Influence of the Intracranial Contents on the Head Motion under Bone Conduction.

INTRODUCTION: The mechanism of non-osseous bone conduction pathways, involving the intracranial contents (ICC) of the skull, is still not well understood. This study aims to investigate the influence of the ICC on the skull bone wave propagation, including dependence on stimulation location and coupling. METHODS: Three Thiel embalmed whole-head cadaver specimens were studied before and after the removal of the ICC. Stimulation was via the electromagnetic actuators from commercial bone conduction hearing aids. Osseous pathways were sequentially activated by mastoid, forehead and BAHA location stimulation via a 5-Newton steel headband or percutaneously implanted screw. Non-osseous pathways were activated by stimulation on the eye and dura via a 5-Newton steel headband and a custom-made pneumatic holder. Under each test condition, the 3D motion of the superior skull bone was monitored at ~200 points. RESULTS: The averaged response of the skull surface showed limited differences due to the removal of the ICC. In some isolated cases, the modal pattern on the skull surface showed a trend for an upshift (~1/2 octave) in the observed natural frequencies for drained heads. This was also consistent with an observed trend for an upshift in the transition frequency in the estimated deformation across the lateral surfaces of the temporal bones. Such changes were consistent with the expected reduction in mass and damping due to the absence of the ICC. CONCLUSION: Overall, the ICC affect to a limited extent the motion of the skull bone, with a limited trend for a reduction of its natural frequencies.

Intraoperative ultrasonography in microsurgical resection of vestibular schwannomas via retrosigmoid approach: surgical technique and proof-of-concept illustrative case series.

PURPOSE: Intraoperative ultrasonography (ioUS) is an established tool for the real-time intraoperative orientation and resection control in intra-axial oncological neurosurgery. Conversely, reports about its implementation in the resection of vestibular schwannomas (VS) are scarce. The aim of this study is to describe the role of ioUS in microsurgical resection of VS. METHODS: ioUS (Craniotomy Transducer N13C5, BK5000, B Freq 8 MHz, BK Medical, Burlington, MA, USA) is integrated into the surgical workflow according to a 4-step protocol (transdural preresection, intradural debulking control, intradural resection control, transdural postclosure). Illustrative cases of patients undergoing VS resection through a retrosigmoid approach with the use of ioUS are showed to illustrate advantages and pitfalls of the technique. RESULTS: ioUS allows clear transdural identification of the VS and its relationships with surgically relevant structures of the posterior fossa and of the cerebellopontine cistern prior to dural opening. Intradural ioUS reliably estimates the extent of tumor debulking, thereby helping in the choice of the right moment to start peripheral preparation and in the optimization of the extent of resection in those cases where subtotal resection is the ultimate goal of surgery. Transdural postclosure ioUS accurately depicts surgical situs. CONCLUSION: ioUS is a cost-effective, safe, and easy-to-use intraoperative adjunctive tool that can provide a significant assistance during VS surgery. It can potentially improve patient safety and reduce complication rates. Its efficacy on clinical outcomes, operative time, and complication rate should be validated in further studies.

Treatment of Acute Otitis Media with Inner Ear Involvement in Adults.

Inner ear involvement (IED) is a rare local complication of the very common acute otitis media (AOM). The most beneficial treatment for IED remains a matter of debate. The aim of this study is to analyze different treatment modalities based on hearing outcomes to contribute to the discussion of therapy for IED in AOM. This retrospective study includes 112 adult patients diagnosed with AOM with IED between 2000 and 2020. Patients either received conservative (systemic antibiotic and systemic steroid therapy), interventional (conservative plus myringotomy and tympanic tube) or operative (interventional plus antrotomy) treatment. Pre- and post-treatment pure tone audiometry was performed. The hearing outcome was compared, and hearing recovery was analyzed based on modified Siegel's criteria. The pre-treatment pure tone average (PTA) was significantly (p < 0.05) higher in the operative group than in the other groups. All treatment modalities led to a significant hearing improvement (p < 0.001). The pre- and post-treatment hearing loss was predominantly observed in high frequencies 2-4 kHz. The operative group showed the highest rate of complete hearing recovery. While all treatment modalities led to a significant improvement in hearing, the operative group showed the most beneficial hearing results in patients with high pre-treatment hearing loss. It remains to be shown if the findings in patients with high pre-treatment hearing loss can be generalized to patients with mild or moderate pre-treatment hearing loss.

Classification of Acoustic Hearing Preservation After Cochlear Implantation Using Electrocochleography.

The objective to preserve residual hearing during cochlear implantation has recently led to the use of intracochlear electrocochleography (ECochG) as an intraoperative monitoring tool. Currently, a decrease in the amplitude of the difference between responses to alternating-polarity stimuli (DIF response), predominantly reflecting the hair cell response, is used for providing feedback. Including other ECochG response components, such as phase changes and harmonic distortions, could improve the accuracy of surgical feedback. The objectives of the present study were (1) to compare simultaneously recorded stepwise intracochlear and extracochlear ECochG responses to 500 Hz tone bursts, (2) to explore patterns in features extracted from the intracochlear ECochG recordings relating to hearing preservation or hearing loss, and (3) to design support vector machine (SVM) and random forest (RF) classifiers of acoustic hearing preservation that treat each subject as a sample and use all intracochlear ECochG recordings made during electrode array insertion for classification. Forty subjects undergoing cochlear implant (CI) surgery at the Oslo University Hospital, St. Thomas' Hearing Implant Centre, or the University Hospital of Zurich were prospectively enrolled. In this cohort, DIF response amplitude decreases did not relate to postoperative acoustic hearing preservation. Exploratory analysis of the feature set extracted from the ECochG responses and preoperative audiogram showed that the features were not discriminative between outcome classes. The SVM and RF classifiers that were trained on these features could not distinguish cases with hearing loss and hearing preservation. These findings suggest that hearing loss following CI surgery is not always reflected in intraoperative ECochG recordings.

[Health-related quality of life in chronic otitis media-measurement methods and their application in surgical therapy]. / Gesundheitsbezogene Lebensqualität bei der chronischen Otitis media ­ Messmethoden und deren Anwendung bei chirurgischen Therapien.

BACKGROUND: Chronic otitis media (COM) can lead to significant impairment of health-related quality of life (HRQoL) due to symptoms such as otorrhea, pain, hearing loss, tinnitus, or dizziness. A systematic assessment of HRQoL in COM is becoming increasingly important as it complements (semi-)objective outcome parameters in clinical practice and research. HRQoL is measured by means of patient-reported outcome measures (PROMs). There are two disease-specific validated PROMs available for COM in German-the Chronic Otitis Media Outcome Test (COMOT-15) and the Zurich Chronic Middle Ear Inventory (ZCMEI-21)-which have become increasingly popular in recent years. OBJECTIVE: The purpose of this narrative review is to present the current state of research on measuring HRQoL in COM before and after surgical procedures. RESULTS AND CONCLUSION: Hearing is the most important factor influencing HRQoL in COM. Surgical procedures usually result in a clinically relevant improvement in HRQoL in COM with or without cholesteatoma. However, if cholesteatoma is present, its extent does not correlate with HRQoL. While HRQoL plays a secondary role in establishment of the indication for surgical therapy in COM with cholesteatoma, it plays an important role in terms of relative surgical indications, e.g., a symptomatic open mastoid cavity after resection of the posterior canal wall. We encourage the regular use of disease-specific PROMs preoperatively as well as during follow-up to assess HRQoL in COM in individual patients, in research, and in the context of quality monitoring.

Intracochlear pressure and temporal bone motion interaction under bone conduction stimulation.

BACKGROUND: Under bone conduction (BC) stimulation, the otic capsule, and surrounding temporal bone, undergoes a complex 3-dimentional (3D) motion that depends on the frequency, location and coupling of the stimulation. The correlation between the resultant intracochlear pressure difference across the cochlear partition and the 3D motion of the otic capsule is not yet known and is to be investigated. METHODS: Experiments were conducted in 3 fresh frozen cadaver heads, individually on each temporal bone, resulting in a total of 6 samples. The skull bone was stimulated, via the actuator of a BC hearing aid (BCHA), in the frequency range of 0.1-20 kHz. Stimulation was applied at the ipsilateral mastoid and the classical BAHA location via a conventional transcutaneous (5-N steel headband) and percutaneous coupling, sequentially. Three-dimensional motions were measured across the lateral and medial (intracranial) surfaces of the skull, the ipsilateral temporal bone, the skull base, as well as the promontory and stapes. Each measurement consisted of 130-200 measurement points (∼5-10 mm pitch) across the measured skull surface. Additionally, intracochlear pressure in the scala tympani and scala vestibuli was measured via a custom-made intracochlear acoustic receiver. RESULTS: While there were limited differences in the magnitude of the motion across the skull base, there were major differences in the deformation of different sections of the skull. Specifically, the bone near the otic capsule remained primarily rigid across all test frequency (above 10 kHz), in contrast to the skull base, which deformed above 1-2 kHz. Above 1 kHz, the ratio, between the differential intracochlear pressure and the promontory motion, was relatively independent of coupling and stimulation location. Similarly, the stimulation direction appears to have no influence on the cochlear response, above 1 kHz. CONCLUSIONS: The area around the otic capsule appears rigid up to significantly higher frequencies than the rest of the skull surface, resulting in primarily inertial loading of the cochlear fluid. Further work should be focused at the investigation of the solid-fluid interaction between the bony walls of the otic capsule and the cochlear contents.

Generation of distortion product otoacoustic emissions in infants with a combined air and bone conduction stimulus.

OBJECTIVES: Evaluation of Distortion Product Otoacoustic Emissions (DPOAEs) by combining Air Conduction (AC) and Bone Conduction (BC) stimuli in infants. METHODS: Measurements were performed in 19 normal hearing infants, and in 23 adults serving as a control group. The stimulus consisted either of two AC tones, or of combined AC/BC tones. DPOAEs were measured for f2 at 0.7, 1, 2, 4 kHz, and a constant ratio of f2/f1 = 1.22. Sound pressure level of the primary stimulus L1 was held constant at 70 dB SPL, while the level of L2 was decreased in 10 dB steps from 70 to 40 dB SPL. A response was included for further analysis when DPOAEs reached a Signal to Noise Ratio (SNR) of ≥6 dB. Additional DPOAE responses of <6 dB SNR were included when visual inspection of the measurements indicated clear DPOAEs. RESULTS: DPOAEs could be elicited in infants at 2 and 4 kHz for the AC/BC stimulus. DPOAE amplitudes evoked by the AC/AC stimulus were larger than those by the AC/BC stimulus, with the exception of 1 kHz. The highest amplitudes of DPOAEs were registered for a stimulation level of L1 = L2 = 70 dB, with the exception of AC/AC at 1 kHz, where the highest amplitudes were with L1-L2 = 10 dB. CONCLUSIONS: We demonstrated that DPOAEs can be generated in infants by a combined AC/BC stimulus at 2 and 4 kHz. The high noise floor needs to be further reduced to achieve more valid measurements in frequencies <2 kHz.

Effects of preloads on middle-ear transfer function and acoustic reflex in ossiculoplasty with PORP.

INTRODUCTION: Surgical outcomes in ossiculoplasty with partial ossicular replacement prostheses (PORPs) are greatly influenced by the amount of preload imposed on the PORP. In this study, the attenuation of the middle-ear transfer function (METF) was experimentally investigated for prosthesis-related preloads in different directions, with and without concurrent application of stapedial muscle tension. Different PORP designs were assessed to determine functional benefits of specific design features under preload conditions. METHODS: The experiments were performed on fresh-frozen human cadaveric temporal bones. The effect of preloads along different directions were experimentally assessed by simulating anatomical variance and postoperative position changes in a controlled setup. The assessments were performed for three different PORP designs featuring either a fixed shaft or ball joint and a Bell-type or Clip-interface. Further, the combined effect of the preloads towards the medial direction with tensional forces of the stapedial muscle was assessed. The METF was obtained via laser-Doppler vibrometry for each measurement condition. RESULTS: The preloads as well as the stapedial muscle tension primarily attenuated the METF between 0.5 and 4 kHz. The largest attenuations resulted from the preload towards the medial direction. The attenuation of the METF with stapedial muscle tension was reduced with concurrent PORP preloads. PORPs with a ball joint resulted in reduced attenuation only for preloads along the long axis of the stapes footplate. In contrast to the clip interface, the Bell-type interface was prone to lose coupling with the stapes head for preloads in the medial direction. CONCLUSIONS: The experimental study of the preload effects indicates a direction-dependent attenuation of the METF, with the most pronounced effects resulting from preloads towards the medial direction. Based on the obtained results, the ball joint offers tolerance for angular positioning while the clip interface prevents PORP dislocations for preloads in lateral direction. At high preloads, the attenuation of the METF with stapedial muscle tension is reduced, which should be considered for the interpretation of postoperative acoustic reflex tests.

Three-dimensional quasi-static displacement of human middle-ear ossicles under static pressure loads: Measurement using a stereo camera system.

The time delay and/or malfunctioning of the Eustachian tube may cause pressure differences across the tympanic membrane, resulting in quasi-static movements of the middle-ear ossicles. While quasi-static displacements of the human middle-ear ossicles have been measured one- or two-dimensionally in previous studies, this study presents an approach to trace three-dimensional movements of the human middle-ear ossicles under static pressure loads in the ear canal (EC). The three-dimensional quasi-static movements of the middle-ear ossicles were measured using a custom-made stereo camera system. Two cameras were assembled with a relative angle of 7° and then mounted onto a robot arm. Red fluorescent beads of a 106-125 µm diameter were placed on the middle-ear ossicles, and quasi-static position changes of the fluorescent beads under static pressure loads were traced by the stereo camera system. All the position changes of the ossicles were registered to the anatomical intrinsic frame based on the stapes footplate, which was obtained from µ-CT imaging. Under negative ear-canal pressures, a rotational movement around the anterior-posterior axis was dominant for the malleus-incus complex, with small relative movements between the two ossicles. The stapes showed translation toward the lateral direction and rotation around the long axis of the stapes footplate. Under positive EC pressures, relative motion between the malleus and the incus at the IMJ became larger, reducing movements of the incus and stapes considerably and thus performing a protection function for the inner-ear structures. Three-dimensional tracing of the middle-ear ossicular chain provides a better understanding of the protection function of the human middle ear under static pressured loads as immediate responses without time delay.

Gustatory Function of Patients With and Without Cholesteatoma Undergoing Middle Ear Surgery.

OBJECTIVE: To compare measured and perceived taste function before and after surgery of patients with chronic otitis media with cholesteatoma (OMCC) to patients without cholesteatoma (patients with chronic suppurative otitis media [CSOM] and patients with lateral skull base lesions [LSB]). METHODS: This prospective cohort study included 29 patients undergoing surgery for unilateral OMCC. The chorda tympani nerve (CTN) was resected in 8 of these patients. Fourteen patients undergoing surgery for unilateral CSOM and 5 patients undergoing surgery for unilateral LSB (with CTN resection) served as the comparison group. Taste function was measured using taste strips on both sides of the tongue before surgery, 2 weeks postoperatively and 3 months postoperatively. The affected side of the tongue was compared to the unaffected side. A questionnaire on taste perception was completed at each visit. RESULTS: Preoperatively, cholesteatoma patients showed higher taste strip scores than non-cholesteatoma patients, indicating a larger difference between the healthy and affected sides of the tongue. Despite this difference in measured taste function few cholesteatoma patients reported taste alteration before surgery (3/29 [10.3%]). Postoperatively, patients with CTN resection (OMCC patients with CTN resection and LSB patients) showed a decreased measured taste function. Subjectively, only approximately 20% of these patients reported taste alteration 3 months postoperatively. CONCLUSIONS: Before surgery, cholesteatoma patients displayed an impaired measured taste function compared to patients without cholesteatoma (CSOM, LSB). Subjectively this was often unnoticed. After surgery, despite removal of the CTN and consequent reduction of measured taste function, few patients reported taste alteration and subjective taste perception was seen to be improving. In regards to middle ear surgery, perceived taste function does not seem to reflect measured gustatory function.

Prevalence of Endolymphatic Hydrops in Cochlear Implant Candidates with Idiopathic Profound Sensorineural Hearing Loss.

OBJECTIVE: To determine the prevalence of endolymphatic hydrops (EH) in cochlear implant (CI) candidates with idiopathic profound sensorineural hearing loss (SNHL) and its influence on the preservation of audiovestibular function after cochlear implantation. STUDY DESIGN: Prospective case series. SETTING: Tertiary referral center. PATIENTS: CI candidates with idiopathic progressive SNHL, but without classic EH-associated symptoms. INTERVENTIONS: Delayed intravenous gadolinium-enhanced inner ear fluid-attenuated inversion recovery magnetic resonance imaging as well as pure-tone audiograms, video head impulse tests, and vestibular evoked myogenic potentials before and 4 weeks after cochlear implantation. MAIN OUTCOME MEASURES: Prevalence of EH before cochlear implantation, audiovestibular function before and after surgery in hydropic and nonhydropic ears. RESULTS: Thirty-two ears in 16 CI candidates were included. Nine ears (28%) with EH were detected. Although preoperative hearing thresholds, utricular function, and semicircular canal function were not different between the two groups, saccular function was reduced in hydropic ears. Ten subjects received a unilateral CI. Of these, 3 (30%) showed EH on the implanted side. There was no difference regarding postoperative hearing loss between the two groups, but the results point toward a higher vulnerability of hydropic ears with respect to loss of otolith function after cochlear implantation. CONCLUSIONS: This is the first study showing that EH can be assumed in about one third of CI candidates with idiopathic profound SNHL, but no classic EH-associated symptoms. Preliminary results suggest that EH has no influence on the preservation of cochlear function but could be a risk factor for loss of otolith function after cochlear implantation.

Intracochlear pressure in cadaver heads under bone conduction and intracranial fluid stimulation.

BACKGROUND: The frequency dependent contributions of the various bone conduction pathways are poorly understood, especially the fluid pathway. The aim of this work is to measure and investigate sound pressure propagation from the intracranial space to the cochlear fluid. METHODS: Stimulation was provided sequentially to the bone (BC) or directly to the intracranial contents (hydrodynamic conduction, or HC) in four cadaver heads, where each ear was tested individually, for a total of 8 samples. Intracranial pressure was generated and monitored via commercial hydrophones, while the intracochlear sound pressure (ICSP) levels were monitored via custom-made intracochlear acoustic receivers (ICAR). In parallel, measurements of the 3D motion of the cochlear promontory and stapes were made via 3D Laser Doppler Vibrometer (3D LDV). RESULTS: Reliability of the intracochlear sound pressure measurements depends on the immobilization of the ICAR relative to the otic capsule. Regardless of the significant differences in absolute stapes and promontory motion, the ratios between the otic capsule velocity, the stapes volume velocity (relative to the cochlea), and the intracochlear pressure were very similar under BC and HC stimulus. Under HC, the cochlear fluid appears be activated by an osseous pathway, rather than a direct non-osseous pathway from the cerebrospinal fluid (CSF), however, the osseous pathway itself is activated by the CSF pressure. CONCLUSIONS: Data suggests that the skull bone surrounding the brain and CSF could play a role in the interaction between the two CSF and the cochlea, under both stimulation conditions, at high frequencies, while inertia is dominant factor at low frequencies. Further work should be focused on the investigation of the solid-fluid interaction between the skull bone walls and the intracranial content.

Wave propagation across the skull under bone conduction: Dependence on coupling methods.

This study is aimed at the quantitative investigation of wave propagation through the skull bone and its dependence on different coupling methods of the bone conduction hearing aid (BCHA). Experiments were conducted on five Thiel embalmed whole head cadaver specimens. An electromagnetic actuator from a commercial BCHA was mounted on a 5-Newton steel headband, at the mastoid, on a percutaneously implanted screw (Baha® Connect), and transcutaneously with a Baha® Attract (Cochlear Limited, Sydney, Australia), at the clinical bone anchored hearing aid (BAHA) location. Surface motion was quantified by sequentially measuring ∼200 points on the skull surface via a three-dimensional laser Doppler vibrometer (3D LDV) system. The experimental procedure was repeated virtually, using a modified LiUHead finite element model (FEM). Both experiential and FEM methods showed an onset of deformations; first near the stimulation area, at 250-500 Hz, which then extended to the inferior ipsilateral skull surface, at 0.5-2 kHz, and spread across the whole skull above 3-4 kHz. Overall, stiffer coupling (Connect versus Headband), applied at a location with lower mechanical stiffness (the BAHA location versus mastoid), led to a faster transition and lower transition frequency to local deformations and wave motion. This behaviour was more evident at the BAHA location, as the mastoid was more agnostic to coupling condition.

Subjective Sound Quality Detection (HISQUI) over Time after Vibrant Soundbridge Implantation.

BACKGROUND: To evaluate the long-term audiological outcomes combined with the Hearing Implant Sound Quality Index (HISQUI) after Vibrant Soundbridge (VSB) implantation. METHODS: Prospective recall cohort study of patients who received a VSB in a tertiary academic medical center between 1996 and 2017. Air conduction (AC) and bone conduction (BC), sound field thresholds in aided and unaided conditions, and speech discrimination in noise (Oldenburger sentence test) were measured. Postoperative results were compared with preoperative audiograms. Furthermore, the HISQUI was evaluated. RESULTS: Ten patients (eleven implants) were included, the mean follow up period was nine years. The mean AC threshold preoperatively was between 63 and 70 dB, and the BC was between 38 and 49 dB from 500 to 4000 Hz. In the free-field audiogram, the mean threshold was between 61 and 77 dB unaided vs. between 28 and 52 dB in the aided condition. The average signal to noise ratio (SNR) in the Oldenburger sentence test in the unaided condition was 10 dB ± 6.7 dB vs. 2 dB ± 5.4 dB in the aided condition. Three patients reported a good to very good hearing result, four patients a moderate, and three patients a poor hearing result. There was a significant association between the years of implantation and the HISQUI (p = 0.013), as well as a significant decrease by 14 HISQUI points per 10 dB SPL decline (SE 5.2, p = 0.023). There was a significant difference between the change of BC over the years and the HISQUI, as well as the number of years after implantation and the HISQUI. On average, per dB decrease in BC, the HISQUI decreases by 1.4 points, and every year after implantation the HISQUI decreases by 2.7 points. CONCLUSIONS: The aided threshold in free field and speech understanding in noise improved significantly with VSB. An increase over time of BC thresholds was observed as well as a decrease in HISQUI score. This decrease in BC thresholds over time may be due to presbycusis. Therefore, monitoring of these patients over time should be considered to discuss alternative hearing rehabilitation measures in a timely manner.

Calcium sulfate matrix as local antibiotic carrier in the mastoid.

We describe the use of calcium sulfate beads as antibiotic carrier in a patient, who suffered from chronic mastoiditis with consecutive otogenic meningitis due to Burkholderia cenocepacia. Our findings suggest a possible role of calcium sulfate matrix as a local antibiotic carrier in the mastoid in complicated mastoiditis cases.

Predicting Cochlear Implant Electrode Placement Using Monopolar, Three-Point and Four-Point Impedance Measurements.

OBJECTIVE: This study aimed to investigate the relationship between cochlear implant (CI) electrode distances to the cochlea's inner wall (the modiolus) and electrical impedance measurements made at the CI's electrode contacts. We introduced a protocol for "three-point impedances" in which we recorded bipolar impedances in response to monopolar stimulation at a neighboring electrode. We aimed to assess the usability of three-point impedances and two existing CI impedance measurement methods (monopolar and four-point impedances) for predicting electrode positioning during CI insertion. METHODS: Impedances were recorded during stepwise CI electrode array insertions in cadaveric human temporal bones. The positioning of the electrodes with respect to the modiolus was assessed at each step using cone beam computed tomography. Linear mixed regression analysis was performed to assess the relationship between the impedances and electrode-modiolar distances. The experimental results were compared to clinical impedance data and to an existing lumped-element model of an implanted CI. RESULTS: Three-point and four-point impedances strongly correlated with electrode-modiolar distance. In contrast, monopolar impedances were only minimally affected by changes in electrode positioning with respect to the modiolus. An overall model specificity of 62% was achieved when incorporating all impedance parameters. This specificity could be increased beyond 73% when prior expectations of electrode positioning were incorporated in the model. CONCLUSION: Three-point and four-point impedances are promising measures to predict electrode-modiolar distance in real-time during CI insertion. SIGNIFICANCE: This work shows how electrical impedance measurements can be used to predict the CI's electrode positioning in a biologically realistic model.

Transcutaneous and percutaneous bone conduction sound propagation in single-sided deaf patients and cadaveric heads.

OBJECTIVE: To investigate transcranial transmission (TT) and the dampening effect of the skin in patients and cadaver heads. DESIGN: In patients a pure tone bone conduction audiogram for ipsilateral and contralateral stimulation was performed. The TT was defined as the difference between ipsilateral and contralateral hearing thresholds. In cadaver heads ipsilateral and contralateral promontory motion was measured using a three-dimensional Laser Doppler Vibrometer system. STUDY SAMPLE: Seven single-sided deaf patients fitted with a Baha® Connect, fifteen single-sided deaf patients without a bone conduction hearing aid and five Thiel-embalmed cadaver heads were included. RESULTS: The TT decreased with increasing frequency in patients and cadaver heads. No significant difference was seen between patients and cadaver heads. Measurements on patients and cadaver heads showed increasing skin attenuation with increasing frequency. However, the dampening effect was 3-12 dB higher in patients than in cadavers at all frequencies. CONCLUSION: The TT was not significantly different for patients compared to cadaver heads. The value of promontory motion to estimate TT in patients need to be further evaluated. The skin attenuates a BC stimulus by 10-20 dB in patients and by a smaller amount in cadaver heads, probably due to changes in the properties of the Thiel-conserved skin.

Implications of Phase Changes in Extracochlear Electrocochleographic Recordings During Cochlear Implantation.

OBJECTIVE: To assess the prevalence and implications of phase changes in extracochlear electrocochleography (ECochG) recordings during cochlear implantation. MATERIALS AND METHODS: Extracochlear ECochG recordings were performed before and after insertion of the cochlear implant (CI) electrode by a recording electrode placed on the promontory. Acoustic stimuli were tone bursts at 250, 500, 750, and 1,000 Hz. The pure tone average (PTA) was determined before and approximately 4 weeks after surgery. RESULTS: Extracochlear ECochG recordings in 69 ears of 68 subjects were included. At 250 Hz, the mean phase change was 43° (n = 50, standard deviation (SD) 44°), at 500 Hz 36° (n = 64, SD 36°), at 750 Hz 33° (n = 42, SD 39°), and at 1,000 Hz 22° (n = 54, SD 27°). Overall, in 48 out of 210 ECochG recordings a phase change of ≥45° (23%) was detectable. Ears with an amplitude drop >3 dB and a phase change ≥45° (n = 3) had a complete or near complete loss of residual cochlear function in all cases. A phase change of ≥90° in one recording was not associated with a larger amplitude change of the ECochG signal (1.9 dB vs. -0.9 dB, p = 0.1052, n = 69), but with a significantly larger postoperative hearing loss (17 dB vs. 26 dB, p = 0.0156, n = 69). CONCLUSIONS: Phase changes occur regularly in extracochlear ECochG recordings during cochlear implantation. Phase changes of ≥90° with or without amplitude changes in the ECochG signal are associated with a larger postoperative hearing loss and could therefore represent an independent marker for cochlear trauma or changes of inner ear mechanics relevant for the postoperative hearing outcome.

Development of a finite element model of a human head including auditory periphery for understanding of bone-conducted hearing.

A three-dimensional finite-element (FE) model of a human head including the auditory periphery was developed to obtain a better understanding of bone-conducted (BC) hearing. The model was validated by comparison of cochlear and head responses in both air-conducted (AC) and BC hearing with experimental data. Specifically, the FE model provided the cochlear responses such as basilar membrane velocity and intracochlear pressure corresponding to BC stimulations applied to the mastoid or the conventional bone-anchored-hearing-aid (BAHA) positions. This is a strength of the model because it is difficult to obtain the cochlear responses from experiments corresponding to the BC stimulation applied at a specific position on the head surface. In addition, there have been few studies based on an FE model that can calculate the head and cochlear responses simultaneously from a BC stimulation. Moreover, in this study, the intracochlear sound pressure at multi-positions along the BM length was calculated and used to clarify the effect of stimulating force direction on the cochlear and promontory velocities in BC hearing. Also, the relationship between BC and AC stimulation and the basilar membrane velocity in the FE model was used to calculate the stimulation level at hearing thresholds which has been investigated only by psychoacoustical methods.