A Comparison of Intracochlear Pressures During Ipsilateral and Contralateral Stimulation With a Bone Conduction Implant.

OBJECTIVES: To compare contralateral to ipsilateral stimulation with percutaneous and transcutaneous bone conduction implants. BACKGROUND: Bone conduction implants (BCIs) effectively treat conductive and mixed hearing losses. In some cases, such as in single-sided deafness, the BCI is implanted contralateral to the remaining healthy ear in an attempt to restore some of the benefits provided by binaural hearing. While the benefit of contralateral stimulation has been shown in at least some patients, it is not clear what cues or mechanisms contribute to this function. Previous studies have investigated the motion of the ossicular chain, skull, and round window in response to bone vibration. Here, we extend those reports by reporting simultaneous measurements of cochlear promontory velocity and intracochlear pressures during bone conduction stimulation with two common BCI attachments, and directly compare ipsilateral to contralateral stimulation. METHODS: Fresh-frozen whole human heads were prepared bilaterally with mastoidectomies. Intracochlear pressure (PIC) in the scala vestibuli (PSV) and tympani (PST) was measured with fiber optic pressure probes concurrently with cochlear promontory velocity (VProm) via laser Doppler vibrometry during stimulation provided with a closed-field loudspeaker or a BCI. Stimuli were pure tones between 120 and 10,240 Hz, and response magnitudes and phases for PIC and VProm were measured for air and bone conducted sound presentation. RESULTS: Contralateral stimulation produced lower response magnitudes and longer delays than ipsilateral in all measures, particularly for high-frequency stimulation. Contralateral response magnitudes were lower than ipsilateral response magnitudes by up to 10 to 15 dB above ~2 kHz for a skin-penetrating abutment, which increased to 25 to 30 dB and extended to lower frequencies when applied with a transcutaneous (skin drive) attachment. CONCLUSIONS: Transcranial attenuation and delay suggest that ipsilateral stimulation will be dominant for frequencies over ~1 kHz, and that complex phase interactions will occur during bilateral or bimodal stimulation. These effects indicate a mechanism by which bilateral users could gain some bilateral advantage.

A2ML1 and otitis media: novel variants, differential expression, and relevant pathways.

A genetic basis for otitis media is established, however, the role of rare variants in disease etiology is largely unknown. Previously a duplication variant within A2ML1 was identified as a significant risk factor for otitis media in an indigenous Filipino population and in US children. In this report exome and Sanger sequencing was performed using DNA samples from the indigenous Filipino population, Filipino cochlear implantees, US probands, Finnish, and Pakistani families with otitis media. Sixteen novel, damaging A2ML1 variants identified in otitis media patients were rare or low-frequency in population-matched controls. In the indigenous population, both gingivitis and A2ML1 variants including the known duplication variant and the novel splice variant c.4061 + 1 G>C were independently associated with otitis media. Sequencing of salivary RNA samples from indigenous Filipinos demonstrated lower A2ML1 expression according to the carriage of A2ML1 variants. Sequencing of additional salivary RNA samples from US patients with otitis media revealed differentially expressed genes that are highly correlated with A2ML1 expression levels. In particular, RND3 is upregulated in both A2ML1 variant carriers and high-A2ML1 expressors. These findings support a role for A2ML1 in keratinocyte differentiation within the middle ear as part of otitis media pathology and the potential application of ROCK inhibition in otitis media.

Air- and Bone-Conducted Sources of Feedback With an Active Middle Ear Implant.

OBJECTIVES: Active middle ear implants (AMEI) have been used to treat hearing loss in patients for whom conventional hearing aids are unsuccessful for varied biologic or personal reasons. Several studies have discussed feedback as a potential complication of AMEI usage, though the feedback pathway is not well understood. While reverse propagation of an acoustic signal through the ossicular chain and tympanic membrane constitutes an air-conducted source of feedback, the implanted nature of the device microphone near the mastoid cortex suggests that bone conduction pathways may potentially be another significant factor. This study examines the relative contributions of potential sources of feedback during stimulation with an AMEI. DESIGN: Four fresh-frozen, hemi-sectioned, human cadaver specimens were prepared with a mastoid antrostomy and atticotomy to visualize the posterior incus body. A Carina active middle ear implant actuator (Cochlear Ltd., Boulder, CO) was coupled to the incus by two means: (1) a stereotactic arm mounted independently of the specimen and (2) a fixation bracket anchored directly to the mastoid cortical bone. The actuator was driven with pure-tone frequencies in 1/4 octave steps from 500 to 6000 Hz. Acoustic sound intensity in the ear canal was measured with a probe tube microphone (Bruel & Kjær, Nærum, Denmark). Bone-conducted vibration was quantified with a single-axis laser Doppler vibrometer (Polytec Inc., Irvine, CA) from both a piece of reflective tape placed on the skin overlying the mastoid and a bone-anchored titanium screw and pedestal (Cochlear Ltd., Centennial, CO) implanted in the cortical mastoid bone. RESULTS: Microphone measurements revealed ear-canal pressures of 60-89 dB SPL, peaking in the frequency range below 2 kHz. Peak LDV measurements were greatest on the mastoid bone (0.32-0.79 mm/s with mounting bracket and 0.21-0.36 mm/s with the stereotactic suspension); peak measurements on the skin ranged from 0.05 to 0.15 mm/s with the bracket and 0.03 to 0.13 mm/s with stereotactic suspension. CONCLUSION: AMEI produce both air- and bone-conducted signals of adequate strength to be detected by the implanted device microphone, potentially resulting in reamplification. Understanding the relative contribution of these sources may play an important role in the development of targeted mitigation algorithms, as well as surgical techniques emphasizing acoustic isolation.

Long-Term Outcome Data in Patients following One Year's Use of a Fully Implantable Active Middle Ear Implant.

This study examined the safety and efficacy of a fully implantable active middle ear (AMEI) system. Outcome measures assessed AMEI performance compared with an optimally fitted conventional hearing aid (CHA). Fifty adults with stable, symmetric moderate-to-severe sensorineural hearing loss were implanted at 9 ambulatory settings. Consonant-Nucleus-Consonant (CNC) words, Bamford-Kowel-Bench Speech in Noise test (BKB-SIN), Abbreviated Profile of Hearing Aid Benefit (APHAB), and unaided hearing thresholds in the implanted ear were compared to baseline measures obtained using a personal CHA. Changes in thresholds were observed from pre- to 12-month postoperative assessments. CNC word scores decreased (within 10%), and the BKB-SIN showed no change from pre- to 12-month postoperative time points. The APHAB revealed improvement. Findings suggest no difference in performance between an appropriately fit CHA and the AMEI at 12 months. This study indicates AMEIs have the potential to help individuals who choose not to use CHAs.

Novel candidate genes for cholesteatoma in chronic otitis media.

Cholesteatoma is a rare and benign disease, but its propensity to cause erosive damage through uninhibited growth can be detrimental to hearing and health. Prior reports indicated a genetic component to pathogenesis in at least a subset of patients. In this study, we aimed to identify rare DNA variants in affected patients. The salivary DNA of six patients whose middle ear tissues were obtained during tympanoplasty/mastoidectomy surgeries were submitted for exome sequencing. Tissue samples from the same patients were previously submitted for mRNA sequencing and analyzed for differentially expressed genes (DEGs). From the generated exome sequence data, rare predicted-to-be-damaging variants were selected within previously identified DEGs, and the candidate genes within which these rare variants lie were used for network analysis. Exome sequencing of six DNA samples yielded 5,078 rare variants with minor allele frequency <.001. A total of 510 variants were predicted to be deleterious and 52 were found to lie within previously identified DEGs. After selecting variants based on quality control measures, 12 variants were identified all from one pediatric patient. Network analysis identified ten significant cellular pathways, including protein transport, viral process, regulation of catalytic activity and cell cycle, and apoptotic and rhythmic processes. We hypothesize that the candidate genes identified in this study may be part of key signaling pathways during the mucosal response to middle ear infection. The occurrence of multiple rare variants may play a role in earlier onset of cholesteatoma formation in chronic otitis media.

The Outcome of Cochlear Implantations in Deaf-Blind Patients: A Multicenter Observational Study.

OBJECTIVE: This multicenter study aimed to evaluate the auditory and speech outcomes of cochlear implantation (CI) in deaf-blind patients compared with deaf-only patients. STUDY DESIGN: Retrospective cohort study. SETTING: Multiple cochlear implant centers. PATIENTS: The current study was conducted on 17 prelingual deaf-blind children and 12 postlingual deaf-blind adults who underwent CI surgery. As a control group, 17 prelingual deaf children and 12 postlingual deaf adults were selected. INTERVENTION: Cochlear implantation. MAIN OUTCOME MEASURES: Auditory and linguistic performances in children were assessed using the categories of auditory performance (CAP) and Speech Intelligibility Rating (SIR) scales, respectively. The word recognition score (WRS) was also used to measure speech perception ability in adults. The mean CAP, SIR, and WRS cores were compared between the deaf-only and deaf-blind groups before CI surgery and at "12 months" and "24 months" after device activation. Cohen's d was used for effect size estimation. RESULTS: We found no significant differences in the mean CAP and SIR scores between the deaf-blind and deaf-only children before the CI surgery. For both groups, SIR and CAP scores improved with increasing time after the device activation. The mean CAP scores in the deaf-only children were either equivalent or slightly higher than those of the deaf-blind children at "12 months post-CI" (3.94 ± 0.74 vs 3.24 ± 1.25; mean difference score, 0.706) and "24 months post-CI" (6.01 ± 0.79 vs 5.47 ± 1.06; mean difference score, 0.529) time intervals, but these differences were not statistically significant. The SIR scores in deaf-only implanted children were, on average, 0.870 scores greater than the deaf-blind children at "12 months post-CI" (2.94 ± 0.55 vs 2.07 ± 1.4; p = 0.01, d = 0.97) and, on average, 1.067 scores greater than deaf-blind children at "24 months post-CI" (4.35 ± 0.49 vs 3.29 ± 1.20; p = 0.002; d = 1.15) time intervals. We also found an improvement in WRS scores from the "preimplantation" to the "12-month post-CI" and "24-month post-CI" time intervals in both groups. Pairwise comparisons indicated that the mean WRS in the deaf-only adults was, on average, 10.61% better than deaf-blind implanted adults at "12 months post-CI" (62.33 ± 9.09% vs 51.71 ± 10.73%, p = 0.034, d = 1.06) and, on average, 15.81% better than deaf-blind adults at "24-months post-CI" (72.67 ± 8.66% vs 56.8 ± 9.78%, p = 0.002, d = 1.61) follow-ups. CONCLUSION: Cochlear implantation is a beneficial method for the rehabilitation of deaf-blind patients. Both deaf-blind and deaf-only implanted children revealed similar auditory performances. However, speech perception ability in deaf-blind patients was slightly lower than the deaf-only patients in both children and adults.

Round Window Stimulation of the Cochlea.

Mixed hearing loss associated with a sensorineural component and an impaired conductive mechanism for sound from the external ear canal to the cochlea represents a challenge for rehabilitation using either surgery or traditional hearing amplification. Direct stimulations of the ossicular chain and the round window (RW) membrane have allowed an improved hearing in this population. The authors review the developments in basic and clinical research that have allowed the exploration of new routes for inner ear stimulation. Similar changes occur in the electrophysiological measures in response to auditory stimulation through the traditional route and direct mechanical stimulation of the RW. The latter has proven to be very effective as a means of hearing rehabilitation in a group of patients with significant difficulties with hearing and communication.

The FUT2 Variant c.461G>A (p.Trp154*) Is Associated With Differentially Expressed Genes and Nasopharyngeal Microbiota Shifts in Patients With Otitis Media.

Otitis media (OM) is a leading cause of childhood hearing loss. Variants in FUT2, which encodes alpha-(1,2)-fucosyltransferase, were identified to increase susceptibility to OM, potentially through shifts in the middle ear (ME) or nasopharyngeal (NP) microbiotas as mediated by transcriptional changes. Greater knowledge of differences in relative abundance of otopathogens in carriers of pathogenic variants can help determine risk for OM in patients. In order to determine the downstream effects of FUT2 variation, we examined gene expression in relation to carriage of a common pathogenic FUT2 c.461G>A (p.Trp154*) variant using RNA-sequence data from saliva samples from 28 patients with OM. Differential gene expression was also examined in bulk mRNA and single-cell RNA-sequence data from wildtype mouse ME mucosa after inoculation with non-typeable Haemophilus influenzae (NTHi). In addition, microbiotas were profiled from ME and NP samples of 65 OM patients using 16S rRNA gene sequencing. In human carriers of the FUT2 variant, FN1, KMT2D, MUC16 and NBPF20 were downregulated while MTAP was upregulated. Post-infectious expression in the mouse ME recapitulated these transcriptional differences, with the exception of Fn1 upregulation after NTHi-inoculation. In the NP, Candidate Division TM7 was associated with wildtype genotype (FDR-adj-p=0.009). Overall, the FUT2 c.461G>A variant was associated with transcriptional changes in processes related to response to infection and with increased load of potential otopathogens in the ME and decreased commensals in the NP. These findings provide increased understanding of how FUT2 variants influence gene transcription and the mucosal microbiota, and thus contribute to the pathology of OM.

Round window membrane implantation with an active middle ear implant: a study of the effects on the performance of round window exposure and transducer tip diameter in human cadaveric temporal bones.

OBJECTIVES: To assess the importance of 2 variables, transducer tip diameter and resection of the round window (RW) niche, affecting the optimization of the mechanical stimulation of the RW membrane with an active middle ear implant (AMEI). MATERIALS AND METHODS: Ten temporal bones were prepared with combined atticotomy and facial recess approach to expose the RW. An AMEI stimulated the RW with 2 ball tip diameters (0.5 and 1.0 mm) before and after the resection of the bony rim of the RW niche. The RW drive performance, assessed by stapes velocities using laser Doppler velocimetry, was analyzed in 3 frequency ranges: low (0.25-1 kHz), medium (1-3 kHz) and high (3-8 kHz). RESULTS: Driving the RW produced mean peak stapes velocities (H(EV)) of 0.305 and 0.255 mm/s/V at 3.03 kHz, respectively, for the 1- and 0.5-mm tips, with the RW niche intact. Niche drilling increased the H(EV) to 0.73 and 0.832 mm/s/V for the 1- and 0.5-mm tips, respectively. The tip diameter produced no difference in output at low and medium frequencies; however, the 0.5-mm tip was 5 and 6 dB better than the 1-mm tip at high frequencies before and after niche drilling, respectively. Drilling the niche significantly improved the output by 4 dB at high frequencies for the 1-mm tip, and by 6 and 10 dB in the medium- and high-frequency ranges for the 0.5-mm tip. CONCLUSION: The AMEI was able to successfully drive the RW membrane in cadaveric temporal bones using a classical facial recess approach. Stimulation of the RW membrane with an AMEI without drilling the niche is sufficient for successful hearing outputs. However, the resection of the bony rim of the RW niche significantly improved the RW stimulation at medium and higher frequencies. Drilling the niche enhances the exposure of the RW membrane and facilitates positioning the implant tip.

Implantable Hearing Aids: Where are we in 2020?

Beginning in the late 20th century, implantable hearing aids were developed and used as an alternative for individuals who were unable to tolerate conventional hearing aids. Since that time, several devices have been developed, with four currently remaining on the international market (Med-el Vibrant Soundbridge, Envoy Esteem, Ototronix MAXUM, and Cochlear Carina). This review will briefly examine the history of middle ear implant development, describe current available devices, evaluate the benefits and limits of the technology, and consider the future directions of research in the field of implantable hearing aids.

Multi-omic studies on missense PLG variants in families with otitis media.

Otitis media (OM), a very common disease in young children, can result in hearing loss. In order to potentially replicate previously reported associations between OM and PLG, exome and Sanger sequencing, RNA-sequencing of saliva and middle ear samples, 16S rRNA sequencing, molecular modeling, and statistical analyses including transmission disequilibrium tests (TDT) were performed in a multi-ethnic cohort of 718 families and simplex cases with OM. We identified four rare PLG variants c.112A > G (p.Lys38Glu), c.782G > A (p.Arg261His), c.1481C > T (p.Ala494Val) and c.2045 T > A (p.Ile682Asn), and one common variant c.1414G > A (p.Asp472Asn). However TDT analyses for these PLG variants did not demonstrate association with OM in 314 families. Additionally PLG expression is very low or absent in normal or diseased middle ear in mouse and human, and salivary expression and microbial α-diversity were non-significant in c.1414G > A (p.Asp472Asn) carriers. Based on molecular modeling, the novel rare variants particularly c.782G > A (p.Arg261His) and c.2045 T > A (p.Ile682Asn) were predicted to affect protein structure. Exploration of other potential disease mechanisms will help elucidate how PLG contributes to OM susceptibility in humans. Our results underline the importance of following up findings from genome-wide association through replication studies, preferably using multi-omic datasets.

Identification of Novel Genes and Biological Pathways That Overlap in Infectious and Nonallergic Diseases of the Upper and Lower Airways Using Network Analyses.

Previous genetic studies on susceptibility to otitis media and airway infections have focused on immune pathways acting within the local mucosal epithelium, and outside of allergic rhinitis and asthma, limited studies exist on the overlaps at the gene, pathway or network level between the upper and lower airways. In this report, we compared [1] pathways identified from network analysis using genes derived from published genome-wide family-based and association studies for otitis media, sinusitis, and lung phenotypes, to [2] pathways identified using differentially expressed genes from RNA-sequence data from lower airway, sinus, and middle ear tissues, in particular cholesteatoma tissue compared to middle ear mucosa. For otitis media, a large number of genes (n = 1,806) were identified as differentially expressed between cholesteatoma and middle ear mucosa, which in turn led to the identification of 68 pathways that are enriched in cholesteatoma. Two differentially expressed genes CR1 and SAA1 overlap in middle ear, sinus, and lower airway samples and are potentially novel genes for otitis media susceptibility. In addition, 56 genes were differentially expressed in both tissues from the middle ear and either sinus or lower airways. Pathways that are common in upper and lower airway diseases, whether from published DNA studies or from our RNA-sequencing analyses, include chromatin organization/remodeling, endocytosis, immune system process, protein folding, and viral process. Taken together, our findings from genetic susceptibility and differential tissue expression studies support the hypothesis that the unified airway theory wherein the upper and lower respiratory tracts act as an integrated unit also applies to infectious and nonallergic airway epithelial disease. Our results may be used as reference for identification of genes or pathways that are relevant to upper and lower airways, whether common across sites, or unique to each disease.

Otologics fully implantable hearing system: Phase I trial 1-year results.

OBJECTIVE: To assess the safety of the Otologics fully implantable hearing system after 1 year of use in a Phase I clinical trial. STUDY DESIGN: Repeated-measures within-subjects design. SETTING: Procedures were performed in a variety of facilities, including a university, military, and private hospital's ambulatory surgical center and outpatient clinical audiologic test facilities. PATIENTS: Adult patients with bilateral moderate to severe sensorineural hearing loss. INTERVENTION(S): Surgical insertion of this prosthesis included an atticotomy to expose the incus, securing the transducer to the mastoid bone, attaching the transducer tip to the incus via insertion into a laser-drilled hole, and postauricular implantation of the microphone/battery/electronics capsule. MAIN OUTCOME MEASURE(S): Subjective patient benefit, aided sound field thresholds, and speech discrimination with the subject's own, appropriately fit, walk-in hearing aid(s) and the prosthesis were assessed. RESULTS: There were no pre-post-implant differences noted for bone conduction: slight differences were noted in the pre-post-implant air conduction results (p < 0.05). These differences were attributed to the healing process and reversed to almost preimplant assessment levels by the third-month evaluation. Pure-tone averages and monaural word recognition scores were slightly better for the walk-in-aided condition (p < 0.05), whereas the patient benefit scales favored the postoperative implant-aided conditions.Adverse effects of the implant were encountered on 14 occasions after the implantation of the 20 subjects. With the exception of partial device extrusions (that occurred later), all were rectified by the time of initial activation. At the 12-month data collection point, problems that had been encountered by subjects included 1) partial device extrusion (3 subjects), necessitating explantation in 2; 2) loss of external communication (2 subjects), resulting in 1 explantation; and 3) increased charging times beyond 1.5 hours (7), resulting in 3 explantations and 2 patients not using their device while awaiting explantation. CONCLUSION: Phase I trial results provide evidence that this fully implantable device can provide sound amplification to sensorineural hearing loss patients, with performance results similar to the patients' walk-in hearing aids.

Reliability of vestibular evoked myogenic potentials in healthy subjects.

OBJECTIVE: To analyze test-retest reliability of vestibular evoked myogenic potential (VEMP) responses with and without the use of electromyography (EMG) monitoring in people with normal audiovestibular function. PATIENTS: Twenty adult volunteers with no history of ear disease, normal otoscopic examination, normal pure-tone audiometry thresholds, and normal tympanograms. INTERVENTIONS: Prospective evaluation of VEMP responses with and without the use of EMG monitoring in 2 separate sessions 1 to 4 weeks apart. MAIN OUTCOME MEASURES: Threshold repeatability, p13 and n23 latency, p13-n23 interlatency, and interamplitude and interaural amplitude difference from the first and the second sessions were assessed via the intraclass correlation coefficient. RESULTS: Test-retest reliability of p13-n23 interamplitude was found to be excellent, and the reliability of threshold and latency was found to be fair to good (with the exception of poor reliability for p13 latency in the EMG monitoring condition). CONCLUSION: Overall, VEMP response parameters were found to have fair to good test-retest reliability. The intraclass correlation coefficient value for amplitude was found to be more reliable than latency, with the latency of n23 more reliable than the latency of p13. Clinicians should consider these findings when interpreting VEMP responses. Maintenance of symmetric head rotation with and without EMG monitoring produced reliably reproducible results, the VEMP amplitude being the best criteria.

Lateral Semicircular Canal Pressures During Cochlear Implant Electrode Insertion: a Possible Mechanism for Postoperative Vestibular Loss.

HYPOTHESIS: Insertion of cochlear implant electrodes generates transient pressure spikes within the vestibular labyrinth equivalent to high-intensity acoustic stimuli. BACKGROUND: Though cochlear implant (CI) surgery is regarded as having low risk of impacting the vestibular system, several studies have documented changes in vestibular function after implantation. The mechanism of these changes is not understood. We have previously established that large, potentially damaging pressure transients can be generated in the cochlea during electrode insertion, but whether pressure transients occur within the vestibular labyrinth has yet to be determined. Here, we quantify the exposure of the vestibular system to potentially damaging pressure transients during CI surgery. METHODS: Five human cadaveric heads were prepared with an extended facial recess and implanted sequentially with eight different CI electrode styles via a round window approach. Fiber-optic sensors measured intralabyrinthine pressures in scala vestibuli, scala tympani, and the lateral semicircular canal during insertions. RESULTS: Electrode insertion produced a range of high-intensity pressure spikes simultaneously in the cochlea and lateral semicircular canal with all electrodes tested. Pressure transients recorded were found to be significantly higher in the vestibular labyrinth than the cochlea and occurred at peak levels known to cause acoustic trauma. CONCLUSION: Insertion of CI electrodes can produce transients in intralabyrinthine fluid pressure levels equivalent to high-intensity, impulsive acoustic stimuli. Results from this investigation affirm the importance of atraumatic surgical techniques and suggest that in addition to the cochlea, the vestibular system is potentially exposed to damaging fluid pressure waves during cochlear implantation.

Intracochlear Pressures in Simulated Otitis Media With Effusion: A Temporal Bone Study.

HYPOTHESIS: Simulated otitis media with effusion reduces intracochlear pressures comparable to umbo velocity. BACKGROUND: Otitis media with effusion is a common cause of temporary hearing loss, particularly in children, producing deficits of 30 to 40 dB. Previous studies measured the effects of simulated effusion on ossicular mechanics; however, no studies have measured cochlear stimulation directly. Here, we compare pressures in the scala vestibuli and tympani to umbo velocity, before and after induction of simulated effusion in cadaveric human specimens. METHODS: Eight cadaveric, hemi-cephalic human heads were prepared with complete mastoidectomies. Intracochlear pressures were measured with fiber optic pressure probes, and umbo velocity measured via laser Doppler vibrometry (LDV). Stimuli were pure tones (0.1-14 kHz) presented in the ear canal via a custom speculum sealed with a glass cover slip. Effusion was simulated by filling the mastoid cavity and middle ear space with water. RESULTS: Acoustic stimulation with middle ear effusion resulted in decreased umbo velocity up to ∼26 dB, whereas differential pressure (PDiff) at the base of the cochlea decreased by only ∼16 dB. CONCLUSION: Simulating effusion leads to a frequency-dependent reduction in intracochlear sound pressure levels consistent with audiological presentation and prior reports. Results reveal that intracochlear pressure measurements (PSV and PST) decrease less than expected, and less than the decrease in PDiff. The observed decrease in umbo velocity is greater than in the differential intracochlear pressures, suggesting that umbo velocity overestimates the induced conductive hearing loss. These results suggest that an alternate sound conduction pathway transmits sound to the inner ear during effusion.

Anatomical vibrations that implantable microphones must overcome.

HYPOTHESIS: The goal of this study was to measure the tissue vibration amplitude that would be associated with an implantable microphone. BACKGROUND: Totally implantable hearing devices have been desired by the hard-of-hearing community for some time. However, an implanted microphone must pick up desired acoustic signals in the presence of undesired signals, including vibration. To design an effective microphone, the level of tissue vibrations originating from anatomical sources and the implanted transducer must be understood. METHODS: Using a laser Doppler vibrometer and an accelerometer, tissue vibrations were measured under the following conditions: (1) Normal control subjects during vocalization (n=4); (2) Vocalization and biological sounds measured on cranium and in soft tissue on normal subjects (n=6); (3) Transducer vibration measured on Otologics semi-implantable hearing device wearer (n=1) and human cadavers (n=4 ears). RESULTS: Anatomical noise vibrations are 20 to 25 dB greater in soft tissue for frequencies less than 1,000 Hz than on the cranium, whereas vibrations due to implanted transducers are 20 to 25 dB greater on the cranium than in soft tissue inferior to the mastoid. Chewing vibrations are 10 to 15 dB greater than vocalization on the mastoid. Mastoid vibration levels measured in patients are equivalent to those in cadavers. Vibration levels do not vary significantly with respect to location on the cranium next to the pinna. CONCLUSION: The greatest anatomical vibrations that an implanted microphone must overcome are because of vocalization in the soft tissue inferior to the mastoid and chewing vibrations on the mastoid. A human cadaver is an appropriate model for transducer cranial vibration studies. If the implantable microphone is placed on the cranium near the pinna, it makes little difference with regard to actual location.

U.S. Phase I preliminary results of use of the Otologics MET Fully-Implantable Ossicular Stimulator.

OBJECTIVES: The safety of the Otologics Fully-Implantable MET Ossicular Stimulator was assessed in adult patients with bilateral moderate to severe sensorineural hearing loss. METHODS: Surgical implantation of the ossicular stimulator was performed. A repeated-measure, within-subjects design assessed safety and aided sound field thresholds and speech performances with the subject's own, appropriately fitted, walk-in hearing aid(s) and the Otologics Fully-Implantable MET Ossicular Stimulator. RESULTS: Twenty patients were implanted and activated as part of the Phase I clinical trial. Results demonstrated 10-20 dB of functional gain across audiometric frequencies. Pure tone averages and monaural word recognition scores were slightly better for the walk-in-aided condition, while patient benefit scales favored the postoperative implant-aided conditions. CONCLUSION/SIGNIFICANCE: Although monaural word scores and aided thresholds favored the walk-in-aided condition, preliminary results indicate that the Otologics MET Fully-Implantable Ossicular Stimulator is an alternative to currently available hearing aids in patients with sensorineural hearing loss.

Intraoperative ossicular loading with the Otologics fully implantable hearing device.

CONCLUSIONS: Use of the recently introduced intraoperative loading instrumentation during surgery improves the coupling efficiency and consistency of a fully implantable hearing device to the ossicles and ultimately leads to better patient performance with the device. BACKGROUND: Patient performance with an implantable hearing device is dependent on effective coupling of the implant to the middle ear ossicles. New intraoperative instrumentation aids the surgeon in coupling the implantable hearing device and consistently optimizes patient performance. MATERIALS AND METHODS: The middle ear transfer function for the Otologics MET Ossicular Stimulator (METF(MET)) is a measure of transducer coupling efficiency, defined as acoustic threshold (in dB HL) minus implant threshold (in dB MET). This transfer function was measured in the Otologics US Phase I Semi-Implantable Clinical Trial without intraoperative loading instrumentation and in the Otologics US Phase I Fully Implantable Clinical Trial with intraoperative loading instrumentation. The same operative techniques and transducer design were used in both studies. The theory of operation and surgical technique for using this instrumentation are described. RESULTS: In the semi-implantable clinical trials, METF(MET) was -10 to -15 dB for frequencies above 1 kHz, and dropped to -15 to -20 dB for lower frequencies. Fully implantable clinical trial results were 10-20 dB better than the semi-implantable trial results, with less variability at all frequencies. These findings indicate more consistent and better coupling efficiency of the transducer to the ossicles.

Stapes displacement and intracochlear pressure in response to very high level, low frequency sounds.

The stapes is held in the oval window by the stapedial annular ligament (SAL), which restricts total peak-to-peak displacement of the stapes. Previous studies have suggested that for moderate (<130 dB SPL) sound levels intracochlear pressure (PIC), measured at the base of the cochlea far from the basilar membrane, increases directly proportionally with stapes displacement (DStap), thus a current model of impulse noise exposure (the Auditory Hazard Assessment Algorithm for Humans, or AHAAH) predicts that peak PIC will vary linearly with DStap up to some saturation point. However, no direct tests of DStap, or of the relationship with PIC during such motion, have been performed during acoustic stimulation of the human ear. In order to examine the relationship between DStap and PIC to very high level sounds, measurements of DStap and PIC were made in cadaveric human temporal bones. Specimens were prepared by mastoidectomy and extended facial recess to expose the ossicular chain. Measurements of PIC were made in scala vestibuli (PSV) and scala tympani (PST), along with the SPL in the external auditory canal (PEAC), concurrently with laser Doppler vibrometry (LDV) measurements of stapes velocity (VStap). Stimuli were moderate (∼100 dB SPL) to very high level (up to ∼170 dB SPL), low frequency tones (20-2560 Hz). Both DStap and PSV increased proportionally with sound pressure level in the ear canal up to approximately ∼150 dB SPL, above which both DStap and PSV showed a distinct deviation from proportionality with PEAC. Both DStap and PSV approached saturation: DStap at a value exceeding 150 µm, which is substantially higher than has been reported for small mammals, while PSV showed substantial frequency dependence in the saturation point. The relationship between PSV and DStap remained constant, and cochlear input impedance did not vary across the levels tested, consistent with prior measurements at lower sound levels. These results suggest that PSV sound pressure holds constant relationship with DStap, described by the cochlear input impedance, at these, but perhaps not higher, stimulation levels. Additionally, these results indicate that the AHAAH model, which was developed using results from small animals, underestimates the sound pressure levels in the cochlea in response to high level sound stimulation, and must be revised.