Electrical Auditory Brainstem Response Research Articles

Intraoperative assessment of cochlear nerve functionality in various vestibular schwannoma scenarios: Lessons learned

The use of cochlear implants (CIs) is on the rise for patients with vestibular schwannoma (VS). Besides CI following tumor resection, new scenarios such as implantation in observed and/or irradiated tumors are becoming increasingly common. A significant emerging trend is the need of intraoperative evaluation of the functionality of the cochlear nerve in order to decide if a CI would be placed. The purpose of this paper is to explore the experience of a tertiary center with the application of the Auditory Nerve Test System (ANTS) in various scenarios regarding VS patients. The results are compared to that of the studies that have previously used the ANTS in this condition.Patients with unilateral or bilateral VS (NF2) who were evaluated with the ANTS prior to considering CI in a tertiary center between 2021 and 2023 were analyzed. The presence of a robust wave V was chosen to define a positive electrical auditory brainstem response (EABR). Two patients underwent promontory stimulation (PromStim) EABR previous to ANTS evaluation.Seven patients, 2 NF-2 and 5 with sporadic VS were included. The initial scenario was simultaneous translabyrinthine (TL) tumor resection and CI in 3 cases while a CI placement without tumor resection was planned in 4 cases. The ANTS was positive in 4 cases, negative in 2 cases, and uncertain in one case. Two patients underwent simultaneous TL and CI, 1 patient simultaneous TL and auditory brainstem implant, 3 patients posterior tympanotomy with CI, and 1 patient had no implant placement. In the 5 patients undergoing CI, sound detection was present. There was a good correlation between the PromStim and ANTS EABR. The literature research yielded 35 patients with complete information about EABR response. There was one false negative and one false positive case; that is, the 28 implanted cases with a present wave V following tumor resection had some degree of auditory perception in all but one case.The ANTS is a useful intraoperative tool to asses CI candidacy in VS patients undergoing observation, irradiation or surgery. A positive strongly predicts at least sound detection with the CI.

Electric Auditory Brainstem Response (EABR) as A predictor of Speech Perception Outcome in Cochlear Implanted Children

Electric Auditory Brainstem Response (EABR) as A predictor of Speech Perception Outcome in Cochlear Implanted Children

Liquid Metal‐Based High‐Density Interconnect Technology for Stretchable Printed Circuits

AbstractHigh‐density interconnect (HDI) technology for liquid metal (LM)‐based stretchable printed circuit boards is crucial for expanding their applicability. HDI technology provides high‐resolution multilayer circuits with a high density of components, as required for next generation of neuroprobes and ultrasonic and sensor arrays. This study presents a HDI technique utilizing laser engraved micro grooves in silicone with a protective lift‐off mask of polyvinyl alcohol (PVA) and subsequent microscale LM particle spray deposition. This approach achieves high‐resolution LM patterns and enables multilayer connectivity and high‐density integration of components simultaneously, that is, realizing HDI technology. It is demonstrated using a stretchable 0201 LED display with a density of six leads per mm2 and a cochlear implant (CI) electrode array. The demonstrated manufacturing of the CI has the potential to enable fully automated printed circuit board manufacturing of such implants with increased precision and throughput. Implants in guinea pigs show that the CI is capable of activating the auditory neuron with electrical auditory brainstem response (eABR) and electrical compound action potential (eCAP) of high quality. Moreover, the U‐shaped cross section of the LM interconnects provides a higher mechanical shock resistance of the circuit than that of normal rectangular cross sections.

Intra-operative test electrode and electrical auditory brainstem response after preoperative assessment in cochlear implant candidacy

Abstract Introduction: Over the last years, in doubt of cochlear implant (CI) candidacy, assessment of excitability of the auditory nerve is performed with pre-operative tests. These tests are the pre-operative (pre-op.) performed electrical auditory brainstem (EABR) and the late response (EALR) recorded with trans-tympanic promontory stimulation in local anesthesia. But in some cases after such preoperative tests there is still doubt about the excitability of the auditory pathway. The most reliable EABR is recorded with using stimulation via the CI. However, before CI implantation,, an intra-cochlear test electrode could be used in order to achieve similar EABR results. Methods: In doubtful cases of patients who underwent pre-op. EABR, we performed EABR by a test electrode, part of the auditory nerve test system. This measurement was used to confirm the pre-operative results just before CI implantation. Additionally, EABR using CI stimulation was performed intra-operatively right after the CI implantation to confirm EABR using the test stimulation electrode results. Results: Six subjects were included in this study. They were tested by pre-op. EABR (n=6), pre-op. EALR (n=5), intra-op. EABR using test electrode (n=6), intraop. EABR via CI (n=6), and post-op. EABR (n=2), and postop. EALR (n=2). In two cases, intra-operative EABR showed a positive, i.e. clearly measureable, response whereas there was a doubtful response in pre-op. EABR. Intra-op. EABRs (test electrode and CI stimulation) showed the same results in all cases. Waveforms of EABR using test electrode look similar to EABR using CI stimulation but with more defined peaks compare to the pre-op. EABR. In one case with all-over positive EABR, pre-op. EALR, and post-operative EALR were matching. Conclusion: Intra-op. EABR using test electrode was easy to record and it shows similar results to EABR using CI stimulation. Intra-op. EABR using test electrode may help in confirming the results of not clear preop. EABR with a minimal increase in recording time.

Preoperative EABR evaluation of auditory pathway integrity in patients with different etiology and postoperative effect estimation.

To evaluate the effect of electrical auditory brainstem response (EABR) on the integrity evaluation of auditory pathway and the prediction of postoperative effect of cochlear implantation in patients with different etiology of hearing loss. A total of 580 patients with neuropathic deafness who underwent cochlear implantation surgery from August 2011 to December 2020 were selected for EABR test. The preoperative EABR waveform was analyzed, and parameters such as V wave amplitude, threshold, latency and interval of each wave, and slope of V wave I/O curve were measured. Neural response telemetry (NRT) test was performed during MAP 1month after operation, and C and T values of the machine were recorded. The total EABR extraction rate was 98.45% among 580 patients, including 100% for the normal structure group and enlarged vestibular aqueduct group (LVAS), 92.44% for other malformed group. The average threshold of V wave in patients with normal cochlear structure was significantly better than the malformation groups (p < 0.05). The total extraction rate of NRT was 78.62%, including 99.72% in the group with normal structure, 95.65% in the LVAS group, 1.85-88.24% in the group with other malformations, and 0% in the cochlear ossification group. The correlation analysis showed a statistically significant correlation between the average preoperative EABR threshold and the C value of NRT. Preoperative EABR could evaluate the integrity of auditory conduction pathway of patients with cochlear implantation and predict the postoperative hearing rehabilitation effect.

Visualizing Contralateral Suppression of Hearing Sensitivity via Acoustic and Electric Brainstem Audiometry in Bimodal Cochlear Implant Patients: A Feasibility Study

Introduction: The medial olivocochlear reflex (MOCR) is a part of the binaural processing strategies and influences the efferent auditory pathway in normal-hearing individuals. Patients with asymmetric hearing loss often benefit from a bimodal hearing solution with a cochlear implant (CI) and a hearing aid (HA). However, hearing performances may vary with some surprisingly high- or low-performing CI/HA users. A potential role of the MOCR among these patients warrants further investigation. Otoacustics emissions are an established method to visualize the reflex; however, this technique implies some disadvantages. To visualize the MOCR via auditory brainstem response (ABR) could be a promising alternative. Methods: Twenty-three bimodal CI/HA users were enrolled. Experimental setup was as follows: I. electrical ABR on the CI side was recorded with and without simultaneous contralateral noise signal at the HA side, II. acoustic ABR was recorded on the HA side with and without simultaneous contralateral noise at the CI side. Brainstem thresholds and amplitudes of waveforms I–V with and without contralateral noise were compared. Potential correlations of patient-related factors and hearing performances were analysed. Results: In four individuals, a reduction of brainstem audiometry thresholds could be observed at the acoustic brainstem audiometry. In these cases, results could be reproduced. Summarizing ABR measurements at the HA side of all individuals, no relevant changes of ABR thresholds (dB nHL) or waveform amplitude reductions (nV) could be observed irrespective of the presence or absence of a contralateral suppression signal. Conclusion: Threshold changes of acoustic ABR upon presentation of a contralateral suppression signal could not generally be measured in bimodal CI users. However, in a subgroup, a highly reproducible effect was demonstrated if a contralateral suppression signal was applied. A reactivated rather than rehabilitated MOCR may have accounted for this effect in this subgroup. One could speculate that in these patients, bimodal fitting could be affected by the MOCR efferents.

LA-TT-EALR / PromCERA: Comparison of preoperatively performed electrically evoked auditory potentials at the brainstem and cortical level during local anesthesia

Abstract Introduction: In the past years, some groups established methods to use promontory stimulation and subjective responses as a tool for preoperative stimulation of the cochlea before cochlear implant (CI) surgery by a temporary transtympanic needle placed on the middle ear. Our research group tested CI candidates when the presence of the auditory nerve could not be confirmed by other pre-operative tests and analyzed objective results of electrical auditory brainstem response recorded with trans-tympanic promontory stimulation in local anesthesia (LA-TT-EABR) with a “golfclub” electrode placed on the round window niche (Polterauer et al. 2018). However, EABR recording suffers from an electrical artifact from the stimulation and focuses on the excitability of the solely auditory nerve. We hypothesize that late evoked potential response (EALR) can be used for the assessment of the auditory pathway up to the cortical area with less electrical artifact interference. Methods: The trans-tympanic electrically evoked auditory late response in local anesthesia (LA-TT-EALR) was added to our protocol right after the LA-TT-EABR in a unique recording session. In this study, we investigated the feasibility of LA-TT-EALR using MED-EL hardware and software. These two pre-operative trans-tympanic measurements, LATT- EABR and LA-TT-EALR, were compared. Results: In a total n=18 tested subjects, it could be possible to record LA-TT-EABR in 10 and LA-TT-EALR in 13. In contrast to the fact that acoustically evoked auditory late responses are often hard to detect, and an electrical artifact heavily affects LA-TT-EABR, we did not experience these problems on LA-TT-EALR recordings. The matching between two measurements was present in 67% of the cases. Conclusion: LA-TT-EALR may be a complement to the existing state-of-the-art LA-TT-EABR for pre-operative assessment before cochlear implantation offering information about auditory pathways in the auditory brainstem and cortex with a small increase of recording time. The equivalency of these two methods is encouraging.

Intraoperative Cochlear Nerve Monitoring for Vestibular Schwannoma Resection and Simultaneous Cochlear Implantation in Neurofibromatosis Type 2: A Case Series

Neurofibromatosis type 2 (NF2) often results in profound hearing loss and cochlear implantation is an emerging hearing rehabilitation option. However, cochlear implant (CI) outcomes in this population vary, and intraoperative monitoring to predict cochlear nerve viability and subsequent outcomes is not well-established. To review the use of intraoperative electrically evoked cochlear nerve monitoring in patients with NF2 simultaneous translabyrinthine (TL) vestibular schwannoma (VS) resection and cochlear implantation. A retrospective review was performed of 3 patients with NF2 that underwent simultaneous TL VS resection and cochlear implantation with electrical auditory brainstem response (eABR) measured throughout tumor resection. Patient demographics, preoperative assessments, surgical procedures, and outcomes were reviewed. Patients 1 and 3 had a reliable eABR throughout tumor removal. Patient 2 had eABR pretumor removal, but post-tumor removal eABR presence could not be reliably determined because of electrical artifact interference. All patients achieved auditory percepts upon CI activation. Patients 1 and 2 experienced a decline in CI performance after 1 yr and after 3 mo, respectively. Patient 3 continues to perform well at 9 mo. Patients 2 and 3 are daily users of their CI. Cochlear implantation is attainable in cases of NF2-associated VS resection. Intraoperative eABR may facilitate cochlear nerve preservation during tumor removal, though more data and long-term outcomes are needed to refine eABR methodology and predictive value for this population.

Is Cochlear Implantation Effective for Auditory Rehabilitation Following Vestibular Schwannoma Treatment?

Hearing loss in patients with vestibular schwannoma (VS), before and after treatment, is known to negatively impact quality of life. A variety of treatment options are available for auditory rehabilitation. Contralateral routing hearing aids (CROS) and osseointegrated conduction devices can shuttle the auditory stimuli to the contralateral ear after treatment in unilateral vestibular schwannoma patients but cannot improve sound localization. Auditory Brainstem Implantation (ABI) is approved by FDA for patient 12 years and older with Neurofibromatosis Type 2 (NF2) and open-set speech after ABI is an exception rather than the rule.1 Increasingly, cochlear implantation (CI) is being recognized as a feasible option in VS patients. In this Triological Society Best Practice, we review the current evidence to determine if CI is an effective intervention for auditory rehabilitation after VS treatment. The largest systematic review to date on CI outcomes following VS resection was published by Wick et al.1 They identified 93 patients across 29 studies that met their inclusion criteria and compared open-set speech and daily device usage between two patient groups. The first group included 46 patients that underwent translabyrinthine (TL) VS resection with simultaneous CI. The second group included 47 patients who underwent delayed CI after tumor resection by TL, middle fossa (MF), or retrosigmoid (RS) approaches with variable time delays to CI across cases. Some of these patients underwent placement of dummy prosthesis to mitigate cochlear obliteration per surgeon preference, while others did not. Authors identified a high degree of heterogeneity in reporting of CI postoperative outcomes between different studies, which was attributed to differences in language and institutional protocols. Four cases were reportedly noted to have cochlear fibrosis causing difficulty with lead insertion, all of these were in the delayed group. Overall, they reported that open-set mean word scores of 52% and 37.9% in the simultaneous and delayed groups, respectively. The mean sentence scores were 65.4% in the simultaneous CI group versus 49.6% in the delayed group. About 70% of NF2 patients reported lower daily CI usage compared to 93% sporadic VS group negatively influencing their CI performance. Subsequently, Dahm et al. studied the value of electrical auditory brainstem response (eABR) testing on patients undergoing simultaneous VS resection and CI.2 The study included five patients with unilateral sporadic VS who underwent TL VS resection. Two patients had a history of presbycusis, one patient had undergone previous RS resection for VS, and another had previous stereotactic radiosurgery (SRS). Preoperative eABR was completed using a trans-tympanic promontory electrode, and it was positive in all tested patients. Intraoperative eABR testing was also performed and was negative in three of five cases after tumor resection. Nonetheless, all five patients underwent CI. Only one of three patients with negative intraoperative eABR subsequently had auditory perception. Three out of five patients were reported as daily users with open-set speech recognition at 12 month follow-up. Four out of five patients in this small cohort completed quality of life (QoL), Speech, Spatial and Qualities of hearing scale abbreviated-12 (SSQ12), the Assessment of Quality of Life-8D (AqoL-8D) and the Tinnitus questionnaires (mini-TQ). The SSQ12 showed an increased or stable hearing specific QoL; the AqoL-8D showed an increase in all patients. The mini-TQ showed more or less stable results except in one patient who had an increase in the score after CI. Authors concluded that CI was a promising option with a favorable complication profile for sporadic vestibular schwannoma patients and that preservation of eABR response following surgical resection predicted good outcome. In 2021, Deep et al. published a retrospective series on CI outcomes in 24 NF2 patients with a mean follow-up of 4 years.3 Of the 24, 12 patients underwent microsurgical VS resection by TL, RS, or MF approach, while the other 12 patients were either observed or underwent SRS. One surgical patient underwent simultaneous CI, while the rest underwent delayed implantation. The inclusion criteria for CI were the presence of an intact cochlear nerve and presence of T2 signal in cochlea. Eight of the 12 surgery patients achieved postoperative open-set speech recognition with mean word score of 43%. Of note, three of those eight patients experienced tumor growth and subsequently lost CI functionality at later follow-up. Partial obliteration of the cochlea was encountered in three cases with reduced preoperative T2 MRI signal. The time delay to their implantation was quite variable, ranging from 6 months to 10 years. The authors concluded that while nonoperative therapies may yield better hearing outcomes for NF2 patients with larger tumors, CI are effective if the cochlear nerve is intact regardless of the modality of tumor management. In addition to presence of eABR and intact cochlear nerve, Patel et al. reported that the presence of fluid signal in the cochlea on T2-weighted MRI is also a predictor of better CI outcome. They studied nine patients with sporadic VS and 13 with retrocochlear pathologies (neurosarcoidosis, pontine stroke, and head neck malignancies post irradiation) who underwent CI with a mean follow-up of 2 years.4 All patients had cochlear fluid signal on imaging and intact cochlear nerve by preoperative promontory stimulation testing; intraoperative electrical testing was not performed. Of the nine patients with sporadic VS group: four underwent TL or MF resection with simultaneous CI and five underwent SRS or observation and CI. A mean Consonant Nucleus Consonant (CNC) word score of 55% post-CI was achieved in patients with retrocochlear pathologies compared to 18% in two sporadic VS patients with follow-up of less than 6 months post-activation. Of the other seven sporadic VS patients, two were nonusers, two used CI for less than 6 hours daily and no data were available for three patients. The authors concluded that patients with sporadic VS exhibited guarded hearing outcomes compared to those with non-VS retrocochlear pathologies. Similarly, Medina et al. investigated the impact of intact cochlear nerve on CI outcome in 14 patients that underwent TL VS resection with simultaneous CI; mean follow-up was 12 months.5 To assess nerve function, they used a disposable intracochlear test electrode to perform intraoperative eABR testing. Nine of 14 patients had positive eABR after resection and all of them obtained auditory perception, defined as sound detection at 50 dB or below, with their simultaneous CI. Only one of five patients with negative intraoperative eABR testing had auditory perception with their CI. The authors concluded that eABR is a useful tool to complement surgeon decision-making regarding implantation after VS resection. Although CI is feasible, only some patients can achieve open-set speech recognition. The presence of cochlear fluid signal on T2-weighted MRI, presence of an intact, functioning cochlear nerve, and positive eABR test following tumor resection may assist in predicting CI outcomes. CI outcome data following treatment for VS are highly variable and there are paucity of quality of life studies in this group of patients. Objective patient reported outcome measures and quality of life data are needed to counsel patients and set realistic expectations about CI outcomes in VS patients. The several case series mentioned in this article each represent level IV clinical evidence. The systematic review which includes both case series and case reports, also represents level IV clinical evidence. Larger scale prospective randomized controlled trials (RCTs) with standardized preoperative and postoperative testing and follow-up are needed. We thank Dr Nathan, Chairman, Dept of Otolaryngology and Head Neck Surgery, LSU Health, Shreveport, for her encouragement and support.

Risk Factors for Facial Nerve and Other Nonauditory Side Effects Following Cochlear Implantation.

The purpose of this study was to characterize a cohort of patients with nonauditory side-effects (NASx) following cochlear implant (CI) surgery. Retrospective case review. Tertiary referral center. One hundred twenty three multichannel CI recipients with intraoperative facial nerve stimulation (FNS). Intraoperative electrical auditory brainstem responses (eABR) during CI surgery. Nonauditory side effects post-CI activation. Intraoperative FNS was identified in 2.26% of patients (123/5441), of whom, 34% (42/123) experienced VII stimulation on CI activation. Pain was experienced by 22% (27/123) and vestibular dysfunction was experienced by 4% (5/123) of cases. All case who experienced pain and/or vestibular NASx also experienced VII stimulation. The majority of cases were managed by CI remapping or observation and habituation.Significant relationships were found between etiology of hearing loss and presence of FNS upon initial activation (p < 0.05). No significance was found between FNS intraoperatively and at initial activation for all assumed mechanisms of hearing loss (p > 0.05) with the exceptions of acquired hearing loss of undetermined etiology and toxic etiology group (p < 0.05).There was no significant impact of implant array design (p > 0.05). This study has characterized patients with NASx in a large cohort of CI patients. One third of cases identified with FNS intraoperatively, developed NASx post-CI activation. Risk factors for NASx postactivation include high-risk etiologies and intraoperative objective measures (i.e., eABR). This may assist surgeons and audiologists to identify at-risk patients who may need modifications in CI program planning.

Cochlear Implantation in Cases of Inner Ear Malformation: A Novel and Simple Grading, Intracochlear EABR, and Outcomes of Hearing.

To propose a simple grading of inner ear malformation (IEM) and investigate intracochlear electrical auditory brainstem response (EABR) and outcomes for hearing in terms of the novel grading system. Retrospective case review. Tertiary referral center. Sixty patients with IEMs who received cochlear implants. Grading according to observation of modiolus deficiency and/or internal auditory canal (IAC) cochlear nerve deficiency (CND). Intracochlear EABR and categories of auditory performance (CAP) scores were assessed; children in school were categorized according to the type of school attended. Among 60 patients, 38% were classified as Grade I (modiolus present + normal cochlear nerve), 22% as grade II (modiolus deficiency + normal cochlear nerve), 33% as grade III (modiolus present + IAC CND), and 7% as grade IV (modiolus deficiency + IAC CND). During the operation, 93% of Grade I, 36% of Grade II, 23% of Grade III, and 50% of Grade IV patients showed typical EABR waves. CAP scores of 4 or more were obtained from 91% of Grade I, 62% of Grade II, 35% of Grade III, and 25% of Grade IV. Whereas none of children in Grades III and IV entered main stream school, 55% of Grade I and 25% of Grade II entered mainstream schools. Outcomes of hearing with cochlear implantations in IEM children depend on the severity of IEM and IAC CND. Our novel grading of IEM is simple and can be useful for understanding the severity of IEM.

Effects of different electrodes used in bone-guided extracochlear implants on electrical stimulation of auditory nerves in guinea pigs.

Objective:Conventional cochlear implants provide patients who are deaf with hearing via electrical intracochlear stimulations. Stimulation electrodes are inserted into the cochlea through a cochleostomy or round window membrane (RWM) approach. However, these methods might induce cochlear ossificans and loss of residual hearing by damaging inner ear structures. To avoid an invasive electrode insertion, we developed a novel bone-guided extracochlear implant that stimulated the auditory nerves between the cochlear bones and the RWM to prevent cochlea damage. Power consumption plays an important role in wireless implantable electronic devices. Therefore, we aimed to investigate the effects of different electrodes on the stimulating threshold currents of the auditory nerve and the power consumption of bone-guided extracochlear implants using a commercial stimulator.Materials and Methods:Inert aurum (Au) electrodes were compared with biocompatible platinum (Pt) and iridium oxide (IrOx) electrodes in practical implantable applications. IrOx electrodes were used for their high-charge storage capacity, low impedance, and biocompatibility. The electrodes were fabricated via sputtering and were experimentally characterized with cyclic voltammetry and then examined using in vivo tests.Results:Based on electrical auditory brainstem responses, IrOx electrodes yielded lower acoustic nerve-stimulating threshold currents (132 μA) compared with Au electrodes (204 μA). IrOx electrodes also had a lower acoustic nerve stimulating threshold current (132 μA) compared with Pt electrodes (168 μA).Conclusion:As expected, IrOx electrodes were beneficial in the development of multielectrode bone-guided extracochlear implants, with the lowest acoustic nerve-stimulating threshold and current consumptions compared with Au and Pt electrodes.

E-ABR in Patients with Cochlear Implant: A Comparison between Patients with Malformed Cochlea and Normal Cochlea

This study aims to compare the electrical auditory brainstem response (EABR) following cochlear implant (CI) surgery in pediatric subjects with cochlear malformation and a normal cochlea, in order to assess the sensitivity of EABR and to evaluate the surgery outcome. A total of 26 pediatric subjects who were deaf and scheduled for CI surgery were enrolled into this case control study. Group A (n=20) included subjects with a normo-conformed cochlea. Group B (n=6) included subjects with cochlear malformation. Subjects were evaluated with EABR immediately (T0) and 6 months (T1) post-CI surgery. The EABR Waves III and V average amplitude and latency were compared across time, separately for each group, and across groups, separately for each time. Auditory brainstem response (ABR) could only be recorded in Group A. We were able to record EABR from all subjects at T0 and T1, and waves III and V were present in all the recorded signals. There were no statistically significant differences between T0 and T1 in EABR Waves III and V in terms of average amplitude and latency in neither group. When comparing Groups A and B, the only statistically significant difference was the average amplitude of wave V, both at T0 and T1. EABR is a valid tool to measure the auditory nerve integrity after CI surgery in patients with a normal and malformed cochlea, as shown by its ability to measure waves III and V when ABR is absent. The EABR testing should be performed before and after CI surgery, and EABR should be used as a measure of outcome, especially in patients with a malformed cochlea.

Laminin-coated electrodes improve cochlear implant function and post-insertion neuronal survival

The benefits of Cochlear implant (CI) technology depend among other factors on the proximity of the electrode array to the spiral ganglion neurons. Laminin, a component of the extracellular matrix, regulates Schwann cell proliferation and survival as well as reorganization of actin fibers within their cytoskeleton, which is necessary for myelination of peripheral axons. In this study we explore the effectiveness of laminin-coated electrodes in promoting neuritic outgrowth from auditory neurons towards the electrode array and the ability to reduce acoustic and electric auditory brainstem response (i.e. aABR and eABR) thresholds. In vitro: Schwann cells and neurites are attracted towards laminin-coated surfaces with longer neuritic processes in laminin-coated dishes compared to uncoated dishes. In vivo: Animals implanted with laminin-coated electrodes experience significant decreases in eABR and aABR thresholds at selected frequencies compared to the results from the uncoated electrodes group. At 1 month post implantation there were a greater number of spiral ganglion neurons and neuritic processes projecting into the scala tympani of animals implanted with laminin-coated electrodes compared to animals with uncoated electrodes. These data suggest that Schwann cells are attracted towards laminin-coated electrodes and promote neuritic outgrowth/ guidance and promote the survival of spiral ganglion neurons following electrode insertion trauma.

Evaluating Auditory Pathway by Electrical Auditory Middle Latency Response and Postoperative Hearing Rehabilitation

ABSTRACTObjective: To establish an effective detection method to evaluate auditory pathway in patients by electrical evoked middle latency response (EMLR) before artificial cochlear implantation, and to analyze the relationship between postoperative hearing rehabilitation and auditory cortex functions. Methods: Twenty-three patients with artificial cochlear implant were recruited. EMLR was measured after adjusting the depth of anesthesia. The electrical auditory brainstem response (EABR) mode with monopolar stimulation and two-phase alternating current square waves was selected. The parameters of EMLR waveforms were recorded by the EABR measurement system. Nerve response telemetry (NRT) was examined by measuring threshold level (T value) and comfortable level (C value) 1 month after power-on, and hearing and speech development was followed up 12 months later.Results: The detection rate of EMLR was 95.65%. The waveforms of EMLR were comparable to those of auditory middle latency response (AMLR), showing decreased latency and interval but similar amplitude. The induction rate of NRT was 69.23%, which was much lower than that of EMLR. The EMLR thresholds were significantly correlated to the T and C values, and were comparable to the T values numerically. The Spearman's r value between EMLR waveforms and CAP scores after using the cochlear implant for 12 months was 0.673 (P < 0.01). Conclusion: An effective detection method to measure EMLR before artificial cochlear implant was established. The thresholds of EMLR were lower than those of NRT. The method can be useful for objective evaluation of auditory cortex functions and postoperative hearing rehabilitation.

Usefulness of Electrical Auditory Brainstem Responses to Assess the Functionality of the Cochlear Nerve Using an Intracochlear Test Electrode.

To use an intracochlear test electrode to assess the integrity and the functionality of the auditory nerve in cochlear implant (CI) recipients and to compare electrical auditory brainstem responses (eABR) via the test electrode with the eABR responses with the CI. Otolaryngology department, tertiary referral hospital. Ten subjects (age at implantation 55 yr, range, 19-72) were subsequently implanted with a MED-EL CONCERTO CI on the side without any useful residual hearing. Following identification of the round window (RW), the test electrode was inserted in the cochlea previous to cochlear implantation. To assess the quality of an eABR waveform, scoring criteria from Walton et al. (2008) were chosen. The waveforms in each session were classified by detecting waves III and V by the algorithm and visual assessment of the waveform. Speech performance was evaluated with monosyllables, disyllables, and sentence recognition tests. It was possible to evoke electrical stimulation responses along with both the test electrode and the CI in all subjects. No significant differences in latencies or amplitudes after stimulation were found between the test electrode and the CI. All subjects obtained useful hearing with their CI and use their implants daily. The intracochlear test electrode may be suitable to test the integrity of the auditory nerve by recording eABR signals. This allows for further research on the status of the auditory nerve after tumor removal and correlation with auditory performance.

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.

The relationship between electrical auditory middle-latency response components and measures of auditory performance and speech intelligibility in pediatric cochlear implant recipients

Evidence for the utility of electrically-evoked auditory responses, as measures of objective hearing assessments in pediatric cochlear implant (CI) recipients, is proliferating. Recently, we demonstrated the relationship between electrical auditory brainstem response (EABR) and measures of auditory performance and speech intelligibility in pediatric CI users (Wang, Pan, Deshpande, & Ma, 2015). However, the EABR reflects activity only up to the auditory brainstem. The electrical auditory middle-latency response (EAMLR) is sensitive to the functioning of the sub-cortical structures as well as the auditory cortex and thus has greater utility in predicting auditory perception and processing. Here, we present data from 40 pre-lingually hearing impaired, pediatric CI recipients. The relationship between components of the EAMLR (latencies of Na, Pa, Nb, Pb; Na-Pa amplitude; and Na-Pa interval) and measures of auditory performance and speech intelligibility assessed using care-giver rating scales such as Categories of Auditory Performance (CAP) (Archbold, Lutman, & Marshall, 1995) and Speech Intelligibility Rating (SIR) (Allen, Nikolopoulos, Dyar, & O'Donoghue, 2001), respectively, are analyzed. EAMLR profiles of “good” versus “poor” CI users (based on CAP and SIR ratings) will be discussed. Additionally, the effect of age of implantation on the EAMLR, CAP and SIR outcomes will be considered.

Intracochlear sound sensor-electrode system for fully implantable cochlear implant

We designed, fabricated, and tested an intracochlear sound sensor-electrode system consisting of an intracochlear sound sensor (ISS) and a 50μm Pt-Ir wire electrode. This system was designed to sense acoustic signals and transmit electrical stimuli inside the cochlea. Potential applications include acting as the front end of a fully implantable cochlear implant to treat sensorineural deafness or as a transducer in cochlear mechanics experiments. The ISS was comprised of an array of piezoelectric cantilevers and was built using micro-electrical-mechanical-system (MEMS) techniques. The ISS was tested in air and underwater to compare its functionalities to the numerical predictions. Later, the ISS was implanted in an anesthetized guinea pig and tested in vivo. A 90-100dB SPL pure tone acoustic excitation over 1-30kHz was delivered into the ear canal of the guinea pig, and 0.1-30μV was measured by the ISS. The sensed signal was linear, repeatable, and immune to the electrical interference from the extracochlear and intracochlear environment. When using the electrode, electrical auditory brainstem response (eABR) measurements were performed by sending a 25μs single pulse stimulus to the electrode. Stimulus amplitudes ranging in 220-400μA were found to evoke an eABR. These results show that the concept of sensing acoustic signals and transmitting electrical stimulation inside the living cochlea using one device is feasible.

Long-term Results of ABI in Children With Severe Inner Ear Malformations.

To report the long-term outcomes of children who received auditory brainstem implant (ABI) because of severe inner ear malformations. Retrospective chart review. Tertiary referral otolaryngology clinic. Between July 2006 and October 2014, 60 children received ABI at Hacettepe University. Preoperative work up included otolaryngologic examination, audiological assessment, radiological evaluation together with assessment of language development and psychological status. The surgeries were performed via retrosigmoid approach with a pediatric neurosurgeon. Intraoperatively, electrical auditory brainstem response was utilized. Initial stimulation was done 4 to 5 weeks postoperatively. Outcomes were evaluated with Categories of Auditory Performance (CAP), speech intelligibility rate (SIR), functional auditory performance of cochlear implant (FAPCI) and Manchester Spoken Language Development Scale scores; receptive and expressive language ages were determined. Sixty children who received ABI were between ages of 12 and 64 months. Thirty-five patients with follow up period of at least 1 year, were reported in means of long-term audiological and language results. The most prevelant inner ear malformation was cochlear hypoplasia (n = 19). No major complication was encountered. Majority of the patients were in CAP 5 category, which implies that they can understand common phrases without lip reading. SIR was found out to be better with improving hearing thresholds. Children with ABI were performing worse than average cochlear implantation (CI) users when FAPCI scores were compared. Patients with the best hearing thresholds have expressive vocabulary of 50 to 200 words when evaluated with Manchester Spoken Language Development Scale. There was no relationship between the number of active electrodes and hearing thresholds. The type of inner ear anomaly with the best and the worst hearing thresholds were common cavity and cochlear aperture aplasia, respectively. Patients with additional handicaps had worse outcomes. Among 35 children, 29 had closed set discrimination and 12 developed open set discrimination above 50%. It was determined that, progress of the patients is faster in the initial 2 years when compared with further use of ABI. ABI is an acceptable and effective treatment modality for pediatric population with severe inner ear malformations. Bilateral stimulation together with CI and contralateral ABI should be utilized in suitable cases.