's disease (MD). MATERIALS AND METHODS: We searched PubMed, Embase, the Cochrane Library, China National Knowledge Internet, and Wanfang Data before January 13, 2018. We selected randomized controlled clinical trials, case-controlled studies, and cohort studies that dealt with outcomes of device therapy for the treatment of MD. RESULTS: Sixteen trials met our inclusion criteria. The use of device therapy resulted in improved vertigo control, which was described as a reduction in the number of vertigo days by month (weighted mean difference [WMD]: 3.15, 95% confidence interval [CI]: 2.00-4.31), in the number of vertigo episodes by month (WMD: 7.37, 95% CI: 2.40-12.35), and in the vertigo visual analog score (WMD: 41.51, 95% CI: 34.68-48.34). In addition, the overall complete vertigo control (class A) rate was 50% (95% CI: 37%-64%). The device therapy also reduced the number of sick days by month (WMD: 4.56, 95% CI: 2.15-6.97), and the functional level improved (WMD: 2.66, 95% CI: 2.15-3.17). The electrocochleographic parameters decreased. The device therapy proved beneficial for hearing changes (WMD: 3.19, 95% CI: 0.66-5.71). No publication bias was found in the funnel plot and the results of Egger's test. CONCLUSION: This study showed that the device therapy might reduce vertigo attacks and sick days in patients with MD. Additionally, the function level and hearing level may improve after the device therapy. In addition, the decrease in electrocochleographic parameters showed that inner ear electrophysiology improved after device therapy.

Impedance measures for a better understanding of the electrical stimulation of the inner ear.

The performance of cochlear implant (CI) listeners is limited by several factors among which the lack of spatial selectivity of the electrical stimulation. Recently, many studies have explored the use of multipolar strategies where several electrodes are stimulated simultaneously to focus the electrical field in a restricted region of the cochlea. OBJECTIVE: These strategies are based on several assumptions concerning the electrical properties of the inner ear that need validation. The first, often implicit, assumption is that the medium is purely resistive and that the current waveforms produced by several electrodes sum linearly. The second assumption relates to the estimation of the contribution of each electrode to the overall electrical field. These individual contributions are usually obtained by stimulating each electrode and measuring the resulting voltage with the other inactive electrodes (i.e. the impedance matrix). However, measuring the voltage on active electrodes (i.e. the diagonal of the matrix) is not straightforward because of the polarization of the electrode-fluid interface. In existing multipolar strategies, the diagonal terms of the matrix are therefore inferred using linear extrapolation from measurements made at neighboring electrodes. APPROACH: In experiment 1, several impedance measurements were carried out in vitro and in eight CI users using sinusoidal and pulsatile waveforms to test the resistivity and linearity hypotheses. In experiment 2, we used an equivalent electrical model including a constant phase element in order to isolate the polarization component of the contact impedance. MAIN RESULTS: In experiment 1, high-resolution voltage recordings (1.1 MHz sampling) showed the resistivity assumption to be valid at 46.4 kHz, the highest frequency tested. However, these measures also revealed the presence of parasitic capacitive effects at high frequency that could be deleterious to multipolar strategies. Experiment 2 showed that the electrical model provides a better account of the high-resolution impedance measurements than previous approaches in the CI field that used resistor-capacitance circuit models. SIGNIFICANCE: These results validate the main hypotheses underlying the use of multipolar stimulation but also suggest possible modifications to their implementation, including the use of an impedance model and the modification of the electrical pulse waveform.

[The relationship between the parameters of evoked otoacoustical emission and tympanometry in the children born with the extremely low body weight]. / Vzaimosviaz' parametrov vyzvannoi otoakusticheskoi émissii i timpanometrii u detei, rozhdennykh s ékstremal'no nizkoi massoi tela.

The objective of the present study was to elucidate correlation between the parameters of evoked otoacoustical emission at the distorsion product otoacoustic emissionen frequency (DPOAE) and the results of tympoanometry performed at the probe tone frequencies of 226 Hz and 1 kHz in the children born with the extremely low body weight. The results of the study give evidence of the moderate correlation dependence between the strength of the cochlear acoustic response at DPOAE and the cohlear response amplitude at the frequencies of 2 kHz and 6 kHz from TTP (r=0.3; p=0.000) obtained at the tympanometry probe tone frequency of 1 kHz. The correlation between the magnitude of the acoustic response of the cochlea, the amplitude of this response at the frequencies of 2 kHz and 6 kHz, the width of the tympanograms, and their static compliance obtained in the studies at the tympanometry probe tone frequency of 1,000 Hz (r=0.3-0.5; p=0.001) was documented in the infants at the age of 6 months and 1 year.

Objective audiometry with DPOAEs : New findings for generation mechanisms and clinical applications.

BACKGROUND: Distortion product otoacoustic emissions (DPOAEs) and transient-evoked otoacoustic emissions (TEOAEs) are sound waves generated as byproducts of the cochlear amplifier. These are measurable in the auditory canal and represent an objective method for diagnosing functional disorders of the inner ear. Conventional DPOAE and TEOAE methods permit detection of hearing impairment, but with less than desirable accuracy. OBJECTIVE: By accounting for DPOAE generation mechanisms, the aim is to improve the accuracy of inner-ear diagnosis. METHODS: DPOAEs consist of two components, which emerge at different positions along the cochlea and which may cause artifacts due to mutual interference. Here, the two components are separated in the time domain using short stimulus pulses. Optimized stimulus levels facilitate the acquisition of DPOAEs with maximum amplitudes. DPOAE and Békésy audiograms were recorded from 41 subjects in a clinically relevant frequency range of 1.5-6 kHz. RESULTS: The short stimulus pulses allowed artifact-free measurement of DPOAEs. Semilogarithmic input-output functions yielded estimated distortion product thresholds, which were significantly correlated with the subjectively acquired Békésy thresholds. In addition, they allowed detection of hearing impairment from 20 dB HL, with 95% sensitivity and only a 5% false-positive rate. This accuracy was achieved with a measurement time of about 1-2 min per frequency. CONCLUSION: Compared to conventional DPOAE and TEOAE methods, separation of DPOAE components using short-pulse DPOAEs in combination with optimized stimulus parameters considerably enhances the accuracy of DPOAEs for diagnosing impairment of the cochlear amplifier.

Inner Ear Excitation in Normal and Postmastoidectomy Participants by Fluid Stimulation in the Absence of Air- and Bone-Conduction Mechanisms.

BACKGROUND: Hearing can be induced not only by airborne sounds (air conduction [AC]) and by the induction of skull vibrations by a bone vibrator (osseous bone conduction [BC]), but also by inducing vibrations of the soft tissues of the head, neck, and thorax. This hearing mode is called soft tissue conduction (STC) or nonosseous BC. PURPOSE: This study was designed to gain insight into the mechanism of STC auditory stimulation. RESEARCH DESIGN: Fluid was applied to the external auditory canal in normal participants and to the mastoidectomy common cavity in post-radical mastoidectomy patients. A rod coupled to a clinical bone vibrator, immersed in the fluid, delivered auditory frequency vibratory stimuli to the fluid. The stimulating rod was in contact with the fluid only. Thresholds were assessed in response to the fluid stimulation. STUDY SAMPLE: Eight ears in eight normal participants and eight ears in seven post-radical mastoidectomy patients were studied. DATA COLLECTION AND ANALYSIS: Thresholds to AC, BC, and fluid stimulation were assessed. The postmastoidectomy patients were older than the normal participants, with underlying sensorineural hearing loss (SNHL). Therefore, the thresholds to the fluid stimulation in each participant were corrected by subtracting his BC threshold, which expresses any underlying SNHL. RESULTS: Hearing thresholds were obtained in each participant, in both groups in response to the fluid stimulation at 1.0 and 2.0 kHz. The fluid thresholds, corrected by subtracting the BC thresholds, did not differ between the groups at 1.0 kHz. However, at 2.0 kHz the corrected fluid thresholds in the mastoidectomy patients were 10 dB lower (better) than in the normal participants. CONCLUSIONS: Since the corrected fluid thresholds at 1.0 kHz did not differ between the groups, the response to fluid stimulation in the normal participants at least at 1.0 kHz was probably not due to vibrations of the tympanic membrane and of the ossicular chain induced by the fluid stimulation, since these structures were absent in the mastoidectomy patients. In addition, the fluid in the external canal (normal participants) and the absence of the tympanic membrane and the ossicular chain (mastoidectomy patients) induced a conductive hearing loss (threshold elevation to air-conducted sounds coming from the bone vibrator), so that AC mechanisms were probably not involved in the thresholds to the fluid stimulation. In addition, as a result of the acoustic impedance mismatch between the fluid and skull bone, the audio-frequency vibrations induced in the fluid at threshold would probably not lead to vibrations of the bony wall of the meatus, so that hearing by osseous BC is not likely. Therefore, it seems that the thresholds to the fluid stimulation, in the absence of AC and of osseous BC, represent an example of STC, which is an additional mode of auditory stimulation in which the cochlea is activated by fluid pressures transmitted along a series of soft tissues, reaching and exciting the inner ear directly. STC can explain the mechanism of several auditory phenomena.

Analysis of Vestibular Evoked Myogenic Potentials and Electrocochleography in Noise Induced Hearing Loss.

OBJECTIVE: Our objective was to analyze the electrocochleography (ECoG) and cervical vestibular evoked myogenic potential (cVEMP) results of patients with noise-induced hearing loss (NIHL). MATERIALS AND METHODS: The study included 20 patients with NIHL. Pure-tone audiometry, tympanic membrane ECoG, and cVEMP were performed on all patients. The patients were divided into two groups based on averaged thresholds at 4, 6, and 8 kHz; whereby, group 1 comprised patients who had a threshold higher than 68.3 dB HL, whereas group 2 comprised patients with a threshold lower than 68.3 dB HL. RESULTS: Group 2 had a significantly higher number of patients with abnormal cVEMP values (63% versus 28%) (p=0.028). There was no significant difference in the incidence of ECoG abnormality between the groups (p>0.05), but there was a significant difference in the incidence of recognizable ECoG potentials between the groups (p<0.05). When only patients with vertigo/dizziness were considered, the group with vertigo and a lower degree of hearing loss (group 2) showed a higher incidence of abnormal cVEMP (p<0.05). CONCLUSION: Although the anatomical proximity of the sacculus to the cochlea leads to the consideration of a common involvement of these structures in NIHL, our results did not support the idea of a common and proportional involvement of the vestibular and auditory systems. Our study shows that saccular involvement is disproportionate to auditory involvement in NIHL.

Thymoquinone treatment for inner-ear acoustic trauma in rats.

OBJECTIVE: To investigate whether thymoquinone has any eliminative effects against inner-ear damage caused by acoustic trauma. METHODS: Thirty-two male rats were divided into four groups. Group 1 was only exposed to acoustic trauma. Group 2 was given thymoquinone 24 hours before acoustic trauma and continued to receive it for 10 days after the trauma. Group 3 was only treated with thymoquinone, for 10 days. Group 4, the control group, suffered no trauma and received saline instead of thymoquinone. Groups 1 and 2 were exposed to acoustic trauma using 105 dB SPL white noise for 4 hours. RESULTS: There was a significant decrease in distortion product otoacoustic emission values and an increase in auditory brainstem response thresholds in group 1 on days 1, 5 and 10, compared with baseline measurements. In group 2, a decrease in distortion product otoacoustic emission values and an increase in auditory brainstem response threshold were observed on day 1 after acoustic trauma, but measurements were comparable to baseline values on days 5 and 10. In group 3, thymoquinone had no detrimental effects on hearing. Similarly, the control group showed stable results. CONCLUSION: Thymoquinone was demonstrated to be a reparative rather than preventive treatment that could be used to relieve acoustic trauma.

Usher proteins in inner ear structure and function.

Usher syndrome (USH) is a neurosensory disorder affecting both hearing and vision in humans. Linkage studies of families of USH patients, studies in animals, and characterization of purified proteins have provided insight into the molecular mechanisms of hearing. To date, 11 USH proteins have been identified, and evidence suggests that all of them are crucial for the function of the mechanosensory cells of the inner ear, the hair cells. Most USH proteins are localized to the stereocilia of the hair cells, where mechano-electrical transduction (MET) of sound-induced vibrations occurs. Therefore, elucidation of the functions of USH proteins in the stereocilia is a prerequisite to understanding the exact mechanisms of MET.

Transmission of bone conducted sound - correlation between hearing perception and cochlear vibration.

The vibration velocity of the lateral semicircular canal and the cochlear promontory was measured on 16 subjects with a unilateral middle ear common cavity, using a laser Doppler vibrometer, when the stimulation was by bone conduction (BC). Four stimulation positions were used: three ipsilateral positions and one contralateral position. Masked BC pure tone thresholds were measured with the stimulation at the same four positions. Valid vibration data were obtained at frequencies between 0.3 and 5.0 kHz. Large intersubject variation of the results was found with both methods. The difference in cochlear velocity with BC stimulation at the four positions varied as a function of frequency while the tone thresholds showed a tendency of lower thresholds with stimulation at positions close to the cochlea. The correlation between the vibration velocities of the two measuring sites of the otic capsule was high. Also, relative median data showed similar trends for both vibration and threshold measurements. However, due to the high variability for both vibration and perceptual data, low correlation between the two methods was found at the individual level. The results from this study indicated that human hearing perception from BC sound can be estimated from the measure of cochlear vibrations of the otic capsule. It also showed that vibration measurements of the cochlea in cadaver heads are similar to that measured in live humans.

Air-conducted oVEMPs provide the best separation between intact and superior canal dehiscent labyrinths.

OBJECTIVE: First, to define the best single-step suprathreshold screening test for superior canal dehiscence syndrome (SCDS); second, to obtain further insight into the relative sensitivity of vestibular afferents to sound vibration in the presence of a superior canal dehiscence. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS: Eleven patients with surgically confirmed SCDS (mean, 50 yr; range, 32-66 yr) and 11 age-matched, healthy subjects (right ear only) with no hearing or vestibular deficits (mean, 50 yr; range, 33-66 yr). INTERVENTION: All subjects completed ocular and cervical vestibular evoked myogenic potential (o- and cVEMP) testing in response to air conduction (click and 500 Hz tone burst) and midline bone conduction (reflex hammer and Mini-shaker) stimulation. MAIN OUTCOME MEASURES: OVEMP n10 amplitude and cVEMP corrected peak-to-peak amplitude. RESULTS: OVEMP n10 amplitudes were significantly higher in SCDS when compared with healthy controls in response to all stimuli with the exception of reflex hammer. Likewise, cVEMP-corrected peak-to-peak amplitudes were significantly higher in SCDS when compared with healthy controls for air conduction stimulation (click and 500 Hz toneburst). However, there were no significant differences between groups for midline taps (reflex hammer or mini-shaker). Receiver operating characteristic curves demonstrated that oVEMPs in response to air conduction stimulation provided the best separation between SCDS and healthy controls. CONCLUSION: OVEMPs in response to air conduction stimulation (click and 500 Hz toneburst) provide the best separation between SCDS and healthy controls and are therefore the best single-step screening test for SCDS.

Inner ear decompression sickness in scuba divers: a review of 115 cases.

Inner ear decompression sickness (IEDCS) in scuba divers is increasingly observed, but epidemiological data are limited to small case series and the pathogenesis remains elusive. We report our experience over a 13-year period. We also thought to demonstrate that the development of this injury is mainly attributed to a mechanism of vascular origin. Diving information, clinical data, presence of circulatory right-to-left shunt (RLS), and laboratory investigations of 115 recreational divers were retrospectively analyzed. A follow-up study at 3 months was possible with the last 50 consecutive cases. IEDCS (99 males, 44 ± 11 years) represented 24 % of all the patients treated. The median delay of onset of symptoms after surfacing was 20 min. Violation of decompression procedure was recorded in 3 % while repetitive dives were observed in 33 %. The median time to hyperbaric treatment was 180 min. Pure vestibular disorders were observed in 76.5 %, cochlear deficit in 6 % and combination of symptoms in 17.5 %. Additional skin and neurological disorders were reported in 15 % of cases. In 77 %, a large RLS was detected with a preponderant right-sided lateralization of IEDCS (80 %, P < 0.001). Incomplete recovery was found in 68 % of the followed patients. Time to recompression did not seem to influence the clinical outcome. IEDCS is a common presentation of decompression sickness following an uneventful scuba dive, but the therapeutic response remains poor. The high prevalence of RLS combined with a right-sided predominance of inner ear dysfunction suggests a preferential mechanism of paradoxical arterial gas emboli through a vascular anatomical selectivity.

[Otosclerosis- <> or the loss of the natural variant of inertness (<> of the labyrinth capsule)].

The author suggests an original hypothesis of otosclerosis based on the analyses of the literature publications for many years and his personal clinical observations. The normal labyrinth capsule is considered to be bradytrophic, i.e. inert and showing an extremely low level of metabolic processes. The disturbance of bradytrophicity under the action of individual factors and/or especially their combination make it involved in the maintenance of calcium homeostasis in the body. The validity of this conjecture is confirmed by the results of histological investigations, viz. the appearance of diquide or xplasma-like, bone in the labyrinth of the patients suffering otosclerosis. Such bone resorption is known to occur in other parts of the bony skeletontoo and should be regarded as a normal physiological process contributing to the replenishment of blood calcium deficiency.The subsequent reorganization (remodeling) of any part of the bony skeleton is physiologically neutral. In the labyrinth capsule,with its small size and delicate structure, such reorganization induces the otosclerotic process responsible for dysfunction of the membranaceous labyrinth. The surgical treatment of the patients presenting with otosclerosis should be supplemented by conservative treatment intended to slow down the otosclerotic reorganization and to restore bradytrophicity of the labyrinth capsule.

[The evaluation of the efficiency of kinesitherapy in the patients with mixed-type vertigo]. / Ocena skutecznosci leczenia chorych z zawrotami glowy typu mieszanego za pomoca rehabilitacji ruchowej.

INTRODUCTION: The aim of this work was to evaluate the efficiency of kinesitherapy in the patients with mixed-type vertigo. MATERIAL AND METHODS: The study was conducted on a randomized group of 35 patients, 21 women and 14 men aged 24-75 years (mean age 42.5 years), who were treated at the Department of Otolaryngology and Laryngological Oncology Medical University Teaching Hospital in Lodz for mixed-type vertigo. The inclusion criteria were an interview, physical and otorhinolaryngological examinations, laboratory investigations, complete audiological and otoneurological examinations, including BERA and VNG, USG examination of the blood vessels to the cranium, and CT of the cervical spine. Each patient underwent an individually selected set of habituation exercises, corrective exercises for posture and its orientation in space through 2 months. The efficiency of the implemented therapy was evaluated after two weeks, one month and two months with the use of the complete videonystagmographic test and Silvoniemi's criteria. RESULTS: The mean excitability of the labyrinths was 25.38 degrees/s before rehabilitation and 22.26 degrees/s after rehabilitation, absolute directional preponderance was 7.62 degrees/s and 1.92 degrees/s respectively, relative directional preponderance was 31.36 degrees/s and 12.57 degrees/s, and unilateral deficit 32.12 degrees/s and 14.34 degrees/s. The subjective evaluation of the vertigo intensification based on the 5 stages of Silvoniemi's scale indicates that the mean point-based evaluation reported by the patients at the beginning of the therapy was 3.85 points, whereas after the therapy was 2.91 points after two weeks, 2.35 points after one month, and 1.2 points after two months. CONCLUSIONS: Kinesitherapy is an alternative and very effective method for treating mixed-type vertigo.

[Inner ear morphological study of guinea pigs with acoustically evoked short latency negative response].

OBJECTIVE: To establish a model of ototoxicity in guinea pigs with acoustically evoked short latency negative response (ASNR) and verify the responsible organ of ASNR based on microscopic characteristics of basal membranes, saccules, utricles and ampulla canalis semicircularis of the inner ear. METHODS: Total of 45 guinea pigs were employed in the experiment, which were randomly divided into the control group (15 subjects, 30 ears) and the deafened group (30 subjects, 60 ears). Each animal experienced auditory brainstem response (ABR). A quick treatment was employed for deafened group consisting of a subcutaneous injection of kanamycin at a dose of 400 mg/kg followed by jugular vein injection of ethacrynic acid at a dose of 40 mg/kg one hour later. The animals were performed ABR test from 7 to 10 days after the drug administration. The deafened group was further divided into ASNR group and non-ASNR group based on the presence of ASNR. All the guinea pigs were sacrificed after ABR tests. The Corti organ, macula sacculi, macula utriculi and crista ampullaris were observed by light microscope. RESULTS: In the deafened group (60 ears), 3 subjects died postoperatively, 27 subjects (54 ears) provided full data. ASNR was elicited in 19 ears (35.2%, 19/54), the thresholds of ASNR were from 110 to 125 dBSPL with average of (121.7 ± 4.5) dBSPL. ASNR latency ranges were 1.80 - 2.08 ms, the average latency of thresholds were (1.93 ± 0.07) ms. The stretched preparation results: overall hair-cell density of macula saccule, macula utriculi and crista ampullaris decreased in order of normal control group, ASNR group and non-ASNR group. There was no difference between the normal group and ASNR group for cell density of macula saccule. Apart from this, statistical differences were found among other groups. CONCLUSIONS: The present study evoked ASNR in an ototoxicity guinea pig model which was profound hearing loss with normal saccular function and normal saccular hair cell density. It suggested that ASNR originates from the saccule and have no relation with cochlear, utricle and semicircular canal according to morphological study.

Mature middle and inner ears express Chd7 and exhibit distinctive pathologies in a mouse model of CHARGE syndrome.

Heterozygous mutations in the gene encoding chromodomain-DNA-binding-protein 7 (CHD7) cause CHARGE syndrome, a multiple anomaly condition which includes vestibular dysfunction and hearing loss. Mice with heterozygous Chd7 mutations exhibit semicircular canal dysgenesis and abnormal inner ear neurogenesis, and are an excellent model of CHARGE syndrome. Here we characterized Chd7 expression in mature middle and inner ears, analyzed morphological features of mutant ears and tested whether Chd7 mutant mice have altered responses to noise exposure and correlated those responses to inner and middle ear structure. We found that Chd7 is highly expressed in mature inner and outer hair cells, spiral ganglion neurons, vestibular sensory epithelia and middle ear ossicles. There were no obvious defects in individual hair cell morphology by prestin immunostaining or scanning electron microscopy, and cochlear innervation appeared normal in Chd7(Gt)(/+) mice. Hearing thresholds by auditory brainstem response (ABR) testing were elevated at 4 and 16 kHz in Chd7(Gt)(/+) mice, and there were reduced distortion product otoacoustic emissions (DPOAE). Exposure of Chd7(Gt)(/+) mice to broadband noise resulted in variable degrees of hair cell loss which inversely correlated with severity of stapedial defects. The degrees of hair cell loss and threshold shifts after noise exposure were more severe in wild type mice than in mutants. Together, these data indicate that Chd7(Gt)(/+) mice have combined conductive and sensorineural hearing loss, correlating with changes in both middle and inner ears.

Electrophysiological and morphological development of the inner ear in Belgian Waterslager canaries.

Belgian Waterslager (BW) canaries have an inherited hearing loss due to missing and abnormal hair cells, but it is unclear whether the loss is congenital or developmental. We used auditory brainstem responses and scanning electron microscopy to describe the development of auditory sensitivity and hair cell abnormalities in BW and non-BW canaries. In both strains, adult ABR thresholds were higher than behavioral thresholds, but BW canaries exhibited higher thresholds than non-BW canaries across all frequencies. Immediately post-hatch, ABR thresholds and hair cell numbers were similar in both strains. Two weeks later, thresholds were significantly higher in BW canaries, and hair cell number progressively decreased as the birds aged. These data show that in BW canaries: the peripheral auditory system is functionally similar to non-BW canary from hatch to 2 weeks, ABR thresholds improve during this developmental period, actually becoming better than those of adults, but then worsen as the bird continues to age. Hair cell number and appearance is similar to non-BW canaries at hatch but progressively declines after 30 days of age. These data show that the hearing loss characteristic of BW canaries is, at least in part, developmental and is established by the time song learning begins.