[Application of extra- and intracochlear electrocochleography during and after cochlear implantation]. / Anwendung der extra- und intracochleären Elektrocochleographie während und nach der Cochleaimplantation.

Electrocochleography (ECochG) represents a promising approach for monitoring cochlear function during cochlear implantation and for investigating the causes of residual cochlear function loss after implantation. This paper provides an overview of the current research and application status of ECochG, both during and after cochlear implantation. Intraoperative ECochG can be conducted either via the implant itself or an extracochlear measuring electrode. Postoperative ECochG recordings are also feasible via the implant. Various studies have demonstrated that a significant decrease in ECochG amplitude during electrode insertion correlates with an increased risk of losing residual cochlear function, with critical cochlear events occurring primarily towards the end of the insertion. Postoperative data suggest that the loss of cochlear function mainly occurs in the early postoperative phase. Future research directions include the automation and objectification of signal analysis, as well as a more in-depth investigation into the underlying mechanisms of these signal changes.

Electrocochleographic Patterns Predicting Increased Impedances and Hearing Loss after Cochlear Implantation.

OBJECTIVES: Different patterns of electrocochleographic responses along the electrode array after insertion of the cochlear implant electrode array have been described. However, the implications of these patterns remain unclear. Therefore, the aim of the study was to correlate different peri- and postoperative electrocochleographic patterns with four-point impedance measurements and preservation of residual hearing. DESIGN: Thirty-nine subjects with residual low-frequency hearing which were implanted with a slim-straight electrode array could prospectively be included. Intracochlear electrocochleographic recordings and four-point impedance measurements along the 22 electrodes of the array (EL, most apical EL22) were conducted immediately after complete insertion and 3 months after surgery. Hearing preservation was assessed after 3 months. RESULTS: In perioperative electrocochleographic recordings, 22 subjects (56%) showed the largest amplitude around the tip of the electrode array (apical-peak, AP, EL20 or EL22), whereas 17 subjects (44%) exhibited a maximum amplitude in more basal regions (mid-peak, MP, EL18 or lower). At 3 months, in six subjects with an AP pattern perioperatively, the location of the largest electrocochleographic response had shifted basally (apical-to-mid-peak, AP-MP). Latency was analyzed along the electrode array when this could be discerned. This was the case in 68 peri- and postoperative recordings (87% of all recordings, n = 78). The latency increased with increasing insertion depth in AP recordings (n = 38, median of EL with maximum latency shift = EL21). In MP recordings (n = 30), the maximum latency shift was detectable more basally (median EL12, p < 0.001). Four-point impedance measurements were available at both time points in 90% (n = 35) of all subjects. At the 3-month time point, recordings revealed lower impedances in the AP group (n = 15, mean = 222 Ω, SD = 63) than in the MP (n = 14, mean = 295 Ω, SD= 7 6) and AP-MP groups (n = 6, mean = 234 Ω, SD = 129; AP versus MP p = 0.026, AP versus AP-MP p = 0.023, MP versus AP-MP p > 0.999). The amplitudes of perioperative AP recordings showed a correlation with preoperative hearing thresholds ( r2 =0.351, p = 0.004). No such correlation was detectable in MP recordings ( r2 = 0.033, p = 0.484). Audiograms were available at both time points in 97% (n = 38) of all subjects. The mean postoperative hearing loss in the AP group was 13 dB (n = 16, SD = 9). A significantly larger hearing loss was detectable in the MP and AP-MP groups with 28 (n = 17, SD = 10) and 35 dB (n = 6, SD = 13), respectively (AP versus MP p = 0.002, AP versus AP-MP p = 0.002, MP versus AP-MP p = 0.926). CONCLUSION: MP and AP-MP response patterns of the electrocochleographic responses along the electrode array after cochlear implantation are correlated with higher four-point impedances and poorer postoperative hearing compared to AP response patterns. The higher impedances suggest that MP and AP-MP patterns are associated with increased intracochlear fibrosis.

Influence of Semicircular Canal Dehiscence on Cochlear Implant Outcome.

INTRODUCTION: Semicircular canal dehiscence (SCD) is defined as a defect of the bone overlying the semicircular canal. It has a relatively high prevalence of 3% in the general population, which makes it likely that a certain number of patients receiving a cochlear implant (CI) would have it. However, little is known about the influence of SCD on the CI outcome. Therefore, the aim of this study was to determine the influence of SCD on CI outcome with regard to short- and long-term word perception and hearing preservation. METHODS: This study was a retrospective analysis of postoperative word perception ability in the electric-only condition after 6, 12, and ≥18 months and of hearing preservation 4 weeks after surgery in CI recipients with and without SCD. All patients received a preoperative 1.5- or 3-tesla magnetic resonance imaging. RESULTS: Fifty-five patients were included. Forty-eight patients (87%) had no SCD, and 7 patients (13%) had SCD. Mean postoperative word perception scores were 66% in the non-SCD group versus 50% in the SCD group (p = 0.17) after 6 months, 74 versus 64% (p = 0.28) after 12 months, and 77 versus 73% (p = 0.62) after 18 or more months. The mean postoperative hearing loss in patients with functional residual hearing before surgery (n = 34) was 22 dB in the non-SCD group versus 31 dB in the SCD group (p = 0.15). CONCLUSIONS: CI outcome is comparable between recipients without and with SCD. Specifically, hearing preservation rate and word perception ability in the electric-only condition seem not affected by SCD. The rate of progress of word perception ability in the first 12 months after cochlear implantation is not influenced by SCD.

Simultaneous Intra- and Extracochlear Electrocochleography During Electrode Insertion.

OBJECTIVES: (1) To correlate simultaneously recorded intra- and extracochlear electrocochleography (ECochG) signals during electrode insertion into the cochlea, (2) to track changes in the ECochG signal during insertion and removal of an electrode, and (3) to correlate the findings with the preoperative residual hearing. We hypothesized that intracochlear ECochG recordings show signal changes not reflected in simultaneous extracochlear ECochG recordings. DESIGN: During cochlear implantation in human cochlear implant recipients, a short, slim, custom-made electrode was inserted and removed in a stepwise manner. At each step, ECochG recordings were simultaneously recorded by an extracochlear electrode near the round window and via the inserted electrode. The acoustic stimulus was a 500 Hz tone burst at 110 to 130 dB SPL. RESULTS: The mean amplitude difference between intra- and extracochlear ongoing ECochG responses was 14 dB (range 9 to 24 dB; n = 10) at the beginning of insertion. Intracochlear ECochG responses were larger in all cases. Extracochlear ECochG responses remained stable while intracochlear recordings showed large variations regarding amplitude and phase during the electrode array insertion. Intracochlear signal changes during insertion were reversible with retraction of the electrode. There were only weak to moderate (rs = 0.006 to 0.4), nonsignificant correlations of residual preoperative hearing with maximum amplitudes and amplitude changes during electrode insertion and removal in intracochlear recordings. CONCLUSIONS: Signals in intracochlear ECochG recordings are reliably larger than ECochG signals recorded simultaneously from an extracochlear location. Intracochlear ECochG recordings show reversible amplitude and phase changes during insertion, not reflected in simultaneous extracochlear ECochG recordings. Such changes are most likely due to the movement of the recording electrode in relation to the signal generators. Residual high-frequency hearing is associated with larger ECochG signal amplitudes. Modeling of expected intracochlear ECochG changes during electrode insertions may allow detection of cochlear trauma in the future.

Endolymphatic hydrops mimicking obstructive Eustachian tube dysfunction: preliminary experience and literature review.

PURPOSE: Aural fullness is a common symptom of middle ear diseases, most importantly Eustachian tube dysfunction (ETD). Yet, aural fullness may also be caused by inner ear disorders, such as hydropic ear diseases. Here, we report our experience with endolymphatic hydrops (EH) mimicking ETD. Furthermore, we review the literature related to (i) EH as a differential diagnosis of symptoms suggesting ETD and (ii) the pathophysiology and treatment of aural fullness due to inner ear disorders. METHODS: We retrospectively included adult patients with aural fullness as chief complaint and radiographically diagnosed EH. Hearing and Eustachian tube function were assessed using audiometry, tympanometry, and tubomanometry. Primarily suspected ETD was treated by balloon dilatation of the Eustachian tube (BDET). The endolymphatic space of the inner ear was imaged using gadolinium-enhanced MRI (Gd-MRI) including a 3D-real inversion-recovery sequence after intravenous gadolinium administration. RESULTS: We report three affected ears of two patients (two females, age 42 and age 51) with aural fullness as chief complaint. Audiometry of main speech frequencies was normal in all affected ears. In one ear, there was a type A tympanogram and in two ears, there was a type B tympanogram. In both patients, medical treatment for ETD and BDET were unsuccessful. Gd-MRI of the inner ears revealed cochlear EH in 3/3 ears affected by aural fullness, but not in the unaffected ear. CONCLUSION: EH may underlay cases with aural fullness and could in these cases explain unsuccessful treatment for ETD. As ETD is often treated by invasive procedures, distinguishing ETD from EH as the underlying cause of aural fullness is important. Our findings raise the question whether Gd-MRI to rule out EH is indicated in patients with unexplained aural fullness, in particular after unsuccessful interventional treatment for ETD.

Distorted sound perception and subjective benefit after stapedotomy - a prospective single-centre study.

OBJECTIVE: To evaluate the quality of perceived sound after stapedotomy over a 1-year follow-up period focussing on incidence of dysacusis, particularly distorted sound perception (DSP). DSP was assessed by (i) determination of the frequencies and hearing level that such perceptions are elicited by pure tones (pure-tone-evoked distorted sound perception, PTE-DSP), a novel psychoacoustic measurement introduced in this paper, and (ii) assessment of patient-reported occurrence of DSP using the Amsterdam Post Operative Sound Evaluation (APOSE) questionnaire (APOSE-DSP). DESIGN: Prospective study. STUDY SAMPLE: Patients (n = 23) with otosclerosis undergoing stapedotomy. RESULTS: An air-bone gap of <20 dB was achieved in 100% of the patients. Three weeks postoperatively, 48% of the patients reported measured PTE-DSP and 39% of the patients experienced APOSE-DSP. The PTE-DSP significantly decreased during the 1-year follow-up period (p = 0.03). Postoperatively, APOSE-DSP was associated with a smaller benefit (improvement in air conduction; p = 0.03), yet, a lower bone conduction pure-tone average was associated with PTE-DSP (p = 0.006). CONCLUSIONS: DSP after stapedotomy is associated with a smaller benefit 3 months after stapedotomy. DSP commonly occur after stapedotomy, but decrease over time. This is important information to be included in patient counselling before stapedotomy.

Packaging Technology for an Implantable Inner Ear MEMS Microphone.

Current cochlear implant (CI) systems provide substantial benefits for patients with severe hearing loss. However, they do not allow for 24/7 hearing, mainly due to the external parts that cannot be worn in all everyday situations. One of the key missing parts for a totally implantable CI (TICI) is the microphone, which thus far has not been implantable. The goal of the current project was to develop a concept for a packaging technology for state-of-the-art microelectromechanical systems (MEMS) microphones that record the liquid-borne sound inside the inner ear (cochlea) as a microphone signal input for a TICI. The packaging concept incorporates requirements, such as biocompatibility, long-term hermeticity, a high sensing performance and a form factor that allows sensing inside the human cochlea and full integration into the existing CI electrode array. The present paper (1) describes the sensor packaging concept and the corresponding numerical and experimental design verification process and (2) gives insight into new engineering solutions for sensor packaging. Overall, a packaging concept was developed that enables MEMS microphone technology to be used for a TICI system.

Dynamic Postural Stability and Hearing Preservation after Cochlear Implantation.

OBJECTIVES: (1) To assess dynamic postural stability before and after cochlear implantation using a functional gait assessment (FGA). (2) To evaluate the correlation between loss of residual hearing and changes in dynamic postural stability after cochlear implantation. METHODS: Candidates for first-sided cochlear implantation were prospectively included. The FGAs and pure-tone audiograms were performed before and 4-6 weeks after cochlear implantation. RESULTS: Twenty-three subjects were included. Forty-eight percent (n = 11) showed FGA performance below the age-referenced norm before surgery. One subject had a clinically relevant decrease of the FGA score after cochlear implantation. No significant difference between the mean pre- and postoperative FGA scores was detectable (p = 0.4). Postoperative hearing loss showed no correlation with a change in FGA score after surgery (r = 0.3, p = 0.3, n = 16). CONCLUSION: Single-sided cochlear implantation does not adversely affect dynamic postural stability 5 weeks after surgery. Loss of functional residual hearing is not correlated with a decrease in dynamic postural stability.

Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments.

(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI.

Extra- and Intracochlear Electrocochleography in Cochlear Implant Recipients.

OBJECTIVE: To monitor cochlear function by extra- and intra-cochlear electrocochleography (ECoG) during and after cochlear implantation and thereby to enhance the understanding of changes in cochlear function following cochlear implantation surgery. METHODS: ECoG responses to acoustic stimuli of 250, 500 and 1,000 Hz were recorded in 9 cochlear implant recipients with presurgical residual hearing. During surgery extracochlear ECoG recordings were performed before and after insertion of the cochlear implant electrode array. After insertion of the electrode array, intracochlear ECoG recordings were conducted using intracochlear electrode contacts as recording electrodes. Intracochlear ECoG recordings were performed up to 6 months after implantation.ECoG findings were correlated with findings from audiometric tests. RESULTS: Extra- and intracochlear ECoG responses could be recorded in all subjects. Extracochlear ECoG recordings during surgery showed moderate changes.Loss or reduction of the ECoG signal at all three frequencies did not occur during cochlear implantation. During the first week following surgery, conductive hearing loss, due to middle ear effusion, led to a decrease in intracochlear ECoG signal amplitudes. This was not attributable to changes of cochlear function. All persistent reductions in ECoG response magnitude after normalization of the tympanogram occurred during the first week following implantation. Thresholds of ECoG signals were at or below hearing thresholds in all cases. CONCLUSION: Gross intracochlear trauma during surgery appears to be rare. In the early postoperative phase the ability to assess cochlear status by ECoG recordings was limited due to the regular occurrence of middle ear effusion.Still, intracochlear ECoG along with tympanogram recordings suggests that any changes of low-frequency cochlear function occur mainly during the first week after cochlear implantation. ECoG seems to be a promising tool to objectively assess changes in cochlear function in cochlear implant recipients and may allow further insight into the mechanisms underlying the loss of residual hearing.

ZH-ECochG Bode Plot: A Novel Approach to Visualize Electrocochleographic Data in Cochlear Implant Users.

Background: Various representations exist in the literature to visualize electrocochleography (ECochG) recordings along the basilar membrane (BM). This lack of generalization complicates comparisons within and between cochlear implant (CI) users, as well as between publications. This study synthesized the visual representations available in the literature via a systematic review and provides a novel approach to visualize ECochG data in CI users. Methods: A systematic review was conducted within PubMed and EMBASE to evaluate studies investigating ECochG and CI. Figures that visualized ECochG responses were selected and analyzed. A novel visualization of individual ECochG data, the ZH-ECochG Bode plot (ZH = Zurich), was devised, and the recordings from three CI recipients were used to demonstrate and assess the new framework. Results: Within the database search, 74 articles with a total of 115 figures met the inclusion criteria. Analysis revealed various types of representations using different axes; their advantages were incorporated into the novel visualization framework. The ZH-ECochG Bode plot visualizes the amplitude and phase of the ECochG recordings along the different tonotopic regions and angular insertion depths of the recording sites. The graph includes the pre- and postoperative audiograms to enable a comparison of ECochG responses with the audiometric profile, and allows different measurements to be shown in the same graph. Conclusions: The ZH-ECochG Bode plot provides a generalized visual representation of ECochG data, using well-defined axes. This will facilitate the investigation of the complex ECochG potentials generated along the BM and allows for better comparisons of ECochG recordings within and among CI users and publications. The scripts used to construct the ZH-ECochG Bode plot are provided by the authors.

An intracochlear electrocochleography dataset - from raw data to objective analysis using deep learning.

Electrocochleography (ECochG) measures electrophysiological inner ear potentials in response to acoustic stimulation. These potentials reflect the state of the inner ear and provide important information about its residual function. For cochlear implant (CI) recipients, we can measure ECochG signals directly within the cochlea using the implant electrode. We are able to perform these recordings during and at any point after implantation. However, the analysis and interpretation of ECochG signals are not trivial. To assist the scientific community, we provide our intracochlear ECochG data set, which consists of 4,924 signals recorded from 46 ears with a cochlear implant. We collected data either immediately after electrode insertion or postoperatively in subjects with residual acoustic hearing. This data descriptor aims to provide the research community access to our comprehensive electrophysiological data set and algorithms. It includes all steps from raw data acquisition to signal processing and objective analysis using Deep Learning. In addition, we collected subject demographic data, hearing thresholds, subjective loudness levels, impedance telemetry, radiographic findings, and classification of ECochG signals.

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.

Postural stability and handicap of dizziness after preoperative vestibular ablation and vestibular prehabilitation in patients undergoing vestibular schwannoma resection.

BACKGROUND: Surgical treatment of vestibular schwannoma (VS) leads to acute ipsilateral vestibular loss if there is residual vestibular function before surgery. To overcome the sequelae of acute ipsilateral vestibular loss and to decrease postoperative recovery time, the concept of preemptive vestibular ablation with gentamicin and vestibular prehabilitation before surgery has been developed ("vestibular prehab"). OBJECTIVE: Studying postural stability during walking and handicap of dizziness over a 1-year follow-up period in VS patients undergoing vestibular prehab before surgical treatment of VS. METHODS: A retrospective review of consecutive patients with a diagnosis of a VS undergoing surgical therapy from June 2012 to March 2018 was performed. All patients were included with documentation of the length of hospital duration and the Dizziness Handicap Inventory (DHI) and the Functional Gait Assessment (FGA) assessed preoperatively as well as 6 weeks and 1 year postoperatively. RESULTS: A total 68 VS patients were included, of which 29 patients received preoperative vestibular ablation by intratympanic injection of gentamicin. Mean VS diameter was 20.2 mm (SD 9.4 mm) and mean age at surgery was 49.6 years (SD 11.5 years). Vestibular prehab had no effect on DHI and FGA at any time point studied. CONCLUSIONS: We found no effect of vestibular prehab on postural stability during walking and on the handicap of dizziness. These findings add to the body of knowledge consisting of conflicting results of vestibular prehab. Therefore, vestibular prehab should be applied only in selected cases in an experimental setting.

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.

Objectification of intracochlear electrocochleography using machine learning.

Introduction: Electrocochleography (ECochG) measures inner ear potentials in response to acoustic stimulation. In patients with cochlear implant (CI), the technique is increasingly used to monitor residual inner ear function. So far, when analyzing ECochG potentials, the visual assessment has been the gold standard. However, visual assessment requires a high level of experience to interpret the signals. Furthermore, expert-dependent assessment leads to inconsistency and a lack of reproducibility. The aim of this study was to automate and objectify the analysis of cochlear microphonic (CM) signals in ECochG recordings. Methods: Prospective cohort study including 41 implanted ears with residual hearing. We measured ECochG potentials at four different electrodes and only at stable electrode positions (after full insertion or postoperatively). When stimulating acoustically, depending on the individual residual hearing, we used three different intensity levels of pure tones (i.e., supra-, near-, and sub-threshold stimulation; 250-2,000 Hz). Our aim was to obtain ECochG potentials with differing SNRs. To objectify the detection of CM signals, we compared three different methods: correlation analysis, Hotelling's T2 test, and deep learning. We benchmarked these methods against the visual analysis of three ECochG experts. Results: For the visual analysis of ECochG recordings, the Fleiss' kappa value demonstrated a substantial to almost perfect agreement among the three examiners. We used the labels as ground truth to train our objectification methods. Thereby, the deep learning algorithm performed best (area under curve = 0.97, accuracy = 0.92), closely followed by Hotelling's T2 test. The correlation method slightly underperformed due to its susceptibility to noise interference. Conclusions: Objectification of ECochG signals is possible with the presented methods. Deep learning and Hotelling's T2 methods achieved excellent discrimination performance. Objective automatic analysis of CM signals enables standardized, fast, accurate, and examiner-independent evaluation of ECochG measurements.

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.

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.

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.

Correlation between Speech Perception Outcomes after Cochlear Implantation and Postoperative Acoustic and Electric Hearing Thresholds.

The reliable prediction of cochlear implant (CI) speech perception outcomes is highly relevant and can facilitate the monitoring of postoperative hearing performance. To date, multiple audiometric, demographic, and surgical variables have shown some degree of correlation with CI speech perception outcomes. In the present study, postsurgical acoustic and electric hearing thresholds that are routinely assessed in clinical practice were compared to CI speech perception outcomes in order to reveal possible markers of postoperative cochlear health. A total of 237 CI recipients were included in this retrospective monocentric study. An analysis of the correlation of postoperative pure-tone averages (PTAs) and electric CI fitting thresholds (T-/C-levels) with speech perception scores for monosyllabic words in quiet was performed. Additionally, a correlation analysis was performed for postoperative acoustic thresholds in intracochlear electrocochleography (EcochG) and speech recognition scores in a smaller group (n = 14). The results show that neither postoperative acoustic hearing thresholds nor electric thresholds correlate with postoperative speech perception outcomes, and they do not serve as independent predictors of speech perception outcomes. By contrast, the postoperative intracochlear total EcochG response was significantly correlated with speech perception. Since the EcochG recordings were only performed in a small population, a large study is required to clarify the usefulness of this promising predictive parameter.