What is the current status of care by neuro-otology specialists in Switzerland-A national survey.

Background: Vertigo and dizziness are frequent presenting symptoms in the emergency department and in outpatient centers. While the majority of dizzy patients are evaluated by primary care physicians, specialists are often involved in the diagnostic workup. We aimed to gain more insights into the role of specialists in the care of dizzy patients. Materials and methods: Board-certified neurologists and ear-nose-throat (ENT) physicians working in Switzerland were invited to participate in an online survey. Descriptive statistical analyses were performed, and prospectively defined hypotheses were assessed using correlation analyses. Results: All 111 participating specialists (neurologists = 62; ENT specialists = 49) were familiar with testing for posterior canal benign paroxysmal positional vertigo (BPPV), and 66% regularly applied provocation maneuvers for suspected lateral canal BPPV. Reposition maneuvers for posterior (99%) and lateral (68%) canals were frequently performed. ENT physicians were familiar with lateral canal BPPV repositioning maneuvers significantly more often than neurologists (84 vs. 56%, p ≤ 0.012). Specialists strongly agreed that performing the head impulse test (86%) and looking for deficient eccentric gaze holding (82%) are important. Compared to neurologists, significantly fewer ENT physicians indicated ordering brain MRI in acutely dizzy patients (OR = 0.33 [0.16-0.067], p = 0.002) and physical therapy in patients with acute (50 vs. 20%, p = 0.005) or episodic/chronic dizziness (78 vs. 50%, p = 0.003). Conclusion: We found substantial differences in the care of dizzy patients by neurologists and ENT physicians. This underlines the need for a standardized, guideline-oriented diagnostic workup and treatment across specialties. Dedicated training for performing lateral canal BPPV repositioning maneuvers should be prioritized for neurologists. Similarly, physical therapy should be considered more often by ENT physicians.

Needs and supporting tools for primary care physicians to improve care of patients with vertigo and dizziness: a national survey.

Background: The diagnostic workup and treatment decisions for vertigo or dizziness in primary care can be challenging due to the broad range of possible causes and limited time and expertise of physicians. This can lead to delays in treatment and unnecessary tests. We aimed to identify the unmet needs of primary care physicians (PCPs) and strategies to improve care for dizzy patients. Materials and methods: An online survey was conducted among board-certified PCPs in Switzerland to explore needs in caring for dizzy patients and potential educational approaches. Results: Based on responses from 152 participating PCPs, satisfaction and confidence were higher in diagnosing (82%) and treating (76%) acute dizziness compared to episodic/chronic cases (63 and 59%, respectively). Younger PCPs had lower diagnostic yield and confidence. Areas for improvement in specialist interactions included communication between physicians (23%/36%; always/often true), shorter waiting times for consultations (19%/40%), more detailed feedback (36%/35%), and consistent patient back referrals (31%/30%). PCPs expressed interest in hands-on courses, workshops, practical guidelines, web-based algorithms, and digital tools such as printed dizzy diaries and apps for follow-up. Conclusion: Enhanced dialog between PCPs and specialists is crucial to address the most common unmet needs. Reducing waiting times for referrals and providing clear instructions to specialists for triage are essential. The findings from this survey will guide the development of tools to improve the diagnosis and treatment of dizzy patients. Younger PCPs, who face higher diagnostic uncertainty, should be prioritized for educational approaches such as hands-on courses, workshops, and practical recommendations.

What is the current status of primary care in the diagnosis and treatment of patients with vertigo and dizziness in Switzerland? A national survey.

Background: Vertigo and dizziness are among the most frequent presenting symptoms in the primary care physicians' (PCPs) office. With patients facing difficulties in describing their complaints and clinical findings often being subtle and transient, the diagnostic workup of the dizzy patient remains challenging. We aimed to gain more insights into the current state of practice in order to identify the limitations and needs of the PCPs and define strategies to continuously improve their knowledge in the care of the dizzy patient. Materials and methods: Board-certified PCPs working in Switzerland were invited to participate in an online survey. A descriptive statistical analysis was performed, and prospectively defined hypotheses were assessed using regression analyses. Results: A vast majority of participating PCPs (n = 152) were familiar with the key questions when taking the dizzy patient's history and with performing provocation/repositioning maneuvers when posterior-canal benign paroxysmal positional vertigo (BPPV) was suspected (91%). In contrast, strong agreement that performing the alternating cover test (21%), looking for a spontaneous nystagmus with fixation removed (42%), and performing the head-impulse test (47%) were important was considerably lower, and only 19% of PCPs were familiar with lateral-canal BPPV treatment. No specific diagnosis could be reached in substantial fractions of patients with acute (35% [25; 50%], median [inter-quartile range]) and episodic/chronic (50% [40; 65.8%]) dizziness/vertigo. Referral to specialists was higher in patients with episodic/chronic dizziness than in acutely dizzy patients (50% [20.3; 75] vs. 30% [20; 50]), with younger PCPs (aged 30-40 years) demonstrating significantly increased odds of referral to specialists (odds ratio = 2.20 [1.01-4.81], p = 0.048). Conclusion: The assessment of dizzy patients takes longer than that of average patients in most primary care practices. Many dizzy patients remain undiagnosed even after a thorough examination, highlighting the challenges faced by PCPs and potentially leading to frequent referrals to specialists. To address this, it is crucial to promote state-of-the-art neuro-otological examination and treatment techniques that are currently neglected by most PCPs, such as "HINTS" and lateral-canal BPPV treatment. This can help reduce referral rates allowing more targeted treatment and referrals.

The Effects of Vibro-Tactile Biofeedback Balance Training on Balance Control and Dizziness in Patients with Persistent Postural-Perceptual Dizziness (PPPD).

BACKGROUND: Patients with persistent postural-perceptual dizziness (PPPD) frequently report having problems with balance control. Artificial systems providing vibro-tactile feedback (VTfb) of trunk sway to the patient could aid recalibration of "falsely" programmed natural sensory signal gains underlying unstable balance control and dizziness. Thus, the question we examine, retrospectively, is whether such artificial systems improve balance control in PPPD patients and simultaneously reduce the effects of dizziness on their living circumstances. Therefore, we assessed in PPPD patients the effects of VTfb of trunk sway on balance control during stance and gait tests, and on their perceived dizziness. METHODS: Balance control was assessed in 23 PPPD patients (11 of primary PPPD origin) using peak-to-peak amplitudes of trunk sway measured in the pitch and roll planes with a gyroscope system (SwayStar™) during 14 stance and gait tests. The tests included standing eyes closed on foam, walking tandem steps, and walking over low barriers. The measures of trunk sway were combined into a Balance Control Index (BCI) and used to determine whether the patient had a quantified balance deficit (QBD) or dizziness only (DO). The Dizziness Handicap Inventory (DHI) was used to assess perceived dizziness. The subjects first underwent a standard balance assessment from which the VTfb thresholds in eight directions, separated by 45 deg, were calculated for each assessment test based on the 90% range of the trunk sway angles in the pitch and roll directions for the test. A headband-mounted VTfb system, connected to the SwayStar™, was active in one of the eight directions when the threshold for that direction was exceeded. The subjects trained for 11 of the 14 balance tests with VTfb twice per week for 30 min over a total of 2 consecutive weeks. The BCI and DHI were reassessed each week and the thresholds were reset after the first week of training. RESULTS: On average, the patients showed an improved balance control in the BCI values after 2 weeks of VTfb training (24% p = 0.0001). The improvement was greater for the QBD patients than for the DO patients (26 vs. 21%), and greater for the gait tests than the stance tests. After 2 weeks, the mean BCI values of the DO patients, but not the QBD patients, were significantly less (p = 0.0008) than the upper 95% limit of normal age-matched reference values. A subjective benefit in balance control was spontaneously reported by 11 patients. Lower (36%), but less significant DHI values were also achieved after VTfb training (p = 0.006). The DHI changes were identical for the QBD and DO patients and approximately equal to the minimum clinical important difference. CONCLUSIONS: These initial results show, as far as we are aware for the first time, that providing VTfb of trunk sway to PPPD subjects yields a significant improvement in balance control, but a far less significant change in DHI-assessed dizziness. The intervention benefitted the gait trials more than the stance trials and benefited the QBD group of PPPD patients more than the DO group. This study increases our understanding of the pathophysiologic processes underlying PPPD and provides a basis for future interventions.

What neuro-otology specialists need for better care of dizzy patients: a national survey.

Background: A substantial fraction of dizzy patients are assessed by neurologists and ear-nose-throat (ENT) physicians. With the differential diagnosis being broad and often different specialties involved, we aimed to assess the interaction with generalists from the specialists' perspective to identify limitations and needs and to define strategies for improvement in patient care and education by the specialist. Methods: One hundred eleven board-certified neurologists (n = 62) and ENT physicians (n = 49) working in Switzerland participated in an online survey. Here, we focused on limitations faced in the diagnostic workup and treatment of the dizzy patient and potential strategies to improve the standard of care and the interaction between generalists and specialists. Descriptive statistical analyses were performed. We hypothesized that those specialists applying modern concepts in history-taking and bedside examination techniques reach a specific diagnosis more often and request fewer referrals. Results: Specialists indicated higher confidence in reaching a specific diagnosis for patients presenting with acute dizziness than episodic/chronic dizziness (80% vs. 60%) at the first consultation. Knowledge of the timing-and-trigger concept [odds ratio (OR) = 0.81 (0.67-0.98), p = 0.034], as well as of subtle oculomotor/vestibular signs [OR = 0.80 (0.68-0.94), p = 0.007] was predictive of the self-reported probability of reaching a specific diagnosis in patients with episodic/chronic dizziness, while no such differences were observed in the care of acutely dizzy patients. Further referrals of acutely dizzy patients were significantly higher in neurologists than in ENT physicians (17% vs. 10%, p < 0.001) and in specialists located in the Latin part of Switzerland [OR = 2.84 (1.63-4.93), p < 0.001], while this was not the case for patients with episodic/chronic dizziness. Identified unmet needs included regular communication between physicians (27%/53%; always/often true) and sufficiently detailed information on the previous workup from the referrals (27%/53%). Specialists expressed most interest in hands-on courses/workshops, webinars, and practical guidelines for education. Conclusion: In our survey, bedside state-of-the-art assessments were key in reducing the fraction of unclear dizzy cases. Several gaps were identified that should be addressed. Specifically, referring physicians should provide more comprehensive details regarding urgency, prior diagnostics, and treatment. Specifically, when promoting the knowledge of neurologists and ENT physicians, this should be preferentially done by offering a combination of hands-on courses and webinars.

Multicenter Study Investigating Foreign Language Acquisition at School in Children, Adolescents, and Young Adults With Uni- or Bilateral Cochlear Implants in the Swiss German Population.

OBJECTIVES: Evaluation of foreign language acquisition at school in cochlear implant patients. STUDY DESIGN: Multicenter cohort study. SETTING: CI centers. PATIENTS: One hundred twenty-five CI users (10-18 yr) in the German-speaking part of Switzerland were enrolled. Demographic data were obtained by means of written questionnaires. German-speaking children with mainstream foreign language tuition (English and/or French) were enrolled for further testing. The control group of normal-hearing individuals was matched on age, class, and number of foreign language lessons attended. RESULTS: Overall, 100 questionnaires were returned. The 12 CI users without foreign language learning attended special schools. CI users who attended foreign language classes had better German speech comprehension compared with those without foreign language tuition (89 versus 51%; p < 0.05). Thirty-one CI users of different grades were further tested. All (10/10) CI 6th graders attained the school objectives for both English reading and listening skills. French performance at 6th grade for reading was 3/7 and for listening only 1/7. There were 13 matched normal-hearing pairs for English and 10 for French. The total scores were on average 7% higher, with a statistical significance for English reading (p < 0.05). CONCLUSIONS: Almost 90% of CI children in Switzerland learn foreign language(s) at school. All the tested patients reached the current school objectives for English reading. The success rate for French was lower, especially regarding listening tasks. The 13 matched pairs with normal-hearing did not score substantially better.

Audiological monitoring in Swiss childhood cancer patients.

BACKGROUND: Full audiological monitoring is the best strategy to detect hearing loss early and to provide timely intervention in the absence of a clinical method of otoprotection. Full monitoring requires audiological evaluation before, and then during and after ototoxic cancer treatment. In a worldwide context of monitoring protocols that vary substantially, we analyzed the audiological monitoring of childhood cancer patients over the last decade across treatment centers in Switzerland. PROCEDURE: We retrospectively searched for audiological evaluations in all nine Swiss Pediatric Oncology Centers. We analyzed proportions of patients who had audiological monitoring and described type and timing of monitoring. We determined predictors of audiological monitoring using multivariable logistic regression and described time trends. RESULTS: We included 185 patients from the Swiss Childhood Cancer Registry diagnosed from 2005 to 2013 who had platinum chemotherapy and/or cranial radiation ≥30 Gray and who were alive at time of study. Less than half of children, 43%, had full audiological monitoring (before, during, and after treatment), while 72% were tested after cancer treatment. Nonstudy patients were less likely to have had monitoring in all phases of cancer treatment. Patients who received treatment with cisplatin or both platinum chemotherapy and cranial radiation were more likely to have had monitoring after treatment. Monitoring during and after treatment increased over the study period, but monitoring before treatment was insufficient in all time periods. CONCLUSIONS: Our population-based study indicates that audiological monitoring is insufficient in Switzerland, particularly for nonstudy patients. Clinicians must become more aware of the importance of full audiological monitoring.

In situ Probe Microphone Measurement for Testing the Direct Acoustical Cochlear Stimulator.

Hypothesis: Acoustical measurements can be used for functional control of a direct acoustic cochlear stimulator (DACS). Background: The DACS is a recently released active hearing implant that works on the principle of a conventional piston prosthesis driven by the rod of an electromagnetic actuator. An inherent part of the DACS actuator is a thin titanium diaphragm that allows for movement of the stimulation rod while hermetically sealing the housing. In addition to mechanical stimulation, the actuator emits sound into the mastoid cavity because of the motion of the diaphragm. Methods: We investigated the use of the sound emission of a DACS for intra-operative testing. We measured sound emission in the external auditory canal (PEAC) and velocity of the actuators stimulation rod (Vact) in five implanted ears of whole-head specimens. We tested the influence various positions of the loudspeaker and a probe microphone on PEAC and simulated implant malfunction in one example. Results: Sound emission of the DACS with a signal-to-noise ratio >10 dB was observed between 0.5 and 5 kHz. Simulated implant misplacement or malfunction could be detected by the absence or shift in the characteristic resonance frequency of the actuator. PEAC changed by <6 dB for variations of the microphone and loudspeaker position. Conclusion: Our data support the feasibility of acoustical measurements for in situ testing of the DACS implant in the mastoid cavity as well as for post-operative monitoring of actuator function.

[Benefit of Bimodal Stimulation with Cochlear Implant and Hearing Aid in Elderly Patients]. / Cochlea-Implantation ab dem 70. Lebensjahr ­ Nutzen der bimodalen Versorgung mit Hörgerät und CI.

Cochlear implant (CI) surgery is the standard of care for postlingual deafness in adults. A hearing aid (HA) for the non-implanted ear is normally used if residual hearing is available. There is limited data on bimodal stimulation in elderly patients. We compare the outcome of bimodal stimulation and analyzed the correlation of bimodal benefit and residual hearing in elderly patients. 22 patients≥70 years were implanted with a single-sided CI from 2002 till 2014. 17 patients use a HA on the non-implanted ear (bimodal). In a retrospective chart review we analyzed the audiological benefit (pure tone average, speech recognition). Time to follow-up was 6 month to 12 years. The subjective benefit was assessed using a structured questionnaire. The speech recognition (monosyllabic word testing in quiet @ 65 dB SPL) showed a score of 61% in bimodal condition vs. 53% with CI alone (p=0.35). There was no statistically significant correlation between residual hearing in the lower frequencies (250 Hz, 500 Hz and 1 kHz) and bimodal benefit. Most elderly patients benefit from bimodal stimulation. In quiet and in comparison with CI alone, most patients showed some improvement in word recognition scores using bimodal fitting, and all of them were using the contralateral hearing aid all day long. Postlingual deafened elderly patients fitted with a unilateral CI require a short rehabilitation period. In case of contralateral hearing aid fitting, regular control of the hearing aid should not be overlooked.

Single-Center Study Investigating Foreign Language Acquisition at School in Children, Adolescents, and Young Adults With Uni- or Bilateral Cochlear Implants in the Swiss German Population.

OBJECTIVE: To evaluate foreign language acquisition at school in cochlear implant patients. STUDY DESIGN: Cohort study. SETTING: CI center. PATIENTS: Forty three cochlear implants (CI) patients (10-18 yr) were evaluated. CI nonusers and patients with CI-explantation, incomplete datasets, mental retardation, or concomitant medical disorders were excluded. INTERVENTION(S): Additional data (type of schooling, foreign language learning, and bilingualism) were obtained with questionnaires. German-speaking children with foreign tuition language (English and/or French) at school were enrolled for further testing. MAIN OUTCOME MEASURE(S): General patient data, auditory data, and foreign language data from both questionnaires and tests were collected and analyzed. RESULTS: Thirty seven out of 43 questionnaires (86%) were completed. Sixteen (43%) were in mainstream education. Twenty-seven CI users (73%) have foreign language learning at school. Fifteen of these were in mainstream education (55%), others in special schooling. From 10 CI users without foreign language learning, one CI user was in mainstream education (10%) and nine patients (90%) were in special schooling. Eleven German-speaking CI users were further tested in English and six additionally in French. For reading skills, the school objectives for English were reached in 7 of 11 pupils (64%) and for French in 3 of 6 pupils (50%). For listening skills, 3 of 11 pupils (27%) reached the school norm in English and none in French. CONCLUSIONS: Almost 75% of our CI users learn foreign language(s) at school. A small majority of the tested CI users reached the current school norm for in English and French in reading skills, whereas for hearing skills most of them were not able to reach the norm.

Predisposing factors for adverse skin reactions with percutaneous bone anchored hearing devices implanted with skin reduction techniques.

We present an analysis of adverse events after implantation of bone anchored hearing device in our patient population with focus on individual risk factors for peri-implant skin reactions. The investigation involved a chart review of adult Baha patients (n = 179) with 203 Bahas implanted with skin reduction techniques between 1993 and 2009, a questionnaire (n = 97) and a free clinical examination (n = 47). Skin reactions were graded by severity from 0 (no skin reaction) to 4 (implant loss resulting from infection) according to Holgers. We analyzed the skin reaction rate (SRR) defined as the number of skin reactions per year and the worst Holgers grade (WHG), which indicates the grade of the worst skin reaction per implant. We defined 20 parameters including the demographic characteristics, surgery details, subjective benefits, handling and individual factors. The most frequent adverse events (85 %) were skin reactions. The average SRR was 0.426 per Baha year. Six parameters showed an association with the SRR or the WHG. The clinically most relevant factors are an elevated Body Mass Index (BMI, p = 0.02) and darker skin type (p = 0.03). The SRR increased with the distance between the tragus and the implant (p = 0.02). Regarding the identified risk factors, the SRR might be reduced by selecting a location for the implant near the pinna and by specific counseling regarding post-operative care for patients with darker skin type or an elevated Body Mass Index (BMI). Few of the factors analyzed were found to influence the SRR and WHG. Since most adverse skin reactions could be treated easily with local therapy, our results suggest that in adult patients, individual risk factors for skin reactions are not a contraindication for Baha implantation. Thus, patients can be selected purely on audiological criteria.

Lamb Temporal Bone as a Surgical Training Model of Round Window Cochlear Implant Electrode Insertion.

OBJECTIVE: The preservation of residual hearing in cochlear implantation opens the door for optimal functional results. This atraumatic surgical technique requires training; however, the traditional human cadaveric temporal bones have become less available or unattainable in some institutions. This study investigates the suitability of an alternative model, using cadaveric lamb temporal bone, for surgical training of atraumatic round window electrode insertion. INTERVENTION: A total of 14 lamb temporal bones were dissected for cochlear implantation by four surgeons. After mastoidectomy, visualization, and drilling of the round window niche, an atraumatic round window insertion of a Medel Flex24 electrode was performed. Electrode insertion depth and position were verified by computed tomography scans. MAIN OUTCOME MEASURE: All cochleas were successfully implanted using the atraumatic round window approach; however, surgical access through the mastoid was substantially different when compared human anatomy. The mean number of intracochlear electrode contacts was 6.5 (range, 4-11) and the mean insertion depth 10.4 mm (range, 4-20 mm), which corresponds to a mean angular perimodiolar insertion depth of 229 degrees (range 67-540°). Full insertion of the electrode was not possible because of the smaller size of the lamb cochlea in comparison to that of the human. CONCLUSION: The lamb temporal bone model is well suited as a training model for atraumatic cochlear implantation at the level of the round window. The minimally pneumatized mastoid as well as the smaller cochlea can help prepare a surgeon for difficult cochlear implantations. Because of substantial differences to human anatomy, it is not an adequate training model for other surgical techniques such as mastoidectomy and posterior tympanotomy as well as full electrode insertion.

Laser Doppler vibrometric assessment of middle ear motion in Thiel-embalmed heads.

HYPOTHESIS: Thiel-embalmed human whole head specimens represent an alternative model in middle ear research. BACKGROUND: Research into middle ear mechanics and the evaluation of active middle ear implants are generally performed on fresh human temporal bone specimens. A drawback of this method is the limited period during which the specimen can be used before tissue decay begins. Tissue conservation that preserves mechanical properties is desirable. METHODS: Using laser Doppler vibrometry, the movement of the tympanic membrane, stapes, and round window were measured in 23 ears from 15 human whole head specimens embalmed according to Thiel. The ears were acoustically stimulated through the intact external auditory canal. The measurement results were compared with data from the literature. RESULTS: The results were similar to those measured in living subjects and from fresh temporal bones, after excluding measurements with nontypical shapes or low amplitudes, that is, 9% for tympanic membrane, 38% for stapes, and 67% for round window. The best agreement was found for the tympanic membrane (mean difference between 0 and 5.2 dB) and for the stapes measurements (mean difference between 0 and 7.4 dB). Larger differences were found for the round window measurements (mean difference between 3 and 19 dB). For the stimulation levels used, the Thiel specimens behaved linearly in amplitude. The results remained reproducible for more than 20 hours in ambient air, and when the specimen was put back into Thiel solution, the measurements were stable for up to several months between measurements. CONCLUSION: Our results showed that the middle ears of Thiel-embalmed human whole head specimens can be used to study human middle ear mechanics; however, significant differences in some frequencies, particularly at the round window, have to be considered.

Molecular analysis of aquaporin genes 1 to 4 in patients with Menière's disease.

BACKGROUND: Menière's Disease (MD) is an episodic cochleovestibular dysfunction of unknown etiology, still lacking a specific test and therapy. The proposed theories on the pathophysiology include genetic factors and factors relating to inner ear homeostasis. Various aquaporins (AQP), water channels, expressed in the inner ear and the vestibular organ, are involved in homeostasis. Mutations in AQP genes could result in disturbed inner ear homeostasis and endolymphatic hydrops, and therefore be involved in the pathogenesis of MD. AIM: To search for mutations in AQP1 to 4 in patients suffering from MD. METHODS: In patients with definite MD, DNA was extracted from whole blood. The coding sequences of AQP1 to 4 were amplified by PCR reaction and sequenced. RESULTS: One sequence alteration, homozygous c.105G->C (conservative change without alteration of amino acid) in AQP3 was detected in 11 out of 34 patients but not in 100 control chromosomes. CONCLUSION: By itself the detected alteration is unlikely to play a role in the pathogenesis of MD. However, together with an additional modifying gene an effect can not be excluded. Additional regions (introns, splice-sites) and other genes involved in inner ear homeostasis need to be analyzed to identify a possible molecular alteration in MD.

Factors improving the vibration transfer of the floating mass transducer at the round window.

OBJECTIVES: With the placement of a floating mass transducer (FMT) at the round window, a new approach of coupling an implantable hearing system to the cochlea has been introduced. The aim of the present experimental study is to examine the influence of different ways of FMT placement at the round window on the vibration energy transfer to the cochlea. MATERIAL AND METHODS: Experiments were performed on 8 ears of human whole head specimens. A mastoidectomy and facial recess approach were performed to access the middle ear structures. Seven different conditions were compared, that is, a perpendicular or 90-degree rotated position of the FMT in the round window niche, overlaid or underlaid with connective tissue or with tight fixation and disrupted ossicular chain. The FMT was stimulated electrically and the movements at the FMT, the stapes head, and the promontory were measured using laser Doppler vibrometry. RESULTS: Vibration transmission to the cochlear fluids was best with the FMT placed perpendicular to the round window membrane and underlaid with connective tissue. The energy transfer to the inner ear was up to 45 dB higher compared with tight fixation condition, where the poorest energy transfer was found. Underlaying the FMT with connective tissue improved energy transfer even for a suboptimal orientation of the FMT. CONCLUSION: The way of coupling of the FMT to the round window has a substantial influence on the vibration transmission. Energy transfer to the inner ear is highest with the FMT placed in the round window and underlaid with tissue.

The floating mass transducer at the round window: direct transmission or bone conduction?

The round window placement of a floating mass transducer (FMT) is a new approach for coupling an implantable hearing system to the cochlea. We evaluated the vibration transfer to the cochlear fluids of an FMT placed at the round window (rwFMT) with special attention to the role of bone conduction. A posterior tympanotomy was performed on eleven ears of seven human whole head specimens. Several rwFMT setups were examined using laser Doppler vibrometry measurements at the stapes and the promontory. In three ears, the vibrations of a bone anchored hearing aid (BAHA) and an FMT fixed to the promontory (pFMT) were compared to explore the role of bone conduction. Vibration transmission to the measuring point at the stapes was best when the rwFMT was perpendicularly placed in the round window and underlayed with connective tissue. Fixation of the rwFMT to the round window exhibited significantly lower vibration transmission. Although measurable, bone conduction from the pFMT was much lower than that of the BAHA. Our results suggest that the rwFMT does not act as a small bone anchored hearing aid, but instead, acts as a direct vibratory stimulator of the round window membrane.

Distortion product otoacoustic emissions show exceptional resistance to noise exposure in MOLF/Ei mice.

Baseline distortion-product otoacoustic emissions (DPOAEs) at several primary-tone levels were compared between naive 2- to 3-month old inbred CBA/CaJ (CBA) and wild-derived MOLF/Ei (MOLF) mice. Only minor DPOAE differences were noted between the two strains and these differences were not systematic across frequency or test levels. These emission findings were consistent with earlier results on auditory brainstem response thresholds reported by others [Zheng et al., Hear. Res. 130 (1999) 94-107] thus suggesting that both CBA and MOLF strains have normal hearing. Subsequent episodes of over-exposure to a 105-dB SPL, octave-band noise centered at 10 kHz for 8 h revealed that MOLF DPOAEs were exceptionally resistant to the adverse aftereffects of excessive noise exposure as compared to CBA mice. Unlike the noise-exposure resistant inbred 129/SvEvTac strain, which has reduced baseline DPOAE levels especially at high frequencies, MOLF mice have normal DPOAEs making the interpretation of noise-exposure effects more straightforward.