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Intraoperative Electrocochleography in Patients With Menière's Disease Undergoing Endolymphatic Sac Decompression and Shunt Surgery. Otol Neurotol 2019; 40:1208-1216. [DOI: 10.1097/mao.0000000000002345] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Pappa AK, Hutson KA, Scott WC, Wilson JD, Fox KE, Masood MM, Giardina CK, Pulver SH, Grana GD, Askew C, Fitzpatrick DC. Hair cell and neural contributions to the cochlear summating potential. J Neurophysiol 2019; 121:2163-2180. [PMID: 30943095 DOI: 10.1152/jn.00006.2019] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The cochlear summating potential (SP) to a tone is a baseline shift that persists for the duration of the burst. It is often considered the most enigmatic of cochlear potentials because its magnitude and polarity vary across frequency and level and its origins are uncertain. In this study, we used pharmacology to isolate sources of the SP originating from the gerbil cochlea. Animals either had the full complement of outer and inner hair cells (OHCs and IHCs) and an intact auditory nerve or had systemic treatment with furosemide and kanamycin (FK) to remove the outer hair cells. Responses to tone bursts were recorded from the round window before and after the neurotoxin kainic acid (KA) was applied. IHC responses were then isolated from the post-KA responses in FK animals, neural responses were isolated from the subtraction of post-KA from pre-KA responses in NH animals, and OHC responses were isolated by subtraction of post-KA responses in FK animals from post-KA responses in normal hearing (NH) animals. All three sources contributed to the SP; OHCs with a negative polarity and IHCs and the auditory nerve with positive polarity. Thus the recorded SP in NH animals is a sum of contributions from different sources, contributing to the variety of magnitudes and polarities seen across frequency and intensity. When this information was applied to observations of the SP recorded from the round window in human cochlear implant subjects, a strong neural contribution to the SP was confirmed in humans as well as gerbils. NEW & NOTEWORTHY Of the various potentials produced by the cochlea, the summating potential (SP) is typically described as the most enigmatic. Using combinations of ototoxins and neurotoxins, we show contributions to the SP from the auditory nerve and from inner and outer hair cells, which differ in polarity and vary in size across frequency and level. This complexity of sources helps to explain the enigmatic nature of the SP.
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Affiliation(s)
- Andrew K Pappa
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Kendall A Hutson
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - William C Scott
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - J David Wilson
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Kevin E Fox
- Campbell University School of Osteopathic Medicine, Lillington, North Carolina
| | - Maheer M Masood
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Christopher K Giardina
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Stephen H Pulver
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Gilberto D Grana
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Charles Askew
- Gene Therapy Center, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
| | - Douglas C Fitzpatrick
- Department of Otolaryngology and Head and Neck Surgery, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina
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Response Changes During Insertion of a Cochlear Implant Using Extracochlear Electrocochleography. Ear Hear 2019; 39:1146-1156. [PMID: 29554036 DOI: 10.1097/aud.0000000000000571] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Electrocochleography is increasingly being utilized as an intraoperative monitor of cochlear function during cochlear implantation (CI). Intracochlear recordings from the advancing electrode can be obtained through the device by on-board capabilities. However, such recordings may not be ideal as a monitor because the recording electrode moves in relation to the neural and hair cell generators producing the responses. The purposes of this study were to compare two extracochlear recording locations in terms of signal strength and feasibility as intraoperative monitoring sites and to characterize changes in cochlear physiology during CI insertion. DESIGN In 83 human subjects, responses to 90 dB nHL tone bursts were recorded both at the round window (RW) and then at an extracochlear position-either adjacent to the stapes or on the promontory just superior to the RW. Recording from the fixed, extracochlear position continued during insertion of the CI in 63 cases. RESULTS Before CI insertion, responses to low-frequency tones at the RW were roughly 6 dB larger than when recording at either extracochlear site, but the two extracochlear sites did not differ from one another. During CI insertion, response losses from the promontory or adjacent to the stapes stayed within 5 dB in ≈61% (38/63) of cases, presumably indicating atraumatic insertions. Among responses which dropped more than 5 dB at any time during CI insertion, 12 subjects showed no response recovery, while in 13, the drop was followed by partial or complete response recovery by the end of CI insertion. In cases with recovery, the drop in response occurred relatively early (<15 mm insertion) compared to those where there was no recovery. Changes in response phase during the insertion occurred in some cases; these may indicate a change in the distributions of generators contributing to the response. CONCLUSIONS Monitoring the electrocochleography during CI insertion from an extracochlear site reveals insertions that are potentially atraumatic, show interaction with cochlear structures followed by response recovery, or show interactions such that response losses persist to the end of recording.
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Changes of Electrocochleographic Responses During Cochlear Implantation Presented at the Annual Meeting of ADANO 2016 in Berlin. Otol Neurotol 2019; 40:e424-e429. [DOI: 10.1097/mao.0000000000001939] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Helmstaedter V, Lenarz T, Erfurt P, Kral A, Baumhoff P. The Summating Potential Is a Reliable Marker of Electrode Position in Electrocochleography: Cochlear Implant as a Theragnostic Probe. Ear Hear 2019; 39:687-700. [PMID: 29251689 DOI: 10.1097/aud.0000000000000526] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE For the increasing number of cochlear implantations in subjects with residual hearing, hearing preservation, and thus the prevention of implantation trauma, is crucial. A method for monitoring the intracochlear position of a cochlear implant (CI) and early indication of imminent cochlear trauma would help to assist the surgeon to achieve this goal. The aim of this study was to evaluate the reliability of the different electric components recorded by an intracochlear electrocochleography (ECochG) as markers for the cochleotopic position of a CI. The measurements were made directly from the CI, combining intrasurgical diagnostics with the therapeutical use of the CI, thus, turning the CI into a "theragnostic probe." DESIGN Intracochlear ECochGs were measured in 10 Dunkin Hartley guinea pigs of either sex, with normal auditory brainstem response thresholds. All subjects were fully implanted (4 to 5 mm) with a custom six contact CI. The ECochG was recorded simultaneously from all six contacts with monopolar configuration (retroauricular reference electrode). The gross ECochG signal was filtered off-line to separate three of its main components: compound action potential, cochlear microphonic, and summating potential (SP). Additionally, five cochleae were harvested and histologically processed to access the spatial position of the CI contacts. Both ECochG data and histological reconstructions of the electrode position were fitted with the Greenwood function to verify the reliability of the deduced cochleotopic position of the CI. RESULTS SPs could be used as suitable markers for the frequency position of the recording electrode with an accuracy of ±1/4 octave in the functioning cochlea, verified by histology. Cochlear microphonics showed a dependency on electrode position but were less reliable as positional markers. Compound action potentials were not suitable for CI position information but were sensitive to "cochlear health" (e.g., insertion trauma). CONCLUSIONS SPs directly recorded from the contacts of a CI during surgery can be used to access the intracochlear frequency position of the CI. Using SP monitoring, implantation may be stopped before penetrating functioning cochlear regions. If the technique was similarly effective in humans, it could prevent implantation trauma and increase hearing preservation during CI surgery. Diagnostic hardware and software for recording biological signals with a CI without filter limitations might be a valuable add-on to the portfolios of CI manufacturers.
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Affiliation(s)
- Victor Helmstaedter
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence "Hearing 4 All" (DFG EXC 1077), Hannover, Germany
| | - Thomas Lenarz
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence "Hearing 4 All" (DFG EXC 1077), Hannover, Germany
| | - Peter Erfurt
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Andrej Kral
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany.,Cluster of Excellence "Hearing 4 All" (DFG EXC 1077), Hannover, Germany.,Department of Experimental Otology & Institute of AudioNeuroTechnology (VIANNA), Hannover, Germany
| | - Peter Baumhoff
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany.,Department of Experimental Otology & Institute of AudioNeuroTechnology (VIANNA), Hannover, Germany
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Kamerer AM, Chertoff ME. An analytic approach to identifying the sources of the low-frequency round window cochlear response. Hear Res 2019; 375:53-65. [PMID: 30808536 DOI: 10.1016/j.heares.2019.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 01/18/2019] [Accepted: 02/06/2019] [Indexed: 01/19/2023]
Abstract
The cochlear microphonic, traditionally thought of as an indication of electrical current flow through hair cells, in conjunction with suppressing high-pass noise or tones, is a promising method of assessing the health of outer hair cells at specific locations along the cochlear partition. We propose that the electrical potential recorded from the round window in gerbils in response to low-frequency tones, which we call cochlear response (CR), contains significant responses from multiple cellular sources, which may expand its diagnostic purview. In this study, CR is measured in the gerbil and modeled to identify its contributing sources. CR was recorded via an electrode placed in the round window niche of sixteen Mongolian gerbils and elicited with a 45 Hz tone burst embedded in 18 high-pass filtered noise conditions to target responses from increasing regions along the cochlear partition. Possible sources were modeled using previously-published hair cell and auditory nerve response data, and then weighted and combined using linear regression to produce a model response that fits closely to the mean CR waveform. The significant contributing sources identified by the model are outer hair cells, inner hair cells, and the auditory nerve. We conclude that the low-frequency CR contains contributions from several cellular sources.
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Affiliation(s)
- Aryn M Kamerer
- Center for Hearing Research, Boys Town National Research Hospital, Omaha, NE, USA.
| | - Mark E Chertoff
- Department of Hearing & Speech, University of Kansas Medical Center, Kansas City, KS, USA
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Tejani VD, Abbas PJ, Brown CJ, Woo J. An improved method of obtaining electrocochleography recordings from Nucleus Hybrid cochlear implant users. Hear Res 2019; 373:113-120. [PMID: 30665078 DOI: 10.1016/j.heares.2019.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 12/26/2018] [Accepted: 01/04/2019] [Indexed: 11/16/2022]
Abstract
Interest in electrocochleography (ECoG) has recently resurged as a potential tool to assess peripheral auditory function in cochlear implant (CI) users. ECoG recordings can be evoked using acoustic stimulation and recorded from an extra- or intra-cochlear electrode in CI users. Recordings reflect contributions from cochlear hair cells and the auditory nerve. We recently demonstrated the feasibility of using Custom Sound EP (clinically available software) to record ECoG responses in Nucleus Hybrid CI users with preserved acoustic hearing in the implanted ear (Abbas et al, 2017). While successful, the recording procedures were time intensive, limiting clinical applications. The current report describes how we improved data collection efficiency by writing custom software using Python programming language. The software interfaced with Nucleus Implant Communicator (NIC) routines to record responses from an intracochlear electrode. ECoG responses were recorded in eight CI users with preserved acoustic hearing using Custom Sound EP and the Python-based software. Responses were similar across both recording systems, but the recording time decreased significantly using the Python-based software. Seven additional CI users underwent repeated testing using the Python-based software and showed high test-retest reliability. The improved efficiency and high reliability increases the likelihood of translating intracochlear ECoG to clinical practice.
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Affiliation(s)
- Viral D Tejani
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Paul J Abbas
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Carolyn J Brown
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Jihwan Woo
- Department of Biomedical Engineering, University of Ulsan, Ulsan, Republic of Korea.
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Kim JS, Tejani VD, Abbas PJ, Brown CJ. Postoperative Electrocochleography from Hybrid Cochlear Implant users: An Alternative Analysis Procedure. Hear Res 2018; 370:304-315. [PMID: 30393003 DOI: 10.1016/j.heares.2018.10.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 10/18/2018] [Accepted: 10/26/2018] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Shorter electrode arrays and soft surgical techniques allow for preservation of acoustic hearing in many cochlear implant (CI) users. Recently, we developed a method of using the Neural Response Telemetry (NRT) system built in Custom Sound EP clinical software to record acoustically evoked electrocochleography (ECoG) responses from an intracochlear electrode in Nucleus Hybrid CI users (Abbas et al., 2017). We recorded responses dominated by the hair cells (cochlear microphonic, CM/DIF) and the auditory nerve (auditory nerve neurophonic, ANN/SUM). Unfortunately, the recording procedure was time consuming, limiting potential clinical applications. This report describes a modified method to record the ECoG response more efficiently. We refer to this modified technique as the "short window" method, while our previous technique (Abbas et al., 2017) is referred as the "long window" method. In this report, our goal was to 1) evaluate the feasibility of the short window method to record the CM/DIF and ANN/SUM responses, 2) characterize the reliability and sensitivity of the measures recorded using the short window method, and 3) evaluate the relationship between the CM/DIF and ANN/SUM measures recorded using the modified method and audiometric thresholds. METHOD Thirty-four postlingually deafened adult Hybrid CI users participated in this study. Acoustic tone bursts were presented at four frequencies (250, 500, 750, and 1000 Hz) at various stimulation levels via an insert earphone in both condensation and rarefaction polarities. Acoustically evoked ECoG responses were recorded from the most apical electrode in the intracochlear array. These two responses were subtracted to emphasize the CM/DIF responses and added to emphasize the ANN/SUM responses. Response thresholds were determined based on visual inspection of time waveforms, and trough-to-peak analysis technique was used to quantify response amplitudes. Within-subject comparison of responses measured using both short and long window methods were obtained from seven subjects. We also assessed the reliability and sensitivity of the short window method by comparing repeated measures from 19 subjects at different times. Correlations between CM/DIF and ANN/SUM measures using the short window recording method and audiometric thresholds were also assessed. RESULTS Regardless of the recording method, CM/DIF responses were larger than ANN/SUM responses. Responses obtained using the short window method were positively correlated to those obtained using the conventional long window method. Subjects who had stable acoustic hearing at two different time points had similar ECoG responses at those points, confirming high test-retest reliability of the short window method. Subjects who lost hearing between two different time points showed increases in ECoG thresholds, suggesting that physiologic ECoG responses are sensitive to audiometric changes. Correlations between CM/DIF and ANN/SUM thresholds and audiometric thresholds at all tested frequencies were significant. CONCLUSION This study compares two different recording methods. Intracochlear ECoG measures recorded using the short window technique were efficient, reliable, and repeatable. We were able to collect more frequency specific data with the short window method, and observed similar results between the long window and short window methods. Correlations between physiological thresholds and audiometric thresholds were similar to those reported previously using the long window method (Abbas et al., 2017). This is an important finding because it demonstrates that clinically-available software can be used to measure frequency-specific ECoG responses with enhanced efficiency, increasing the odds that this technique might move from the laboratory into clinical practice.
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Affiliation(s)
- Jeong-Seo Kim
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology - Head & Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA.
| | - Viral D Tejani
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology - Head & Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Paul J Abbas
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology - Head & Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Carolyn J Brown
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA; Department of Otolaryngology - Head & Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
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In Vivo Electrocochleography in Hybrid Cochlear Implant Users Implicates TMPRSS3 in Spiral Ganglion Function. Sci Rep 2018; 8:14165. [PMID: 30242206 PMCID: PMC6154996 DOI: 10.1038/s41598-018-32630-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 09/10/2018] [Indexed: 11/16/2022] Open
Abstract
Cochlear implantation, a surgical method to bypass cochlear hair cells and directly stimulate the spiral ganglion, is the standard treatment for severe-to-profound hearing loss. Changes in cochlear implant electrode array design and surgical approach now allow for preservation of acoustic hearing in the implanted ear. Electrocochleography (ECochG) was performed in eight hearing preservation subjects to assess hair cell and neural function and elucidate underlying genetic hearing loss. Three subjects had pathogenic variants in TMPRSS3 and five had pathogenic variants in genes known to affect the cochlear sensory partition. The mechanism by which variants in TMPRSS3 cause genetic hearing loss is unknown. We used a 500-Hz tone burst to record ECochG responses from an intracochlear electrode. Responses consist of a cochlear microphonic (hair cell) and an auditory nerve neurophonic. Cochlear microphonics did not differ between groups. Auditory nerve neurophonics were smaller, on average, in subjects with TMPRSS3 deafness. Results of this proof-of-concept study provide evidence that pathogenic variants in TMPRSS3 may impact function of the spiral ganglion. While ECochG as a clinical and research tool has been around for decades, this study illustrates a new application of ECochG in the study of genetic hearing and deafness in vivo.
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Electrocochleographic Responses Before and After Short-Term Suprathreshold Electrical Stimulation in Human Cochlear Implant Recipients. Otol Neurotol 2018; 39:e635-e641. [DOI: 10.1097/mao.0000000000001889] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Synaptopathy in the Aging Cochlea: Characterizing Early-Neural Deficits in Auditory Temporal Envelope Processing. J Neurosci 2018; 38:7108-7119. [PMID: 29976623 DOI: 10.1523/jneurosci.3240-17.2018] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 06/27/2018] [Accepted: 06/28/2018] [Indexed: 12/12/2022] Open
Abstract
Aging listeners, even in the absence of overt hearing loss measured as changes in hearing thresholds, often experience impairments processing temporally complex sounds such as speech in noise. Recent evidence has shown that normal aging is accompanied by a progressive loss of synapses between inner hair cells and auditory nerve fibers. The role of this cochlear synaptopathy in degraded temporal processing with age is not yet understood. Here, we used population envelope following responses, along with other hair cell- and neural-based measures from an age-graded series of male and female CBA/CaJ mice to study changes in encoding stimulus envelopes. By comparing responses obtained before and after the application of the neurotoxin ouabain to the inner ear, we demonstrate that we can study changes in temporal processing on either side of the cochlear synapse. Results show that deficits in neural coding with age emerge at the earliest neural stages of auditory processing and are correlated with the degree of cochlear synaptopathy. These changes are seen before losses in neural thresholds and particularly affect the suprathreshold processing of sound. Responses obtained from more central sources show smaller differences with age, suggesting compensatory gain. These results show that progressive cochlear synaptopathy is accompanied by deficits in temporal coding at the earliest neural generators and contribute to the suprathreshold sound processing deficits observed with age.SIGNIFICANCE STATEMENT Aging listeners often experience difficulty hearing and understanding speech in noisy conditions. The results described here suggest that age-related loss of cochlear synapses may be a significant contributor to those performance declines. We observed aberrant neural coding of sounds in the early auditory pathway, which was accompanied by and correlated with an age-progressive loss of synapses between the inner hair cells and the auditory nerve. Deficits first appeared before changes in hearing thresholds and were largest at higher sound levels relevant to real world communication. The noninvasive tests described here may be adapted to detect cochlear synaptopathy in the clinical setting.
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Patterns Seen During Electrode Insertion Using Intracochlear Electrocochleography Obtained Directly Through a Cochlear Implant. Otol Neurotol 2018; 38:1415-1420. [PMID: 28953607 DOI: 10.1097/mao.0000000000001559] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
HYPOTHESIS Intraoperative, intracochlear electrocochleography (ECochG) will provide a means to monitor cochlear hair cell and neural response during cochlear implant (CI) electrode insertion. Distinct patterns in the insertion track can be characterized. BACKGROUND Conventional CI surgery is performed without a means of actively monitoring cochlear hair cell and neural responses. Intracochlear ECochG obtained directly through the CI may be a source of such feedback. Understanding the patterns observed in the "insertion track" is an essential step toward refining intracochlear ECochG as a tool that can be used to assist in intraoperative decision making and prognostication of hearing preservation. METHODS Intracochlear ECochG was performed in 17 patients. During electrode insertion, a 50-ms tone burst acoustic stimulus was delivered with a frequency of 500 Hz at 110 dB SPL. The ECochG response was monitored from the apical-most electrode. The amplitude of the first harmonic was plotted and monitored in near real time by the audiologist-surgeon team during CI electrode insertion. RESULTS Three distinct patterns in first harmonic amplitude change were observed across subjects during insertion: Type A (52%), overall increase in amplitude from the beginning of insertion until completion; Type B (11%), a maximum amplitude at the beginning of insertion, with a decrease in amplitude as insertion progressed to completion; and Type C (35%), comparable amplitudes at the beginning and completion of the insertion with the maximum amplitude mid-insertion. CONCLUSION Three ECochG patterns were observed during electrode advancement into the cochlea. Ongoing and future work will broaden our scope of knowledge regarding the relationship among these patterns, the presence of cochlear trauma, and functional outcomes related to hearing preservation.
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Abbas PJ, Tejani VD, Scheperle RA, Brown CJ. Using Neural Response Telemetry to Monitor Physiological Responses to Acoustic Stimulation in Hybrid Cochlear Implant Users. Ear Hear 2018; 38:409-425. [PMID: 28085738 PMCID: PMC5482777 DOI: 10.1097/aud.0000000000000400] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE This report describes the results of a series of experiments where we use the neural response telemetry (NRT) system of the Nucleus cochlear implant (CI) to measure the response of the peripheral auditory system to acoustic stimulation in Nucleus Hybrid CI users. The objectives of this study were to determine whether they could separate responses from hair cells and neurons and to evaluate the stability of these measures over time. DESIGN Forty-four CI users participated. They all had residual acoustic hearing and used a Nucleus Hybrid S8, S12, or L24 CI or the standard lateral wall CI422 implant. The NRT system of the CI was used to trigger an acoustic stimulus (500-Hz tone burst or click), which was presented at a low stimulation rate (10, 15, or 50 per second) to the implanted ear via an insert earphone and to record the cochlear microphonic, the auditory nerve neurophonic and the compound action potential (CAP) from an apical intracochlear electrode. To record acoustically evoked responses, a longer time window than is available with the commercial NRT software is required. This limitation was circumvented by making multiple recordings for each stimulus using different time delays between the onset of stimulation and the onset of averaging. These recordings were then concatenated off-line. Matched recordings elicited using positive and negative polarity stimuli were added off-line to emphasize neural potentials (SUM) and subtracted off-line to emphasize potentials primarily generated by cochlear hair cells (DIF). These assumptions regarding the origin of the SUM and DIF components were tested by comparing the magnitude of these derived responses recorded using various stimulation rates. Magnitudes of the SUM and DIF components were compared with each other and with behavioral thresholds. RESULTS SUM and DIF components were identified for most subjects, consistent with both hair cell and neural responses to acoustic stimulation. For a subset of the study participants, the DIF components grew as stimulus level was increased, but little or no SUM components were identified. Latency of the CAPs in response to click stimuli was long relative to reports in the literature of recordings obtained using extracochlear electrodes. This difference in response latency and general morphology of the CAPs recorded was likely due to differences across subjects in hearing loss configuration. The use of high stimulation rates tended to decrease SUM and CAP components more than DIF components. We suggest this effect reflects neural adaptation. In some individuals, repeated measures were made over intervals as long as 9 months. Changes over time in DIF, SUM, and CAP thresholds mirrored changes in audiometric threshold for the subjects who experienced loss of acoustic hearing in the implanted ear. CONCLUSIONS The Nucleus NRT software can be used to record peripheral responses to acoustic stimulation at threshold and suprathreshold levels, providing a window into the status of the auditory hair cells and the primary afferent nerve fibers. These acoustically evoked responses are sensitive to changes in hearing status and consequently could be useful in characterizing the specific pathophysiology of the hearing loss experienced by this population of CI users.
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Affiliation(s)
- Paul J Abbas
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Viral D Tejani
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
| | - Rachel A. Scheperle
- Department of Communication Sciences and Disorders, Montclair State University, Bloomfield, NJ, USA
| | - Carolyn J. Brown
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, IA, USA
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Pienkowski M, Adunka OF, Lichtenhan JT. Editorial: New Advances in Electrocochleography for Clinical and Basic Investigation. Front Neurosci 2018; 12:310. [PMID: 29867322 PMCID: PMC5951982 DOI: 10.3389/fnins.2018.00310] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 04/20/2018] [Indexed: 12/22/2022] Open
Affiliation(s)
| | - Oliver F Adunka
- Wexner Medical Center, The Ohio State University, Columbus, OH, United States
| | - Jeffery T Lichtenhan
- School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
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Dalbert A, Pfiffner F, Hoesli M, Koka K, Veraguth D, Roosli C, Huber A. Assessment of Cochlear Function during Cochlear Implantation by Extra- and Intracochlear Electrocochleography. Front Neurosci 2018; 12:18. [PMID: 29434534 PMCID: PMC5790789 DOI: 10.3389/fnins.2018.00018] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 01/10/2018] [Indexed: 11/24/2022] Open
Abstract
Objective: The aims of this study were: (1) To investigate the correlation between electrophysiological changes during cochlear implantation and postoperative hearing loss, and (2) to detect the time points that electrophysiological changes occur during cochlear implantation. Material and Methods: Extra- and intracochlear electrocochleography (ECoG) were used to detect electrophysiological changes during cochlear implantation. Extracochlear ECoG recordings were conducted through a needle electrode placed on the promontory; for intracochlear ECoG recordings, the most apical contact of the cochlear implant (CI) electrode itself was used as the recording electrode. Tone bursts at 250, 500, 750, and 1000 Hz were used as low-frequency acoustic stimuli and clicks as high-frequency acoustic stimuli. Changes of extracochlear ECoG recordings after full insertion of the CI electrode were correlated with pure-tone audiometric findings 4 weeks after surgery. Results: Changes in extracochlear ECoG recordings correlated with postoperative hearing change (r = −0.44, p = 0.055, n = 20). Mean hearing loss in subjects without decrease or loss of extracochlear ECoG signals was 12 dB, compared to a mean hearing loss of 22 dB in subjects with a detectable decrease or a loss of ECoG signals (p = 0.0058, n = 51). In extracochlear ECoG recordings, a mean increase of the ECoG signal of 4.4 dB occurred after opening the cochlea. If a decrease of ECoG signals occurred during insertion of the CI electrode, the decrease was detectable during the second half of the insertion. Conclusion: ECoG recordings allow detection of electrophysiological changes in the cochlea during cochlear implantation. Decrease of extracochlear ECoG recordings during surgery has a significant correlation with hearing loss 4 weeks after surgery. Trauma to cochlear structures seems to occur during the final phase of the CI electrode insertion. Baseline recordings for extracochlear ECoG recordings should be conducted after opening the cochlea. ECoG responses can be recorded from an intracochlear site using the CI electrode as recording electrode. This technique may prove useful for monitoring cochlear trauma intraoperatively in the future.
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Affiliation(s)
- Adrian Dalbert
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Flurin Pfiffner
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Marco Hoesli
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Kanthaiah Koka
- Department of Research and Technology, Advanced Bionics LLC, Valencia, CA, United States
| | - Dorothe Veraguth
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Christof Roosli
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Alexander Huber
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
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Dalbert A, Pfiffner F, Hoesli M, Koka K, Veraguth D, Roosli C, Huber A. Assessment of Cochlear Function during Cochlear Implantation by Extra- and Intracochlear Electrocochleography. Front Neurosci 2018. [PMID: 29434534 DOI: 10.3389/fnins.2018.00018/bibtex] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2023] Open
Abstract
Objective: The aims of this study were: (1) To investigate the correlation between electrophysiological changes during cochlear implantation and postoperative hearing loss, and (2) to detect the time points that electrophysiological changes occur during cochlear implantation. Material and Methods: Extra- and intracochlear electrocochleography (ECoG) were used to detect electrophysiological changes during cochlear implantation. Extracochlear ECoG recordings were conducted through a needle electrode placed on the promontory; for intracochlear ECoG recordings, the most apical contact of the cochlear implant (CI) electrode itself was used as the recording electrode. Tone bursts at 250, 500, 750, and 1000 Hz were used as low-frequency acoustic stimuli and clicks as high-frequency acoustic stimuli. Changes of extracochlear ECoG recordings after full insertion of the CI electrode were correlated with pure-tone audiometric findings 4 weeks after surgery. Results: Changes in extracochlear ECoG recordings correlated with postoperative hearing change (r = -0.44, p = 0.055, n = 20). Mean hearing loss in subjects without decrease or loss of extracochlear ECoG signals was 12 dB, compared to a mean hearing loss of 22 dB in subjects with a detectable decrease or a loss of ECoG signals (p = 0.0058, n = 51). In extracochlear ECoG recordings, a mean increase of the ECoG signal of 4.4 dB occurred after opening the cochlea. If a decrease of ECoG signals occurred during insertion of the CI electrode, the decrease was detectable during the second half of the insertion. Conclusion: ECoG recordings allow detection of electrophysiological changes in the cochlea during cochlear implantation. Decrease of extracochlear ECoG recordings during surgery has a significant correlation with hearing loss 4 weeks after surgery. Trauma to cochlear structures seems to occur during the final phase of the CI electrode insertion. Baseline recordings for extracochlear ECoG recordings should be conducted after opening the cochlea. ECoG responses can be recorded from an intracochlear site using the CI electrode as recording electrode. This technique may prove useful for monitoring cochlear trauma intraoperatively in the future.
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Affiliation(s)
- Adrian Dalbert
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Flurin Pfiffner
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Marco Hoesli
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Kanthaiah Koka
- Department of Research and Technology, Advanced Bionics LLC, Valencia, CA, United States
| | - Dorothe Veraguth
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Christof Roosli
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
| | - Alexander Huber
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Zurich, University Hospital of Zurich, Zurich, Switzerland
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67
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Fontenot TE, Giardina CK, Fitzpatrick DC. A Model-Based Approach for Separating the Cochlear Microphonic from the Auditory Nerve Neurophonic in the Ongoing Response Using Electrocochleography. Front Neurosci 2017; 11:592. [PMID: 29123468 PMCID: PMC5662900 DOI: 10.3389/fnins.2017.00592] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 10/09/2017] [Indexed: 12/02/2022] Open
Abstract
Electrocochleography (ECochG) is a potential clinically valuable technique for predicting speech perception outcomes in cochlear implant (CI) recipients, among other uses. Current analysis is limited by an inability to quantify hair cell and neural contributions which are mixed in the ongoing part of the response to low frequency tones. Here, we used a model based on source properties to account for recorded waveform shapes and to separate the combined signal into its components. The model for the cochlear microphonic (CM) was a sinusoid with parameters for independent saturation of the peaks and the troughs of the responses. The model for the auditory nerve neurophonic (ANN) was the convolution of a unit potential and population cycle histogram with a parameter for spread of excitation. Phases of the ANN and CM were additional parameters. The average cycle from the ongoing response was the input, and adaptive fitting identified CM and ANN parameters that best reproduced the waveform shape. Test datasets were responses recorded from the round windows of CI recipients, from the round window of gerbils before and after application of neurotoxins, and with simulated signals where each parameter could be manipulated in isolation. Waveforms recorded from 284 CI recipients had a variety of morphologies that the model fit with an average r2 of 0.97 ± 0.058 (standard deviation). With simulated signals, small systematic differences between outputs and inputs were seen with some variable combinations, but in general there were limited interactions among the parameters. In gerbils, the CM reported was relatively unaffected by the neurotoxins. In contrast, the ANN was strongly reduced and the reduction was limited to frequencies of 1,000 Hz and lower, consistent with the range of strong neural phase-locking. Across human CI subjects, the ANN contribution was variable, ranging from nearly none to larger than the CM. Development of this model could provide a means to isolate hair cell and neural activity that are mixed in the ongoing response to low-frequency tones. This tool can help characterize the residual physiology across CI subjects, and can be useful in other clinical settings where a description of the cochlear physiology is desirable.
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Affiliation(s)
- Tatyana E Fontenot
- Otolaryngology-Head and Neck Surgery, University of North Carolina, Chapel Hill, NC, United States
| | | | - Douglas C Fitzpatrick
- Otolaryngology-Head and Neck Surgery, University of North Carolina, Chapel Hill, NC, United States.,School of Medicine, University of North Carolina, Chapel Hill, NC, United States
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Cook AM, Allsop AJ, O'Beirne GA. Putative Auditory-Evoked Neurophonic Measurements Using a Novel Signal Processing Technique: A Pilot Case Study. Front Neurosci 2017; 11:472. [PMID: 28970782 PMCID: PMC5609548 DOI: 10.3389/fnins.2017.00472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 08/09/2017] [Indexed: 11/22/2022] Open
Abstract
With changes to cochlear implant candidacy and improvements in surgical technique, there is a need for accurate intraoperative assessment of low-frequency hearing thresholds during cochlear implantation. In electrocochleography, onset compound action potentials (CAPs) typically allow estimation of auditory threshold for frequencies above 1 kHz, but they are less accurate at lower frequencies. Auditory nerve neurophonic (ANN) waveforms, on the other hand, may overcome this limitation by allowing phase-locked neural activity to be tracked during a prolonged low-frequency stimulus rather than just at its onset (Henry, 1995). Lichtenhan et al. (2013) have used their auditory nerve overlapped waveform (ANOW) technique to measure these potentials from the round windows of cats and guinea pigs, and reported that in guinea pigs these potentials originate in the cochlear apex for stimuli below 70 dB SPL (Lichtenhan et al., 2014). Human intraoperative round window neurophonic measurements have been reported by Choudhury et al. (2012). We have done the same in hearing impaired awake participants, and present here the results of a pilot study in which we recorded responses evoked by 360, 525, and 725 Hz tone bursts from the cochlear promontory of one participant. We also present a modification to the existing measurement technique which halves recording time, extracting the auditory neurophonic by recording a single averaged waveform, and then subtracting from it a 180° group-delayed version of itself, rather than using alternating condensation and rarefaction sound stimuli. We cannot conclude that the waveforms we measured were purely neural responses originating from the apex of the cochlea: as with all neurophonic measurement procedures, the neural responses of interest cannot be separated from higher harmonics of the cochlear microphonic without forward masking, regardless of electrode location, stimuli or post-processing algorithm. In conclusion, the extraction of putative neurophonic waveforms can easily be incorporated into existing electrocochleographic measurement paradigms, but at this stage such measurements should be interpreted with caution.
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Affiliation(s)
- Alison M Cook
- New Zealand Institute of Language Brain and Behaviour, University of CanterburyChristchurch, New Zealand.,Eisdell Moore CentreAuckland, New Zealand
| | - Ashleigh J Allsop
- New Zealand Institute of Language Brain and Behaviour, University of CanterburyChristchurch, New Zealand
| | - Greg A O'Beirne
- New Zealand Institute of Language Brain and Behaviour, University of CanterburyChristchurch, New Zealand.,Eisdell Moore CentreAuckland, New Zealand
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69
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Dalbert A, Huber A, Veraguth D, Roosli C, Pfiffner F. Assessment of Cochlear Trauma During Cochlear Implantation Using Electrocochleography and Cone Beam Computed Tomography. Otol Neurotol 2017; 37:446-53. [PMID: 26945317 DOI: 10.1097/mao.0000000000000998] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To assess cochlear trauma during cochlear implantation by electrocochleography (ECoG) and cone beam computed tomography (CBCT) and to correlate intraoperative cochlear trauma with postoperative loss of residual hearing. METHODS ECoG recordings to tone bursts at 250, 500, 750, and 1000 Hz and click stimuli were recorded before and after insertion of the cochlear implant electrode array, using an extracochlear recording electrode. CBCTs were conducted within 6 weeks after surgery. Changes of intraoperative ECoG recordings and CBCT findings were correlated with postoperative threshold shifts in pure-tone audiograms. RESULTS Fourteen subjects were included. In three subjects a decrease of low-frequency ECoG responses at 250, 500, 750, and 1000 Hz occurred after insertion of the electrode array. This was associated with no or minimal residual hearing 4 weeks after surgery. ECoG responses to click stimuli were present in six subjects and showed a decrease after insertion of the electrode array in three. This was associated with a mean hearing loss of 21 dB in postoperative pure-tone audiograms. Scalar dislocation of the electrode array was assumed in one subject because of CBCT findings and correlated with a decrease of low-frequency ECoG responses and a complete loss of residual hearing. CONCLUSION Hearing loss of ≤11 dB is not associated with detectable decrease in ECoG recordings during cochlear implantation. However, in a majority of patients with threshold shifts of >11 dB or complete hearing loss, an intraoperative decrease of high- or low-frequency ECoG signals occurs, suggesting acute cochlear trauma.
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Affiliation(s)
- Adrian Dalbert
- University of Zurich and Department of Otorhinolaryngology-Head and Neck Surgery, University Hospital Zurich, Zurich, Switzerland
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Abstract
HYPOTHESIS The compound action potential (CAP) is a purely neural component of the cochlea's response to sound, and may provide information regarding the existing neural substrate in cochlear implant (CI) subjects that can help account for variance in speech perception outcomes. BACKGROUND Measurement of the "total response" (TR), or sum of the magnitudes of spectral components in the ongoing responses to tone bursts across frequencies, has been shown to account for 40 to 50% of variance in speech perception outcomes. The ongoing response is composed of both hair cell and neural components. This correlation may be improved with the addition of the CAP. METHODS Intraoperative round window electrocochleography (ECochG) was performed in adult and pediatric CI subjects (n = 238). Stimuli were tones of different frequencies (250 Hz-4 kHz) at 90 dB nHL. The CAP was assessed in two ways, as an amplitude and with a scaling factor derived from a function fitted to the response. The results were correlated with consonant-nucleus-consonant (CNC) word scores at 6 months post-implantation (n = 51). RESULTS Only about half of the subjects had a measurable CAP at any frequency. The CNC word scores correlated weakly with both amplitude (r = 0.20, p < 0.001) and scaling factor (r = 0.25, p < 0.01). In contrast, the TR alone accounted for 43% of the variance, and addition of either CAP measurement in multiple regression did not account for additional variance. CONCLUSIONS The underlying pathology in CI patients causes the CAP to be often absent and highly variable when present. The TR is a better predictor of speech perception outcomes than the CAP.
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71
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Riggs WJ, Roche JP, Giardina CK, Harris MS, Bastian ZJ, Fontenot TE, Buchman CA, Brown KD, Adunka OF, Fitzpatrick DC. Intraoperative Electrocochleographic Characteristics of Auditory Neuropathy Spectrum Disorder in Cochlear Implant Subjects. Front Neurosci 2017; 11:416. [PMID: 28769753 PMCID: PMC5515907 DOI: 10.3389/fnins.2017.00416] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 07/04/2017] [Indexed: 11/13/2022] Open
Abstract
Auditory neuropathy spectrum disorder (ANSD) is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR) testing. Clinical indicators of ANSD are a present cochlear microphonic (CM) with small or absent wave V. Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI) is indicated. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG) to tone bursts in children (n = 167) and adults (n = 163). Magnitudes of the responses to tones of different frequencies were summed to measure the "total response" (ECochG-TR), a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP) and auditory nerve neurophonic (ANN) as a ranked "Nerve Score". Subjects identified as ANSD (45 ears in children, 3 in adults) had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds.
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Affiliation(s)
- William J Riggs
- Department of Otolaryngology/Head and Neck Surgery, Ohio State University College of MedicineColumbus, OH, United States
| | - Joseph P Roche
- Lab Department of Otolaryngology/Head and Neck Surgery, University of Wisconsin School of MedicineMadison, WI, United States
| | - Christopher K Giardina
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill School of MedicineChapel Hill, NC, United States
| | - Michael S Harris
- Department of Otolaryngology/Head and Neck Surgery, Ohio State University College of MedicineColumbus, OH, United States
| | - Zachary J Bastian
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill School of MedicineChapel Hill, NC, United States
| | - Tatyana E Fontenot
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill School of MedicineChapel Hill, NC, United States
| | - Craig A Buchman
- Department of Otolaryngology/Head and Neck Surgery, Washington University School of Medicine in St. LouisSt. Louis, MO, United States
| | - Kevin D Brown
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill School of MedicineChapel Hill, NC, United States
| | - Oliver F Adunka
- Department of Otolaryngology/Head and Neck Surgery, Ohio State University College of MedicineColumbus, OH, United States
| | - Douglas C Fitzpatrick
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill School of MedicineChapel Hill, NC, United States
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Lichtenhan JT, Lee C, Dubaybo F, Wenrich KA, Wilson US. The Auditory Nerve Overlapped Waveform (ANOW) Detects Small Endolymphatic Manipulations That May Go Undetected by Conventional Measurements. Front Neurosci 2017; 11:405. [PMID: 28769744 PMCID: PMC5513905 DOI: 10.3389/fnins.2017.00405] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 06/29/2017] [Indexed: 11/13/2022] Open
Abstract
Electrocochleography (ECochG) has been used to assess Ménière's disease, a pathology associated with endolymphatic hydrops and low-frequency sensorineural hearing loss. However, the current ECochG techniques are limited for use at high-frequencies only (≥1 kHz) and cannot be used to assess and understand the low-frequency sensorineural hearing loss in ears with Ménière's disease. In the current study, we use a relatively new ECochG technique to make measurements that originate from afferent auditory nerve fibers in the apical half of the cochlear spiral to assess effects of endolymphatic hydrops in guinea pig ears. These measurements are made from the Auditory Nerve Overlapped Waveform (ANOW). Hydrops was induced with artificial endolymph injections, iontophoretically applied Ca2+ to endolymph, and exposure to 200 Hz tones. The manipulations used in this study were far smaller than those used in previous investigations on hydrops. In response to all hydropic manipulations, ANOW amplitude to moderate level stimuli was markedly reduced but conventional ECochG measurements of compound action potential thresholds were unaffected (i.e., a less than 2 dB threshold shift). Given the origin of the ANOW, changes in ANOW amplitude likely reflect acute volume disturbances accumulate in the distensible cochlear apex. These results suggest that the ANOW could be used to advance our ability to identify initial stages of dysfunction in ears with Ménière's disease before the pathology progresses to an extent that can be detected with conventional measures.
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Affiliation(s)
- Jeffery T Lichtenhan
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Choongheon Lee
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Farah Dubaybo
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Kaitlyn A Wenrich
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Uzma S Wilson
- Department of Communication Sciences and Disorders, Northwestern UniversityEvanston, IL, United States
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73
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Real-Time Intracochlear Electrocochleography Obtained Directly Through a Cochlear Implant. Otol Neurotol 2017; 38:e107-e113. [DOI: 10.1097/mao.0000000000001425] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Koka K, Litvak LM. Feasibility of Using Electrocochleography for Objective Estimation of Electro-Acoustic Interactions in Cochlear Implant Recipients with Residual Hearing. Front Neurosci 2017; 11:337. [PMID: 28674482 PMCID: PMC5475389 DOI: 10.3389/fnins.2017.00337] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/29/2017] [Indexed: 11/18/2022] Open
Abstract
Although cochlear implants (CI) traditionally have been used to treat individuals with bilateral profound sensorineural hearing loss, a recent trend is to implant individuals with residual low-frequency hearing. Patients who retain some residual acoustic hearing after surgery often can benefit from electro-acoustic stimulation (EAS) technologies, which combine conventional acoustic amplification with electrical stimulation. However, interactions between acoustic and electrical stimulation may affect outcomes adversely and are time-consuming and difficult to assess behaviorally. This study demonstrated the feasibility of using the Advanced Bionics HiRes90K Advantage implant electronics and HiFocus Mid Scala/1j electrode to measure electrocochleography (ECochG) responses in the presence of electrical stimulation to provide an objective estimate of peripheral physiologic EAS interactions. In general, electrical stimulation reduced ECochG response amplitudes to acoustic stimulation. The degree of peripheral EAS interaction varied as a function of acoustic pure tone frequency and the intra-cochlear location of the electrically stimulated electrode. Further development of this technique may serve to guide and optimize clinical EAS system fittings in the future.
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Affiliation(s)
- Kanthaiah Koka
- Research and Technology, Advanced Bionics LLCValencia, CA, United States
| | - Leonid M Litvak
- Research and Technology, Advanced Bionics LLCValencia, CA, United States
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75
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O'Connell BP, Holder JT, Dwyer RT, Gifford RH, Noble JH, Bennett ML, Rivas A, Wanna GB, Haynes DS, Labadie RF. Intra- and Postoperative Electrocochleography May Be Predictive of Final Electrode Position and Postoperative Hearing Preservation. Front Neurosci 2017; 11:291. [PMID: 28611574 PMCID: PMC5447029 DOI: 10.3389/fnins.2017.00291] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/08/2017] [Indexed: 11/13/2022] Open
Abstract
Introduction: The objectives of the current study were to (1) determine the relationship between electrocochleography (ECochG), measured from the cochlear implant (CI) electrode array during and after implantation, and postoperative audiometric thresholds, (2) determine the relationship between ECochG amplitude and electrode scalar location determined by computerized tomography (CT); and (3) determine whether changes in cochlear microphonic (CM) amplitude during electrode insertion were associated with postoperative hearing. Materials and Methods: Eighteen subjects undergoing CI with an Advanced Bionics Mid-Scala device were prospectively studied. ECochG responses were recorded using the implant coupled to a custom signal recording unit. ECochG amplitude collected intraoperatively concurrent with CI insertion and at activation was compared with audiometric thresholds postoperatively. Sixteen patients also underwent postoperative CT to determine scalar location and the relationship to ECochG measures and residual hearing. Results: Mean low-frequency pure tone average (LFPTA) increased following surgery by an average of 28 dB (range 8–50). Threshold elevation was significantly greater for electrodes with scalar dislocation. No correlation was found between intraoperative ECochG and postoperative behavioral thresholds collapsed across frequency; however, mean differences in thresholds measured by intraoperative ECochG and postoperative audiometry were significantly smaller for electrodes inserted completely within scala tympani (ST) vs. those translocating from ST to scala vestibuli. A significant correlation was observed between postoperative ECochG thresholds and behavioral thresholds obtained at activation. Discussion: Postoperative audiometry currently serves as a marker for intracochlear trauma though thresholds are not obtained until device activation or later. When measured at the same time-point postoperatively, low-frequency ECochG thresholds correlated with behavioral thresholds. Intraoperative ECochG thresholds, however, did not correlate significantly with postoperative behavioral thresholds suggesting that changes in cochlear physiology occur between electrode insertion and activation. ECochG may hold clinical utility providing surgeons with feedback regarding insertion trauma due to scalar translocation, which may be predictive of postoperative hearing preservation. Conclusion: CI insertion trauma is generally not evident until postoperative audiometry when loss of residual hearing is confirmed. ECochG has potential to provide estimates of trauma during insertion as well as reliable information regarding degree of hearing preservation.
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Affiliation(s)
- Brendan P O'Connell
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States
| | - Jourdan T Holder
- Department of Hearing and Speech Sciences, Vanderbilt University Medical CenterNashville, TN, United States
| | - Robert T Dwyer
- Department of Hearing and Speech Sciences, Vanderbilt University Medical CenterNashville, TN, United States
| | - René H Gifford
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States.,Department of Hearing and Speech Sciences, Vanderbilt University Medical CenterNashville, TN, United States
| | - Jack H Noble
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States.,Department of Computer Science and Electrical Engineering, Vanderbilt UniversityNashville, TN, United States
| | - Marc L Bennett
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States
| | - Alejandro Rivas
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States
| | - George B Wanna
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States
| | - David S Haynes
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States
| | - Robert F Labadie
- Department of Otolaryngology, Vanderbilt University Medical CenterNashville, TN, United States.,Department of Computer Science and Electrical Engineering, Vanderbilt UniversityNashville, TN, United States
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Koka K, Saoji AA, Attias J, Litvak LM. An Objective Estimation of Air-Bone-Gap in Cochlear Implant Recipients with Residual Hearing Using Electrocochleography. Front Neurosci 2017; 11:210. [PMID: 28458630 PMCID: PMC5394163 DOI: 10.3389/fnins.2017.00210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 03/28/2017] [Indexed: 11/17/2022] Open
Abstract
Although, cochlear implants (CI) traditionally have been used to treat individuals with bilateral profound sensorineural hearing loss, a recent trend is to implant individuals with residual low-frequency hearing. Notably, many of these individuals demonstrate an air-bone gap (ABG) in low-frequency, pure-tone thresholds following implantation. An ABG is the difference between audiometric thresholds measured using air conduction (AC) and bone conduction (BC) stimulation. Although, behavioral AC thresholds are straightforward to assess, BC thresholds can be difficult to measure in individuals with severe-to-profound hearing loss because of vibrotactile responses to high-level, low-frequency stimulation and the potential contribution of hearing in the contralateral ear. Because of these technical barriers to measuring behavioral BC thresholds in implanted patients with residual hearing, it would be helpful to have an objective method for determining ABG. This study evaluated an innovative technique for measuring electrocochleographic (ECochG) responses using the cochlear microphonic (CM) response to assess AC and BC thresholds in implanted patients with residual hearing. Results showed high correlations between CM thresholds and behavioral audiograms for AC and BC conditions, thereby demonstrating the feasibility of using ECochG as an objective tool for quantifying ABG in CI recipients.
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Affiliation(s)
- Kanthaiah Koka
- Research and Technology, Advanced BionicsValencia, CA, USA
| | - Aniket A Saoji
- Research and Technology, Advanced BionicsValencia, CA, USA
| | - Joseph Attias
- Research and Technology, Advanced BionicsValencia, CA, USA.,Schneider Children's Medical Center of Israel and Rabin Medical CenterPetach Tikva, Israel
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Charaziak KK, Shera CA, Siegel JH. Using Cochlear Microphonic Potentials to Localize Peripheral Hearing Loss. Front Neurosci 2017; 11:169. [PMID: 28420953 PMCID: PMC5378797 DOI: 10.3389/fnins.2017.00169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/14/2017] [Indexed: 11/13/2022] Open
Abstract
The cochlear microphonic (CM) is created primarily by the receptor currents of outer hair cells (OHCs) and may therefore be useful for identifying cochlear regions with impaired OHCs. However, the CM measured across the frequency range with round-window or ear-canal electrodes lacks place-specificity as it is dominated by cellular sources located most proximal to the recording site (e.g., at the cochlear base). To overcome this limitation, we extract the "residual" CM (rCM), defined as the complex difference between the CM measured with and without an additional tone (saturating tone, ST). If the ST saturates receptor currents near the peak of its excitation pattern, then the rCM should reflect the activity of OHCs in that region. To test this idea, we measured round-window CMs in chinchillas in response to low-level probe tones presented alone or with an ST ranging from 1 to 2.6 times the probe frequency. CMs were measured both before and after inducing a local impairment in cochlear function (a 4-kHz notch-type acoustic trauma). Following the acoustic trauma, little change was observed in the probe-alone CM. In contrast, rCMs were reduced in a frequency-specific manner. When shifts in rCM levels were plotted vs. the ST frequency, they matched well the frequency range of shifts in neural thresholds. These results suggest that rCMs originate near the cochlear place tuned to the ST frequency and thus can be used to assess OHC function in that region. Our interpretation of the data is supported by predictions of a simple phenomenological model of CM generation and two-tone interactions. The model indicates that the sensitivity of rCM to acoustic trauma is governed by changes in cochlear response at the ST tonotopic place rather than at the probe place. The model also suggests that a combination of CM and rCM measurements could be used to assess both the site and etiology of sensory hearing loss in clinical applications.
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Affiliation(s)
- Karolina K Charaziak
- Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos Angeles, CA, USA.,Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Hugh Knowles Center, Northwestern UniversityEvanston, IL, USA
| | - Christopher A Shera
- Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos Angeles, CA, USA
| | - Jonathan H Siegel
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Hugh Knowles Center, Northwestern UniversityEvanston, IL, USA
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Bester CW, Campbell L, Dragovic A, Collins A, O'Leary SJ. Characterizing Electrocochleography in Cochlear Implant Recipients with Residual Low-Frequency Hearing. Front Neurosci 2017; 11:141. [PMID: 28386212 PMCID: PMC5363175 DOI: 10.3389/fnins.2017.00141] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/07/2017] [Indexed: 11/23/2022] Open
Abstract
Objective: Lay the groundwork for using electrocochleography (ECochG) as a measure of cochlear health, by characterizing typical patterns of the ECochG response observed across the electrode array in cochlear implant recipients with residual hearing. Methods: ECochG was measured immediately after electrode insertion in 45 cochlear implant recipients with residual hearing. The Cochlear Response Telemetry system was used to record ECochG across the electrode array, in response to 100- or 110-dB SPL pure tones at 0.5-kHz, presented at 14 per second and with alternating polarities. Hair cell activity, as the cochlear microphonic (CM), was estimated by taking the difference (DIF) of the two polarities. Neural activity, as the auditory nerve neurophonic (ANN), was estimated by taking the sum (SUM) of the two polarities. Prior work in humans and animal studies suggested that the expected ECochG pattern in response to a 0.5-kHz pure tone is an apical-peak in CM amplitude and latency. Results: The most prevalent pattern was a peak in the DIF amplitude near the most apical electrode, with a prolongation of latency toward the electrode tip; this was found in 21/39 individuals with successful ECochG recordings. The 21 apical-peak recipients had the best low-frequency hearing. A low amplitude, long-latency DIF response that remained relatively constant across the electrode array was found in 10/39 individuals, in a group with the poorest low- and high-frequency hearing. A third, previously undescribed, pattern occurred in 8/39 participants, with mid-electrode peaks in DIF amplitude. These recipients had the best high-frequency hearing and a progressive prolongation of DIF latency around the mid-electrode peaks consistent with the presence of discrete populations of hair cells. Conclusions: The presence of distinct patterns of the ECochG response with relationships to pre-operative hearing levels supports the notion that ECochG across the electrode array functions as a measure of cochlear health.
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Affiliation(s)
- Christofer W Bester
- Department of Otolaryngology, University of MelbourneMelbourne, VIC, Australia; Royal Victorian Eye and Ear HospitalMelbourne, VIC, Australia
| | - Luke Campbell
- Department of Otolaryngology, University of Melbourne Melbourne, VIC, Australia
| | - Adrian Dragovic
- Department of Otolaryngology, University of Melbourne Melbourne, VIC, Australia
| | - Aaron Collins
- Department of Otolaryngology, University of Melbourne Melbourne, VIC, Australia
| | - Stephen J O'Leary
- Department of Otolaryngology, University of MelbourneMelbourne, VIC, Australia; Royal Victorian Eye and Ear HospitalMelbourne, VIC, Australia
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Mass Potentials Recorded at the Round Window Enable the Detection of Low Spontaneous Rate Fibers in Gerbil Auditory Nerve. PLoS One 2017; 12:e0169890. [PMID: 28085968 PMCID: PMC5234781 DOI: 10.1371/journal.pone.0169890] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 12/22/2016] [Indexed: 11/19/2022] Open
Abstract
Auditory nerve fibers (ANFs) transmit acoustic information from the sensory hair cells to the cochlear nuclei. In experimental and clinical audiology, probing the whole ANF population remains a difficult task, as the ANFs differ greatly in their threshold and onset response to sound. Thus, low spontaneous rate (SR) fibers, which have rather higher thresholds, delay and larger jitter in their first spike latency are not detectable in the far-field compound action potential of the auditory nerve. Here, we developed a new protocol of acoustic stimulation together with electrophysiological signal processing to track the steady state activity of ANFs. Mass potentials at the round window were recorded in response to repetitive 300-ms bursts of 1/3 octave band noise centered on a frequency probe. Analysis was assessed during the last 200-ms of the response to capture the steady-state response of ANFs. To eliminate the microphonic component reflecting the sensory cells activity, repetitive pairs of sounds of opposite polarities were used. The spectral analysis was calculated on the average of two consecutive responses, and the neural gain was calculated by dividing point-by-point the spectrum to sound over unstimulated condition. In response to low-sound-level stimulation, neural gain predominated in the low-frequency cochlear regions, while a second component of responses centered on higher cochlear frequency regions appeared beyond 30 dB SPL. At 60 dB SPL, neural gain showed a bimodal shape, with a notch near 5.6 kHz. In addition to correlate with the functional mapping of ANFs along the tonotopic axis, the deletion of low-SR fibers leads to a reduction in the high-frequency response, where the low-SR fibers are preferentially located. Thus, mass potentials at the round window may provide a useful tool to probe the SR-based distribution of ANFs in humans and in other species in which direct single-unit recordings are difficult to achieve or not feasible.
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81
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Correlation of Electrophysiological Properties and Hearing Preservation in Cochlear Implant Patients. Otol Neurotol 2016; 36:1172-80. [PMID: 25839980 DOI: 10.1097/mao.0000000000000768] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To monitor changes in cochlear function during cochlear implantation using electrocochleography (ECoG) and to correlate changes to postoperative hearing preservation. METHODS ECoG responses to acoustic stimuli of 250, 500, and 1000 Hz were recorded during cochlear implantation. The recording electrode was placed on the promontory and stabilized to fix the position during cochlear implantation. Baseline recordings were obtained after completion of the posterior tympanotomy. Changes of the ongoing ECoG response at suprathreshold intensities were analyzed after full insertion of the cochlear implant electrode array. Audiometric tests were conducted before and 4 weeks after surgery and correlated with electrophysiological findings. RESULTS Ninety-five percent (18/19) of cochlear implant subjects had measurable ECoG responses. Under unchanged conditions, recordings showed a high repeatability without significant differences between 2 recordings (p ≤ 0.01). Ninety-four percent (17/18) of subjects showed no relevant changes in ECoG recordings after insertion of the cochlear implant electrode array. One subject showed decreases in responses at all frequencies indicative of cochlear trauma. This was associated with a complete hearing loss 4 weeks after surgery compared with mean presurgical low-frequency hearing of 78 dB HL. CONCLUSION Extracochlear ECoG is a reliable tool to assess cochlear function during cochlear implantation. Moderate threshold shifts could be caused by postoperative mechanisms or minor cochlear trauma. Detectable changes in extracochlear ECoG recordings, indicating gross cochlear trauma, are probably predictive of complete loss of residual acoustic hearing.
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Adunka OF, Giardina CK, Formeister EJ, Choudhury B, Buchman CA, Fitzpatrick DC. Round window electrocochleography before and after cochlear implant electrode insertion. Laryngoscope 2015; 126:1193-200. [PMID: 26360623 DOI: 10.1002/lary.25602] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2015] [Indexed: 11/09/2022]
Abstract
OBJECTIVE/HYPOTHESIS Previous reports have documented the feasibility of utilizing electrocochleographic (ECoG) responses to acoustic signals to assess trauma caused during cochlear implantation. The hypothesis is that intraoperative round window ECoG before and after electrode insertion will help predict postoperative hearing preservation outcomes in cochlear implant recipients. STUDY DESIGN Prospective cohort study. METHODS Intraoperative round window ECoG responses were collected from 31 cochlear implant recipients (14 children and 17 adults) immediately prior to and just after electrode insertion. Hearing preservation was determined by postoperative changes in behavioral thresholds. RESULTS On average, the postinsertion response was smaller than the preinsertion response by an average of 4 dB across frequencies. However, in some cases (12 of 31) the response increased after insertion. The subsequent hearing loss was greater than the acute loss in the ECoG, averaging 22 dB across the same frequency range (250-1,000 Hz). There was no correlation between the change in the ECoG response and the corresponding change in audiometric threshold. CONCLUSIONS Intraoperative ECoG is a sensitive method for detecting electrophysiologic changes during implantation but had limited prognostic value regarding hearing preservation in the current conventional cochlear implant patient population where hearing preservation was not intended. LEVEL OF EVIDENCE 2b Laryngoscope, 126:1193-1200, 2016.
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Affiliation(s)
- Oliver F Adunka
- Department of Otolaryngology-Head & Neck Surgery, the Ohio State University, Columbus, Ohio, U.S.A.,Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A
| | - Christopher K Giardina
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A
| | - Eric J Formeister
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A
| | - Baishakhi Choudhury
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A
| | - Craig A Buchman
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A
| | - Douglas C Fitzpatrick
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A
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Abstract
OBJECTIVE Electrophysiologic responses to acoustic stimuli are present in nearly all cochlear implant recipients when measured at the round window (RW). Intracochlear recording sites might provide an even larger signal and improve the sensitivity and the potential clinical utility of electrocochleography (ECoG). Thus, the goal of this study is to compare RW to intracochlear recording sites and to determine if such recordings can be used to monitor cochlear function during insertion of a cochlear implant. METHODS Intraoperative ECoG recordings were obtained in subjects receiving a cochlear implant from the RW and from just inside scala tympani (n = 26). Stimuli were tones at high levels (80-100 dB HL). Further recordings were obtained during insertions of a temporary lateral cochlear wall electrode (n = 8). Response magnitudes were determined as the sum of the first and second harmonics amplitudes. RESULTS All subjects had measurable extracochlear responses at the RW. Twenty cases (78%) showed a larger intracochlear response, compared with three (11%) that had a smaller response and three that were unchanged. On average, signal amplitudes increased with increasing electrode insertion depths, with the largest increase between 15 and 20 mm from the RW. CONCLUSION ECoG to acoustic stimuli via an intracochlear electrode is feasible in standard cochlear implant recipients. The increased signal can improve the speed and efficiency of data collection. The growth of response magnitudes with deeper intrascalar electrode positions could be explained by closer proximity or favorable geometry with respect to residual apical signal generators. Reductions in magnitude may represent unfavorable geometry or cochlear trauma.
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Abstract
In the diverse mechanosensory systems that animals evolved, the waveform of stimuli can be encoded by phase locking in spike trains of primary afferents. Coding of the fine structure of sounds via phase locking is thought to be critical for hearing. The upper frequency limit of phase locking varies across species and is unknown in humans. We applied a method developed previously, which is based on neural adaptation evoked by forward masking, to analyze mass potentials recorded on the cochlea and auditory nerve in the cat. The method allows us to separate neural phase locking from receptor potentials. We find that the frequency limit of neural phase locking obtained from mass potentials was very similar to that reported for individual auditory nerve fibers. The results suggest that this is a promising approach to examine neural phase locking in humans with normal or impaired hearing or in other species for which direct recordings from primary afferents are not feasible.
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Round Window Electrocochleography and Speech Perception Outcomes in Adult Cochlear Implant Subjects. Otol Neurotol 2014; 35:e245-52. [DOI: 10.1097/mao.0000000000000557] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Verschooten E, Joris PX. Estimation of neural phase locking from stimulus-evoked potentials. J Assoc Res Otolaryngol 2014; 15:767-87. [PMID: 24890715 DOI: 10.1007/s10162-014-0465-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 05/07/2014] [Indexed: 11/24/2022] Open
Abstract
The frequency extent over which fine structure is coded in the auditory nerve has been physiologically characterized in laboratory animals but is unknown in humans. Knowledge of the upper frequency limit in humans would inform the debate regarding the role of fine structure in human hearing. Of the presently available techniques, only the recording of mass neural potentials offers the promise to provide a physiological estimate of neural phase locking in humans. A challenge is to disambiguate neural phase locking from the receptor potentials. We studied mass potentials recorded on the cochlea and auditory nerve of cat and used several experimental manipulations to isolate the neural contribution to these potentials. We find a surprisingly large neural contribution in the signal recorded on the cochlear round window, and this contribution is in many aspects similar to the potential measured on the auditory nerve. The results suggest that recording of mass potentials through the middle ear is a promising approach to examine neural phase locking in humans.
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Affiliation(s)
- Eric Verschooten
- Laboratory of Auditory Neurophysiology, KU Leuven, Herestraat 49 bus 1021, 3000, Leuven, Belgium,
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