Longitudinal Analysis of the Absence of Intraoperative Neural Response Telemetry in Children using Cochlear Implants

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Severe or profound sensorineural hearing loss causes several deficiencies that are not only sensorial but also social and emotional. Characterized by a lack of perception and speech coding, individuals with this degree of hearing loss might need special resources to minimize the consequences of such a loss.

With the advancement of medicine and technology, the cochlear implant (CI) represents an alternative that allows access to the sounds of speech in individuals with severe to profound hearing loss.1 Such improvements can also be observed in the objective methods used to verify the integrity of the cochlear device and the electrophysiologic response of users. Neural response telemetry (NRT), developed from the studies by Abbas et al,2 is a fast and easily applicable techniquethat assesses the response of the peripheral segment of the auditory nerve to electrical stimulation. The implant used for NRT elicits stimuli and records the electrically evoked compound action potential (ECAP). Given that this is a fast and easily applicable technique, NRT is also used in the intraoperative setting.

The major contribution of NRT is the confirmation of the physiologic integrity of the auditory nerve.3 It is also useful when establishing the electrodes that might be included in a given map, the best stimulation speeds, the speech coding strategies, and the estimation of the stimulation of T (minimumstimulation) and C (maximum stimulation) levels.4 Composed of a negative peak (N1) followed by a positive peak (P2), the ECAP is analyzed with regard to the amplitude of the response. The measurement between N1 and P2 yields the wave amplitude, which varies according to the increased stimulation intensity. The ECAP represents the synchrony of a group of neurons, and the amplitude of response is proportional to the number of neurons activated by a stimulus.

Consequently, the presence of the ECAP allows one to predict a satisfactory postoperative performance,5 which likely corresponds to better synaptic efficiency and synchronization of the neural response.6 Knowledge of the physiology and responses of the auditory nerve to electrical stimuli is important in establishing the current level used for stimulation and other programming adjustments.7 In some cases, the ECAP is not present during surgery,whichmight suggest a dysfunction of the cochlear nerve and existing neural structures. In some of these cases, continual stimulation predicts the appearance of neural response, which might be related to the synchronization of nerve fibers.8 Cafarelli Dees et al9 and van Dijk et al10 suggested the rates of postoperative presence of ECAP to be 96 and 90%, respectively, whereas Guedes et al reported a rate of 80%.3 Guedes et al found that the absence of responses was correlated with limited prognosis.11 The continued use of CIs has tended to
result in the emergence of the action potential after some months of stimulation. Even longitudinal studies on neural responses, however, have failed to mention the possibility of the appearance of a response or the average time required for the onset of such a response.

This study aimed at establishing whether the ECAP of the auditory nerve, when absent intraoperatively, can appear
after continual electrical stimulation. When NRT responses were absent during surgery, we analyzed the evolution of
these responses after at least 3 months of stimulation.

Are auditory steady-state responses a good tool prior to pediatric cochlear implantation?

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ASSR allow frequency-specific evaluation in intensities up to 120 dB HL and detection of residual hearing in patients with severe-to-profound hearing loss. Aim: to compare ASSR thresholds and behavioral test results in children with suspected severe-to-profound hearing loss. Methods: Cross sectional study to compare ASSR and behavioral responses (VRA or audiometry) in 63 pediatric cochlear implant candidates (126 ears) aged between 6 and 72 months. We included children with normal otomicroscopy, absent responses to click-ABR and otoaccoustic emissions. We excluded children with inner ear malformations, auditory neuropathy spectrum disorder or who did not complete VRA or achieve EEG noise < 30 nV during the ASSR test. Air-conduction ASSR stimuli were continuous sinusoidal tones presented at 0.5, 1, 2 and 4 kHz starting at 110 dB HL. Behavioral thresholds weren acquired with warble tones presented at 0.5, 1, 2 and 4 kHz in each ear through insert or head phones at maximum presentation level of 120 dB HL. Results
Behavioral thresholds were obtained in 36.7% (185/504) of all frequencies in all subjects, 9% in intensities >110 dB HL. Among 504 ASSR measurements, 53 thresholds were obtained (10.5%). Overall 89.5% of the tested frequencies did not show any response at 110 dB HL. Most responses were at 500 Hz.
Mean differences between behavioral and ASSR thresholds varied from 0.09 to 8.94 dB. Twenty-seven comparisons of behavioral and ASSR thresholds were obtained: 12 at 0.5 kHz, 9 at 1 kHz, 5 at 2 kHz and 1 at 4 kHz. Absent responses were observed in both tests in 38.1% at 0.5 kHz, 52.4% at 1 kHz, 74.6% at 2 kHz and 81.0% at 4 kHz. Specificity was > 90% at 1, 2 and 4 kHz. In ears with no behavioral response at 120 dB HL all ASSR thresholds were in the profound hearing loss range, 90% of them were 110 dB HL.

Among 63 pediatric CI candidates, absent responses to high-intensity ASSR was the major finding (specificity > 90%) predicting behavioral thresholds in the profound hearing loss range. These findings can be helpful to confirm the decision for cochlear implantation.

Telephone Usage and Cochlear Implant: Auditory Training Benefits

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Difficulties with telephone use by adult users of cochlear implants (CIs) are reported as a limitation in daily life. Studies to improve the speech understanding of CI users on the telephone are scarce in the Brazilian scientific literature.

To develop and evaluate the effectiveness of a training program of auditory abilities on the telephone for an adult CI user. Resumed Report The subject was a 55-year-old woman with a degree in accounting who used a CI for 24 onths. The program consisted of three stages: pretraining evaluation, eight sessions of advanced auditory abilities
raining, and post-training evaluation. Auditory abilities with CI were evaluated before and after training in three conditions: sound field, telephone with the speech processor in the microphone function, and telephone with the speech processor in the telecoil function.

Speech recognition was assessed by three different lists: one with monosyllabic and dissyllabic words, another with nonsense syllables, and another one with sentences. The Client Oriented Scale of Improvement (COSI) was used to assess whether the needs established by the CI user in everyday telephone use situations improved after training. The auditory abilities training resulted in a relevant improvement in the percentage of correct answers in speech tests both in the telephone use conditions and in the sound field condition.

The results obtained with the COSI inventory indicated a performance improvement in all situations presented at the beginning of the program.

Evaluation of Intracochlear Trauma Caused by Insertion of Cochlear Implant Electrode Arrays through Different Quadrants of the Round Window

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Cochlear implants (CIs) represent a well-established treatment for severe and profound bilateral hearing loss. The development ofCIs in the last 30years is consideredoneof the milestones ofmodernmedicine, and, to date, the outcomes of CIs have been remarkable and superior to those of any other type of neural prosthesis [1]. These results have encouraged the expansion of the selection criteria for CIs [2].Therefore, the number of candidates with significant residual hearing who are eligible to receive CIs has increased, fostering several studies on the preservation of postoperative residual hearing in these patients. Intracochlear trauma during CI-related surgical interventions is one of the factors associated with residual hearing loss [3–5]. Previous studies have highlighted the possibility of electrode array insertion using atraumatic surgical techniques, which have been designated as soft surgeries [4, 6–9].

Among the steps involved in soft surgeries, electrode array insertion is the most frequently studied. CI arrays can be inserted via cochleostomy or through the round window (RW). According to Banfai [10], RW was the first choice of Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 236364, 9 pages http://dx.doi.org/10.1155/2015/236364 2 BioMed Research International route for CI electrode array insertion. However, with the development of longer, thicker, and less flexible electrodes, insertion through RW became difficult and necessitated cochleostomy. Over the last few years, the development of thinner and more flexible electrodes has again enabled insertion through RW[11].The possibility of electrode array insertion via these two distinct routes stimulated further comparative studies [12–15]. Numerous studies on cochleostomy have been conducted to determine any variations in intracochlear trauma according to its location. However, to date, no studies have evaluated differences in the degree of intracochlear trauma caused by electrode array insertion through different quadrants of the RWmembrane.

Therefore, this study was conducted to determine differences in intracochlear trauma caused by CI electrode array insertion through the anterosuperior and anteroinferior quadrants of the RWmembrane.

Addendum to the history ofcochlear implants in Brazil

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I would like to congratulate BJORL for the excellent edi-torial published in issue 81, number 2, by Prof. Dr. PedroMangabeira Albernaz on the history of cochlear implants inBrazil.1Professor Pedro Mangabeira was the pioneer in this tech-nique in our country, having been honored at the lastIbero-American Congress of Cochlear Implants.It so happens that in the Editorial, I do not know whetherdue to lack of space, something of extreme historical impor-tance was omitted: the initiative, in 1990, to manufacture inBrazil the first national cochlear implant, developed entirelyin the Bioengineering Department of Instituto do Corac¸ão(the Heart Institute) of HCFMUSP, with the cooperation ofthe FMUSP Otorhinolaryngology Discipline, which won anaward at the time from the Inter-American DevelopmentBank as the best scientific project of 1989. The first workabout it was published in this respected journal, the Brazil-ian Journal of Otorhinolaryngology.2Two patents were generated based on these works andseveral patients were successfully implanted (Patent INPIno. 910.5546-6; on 12/16/1991).3Please cite this article as: Bento RF. Addendum to the history ofcochlear implants in Brazil. Braz J Otorhinolaryngol. 2015;81:576.The researchers involved in this project were Ricardo Fer-reira Bento, Aroldo Miniti, Adolpho Leiner, Carlos AlbertoNunes, Milton Oshiro, Maria Valéria Goffi Gomes.Only five countries have developed cochlear implantdevices, including Brazil with this device. The latter is citedin more than 1000 publications on CI around the world as apioneer in its concepts.

Are Auditory Steady-State Responses Useful to Evaluate Severe-to-Profound Hearing Loss in Children?

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As universal newborn hearing screening programs are established in numerous countries, more children will be diagnosed in early childhoodwith some degree of hearing loss. Early detection and intervention during the critical
period for language and cognitive development can improve individual performance [1].

Children with severe-to-profound bilateral hearing loss are candidates for cochlear implantation (CI) and require
specific audiologic evaluation prior to intervention. As early age of indication and presence of residual hearing are important factors for postimplant speech perception and language development, this has resulted in further decrease of minimum age of surgery [2–7].

In these very young children, behavioral audiologic evaluation can be challenging, may not be obtained in children
younger than 6 months, and usually does not assess each ear separately.Thus the audiologic evaluation of pediatric cochlear implant candidates reliesmore andmore on electrophysiological measures. The most widely used electrophysiological procedure for estimating hearing thresholds in young children is click and tone burst auditory brainstem responses (ABR). Due to the transient nature of the stimuli used to evokeABR,maximum output levels are 95 dB hearing level (HL). In view of that, the possibility of residual hearing at severe-to-profound levels
cannot be investigated with ABR [8]. Hearing assessment of children, using the Auditory Steady-State Responses (ASSR), is made by frequency specific continuous modulated tones and allows increased levels of stimulation intensity. Therefore, ASSR can provide ear and frequency specific threshold information at elevated intensity
Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 579206, 7 pages
http://dx.doi.org/10.1155/2015/579206 2 BioMed Research International levels up to 120 dB HL and higher, providing better and more reliable investigation of ears with minimal residual hearing [9]. Furthermore, ASSR thresholds may be used for hearing aid fitting prior to cochlear implantation.

For such reasons, ASSR is a unique tool for auditory assessment of young cochlear implant candidates. Some authors [10, 11] have investigated the use of ASSR to evaluate patients with severe-to-profound hearing loss. They showed that spurious responses might occur during high stimulus intensities, especially in 500 and 1000Hz. Solutions have been implemented by themanufacturer to reduce artifacts at high-intensity stimulation [12].

Few papers have been published since 2004. One report evaluated 15 childrenwith severe-to-profound hearing loss by
ASSR, but behavioral thresholds were obtained for only one subject [13]. As cochlear implant is the first choice, especially, for the young child with severe-to-profound hearing loss, it is quite important to obtain more data in the pediatric population.

Previously, we performed two studies at the University of S˜ao Paulo. One of them evaluated adults with severe-toprofound hearing loss. The responses of pure tone audiometry (PTA) and ASSR were compared. Patients’ subjective
perception of ASSR stimuli was also evaluated and compared to PTA test results, and no systematic extra-auditory ASSR responses at high intensities were observed [14]. The other study evaluated children with severe-toprofound
hearing loss from 6 to 65 months. Most ASSR responses (48%) were found at 500Hz [15].

The aim of this study was to evaluate Auditory Steady- State Responses (ASSR) at high intensities in pediatric cochlear implant candidates and to compare the results to behavioral test responses.

Cochlear Implantation and Single-sided Deafness: A Systematic Review of the Literature

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Single-sided deafness (SSD) may cause many problems involving communication between people. Permanent acquired
unilateral several-profound hearing loss has been estimated to affect between 12–27 persons in every 100,000 among the general population, with the majority of losses being sudden or idiopathic.1 The most common impairment is difficulty in hearing sounds in the affected side due to the head shadow effect, which attenuates the highfrequency
components of sounds at the ear contra-lateral to their source.2 Other problems involved are: prejudice inword
discrimination, difficulty in understanding speech particularly in noisy environments; constantly adjusting head to try and compensate for the handicap; restriction of onés ability to localize sounds; and, in some cases, leading to social isolation.3

The cochlear implant (CI) is one of the more recent treatment options for such cases. However, there is a concern about the ability of the brain distinguish acoustic and electric stimuli and concern that the hearing from the
cochlear implant would interfere with acoustic signal processing from the good ear. Contralateral routing of sound
(CROS) and osseointegrated implants are also devices used as rehabilitative options for SSD, although they are not
able to provide binaural hearing4 or improve sound localization.5 People with binaural hearing enjoy certain advantages.

The first advantage is better speech-to-noise ratio (SNR), which improves speech understanding in noisy environments. A second advantage results from the processing of the input sound signal by the brain from both ears. The brain is able to separate noise and speech from different locations using distinct interaural timing, spectral cues and level, thus, refining intelligibility. A third possible advantage is related to the summation effect, responsible for improved speech perception through the identification of identical signals arriving in both ears.6

The search in PubMed, Cochrane Library, and Lylacs retrieved a total of 228 articles, but only 17 met the inclusion criteria and were included in the study. Next, the respective studies were appraised, according to evidence-based guidelines of categorization of medical studies (►Table 2), and systematically analyzed. None of the studies were conducted as a randomized controlled trial and only one evaluated a control group.7 Furthermore, blinding was not observed in any study selected. Only prospective comparative studies and case series were to be analyzed in this review.

The operated patients’ demographics and audiometric data were carefully examined to avoid double counting of
cases. Three studies presented data which were also showed in more recent articles, including this review8–10;
thus, they were discarded. Two studies scored low in patient population and did not provide suitable follow-up
(patients had missed follow-up)11,12. Some studies presented incomplete data13 and were excluded for further

Auditory Cortical Maturation in a Child with Cochlear Implant

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The central auditory nervous system starts its development in intrauterine life; however, its maturation persists lifelong. The first phase of development is independent of external neurosensory stimulation. However, the second phase will only be effective from the sensory inputs that will organize and direct the process of connections of neural networks development [1]. It is through sound stimulation that corticalmaturation is achieved, thanks to a phenomenon called neural plasticity: the ability to be modified in order to improve the cortical response front to environmental stimuli. Through these morphological (axon, dendritic, and synaptic structures) and functional (neuronal and synaptic physiology) changes, memory acquisition and subsequent learning become possible, reflecting behavioral changes with the development of auditory and language skills [2–4].

In cases where there is deprivation of sound stimulation, direct stimulation of the auditory nerve fibers through the cochlear implant (CI) has been an alternative for the CANS to receive the stimulation needed for the maturation process and, consequently, the development of auditory and oral language skills [5, 6]. Hence, after the surgical procedure and activation of CI electrodes, precise speech and language therapy is needed, aiming to monitor the development and maturation of central auditory pathways in order to validate the benefits of the rehabilitation process.

Thus, there are outcome measures, standardized and validated for Brazilian Portuguese, that are able to assess
the development of auditory and language skills of this population, providing important information that monitor
the rehabilitation process. Concerning objective methods, electrophysiological assessment of hearing, through analysis ofmorphology and latency of Long Latency Auditory Evoked

Hearing performance as a predictor of postural recovery in cochlear implant users

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Objective: This study aimed to evaluate if hearing performance is a predictor of postural control in cochlear implant (CI) users at least six months after surgery. Methods: Cross-sectional study including (CI) recipients with post-lingual deafness and controls who were divided into the following groups: nine CI users with good hearing performance (G+), five CI users with poor hearing performance (G−), and seven controls (CG). For each patient,
computerized dynamic posturography (CDP) tests, a sensory organization test (SOT), and an adaptation test (ADT) were applied as dual task performance, with first test (FT) and re-test (RT) on the same day, including a 40—60 min interval between them to evaluate the short-term learning ability on postural recovery strategies. The results of the groups were compared.

Comparing the dual task performance on CDP and the weighted average between all test conditions, the G+ group showed better performance on RT in SOT4, SOT5, SOT6, and CS, which was not observed for G−and CG. The G−group had significantly lower levels of shortterm learning ability than the other two groups in SOT5 (p = 0.021), SOT6 (p = 0.025), and CS (p = 0.031).

The CI users with good hearing performance had a higher index of postural recovery when compared to CI users with poor hearing performance. © 2016 Published by Elsevier Editora Ltda. on behalf of Associac¸˜ao Brasileira de Otorrinolaringologia e Cirurgia C´ervico-Facial. This is an open access article under the CC BY license

Minimally Invasive Surgery for Intracochlear Schwannoma Removal and Simultaneous Cochlear Implantation

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Hearing preservation has not yet been reported in patients undergoing resection of intracochlear schwannomas. This study describes a minimally invasive procedure for intracochlear schwannoma resection with simultaneous cochlear implantation that resulted in good hearing.

Objective This study aims to describe a minimally invasive procedure for intracochlear schwannoma resection with simultaneous cochlear implantation. Data Synthesis The technique described in this study was developed for a 55-year-old male with a 20-year history of bilateral progressive hearing loss and tinnitus that had a mass in the left apical turn of the cochleameasuring 0.3 cm. Surgery accessed the apical turn of the cochlea. We performed astoidectomy and posterior tympanotomy and removed incus and tensor tympani muscle to expose the cochlear apex.

The tumor was identified and completely resected. After the cochleawas anatomically preserved, it was implanted with a straight electrode via round window insertion. The histopathological examination confirmed intracochlear schwannoma. Speech perception test revealed 100% speech recognition with closed sentences and the average audiometric threshold (500 to 2000 Hz) was 23 dB.

Our technique led to rehabilitation of the patient and improved hearing without damaging the intracochlear structure, making it possible to perform CI in the same procedure with good results.