Optimization of a Non-invasive Electrophysiological Method for Studying the Functionality of Auditory Nerve Fibers

Study Overview
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Brief Summary
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Acoustic overexposure can induced temporary or hearing loss. Usually hearing loss is associated with cochlear cell damages. Recently, a new pathological entity was described and called hidden hearing loss. In animal model, the histopathology revealed a selective reduction in the number of auditory fibers, resulting in a decrease in the amplitude of wave I of the auditory brainstem response. Electrocochleography (Ecog) is a method for recording the electrical potentials of the cochlea (e.g. wave I). In clinical routine, Ecog is performed invasively with sedation or local anesthesia. Actually, a non invasive approach could be perform but it seems necessary to optimize this method and to define reference values in healthy volunteers.

Detailed Description
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The sound overexposure is a major cause of hearing disorders. The installation of hearing disorders can be temporary or permanent. Most of the time the investigators see a rise in hearing thresholds that can be accompanied by tinnitus. However, sometimes-hearing disorders aren't characterized by higher auditory threshold but by a complaint of understanding in noise. Two explanation are the either possible with a lesion at the peripheral level (sensory organ) or central lesion (auditory pathways). Peripheral damage is easily analysed by conventional tests such as the audiogram. Concerning the central lesions, through to the Electrocochleography, one sees a diminution of the wave I which corresponds to the nerve fiber injury. The wave I can more easily be analysed by the Electrocochleography method. This technique previously used an electrode deposited trans-tympanically in contact with the sensory organ. But, the evolution of a non-invasive technique is now available. However, several assemblies of the electrode are then possible without knowing the impact of these on the morphology of the wave I. Moreover, no normative values are also referenced in the literature on the population without hearing problems. It's in this context that clinical study is carried out in order to optimize the technique on the assembly of the electrode and the acoustic stimulation delivered. After this analyses and obtaining an optimal technique it's envisaged to study the morphology of the wave I in healthy volunteers aged 18-25 years. A pre-inclusion visit will verify the volunteers doesn't have a hearing disorders through a questionnaire, otoscopy, tympanometry and audiometry. Then two steps will be realized. The first is to evaluate the morphology of wave I according to assembly of electrode and acoustic stimulation delivered (machine calibration or calibration in the external auditory canal). The second step will provide normative values for people 18-25 years old who aren't hearing-impaired. Volunteers will have the choice to participate in one or both stages. The aim is to obtain wave I reference values for Electrocochleography technique. The secondary objectives are to analyse the impact of the assembly of the electrode and the adaptation of the acoustic stimulation presented.

Official Title
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Optimization of a Non-invasive Electrophysiological Method for Studying the Functionality of Auditory Nerve Fibers

Conditions
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Healthy Volunteer, Without Hearing Disorders

Intervention / Treatment
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* Diagnostic Test: Electrocochleography, electrophysiology thet for analyse the wave I generated by the auditory pathways


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Between 18 and 55 years old be affiliated to a social security system understand (oral and written) of the French language be a qualified hearing with normal tympanogram and audiogram Exclusion Criteria: have a complaint of hearing have a exposure to noise (professional and/or activities) refusal to participate in the study have ear infections and/or ENT medical history have cardiovascular, metabolic, neurological and psychiatric desease being a protected person healthy volunteer who has received compensation equal to or greader than 4500€ in clinical study

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Cohort 1<br> | Diagnostic Test: Electrocochleography, electrophysiology thet for analyse the wave I generated by the auditory pathways<br>* Electrocochleography is a technique that analyses the functionality of inner ear.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Latency of wave I by electrocochleography | The wave I analyzed at electrocochleography will allow to obtain the latency (milliseconds) of action potential (AP) | Day 180 | 
| Latency of wave I by electrocochleography | The wave I analyzed at electrocochleography will allow to obtain the latency (milliseconds) of action potential (AP) | Day 360 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Hearing thresholds in decibels | The audiometry will make it possible to obtain the hearing thresholds in decibels for all frequency of 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000, 8000, 9000, 10000, 11200, 12500 and 14000 Hz. | Day -1 , Day 180, Day 360 | 
| Acoustic reflex thresholds in decibels | The acoustic reflex allows to evaluate the trigger threshold in decibels of the reflex for the frequencies 500, 1000, 2000, 4000Hz. | Day -1 , Day 180, Day 360 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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hidden hearing loss, questionnaire, hearing screening, electrocochleography