Acoustic component programming in children with cochlear implants using electrocochleography.

OBJECTIVE: Objective measurements improve reliability and effectiveness of hearing assessment and cochlear implant (CI) programming in young children. In CI recipients with acoustic hearing in the implanted ear, electrocochleography (ECochG) can be conducted using intracochlear electrodes. The cochlear microphonic (CM) portion of ECochG has been shown to correlate with pure-tone audiometric thresholds in adult and paediatric CI recipients. Our goal was to determine if ECochG thresholds can be used to appropriately fit the acoustic component to the implanted ear in children. DESIGN: Prospective. STUDY SAMPLE: Eight children (aged 3.5-15.5 years, 10 ears) implanted with Advanced Bionics HiFocus Mid-Scala electrode array were recruited. CI ear acoustic thresholds were measured behaviourally and via ECochG. Two acoustic component enabled CI programs were created using the two sets of thresholds. Age and language appropriate speech outcomes and subjective feedback were obtained. RESULTS: Speech scores were equivalent with the behavioural and ECochG thresholds programs. Subjectively, the ECochG thresholds program was preferred by 7/8 subjects. One subject preferred to use an electric only program. CONCLUSION: Our data suggest that ECochG thresholds can be used to supplement the behavioural clinical methods and aid the reliable fitting of the acoustic component in paediatric CI recipients.

Comparing the sensitivity and specificity of cervical vestibular-evoked myogenic potentials and electrocochleography in the diagnosis of Ménière's disease.

Objective: To compare the sensitivity and specificity of objective cervical vestibular-evoked myogenic potential (cVEMP) tuning curves and electrocochleography (ECochG) for the diagnosis of Ménière's disease (MD). Design: Sensitivity and specificity were calculated from 95% normative ranges of 500 Hz cVEMP threshold and ECochG SP/AP amplitude ratios. Measures: Extra-tympanic ECochG testing to 90 dB nHL clicks and cVEMP threshold tuning curves (250-1000 Hz). Study sample: We tested 15 patients (30 ears) diagnosed with definite bilateral MD based on the clinical criteria proposed by the American Academy of Otolaryngology Head and Neck surgery, 1995 (assumed gold standard) and 20 controls. Results: 500 Hz cVEMP threshold was the most promising parameter to differentiate MD ears from controls. cVEMP and ECochG showed high specificity (83.3 and 100%, respectively) and low to moderate sensitivity (22.2 and 71.4%) for long term MD. ECochG sensitivity increased to 89% during a symptomatic period, compared to 33% for cVEMP. However, ECochG can be difficult to schedule during symptomatic periods. Sensitivity of cVEMP for the diagnosis of MD appears limited. Conclusions: ECochG has higher sensitivity than cVEMP in the diagnosis of Ménière's patients, but the ECochG SP/AP amplitude ratio measure is not perfect for the diagnosis of MD.

A systematic review and meta-analysis of extratympanic electrocochleography in Ménière's disease diagnosis.

Objective: Determine whether a combination of electrocochleography determined summating/action potential (SP/AP) ratio and other audiological measurements has greater sensitivity and specificity than that achieved with electrocochleography SP/AP ratio alone in diagnosing definite Ménière's Disease. Design: Systematic review and meta-analysis. Study sample: Pubmed, Cochrane Library, and Web of Science were searched using search terms "electrocochleography", "ECochG, ,"ECoG", "Ménière's Disease", and "Idiopathic Endolymphatic Hydrops". Inclusion criteria were extratympanic electrocochleography methodology, English language publication between January 2002 and December 2017, and the 1995 American Academy of Otolaryngology and Head and Neck Surgery Ménière's disease diagnostic criteria. Five articles satisfied inclusion criteria and were sufficiently detailed for aggregate quantitative analysis of SP/AP ratio (315 subjects) and combination audiological measures (113 subjects). Results: The diagnostic sensitivity and specificity of the SP/AP amplitude ratio was 47.6% and 83.8% and of combination diagnostic measures 63.5% and 89.3%, respectively. Point estimates of sensitivity (p = 0.248) and specificity (p = 0.969) and the summary Receiver Operator Characteristic Curve (p = 0.407) were not statistically significant. Conclusion: Statistically, combination diagnostic measures do not result in greater accuracy of definite Ménière's disease diagnosis compared to the SP/AP amplitude ratio alone. However, given the small sample size further studies are recommended to arrive at a definitive conclusion.

Validating an Evoked Potential Platform for Electrocochleography During Cochlear Implantation.

OBJECTIVE: To validate electrocochleography (ECochG) between an auditory evoked potential (AEP) machine and an established cochlear implant (CI) manufacturer ECochG system. METHODS: Intraoperative validation study at a tertiary referral center. Patients included adults and children undergoing cochlear implantation. Intraoperative ECochG was measured with both the Intelligent Hearing Systems (IHS) Duet AEP machine and Cochlear Corporation (CC) ECochG platform. Recording electrodes captured extracochlear measurements through a standard facial recess. Tone-bursts were presented from 250 Hz to 2 kHz (~110 dB SPL). A fast Fourier transform (FFT) of ECochG waveforms at key frequencies was summed into a total response (ECochG-TR). Pearson's correlation was utilized to evaluate the relationship between IHS-ECochG-TR and CC-ECochG-TR after confirming normality. RESULTS: Thirty patients were enrolled with an average age of 67 years (SD 18.8). In the ear that was implanted, mean preoperative pure-tone average (PTA; 0.5, 1, 2, and 4 kHz) was 87.4 dB HL (SD 19.3) and mean preoperative word-recognition scores (WRS) was 17.0% correct (SD 19.1). There was strong correlation (r = 0.905, 95% confidence interval: 0.809 to 0.954) between IHS-ECochG-TR (median 2.30 µV, range 0.1-148.26) and CC-ECochG-TR (median 3.00 µV, range 0.1-239.63). Four patients underwent transtympanic ECochG with the IHS system for feasibility evaluation and achieved similar responses. CONCLUSION: Extracochlear ECochG has been predictive of CI speech perception performance. The IHS duet system is a valid measure of extracochlear ECochG for the CI population. Future work will utilize this system for measuring transtympanic ECochG to improve preoperative estimation of CI performance. LEVEL OF EVIDENCE: 3 Laryngoscope, 2024.

The Subjective Visual Vertical and Electrocochleography Tests in Individuals with Meniere's Disease.

Introduction: Meniere's disease is an inner ear disorder not associated with central brain structure involvement. Although the ECochG test has been commonly used to diagnose Meniere's disease recently, it has not demonstrated high sensitivity. Therefore, it is recommended that other complementary tests alongside the ECochG test be used to diagnose Meniere's disease. The SVV test has gained popularity recently for this reason, and in this study, it was decided to use the SVV test in both static and dynamic modes, along with the ECochG test, as a tool for diagnosing Meniere's disease and evaluating its diagnostic features. Materials and Methods: The study was conducted on 53 patients with confirmed unilateral Meniere's disease and a normal group. Means were calculated with a 95% confidence interval for the groups, and the corresponding graphs were plotted. Independent t-tests were used to examine the difference in SVV results between the normal and Meniere's groups. The ROC curve was then used to determine the cutoff point and calculate. Results: After investigating the cutoff point for the three SVV conditions (tilted towards the lesion), a cutoff point of 2.1 degrees with a sensitivity and specificity of approximately 0.7 was identified as the best condition for distinguishing the Meniere's group from the healthy group. Conclusion: Finally, based on the findings, it can be concluded that the SVV test has relatively low sensitivity for diagnosing Meniere's disease. Therefore, more than relying solely on its results to identify Meniere's disease is required, and it is suggested that other measures alongside the ECochG and SVV tests be included in future studies for further investigation.

Identifying Slim Modiolar Electrode Tip Fold-Over With Intracochlear Electrocochleography.

OBJECTIVE: To evaluate the predictive value of intracochlear electrocochleography (ECochG) for identifying tip fold-over during cochlear implantation (CI) using the slim modiolar electrode (SME) array. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary referral center. METHODS: From July 2022 to June 2023, 142 patients, including adults and children, underwent intracochlear ECochG monitoring during and after SME placement. Tone-bursts were presented from 250 Hz to 2 kHz at 108 to 114 dB HL. A fast Fourier transform (FFT) allowed for frequency-specific evaluation of ECochG response. ECochG patterns during insertion and postinsertion were evaluated using sensitivity and specificity analysis to predict tip fold-over. Intraoperative plain radiographs served as a reference standard. RESULTS: Fifteen tip fold-over cases occurred (10.6%) with significant ECochG response (>2 µV). Sixty-one cases without tip fold-over occurred (43.0%) with significant ECochG response. All tip fold-overs had both a nontonotopic postinsertion sweep and nonrobust active insertion pattern. No patients with robust insertion or tonotopic sweep patterns had tip fold-over. Sensitivity of detecting tip fold-over when having both nonrobust insertion and nontonotopic sweep patterns was 100% (95% confidence inteval [CI] 78.2%-100%), specificity was 68.9% (95% CI 55.7%-80.1%), and the overall accuracy was 72.0% (95% CI 60.5%-81.7%). CONCLUSION: Intracochlear ECochG monitoring during cochlear implantation with the SME can be a valuable tool for identifying properly positioned electrode arrays. In cases where ECochG patterns are nonrobust on insertion and nontonotopic for electrode sweeps, there may be a concern for tip fold-over, and intraoperative imaging is necessary to confirm proper insertion.

Click SP/AP Area Ratio Vesrus Tone Burst SP Amplitude to Diagnose Ménière's Disease Using Electrocochleography.

OBJECTIVES: To evaluate the sensitivity and the specificity of summating potential (SP)/action potential (AP) area under the curve (AUC) ratio by a transtympanic electrode and a click stimulus (TT-CS), SP/AP AUC ratio by an extratympanic electrode and a click stimulus (ET-CS) and SP amplitude value by a transtympanic electrode and tone burst stimulus (TT-TBS) in regard of Ménière's disease (MD) diagnosis. This is the first study that compares SP amplitude value performed by a TT-TBS and the SP/AP AUC ratio performed by a TT-CS. STUDY DESIGN: Retrospective comparative study. SETTINGS: Ninety-five patients met the inclusion criteria for electrocochleography (ECochG) testing in a tertiary care center. METHODS: The sensitivity and specificity of our different ECochG protocols were calculated in regard of the diagnosis of MD. RESULTS: The patients' mean age was 54 years old (female predominance). The sensitivity and the specificity of SP/AP area ratio by a TT-CS were 88.5% and 70.0%, respectively. On the other hand, the sensitivity and specificity for the SP amplitude value by a TT-TBS were 60.0% and 55.6%, respectively. SP/AP area ratio by TT-CS was statistically better than SP amplitude value by TT-TBS to detect MD disease (P = .016). However, no difference was identified between SP/AP area ratio by ET-CS and SP amplitude value by a TT-TBS (P = .573). CONCLUSION: SP/AP area ratio by click stimulation has higher sensitivity and specificity to detect MD compared to SP amplitude value by tone burst stimulation. ECochG would be extremely useful in the diagnosis of MD if we use the SP/AP area ratio (sensitivity: 88.5%); therefore, it changes the bad reputation of ECochG sensitivity using SP/AP amplitude ratio (sensitivity: 51.7%) for the diagnosis of MD.

Objective evaluation of intracochlear electrocochleography: repeatability, thresholds, and tonotopic patterns.

Introduction: Intracochlear electrocochleography (ECochG) is increasingly being used to measure residual inner ear function in cochlear implant (CI) recipients. ECochG signals reflect the state of the inner ear and can be measured during implantation and post-operatively. The aim of our study was to apply an objective deep learning (DL)-based algorithm to assess the reproducibility of longitudinally recorded ECochG signals, compare them with audiometric hearing thresholds, and identify signal patterns and tonotopic behavior. Methods: We used a previously published objective DL-based algorithm to evaluate post-operative intracochlear ECochG signals collected from 21 ears. The same measurement protocol was repeated three times over 3 months. Additionally, we measured the pure-tone thresholds and subjective loudness estimates for correlation with the objectively detected ECochG signals. Recordings were made on at least four electrodes at three intensity levels. We extracted the electrode positions from computed tomography (CT) scans and used this information to evaluate the tonotopic characteristics of the ECochG responses. Results: The objectively detected ECochG signals exhibited substantial repeatability over a 3-month period (bias-adjusted kappa, 0.68; accuracy 83.8%). Additionally, we observed a moderate-to-strong dependence of the ECochG thresholds on audiometric and subjective hearing levels. Using radiographically determined tonotopic measurement positions, we observed a tendency for tonotopic allocation with a large variance. Furthermore, maximum ECochG amplitudes exhibited a substantial basal shift. Regarding maximal amplitude patterns, most subjects exhibited a flat pattern with amplitudes evenly distributed over the electrode carrier. At higher stimulation frequencies, we observed a shift in the maximum amplitudes toward the basal turn of the cochlea. Conclusions: We successfully implemented an objective DL-based algorithm for evaluating post-operative intracochlear ECochG recordings. We can only evaluate and compare ECochG recordings systematically and independently from experts with an objective analysis. Our results help to identify signal patterns and create a better understanding of the inner ear function with the electrode in place. In the next step, the algorithm can be applied to intra-operative measurements.

Electrocochleography in the diagnosis of third window conditions.

Introduction: Superior semicircular canal dehiscence (SSCD) is the best-known and most common presentation of so-called "third window conditions." There are a variety of diagnostic measures and tests for this condition in the current literature, including air-bone gap, vestibular-evoked myogenic potentials, and electrocochleography (EcochG). The purpose of this study was to investigate the diagnostic utility of EcochG and its relationship to air-bone gap in a cohort of patients with confirmed SSCD. Methods: We reviewed data from 20 patients (11 female and 9 male subjects, age ranging 21-78 years), with confirmed unilateral or bilateral superior canal dehiscence. In total, 11 patients had unilateral SSCD and 9 patients had bilateral SSCD as determined by high-resolution CT scan. This resulted in the inclusion of twenty-nine ears with superior canal dehiscence and 11 normal ears. Results: Our results indicated that all confirmed SSCD ears presented with an abnormal EcochG SP/AP value and that there was a statistically significant difference between normal and dehiscent ears. There was no statistically significant relationship between air-bone gap and SP/AP ratio in the ears diagnosed with SSCD nor was there a significant difference between dehiscent and normal ears in terms of air-bone gap at three frequencies. Discussion: These results are consistent with previous studies showing the diagnostic utility of EcochG for this condition and the variability of air-bone gap. While an unexpected air-bone gap continues to be a red flag for SSCD, its absence along with the presence of subjective symptoms is a reasonable indicator for further clinical investigation to include EcochG.

Effect of Glycerol Administration on ECochG and VEMP Findings in Individual with Meniere's Disease.

The present study aimed to find the effect of glycerol administration on Electrocochleography (ECochG), cervical and ocular Vestibular Evoked Myogenic Potential (c-VEMP, o-VEMP) findings in individual with Meniere's disease. Sixteen participants (32 ears) diagnosed with Meniere's disease underwent ECochG, c-VEMP and o-VEMP for both pre and 1 h post-glycerol administration. Paired t-test indicated that the SP/AP ratio of ECochG measures was significantly improved with post-glycerol administration. There was no significant difference in the mean amplitude of o-VEMP and c-VEMP between pre and post-glycerol administration. However, while individual differences were compared, 75% of the participants reported either improvement in c-VEMP amplitude or newly emerging c-VEMP& o-VEMP. Based on the recommendation by Adams et al. (Otolaryngol Clin North Am 43(5):995-1009, 2010), the improvement on these tests results with post glycerol administration were considered as a significant indicator for the presence of Meniere's disease.With post glycerol administration, the present study found that 84%of participants were found to have an improvement in the amplitude for ECochG measures. There was an improvement in the amplitude measures of o-VEMP and c-VEMP, which were observed in 75% and 68%of participants respectively with post-glycerol administration. Improvement in the amplitude of test measures with post-glycerol administration were observed to be more for cochlear potentials of ECochG followed by vestibular potentials of c-VEMP and o-VEMP. Thus, improvement of ECochG amplitude with post-glycerol administration might serve as an additional indicator for the presence of Meniere's disease.

Are Electrocochleographic Changes an Early Sign of Cochlear Synaptopathy? A Prospective Study in Tinnitus Patients with Normal Hearing.

The mechanism of tinnitus accompanied by a normal audiogram remains elusive. This study aimed to investigate evidence of primary neural degeneration, also known as cochlear synaptopathy, in tinnitus patients with normal hearing thresholds. We analyzed the differences in electrocochleography (ECochG) measurements between normal-hearing subjects with and without tinnitus. Forty-five subjects were enrolled in this study: 21 were in the tinnitus group, defined by chronic tinnitus of over two months' duration with normal audiometric thresholds, and 24 were in the control group, defined by a lack of tinnitus complaints. Electrocochleograms were evoked by 1, 4, 6, and 8 kHz alternating-polarity tone bursts at sound pressure levels (SPLs) of 90−110 dB. The tinnitus group had smaller action potential (AP) amplitudes than the control group for 1, 4, 6, and 8 kHz tone bursts and showed significant amplitude reduction at 1 kHz 110 dB SPL (p < 0.01), 1 kHz 90 dB SPL (p < 0.05), and 4 kHz 110 dB SPL (p < 0.05). There were no significant differences in the summating potential/action potential (SP/AP) amplitude ratios across the four tested frequencies. A trend of reduced AP amplitudes was found in the tinnitus group, supporting the hypothesis that tinnitus might be associated with primary neural degeneration.

Vestibular Migraine versus Méniere's Disease: Diagnostic Utility of Electrocochleography.

Objectives: The diagnostic criteria for vestibular migraine (VM) and Méniere's disease (MD) present an important overlap, which leads to a difficult diagnosis in patients presenting with headache, vertigo, hearing loss, ear fullness, and tinnitus. The objective of our study is to determine whether the area-under-the-curve ratio of the summating potentials (SP) and action potentials (AP) curves on electrocochleography (ECoG) helps differentiate VM from MD with or without the use of the well-established clinical criteria. Method: A retrospective review of patients filling either VM or MD criteria was undertaken between September 2015 and December 2018. All patients underwent ECoG before the introduction of anti-migraine therapy. The prediction of symptom improvement between the clinical criteria and ECoG results was compared by using the Vertigo Symptom Scale. Results: In total, 119 patients were included. An overlap of 36% exists between patients filling VM and MD criteria. Clinical criteria alone did not demonstrate a significant prediction of symptom response to anti-migraine therapy (VM 83%, MD 51%; p = 0.10). However, ECoG results alone did demonstrate adequate prediction (VM 94%, MD 32%; p < 0.001). A negative ECoG result combined with the clinical criteria of VM (100% symptom improvement) was shown to be more predictive of treatment response when compared to clinical criteria alone (83% symptom improvement) (p = 0.017). Finally, when used in patients filling both the VM and MD criteria (VMMD), ECoG was able to predict symptom improvement, thus better differentiating both diseases (normal ECoG: 95%, abnormal ECoG 29%; p < 0.001). Conclusion: Combining VM criteria with normal ECoG using the AUC ratio seems superior in predicting adequate symptom improvement than VM criteria alone.

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.

Electrophysiology and genetic testing in the precision medicine of congenital deafness: A review.

BACKGROUND: Congenital hearing loss is remarkably heterogeneous, with over 130 deafness genes and thousands of variants, making for innumerable genotype/phenotype combinations. Understanding both the pathophysiology of hearing loss and molecular site of lesion along the auditory pathway permits for significantly individualized counseling. Electrophysiologic techniques such as electrocochleography (ECochG) and electrically-evoked compound action potentials (eCAP) are being studied to localize pathology and estimate residual cochlear vs. neural health. This review describes the expanding roles of genetic and electrophysiologic evaluation in the precision medicine of congenital hearing loss.The basics of genetic mutations in hearing loss and electrophysiologic testing (ECochG and eCAP) are reviewed, and how they complement each other in the diagnostics and prognostication of hearing outcomes. Used together, these measures improve the understanding of insults to the auditory system, allowing for individualized counseling for CI candidacy/outcomes or other habilitation strategies. CONCLUSION: Despite tremendous discovery in deafness genes, the effects of individual genes on neural function remain poorly understood. Bridging the understanding between molecular genotype and neural and functional phenotype is paramount to interpreting genetic results in clinical practice. The future hearing healthcare provider must consolidate an ever-increasing amount of genetic and phenotypic information in the precision medicine of hearing loss.

The possibility of cochlear synaptopathy in young people using a personal listening device.

OBJECTIVE: To evaluate the association of listening to music loudly through personal listening devices with cochlear synaptopathy in young adults. METHODS: Fifty healthy young adults selected among 109 volunteers were included in the study. Participants of high risk (n=25) and low risk (n=25) groups estimated according to ETDNL (estimated total daily noise level) were evaluated using pure tone audiometry, tympanometry, matrix test, electrocochleography (EcochG) and auditory brainstem response (ABR) to evaluate the occurrence of cochlear synaptopathy. RESULTS: Audiometric thresholds between the groups were not significantly different (p>0.05). High risk group participants showed poorer performance than the low-risk group on the TurMatrix test, in non-adaptive noise with -5 SNR and -7.5 SNR, and at the 50% understanding SNR level with headphones (p<0.01). There was no difference in the adaptive free field in noise test at which 50% understanding was achieved (p>0.05). The AP amplitudes on EcochG and wave V amplitudes on ABR were significantly smaller in the high-risk group (p<0.05). There was no association between ETDNL and I/V ratio on ABR. CONCLUSION: Poorer performance in TurMatrix and other electrophysiologic tests revealed the negative effect of personal listening devices on the auditory system. Our findings support the hypothesis that personal listening devices could cause cochlear synaptopathy. Long-term studies are needed to determine the effects of binaural hearing and duration of noise exposure on the auditory system.

Evolution of migraine vertigo in overlapping syndrome with Ménière's disease: prognostic role of instrumental examination.

INTRODUCTION: Migraine vertigo (MV) and Ménière's disease (MD) share several signs and symptoms such as tinnitus, fullness, photophobia, phonophobia, headache and vertigo spells lasting hours. OBJECTIVE: The aim of the present study was to prospectively observe patients with MV with a sporadic audiological symptom evaluated with clinical examination, Vestibular Evoked Myogenic Potentials (VEMPs), ECochG and v-HIT. RESULTS: The finding of VEMP asymmetry, according to our cut-off of 33% of difference between sides, resulted in 20 cases, of which 6 had asymmetry of both c-VEMPs and o-VEMPS, all with development of fluctuating hearing during follow-up. ECochG was positive for endolymphatic hydrops in 12 patients. CONCLUSIONS: The evolution of MV may have a variable course in which some patients may develop symptoms typical of MD. The two diseases may be contextually present at the same time configuring an overlapping syndrome, and asymmetric VEMPs might predict development of fluctuating hearing.

Psychoacoustic and electrophysiological electric-acoustic interaction effects in cochlear implant users with ipsilateral residual hearing.

Cochlear implant users with ipsilateral residual hearing combine acoustic and electric hearing in one ear, this is called electric-acoustic stimulation (EAS). In EAS users, masking can be shown for electric probes in the presence of acoustic maskers and vice versa. Masking effects in acoustic hearing are generally attributed to nonlinearities of the basilar membrane and hair cell adaptation effects. However, similar masking patterns are observed more centrally in electric hearing. Consequently, there is no consensus so far on the level of interaction between the two modalities. Animal studies have shown that electric-acoustic interaction effects can result in reduced physiological responses in the cochlear nerve and the inferior colliculus. In CI users with residual hearing, it has recently become feasible to record intracochlear potentials with a high spatial resolution via the implanted electrode array. An investigation of the electrophysiological effects during combined electric-acoustic stimulation in humans might be used to assess peripheral mechanisms of masking. Seventeen MED-EL Flex electrode users with ipsilateral residual hearing participated in both a behavioral and a physiological electric-acoustic masking experiment. Psychoacoustic methods were used to measure the changes in behavioral thresholds due to the presence of a masker of the opposing modality. Subjects were stimulated electrically with unmodulated pulse trains using a research interface and acoustically with pure tones delivered via headphones. Auditory response telemetry was used to obtain objective electrophysiological changes of electrically evoked compound action potential and electrocochleography for electric, acoustic and combined electric-acoustic presentation in the same subjects. Behavioral thresholds of probe tones, either electric or acoustic, were significantly elevated in the presence of acoustic or electric maskers, respectively. 15 subjects showed significant electric threshold elevation with acoustic masking that did not depend on the electric-acoustic frequency difference (EAFD), a measure for the proximity of stimulation sites in the cochlea. Electric masking showed significant threshold elevation in eleven subjects, which depended significantly on EAFD. In the electrophysiological masking experiment, reduced responses to electric and acoustic stimulation with additional stimulation of the opposing modality were observed. Results showed a similar asymmetry as the psychoacoustic masking experiment. Response reduction was smaller than threshold elevation, especially for electric masking. Some subjects showed reduced responses to acoustic stimulation with electric masking, especially for small EAFD. The reduction of electrically evoked responses was significant in some subjects. No correlation was observed between psychoacoustic and electrophysiological masking results. From present study, it can be concluded that both electric and acoustic stimulation mask each other when presented simultaneously. Electrophysiological measurements indicate that masking effects are already to some extent present in the periphery.

Intratympanic Injection of Dexamethasone and Electrocochleographic Data in Cases of Definite One Sided Refractory Meniere's Disease.

INTRODUCTION: Meniere's disease (MD) is a disease of the inner ear that presents itself with repeated episodes of vertigo (96.2%), tinnitus (91.1%), and sensorineural hearing loss (87.7 %). In this article we sought to assess the effects of intratympanic (IT) injections of dexamethasone on definite cases of MD using electrocochleography (ECOG). MATERIALS AND METHODS: In this hospital-based case series in 36 patients, we measured audiometric values and ECOG in all patients before, 1 month and 6 months after 4-mg/mL IT injections of dexamethasone. RESULTS: Four patients (11%) had improved hearing following the intervention. No difference in pure tone audiometry (PTA) was observed following IT injections (P=0.492), while speech discrimination score (SDS) was significantly improved (P=0.008). There was a significant improvement in vertigo 1 month after IT injections (P<0.001), although this effect did not last for 6 months. No significant change in ECOG was observed between before and after treatment (P=0.052). CONCLUSION: IT dexamethasone injections can improve vertigo in definite cases of MD, although it seems that the effect is only temporary.

The Clinical Uses of Electrocochleography.

The clinical uses of electrocochleography are reviewed with some technical notes on the apparatus needed to get clear recordings under different conditions. Electrocochleography can be used to estimate auditory thresholds in difficult to test children and a golf club electrode is described. The same electrode can be used to obtain electrical auditory brainstem responses (EABR). Diagnostic testing in the clinic can be performed with a transtympanic needle electrode, and a suitable disposable monopolar electrode is described. The use of tone bursts rather than click stimuli gives a better means of diagnosis of the presence of endolymphatic hydrops. Electrocochleography can be used to monitor the cochlear function during surgery and a long coaxial cable, which can be sterilized, is needed to avoid electrical artifacts. Recently electrocochleography has been used to monitor cochlear implant insertion and to record residual hearing using an electrode on the cochlear implant array as the non-inverting (active) electrode.

Tone Burst Electrocochleography for the Diagnosis of Clinically Certain Meniere's Disease.

The technique of transtympanic electrocochleography was initially developed as an objective hearing threshold test by Eggermont. Gibson et al. (1977) claimed that an enlarged direct current component of the action potential (AP) called the summating potential (SP) is an indication of endolymphatic hydrops, later confirmed by Coates who proposed an SP/AP ratio measure. This led to numerous publications using diagnostic ratios of 0.33-0.35. The insensitivity led to an eventual disenchantment with the test as a reliable objective test for Meniere's disease. It was further confused by audiologists employing remote canal or ear drum electrodes which give a response about one-fourth of the magnitude obtained by an electrode in contact with the cochlea. Subsequently Gibson stated that an SP/AP ratio of <0.5 is not diagnostic for hydrops. He then showed that a tone burst stimulus gave the test a significantly higher sensitivity and specificity, which has been supported by others. On MRI inner ear imaging with gadolinium hydrops can be seen, but the quality of images and what is seen may vary according to brand of scanner, settings, mode of gadolinium administration, and the possibility that gadolinium entry may favor the vestibule. Transtympanic tone burst electrocochleography is to date the simplest, cheapest and most sensitive technique for detecting cochlear endolymphatic hydrops to confirm a diagnosis of Meniere's disease.