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Clinical Evaluation of a New Electrocochleography Recording Electrode

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Clinical Evaluation of a New Electrocochleography Recording Electrode Aud Vestib Res (2020);29(2):93-100. DOI: 10.18502/avr.v29i2.2790 RESEARCH ARTICLE Clinical evaluation of a new electrocochleography recording electrode Mostafa Eyvazi1, Akram Pourbakht1, Seyyed Jalal Sameni1*, Mohammad Kamali2,3 1- Department of Audiology, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran 2- Rehabilitation Research Center, Iran University of Medical Sciences, Tehran, Iran 3- Department of Basic Sciences, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Received: 16 Jan 2020, Revised: 28 Feb 2020, Accepted: 11 Mar 2020, Published: 15 Apr 2020 Abstract Background and Aim: Electrocochleography TIP-trode. The mean SP/AP ratio between two is one of the most practically used tests in app- types of electrodes was statistically significant roaching Meniere's disease (MD). To record reli- differences in normal subjects (p = 0.027) and in able response components, the type of applied MD group (p = 0.009). electrode is of particular importance. The TIP- Conclusion: We demonstrated that the utili- trode is an appropriate electrode due to its user- zation of the Gutter electrode in ECochG assess- friendliness. Gutter electrode can be used in ments was considerably effective and beneficial. more than 100 subject. This study aimed to com- It can significantly reduce expenses and be app- pare the results of the Electrocochleography lied in clinical settings. It’s also recommended (ECochG) test responses using TIP-trode and the that 47.22% mean SP/AP amplitude ratio to be Gutter electrode. considered as upper limit of normality by using Methods: This cross-sectional study was perfor- the Gutter electrode. med on 20 normal subjects and 20 patients with Keywords: Electrocochleography; Meniere's MD, who referred to the Audiology Clinic of Iran disease; gutter electrode; TIP-trode; impedance University of Medical Sciences. The ECochG response components were randomly recorded Citation: Eyvazi M, Pourbakht A, Sameni SJ, with TIP-trode and Gutter-electrode consecu- Kamali M. Clinical evaluation of a new tively, and then statistical analysis was accomp- electrocochleography recording electrode. Aud lished. Vestib Res. 2020;29(2):93-100. Results: The mean impedance, action potential, and summation potential amplitudes were not Introduction significantly different between normal subjects Nowadays, electrocochleography (ECochG) is a and people with MD by using two types of elec- highly reliable test in assessment and diagnosis trodes. Moreover, the mean scores of summation of inner ear diseases such as Meniere's disease potential/action potential (SP/AP) ratio of the (MD), auditory neuropathy, superior semicir- Gutter electrode were higher than that of the cular dehiscence, auditory sensitivity estimation, and intraoperative monitoring of cochlea and * Corresponding author: Department of Audiology, auditory nerve [1,2]. The earliest study of the School of Rehabilitation Sciences, Iran University of Medical Sciences, Shahid Shahnazari St., Madar ECochG was performed in 1930 and the recorded Square, Mirdamad Blvd., Tehran, 15459-13487, Iran. responses were attributed to the cochlea. A few Tel: 009821-22228051, E-mail: [email protected] years later, Davis confirmed the result of the http://avr.tums.ac.ir 94 The new Gutter electrode for electrocochleography previous study, however [3]. for the first time in required. Surgery is needed to place the elec- 1970, recorded responses from the cochlea using trodes in the tympanic space and these methods the averaging technique were termed as ECochG should be performed by a physician. However, by Aran [4]. when the test is performed at a supra threshold To address the cochlear function, the ECochG level, the placement of electrodes outside of the can be the best auditory evoked response [1,5]. tympanic membrane is more convenient and reli- Cochlear microphonic (CM) potential is an alter- able [5,11,12]. A silver metal spherical ball elec- nating current that originates from the outer hair trode placed on a promontory or round window cells of the cochlea and is dependent on stimulus. was among the first electrodes administered. Summation potential (SP) which appears as a The type of used electrode varies due to several result of presenting a continuous tone or transient factors including diagnostic purposes, the health signal, is a direct current that originates from the status of the hearing system, the patient's age, outer and inner hair cells of the cochlea and indi- and the availability of medical services. Patient cates active cochlear amplification. The action comfort is an important factor to be considered. potential (AP) response is originated from the Also, the material and appearance of the elec- eighth cranial nerve and appears at about 1.5 ms trode should result in the least resistance along after stimulus presentation [1,5]. ECochG is a with the highest ion exchange [5,12]. proper tool for diagnosing and monitoring MD There have been various electrodes introduced to [1]. MD is an idiopathic disease involving the record cochlear responses and all of them have inner ear, characterized by vertigo, hearing loss, their advantage and disadvantage. butterfly elec- and tinnitus that causes an increase in the endo- trodes are the ear canal type. Due to the improper lymphatic pressure of the inner ear [6]. The exact shape of these electrodes, they do not provide pathophysiology has not been established yet [7]. enough space for the attachment between the skin Researchers expressed the sensitivity of the SP and its surface and sometimes damages the pati- amplitude in diagnosing MD by about 30%. ent's ear canal [5,13]. TIP-trode is another type In addition, the most commonly used indicator of the ear canal electrodes, which has an appro- of ECochG recording parameters with a 60% priate shape and appearance. It is proper for clini- sensitivity in diagnosing MD, is summation cal applications; nonetheless main disadvantage potential/action potential (SP/AP) ratio. This rate of this electrode is its high cost and disposable of sensitivity increases to more than 90% during identity. Its gold coating enhances the detection symptoms recurrence [8-10]. of action potential and N1 wave [5].The Gutter Depends on the purpose of the ECochG recor- electrode is a new type of ear canal electrode that ding, two approaches based on the positioning of was first developed by Sameni and Anvar- electrodes are carried out: intratympanic (pro- samarein and introduced to the 16th Iranian Con- montory and oval window) and extra tympanic gress of Audiology (2017). Its design is in a way (tympanic membrane and external auditory mea- to minimize the weaknesses of the butterfly and tus). The electrodes can also be named based TIP-trode electrode. The electrode is made of on their particular location, commonly known as silver and silver-chloride coating. The physical the tympanic membrane/transtympanic (TM/TT) structure of the Gutter electrode is adjustable electrode and ear canal electrodes including butt- relative to the size of the individual ear canal and erfly, Tip-trode (and now, the Gutter electrode). increases the area of attachment to the skin of the The purpose of using ear canal electrodes is the ear canal wall. Insert earphone are coupled to the facilitation of analysis of action potential compo- Gutter electrode by placing a probe tip, typically nents and summating potential. Generally, to rec- a foam plug into the electrode. The Gutter elec- ord the low amplitude potentials such as when trode is not disposable and it can be sterilized auditory sensitivity estimation and assessment easily and reused. of cochlear function in patients with auditory In this study, we investigated the parameters of neuropathy is needed, more sensitive procedures impedance, AP and SP amplitudes as well as Aud Vestib Res (2020);29(2):93-100. http://avr.tums.ac.ir Eyvazi et al. 95 Fig. 1. The Gutter electrode with and without foam ear tips (a) and TIP-trode (b). SP/AP ratio in the normal subjects and patients pathology of the vestibular system, moderate with MD using TIP-trode and the Gutter elec- (50−60 dB HL) or greater sensory-neural hearing trode. loss at 2−4 kHz, person's unwillingness to conti- nue the study, or not experiencing vertigo attack Methods in the recent years were excluded. Participants This cross-sectional (descriptive-analytical) stu- Procedure dy was randomly performed on 20 normal sub- At first, the ear canal was cleaned by a swab jects (8 women and 12 men) with a mean age of dipped in Nuprep gel. Then, a TIP-trode (b) and 28 ± 4.32 years old and 20 individuals suspected a Gutter electrode (a) (Fig. 1), were randomly to MD (13 women and 7 men) with a mean age inserted into each patient's ear canal. The pati- of 30.7 ± 4.71 years old. Inclusion criteria for ent's ear canal was carefully observed by an normal subjects were included air conduction otoscope, since it was necessary to accurately (AC) audiometry thresholds of less than or equal estimate the size of the canal to determine the to 25 dB HL at all frequencies (250−8000 Hz), size of the Gutter electrode. The patient was also no gap between AC and bone conduction (BC) referred to an otologist if high amount of audiometry results, normal speech audiometry, cerumen in the canal was observed. type An tympanogram, presence of ipsilateral The size of the electrode and consequently its acoustic reflex, having no family history of MD, placement in the ear canal should not cause any and absence of tinnitus and vertigo in addition to pain and it was required to be fully in contact balance dysfunction in the past two years. with the wall. To resize the electrode, first, ear- Patients with MD were entered into the study tips foam was needed to be attached to the insert with symptoms at least six months ago, including device and then connected into the cylindrical sensory-neural hearing loss (in low frequencies), space of the Gutter electrode.
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