Hearing Aids: A Review of What's New

Charcot-Marie-Tooth Disease and Hearing Loss: A Systematic Review With Meta-Analysis

OBJECTIVE

To characterize the pattern of hearing loss in Charcot-Marie-Tooth (CMT) disease to help guide clinical management.

DATABASES REVIEWED

CINAHL, PubMed, and Scopus.

METHODS

Two independent investigators selected studies on CMT patients with pure-tone average (PTA) and auditory brainstem response (ABR) data. Case reports, case series <5 patients, and data that overlapped with another study were excluded. Investigators performed data extraction, quality rating, and risk-of-bias assessment using the Newcastle-Ottawa Scale. Meta-analysis of mean difference using fixed/random effects models was used. Also, data were analyzed using a weighted one-way analysis of variance, with post-hoc Tukey's test for comparison.

RESULTS

Ultimately, 6 prospective studies (N = 197) were included. The most common demyelinating subtype (CMT1A) had significantly prolonged ABR latency values across wave III (0.20 ms, 95% confidence interval [CI]: 0.05-0.35), wave V (0.20 ms, 95% CI: 0.01-0.39), waves I-III (0.20 ms, 95% CI: 0.01-0.39), and waves I-V (0.20 ms, 95% CI: 0.01-0.39) when compared to matched controls. The autosomal recessive demyelinating subtype (CMT4C) had significantly worse PTA when compared to the most common subtype (CMT1A) (Δ 28.93 dB, 95% CI 18.34-39.52) and nondemyelinating subtype (CMT2A) (Δ 28.3 dB, 95% CI: 15.98-40.62).

CONCLUSIONS

Patients with CMT can present with a variety of phenotypes depending on the causative mutation. The ABR interpeak latency values for the most common demyelinating form of CMT are delayed when compared to matched controls. Most subtypes have normal hearing thresholds, apart from CMT4C, which presents with mild hearing loss on average.

Usher syndrome IIIA: a review of the disorder and preclinical research advances in therapeutic approaches

Usher syndrome (USH) is an autosomal recessive disorder characterized by sensorineural hearing loss, progressive pigmentary retinopathy, and vestibular dysfunction. The degree and onset of hearing loss vary among subtypes I, II, and III, while blindness often occurs in the second to fourth decades of life. Usher type III (USH3), characterized by postlingual progressive sensorineural hearing loss, varying levels of vestibular dysfunction, and varying degrees of visual impairment, typically manifests in the first to second decades of life. While USH3 is rare, it is highly prevalent in certain populations. RP61, USH3, and USH3A symbolize the same disorder, with the latter symbol used more frequently in recent literature. This review focuses on the clinical features, epidemiology, molecular genetics, treatment, and research advances for sensory deficits in USH3A.

A New Type of Wireless Transmission Based on Digital Direct Modulation for Use in Partially Implantable Hearing Aids

In this study, we developed a new type of wireless transmission system for use in partially implantable hearing aids. This system was designed for miniaturization and low distortion, and features direct digital modulation. The sigma-delta output, which has a high SNR due to oversampling and noise shaping technology, is used as the data signal and is transmitted using a wireless transmission system to the implant unit through OOK without restoration as an audio signal, thus eliminating the need for additional circuits (i.e., LPF and a reference voltage supply circuit) and improving the ease of implantation and reliability of the circuit. We selected a carrier frequency of 27 MHz after analysis of carrier attenuation by human tissue, and designed the communication coil with reference to both the geometry and required communication distance. Circuit design and simulation for wireless transmission were performed using Multisim 13.0. The system was fabricated based on the circuit design; the size of the device board was 13 mm × 13 mm, the size of the implanted part was 9 mm × 9 mm, the diameter of the transmitting/receiving coil was 26 mm, and the thicknesses of these coils were 0.5 and 0.3 mm, respectively. The difference (error) between the detected and simulation waveforms was about 5%, and was thought to be due to the tolerances of the fabricated communication coil and elements (resistors, capacitors, etc.) used in the circuit configuration of the system. The number of windings was reduced more than 9-fold compared to the communication coil described by Taghavi et al. The measured THD was <1% in the frequency band from 100 Hz to 10 kHz, thus easily meeting the standard specification for hearing aids.

The design of a lumped parameter model considering the stimulus path of round window

BACKGROUND:

Sound normally enters the ear canal, passes through the middle ear, and stimulates the cochlea through the oval window. Alternatively, the cochlea can be stimulated in a reverse manner, namely round window stimulation. The reverse stimulation is not well understood, partly because in classic lumped-parameter models the path of reverse drive during the round window stimulation is usually not considered.

OBJECTIVE:

The study goal is to gain a better understanding of the hearing mechanism during round window stimulation.

METHODS:

A piezo actuator was coupled to the oval and round window of the guinea pigs. The auditory brainstem response produced by the forward and reverse stimulation at four frequencies was recorded.

RESULTS:

The results show that the input voltage of the actuator required at the hearing threshold in the round window drive was higher than that in the oval window drive. In order to understand the data, we designed a lumped-parameter cochlear model that can simulate both forward and reverse drive. The model-predicted results were consistent with the experimental results.

CONCLUSIONS:

The response of the auditory system to stimulus of oval window and round window was quantified through animal experimentation, and guinea pigs were used as experimental animals. When the same stimulus was applied to the oval window and round window of the cochlea, the ABR signals were compared. A lumped parameter model was designed to incorporate the sound transmission paths in both oval and round window stimulation. The simulated results are consistent with those of animal experiments. This model will be useful in understanding the inner-ear response in round window.

Implementation of a fully implantable middle-ear hearing device chip

BACKGROUND AND OBJECTIVE

Recently, with the increase in the population of hearing impaired people, various types of hearing aids have been rapidly developed. In particular, a fully implantable middle ear hearing device (F-IMEHD) is developed for people with sensorineural hearing loss. The F-IMEHD system comprises an implantable microphone, a transducer, and a signal processor. The signal processor should have a small size and consume less power for implantation in a human body.

METHODS

In this study, we designed and fabricated a signal-processing chip using the modified FFT algorithm. This algorithm was developed focusing on eliminating time delay and system complexity in the transform process. The designed signal-processing chip comprises a 4-channel WDRC, a fitting memory, a communication 1control part, and a pulse density modulator. Each channel is separated using a 64-point fast Fourier transform (FFT) method and the gain value is matched using the fitting table in the fitting memory.

RESULTS AND CONCLUSION

The chip was designed by Verilog-HDL and the designed HDL codes were verified by Modelsim-PE 10.3 (Mentor graphics, USA). The chip was fabricated using a 0.18 μm CMOS process (SMIC, China). Experiments were performed on a cadaver to verify the performance of the fabricated chip.

Music Appreciation of Adult Hearing Aid Users and the Impact of Different Levels of Hearing Loss

OBJECTIVES

The main aim of this study was to collect information on music listening and music appreciation from postlingually deafened adults who use hearing aids (HAs). It also sought to investigate whether there were any differences in music ratings from HA users with different levels of hearing loss (HL; mild, versus moderate to moderately-severe, versus severe or worse.

DESIGN

An existing published questionnaire developed for cochlear implant recipients was modified for this study. It had 51 questions divided into seven sections: (1) music listening and music background; (2) sound quality; (3) musical styles; (4) music preferences; (5) music recognition; (6) factors affecting music listening enjoyment; and (7) music training program. The questionnaire was posted out to adult HA users, who were subsequently divided into three groups: (i) HA users with a mild HL (Mild group); (ii) HA users with a moderate to moderately-severe HL (Moderate group); and (iii) HA users with a severe or worse (Severe group) HL.

RESULTS

One hundred eleven questionnaires were completed; of these, 51 participants had a mild HL, 42 had a moderate to moderately-severe loss, and 18 a severe or worse loss. Overall, there were some significant differences noted, predominantly between the Mild and Severe groups, with fewer differences between the Mild and Moderate groups. The respondents with the greater levels of HL reported a greater reduction in their music enjoyment as a result of their HL and that HAs made music sound significantly less melodic for them. It was also observed that the Severe group's mean scores for both the pleasant rating as well as the combined rating for the six different musical styles were lower than both the Mild and Moderate groups' ratings for every style, with just one exception (pop/rock pleasantness rating). There were significant differences between the three groups for the styles of music that were reported to sound the best with HA(s), as well as differences between the ratings on more specific timbre rating scales used to rate different elements of each style. In rating the pleasantness and naturalness of different musical instruments or instrumental groups, there was no difference between the groups. There were also significant differences between the Mild and Severe groups in relation to musical preferences for the pitch range of music, with the Severe group significantly preferring male singers and lower pitched instruments.

CONCLUSIONS

The overall results indicated little difference in music appreciation between those with a mild versus moderate loss. However, poorer appreciation scores were given by those with a severe or worse HL. This would suggest that HAs or HL have a negative impact on music listening, particularly when the HL becomes more significant. There was a large degree of variability in ratings, though, with music listening being satisfactory for some listeners and largely unsatisfactory for others, in all three groups. Music listening preferences also varied significantly, and the reported benefit (or otherwise) provided by the HA for music was also mixed. The overriding variability in listening preferences and ratings leads to the question as to the benefit and effectiveness of generic, manufacturer-derived music programs on HAs. Despite the heterogeneity in the listening habits, preferences, and ratings, it is clear that music appreciation and enjoyment is still challenging for many HA users and that level of HL is one, but not the only factor that impacts on music appreciation.

Design of a dual-coil type electromagnetic actuator for implantable bone conduction hearing devices

BACKGROUND

This paper describes the design and implementation of a dual-coil type electromagnetic actuator for implantable bone conduction hearing devices.

OBJECTIVE

The structure of the proposed actuator was designed to generate maximum Lorentz force via the dual-coil method with a closed magnetic circuit. To satisfy the indications required by implantable bone conduction hearing devices, high output was generated within a specific frequency range using a vibrational membrane with a cantilever.

METHODS

The structure of the membrane consists of a fixed ring, a circular plate, and two cantilevers connected symmetrically. Variable elements of the vibrational membrane affecting the actuator frequency characteristics were analyzed through mathematical modeling and finite element analysis, based on the analysis used to derive the optimum structure of the vibrational membrane. The components of the actuator were fabricated through chemical etching and computer numerical control process, and the bone conduction actuator was fabricated through the precision assembly process.

RESULTS

The output characteristics of the implemented actuator were measured using a laser Doppler vibrometer. As a result of measurement, the proposed actuator generated mechanical resonance at 1.2 kHz.

CONCLUSIONS

By comparing the measured results with the finite element analysis results, we confirmed the validity of the proposed actuator design.

Evaluation of patient satisfaction with different hearing aids: A study of 107 patients

We retrospectively investigated patient satisfaction with different types of hearing aids in 107 patients-60 males and 47 females, aged 8 to 84 years (mean: 53.8)-with unilateral or bilateral hearing loss, each of whom used two different hearing devices for at least 3 years per device. The International Outcome Inventory for Hearing Aids, Turkish edition (IOI-HA-TR) was used to evaluate satisfaction levels; we also calculated our own total individual subjective satisfaction (TISS) scores. We divided 16 different hearing devices into two types: device 1 and device 2; on average, device 2 had more channels, a lower minimum frequency, and a higher maximum frequency. We found that the IOI-HA-TR scores and TISS scores were higher and usage time was greater during device 2 use, and that there was a positive correlation between IOI-HA-TR and TISS scores. A total of 69 patients (64.5%) used device 2 for more than 8 hours per day, while 38 patients (35.5%) used it for 4 to 8 hours per day during the final 2 weeks of the trial. In contrast, 40 patients (37.4%) used device 1 for more than 8 hours, 50 (46.7%) used it for 4 to 8 hours, and the remaining 17 (15.9%) used it for less than 4 hours; the difference in the duration of use of the two devices was statistically significant (p < 0.001). Younger patients and patients with more education were more satisfied with their devices than were older patients and those who were not as well educated. We conclude that devices with good technologic features such as more channels, a lower minimum frequency, and a higher maximum frequency result in better hearing. Also, based on the age difference that we observed, we recommend that psychological support be provided to older patients with aided hearing to enhance their mental health and quality of life.

Patient satisfaction after auditory implant surgery: ten-year experience from a single implanting unit center

CONCLUSIONS

The satisfaction rate of the subjects with an auditory implant appears strictly related to the resulting auditory improvement, and the surgical variables would play a prevailing role in respect to the esthetic factors.

OBJECTIVES

To assess the rate of satisfaction in subjects who underwent the surgical application of an auditory device at a single Implanting Center Unit.

METHOD

A series of validated questionnaires has been administered to subjects who underwent the surgical application of different auditory devices. The Glasgow Benefit Inventory (GBI), the Visual Analog Scale (VAS), and the Abbreviated Profile of Hearing Aid Benefit (APHAB) have been used to compare the implanted situation with the hearing-aided one; a percutaneous bone conductive implant (pBCI) with an active middle ear implant (AMEI) on the round window in mixed hearing loss; and an invisible, fully-implantable device with a frankly and bulky semi-implantable device.

RESULTS

The mean GBI scores were higher in Vibrant Soundbridge (VSB)^® and Bonebridge^® subjects, without significant differences among the various devices. The mean VAS score increased for all the devices in comparison with the conventional hearing aid. The mean APHAB score was similarly better in the implanted condition as total and partial scores.

A tri-coil bellows-type round window transducer with improved frequency characteristics for middle-ear implants

A number of methods to drive the round window (RW) using a floating mass transducer (FMT) have been reported. This method has attracted attention because the FMT is relatively easy to implant in the RW niche. However, the use of an FMT to drive the RW has been proven to produce low outputs at frequencies below approximately 1 kHz. In this study, a new tri-coil bellows-type transducer (TCBT), which has excellent low frequency output and is easy to implant, is proposed. To design the frequency characteristics of the TCBT, mechanical and electrical simulations were performed, and then a comparative analysis was conducted between a floating mass type transducer (like the FMT) and a fixed type transducer (like the TCBT). The features of the proposed TCBT are as follows. First, the TCBT's housing is fixed to the RW niche so that it does not vibrate. Second, the internal end of a tiny bellows is connected to a vibrating three-pole permanent magnet located within three field coils. Finally, the rim of the bellows bottom is attached to the end of the housing that hermetically encloses the three field coils. In this design, the only vibrating element is the bellows itself, which efficiently drives the RW membrane. To evaluate the characteristics of this newly developed TCBT, the transducer was installed in the RW niche of temporal bones and the velocity of the stapes was measured using a laser Doppler vibrometer. The experimental results indicate that the TCBT can produce 100, 111, and 129 dB SPL equivalent pressure outputs at below 1 kHz, 1-3 kHz, and above 3 kHz, respectively. Thus, the TCBT with one side coupled to the RW via a bellows will be easy to implant and offer better performance than an FMT.

Ototoxicity (cochleotoxicity) classifications: A review

OBJECTIVE

Drug-mediated ototoxicity, specifically cochleotoxicity, is a concern for patients receiving medications for the treatment of serious illness. A number of classification schemes exist, most of which are based on pure-tone audiometry, in order to assist non-audiological/non-otological specialists in the identification and monitoring of iatrogenic hearing loss. This review identifies the primary classification systems used in cochleototoxicity monitoring. By bringing together classifications published in discipline-specific literature, the paper aims to increase awareness of their relative strengths and limitations in the assessment and monitoring of ototoxic hearing loss and to indicate how future classification systems may improve upon the status-quo.

DESIGN

Literature review.

STUDY SAMPLE

PubMed identified 4878 articles containing the search term ototox*.

RESULTS

A systematic search identified 13 key classification systems. Cochleotoxicity classification systems can be divided into those which focus on hearing change from a baseline audiogram and those that focus on the functional impact of the hearing loss.

CONCLUSIONS

Common weaknesses of these grading scales included a lack of sensitivity to small adverse changes in hearing thresholds, a lack of high-frequency audiometry (>8 kHz), and lack of indication of which changes are likely to be clinically significant for communication and quality of life.

Middle ear implants for rehabilitation of sensorineural hearing loss: a systematic review of FDA approved devices

OBJECTIVE

To systematically review the safety and efficacy of the 3 Food and Drug Administration-approved middle ear implant (MEI) systems currently in use for the rehabilitation of sensorineural hearing loss.

DATA SOURCES

MEDLINE and Cochrane Library databases were systematically searched by 2 independent reviewers.

STUDY SELECTION

An initial search yielded 3,020 articles that were screened based on title and abstract. A full manuscript review of the remaining 80 articles was performed, of which 17 unique studies satisfied inclusion criteria and were evaluated.

DATA EXTRACTION

Variables including functional gain, speech recognition score improvement, audiometric threshold shift following surgery, adverse events, and patient reported outcome measures were recorded. Study quality was appraised according to author conflict of interest, prospective or retrospective study design, inclusion criteria, number of patients, proper use of study controls, outcome measures reported, length of follow-up, and level of evidence.

DATA SYNTHESIS

Heterogeneous outcome reporting precluded meta-analysis; instead a structured review was performed using best available data.

CONCLUSION

The majority of studies evaluating the safety and efficacy of MEIs are retrospective in nature with limited follow-up. To date, no prospective randomized controlled trial exists comparing contemporary air conduction hearing aid performance and MEI outcomes. Based on available data for patients with sensorineural hearing loss, functional gain and word recognition improvement seems similar between conventional hearing aids and MEIs, whereas patient-perceived outcome measures suggest that MEIs provide enhanced sound quality and eliminate occlusion effect.

Hearing loss in an aging American population: extent, impact, and management

Despite contributing substantially to disability in the United States, age-related hearing loss is an underappreciated public health concern. Loss of hearing sensitivity has been documented in two-thirds of adults aged 70 years and older and has been associated with communication difficulties, lower health-related quality of life, and decreased physical and cognitive function. Management strategies for age-related hearing loss are costly, yet the indirect costs due to lost productivity among people with communication difficulties are also substantial and likely to grow. Hearing aids can improve health-related quality of life, but the majority of people with documented hearing loss do not report using them. Uncovering effective means to improve the utilization of hearing health care services is essential for meeting the hearing health care demands of our aging population. The importance of hearing for general well-being warrants an effort to enhance awareness among the general population of the indications of hearing loss and options for assistance.

Degree of satisfaction of patients fitted with hearing aids at a high complexity service

Some individuals with hearing loss choose to be fitted with hearing aids. Compliance is significantly affected by how satisfied patients are with their hearing aids. Patient satisfaction can be assessed through questionnaires and scales.

Objective

To assess the degree of satisfaction of patients fitted with hearing aids.

Method

Scale “Satisfaction With Amplification in Daily Life” (SADL) was applied to 180 patients fitted with hearing aids; results were categorized based on the mean values observed for global satisfaction scores and scores attained on each subscale. Patients were interviewed for additional information.

Results

Mean global score was 5.6; 48.9% of the subjects were very satisfied, 47.2% were satisfied, and 3.9% were dissatisfied. The mean score on subscale Positive Effects was 5.6; the mean score for Service and Cost was 6.2; for Negative Factors the mean score was 4.9; and the mean score on subscale Personal Image was 5.8. Of the patients fitted with in-the-ear hearing aids, 83.3% were very satisfied. Fifteen percent of the individuals were dissatisfied with their Personal Image. Sensorineural and profound hearing loss patients were less satisfied, with 5.4% and 50.0% of the subjects revealing dissatisfaction with their hearing aids.

Conclusion

Patients were generally very satisfied with their hearing aids. Satisfaction rates were higher among patients fitted with in-the-ear hearing aids. Dissatisfaction was higher in subscale Personal Image. Lesser degrees of satisfaction were seen in patients with sensorineural and profound hearing loss.

Efficacy of the active middle-ear implant in patients with sensorineural hearing loss

Introduction:

This systematic review aims to advise on the effectiveness of the active middle-ear implant in patients with sensorineural hearing loss, compared with external hearing aids.

Methods:

A systematic search of several electronic databases, including PubMed and Embase, was used to identify relevant studies for inclusion.

Results:

Fourteen comparative studies were included. Nine studies reported on the primary outcome of functional gain: one found that the middle-ear implant was significantly better than external hearing aids (p < 0.001), while another found that external hearing aids were generally significantly better than middle-ear implants (p < 0.05). Six of the seven remaining studies found that middle-ear implants were better than external hearing aids, although generally no clinically significant difference (i.e. ≥10 dB) was seen.

Conclusion:

Generally, the active middle-ear implant appears to be as effective as the external hearing aid in improving hearing outcomes in patients with sensorineural hearing loss.

Innovative technology in hearing instruments: matching needs in the developing world

Hearing instrument technology research is almost entirely focused on the projected needs of the consumer market in the developed world. However, two thirds of the world's population with hearing impairment live in developing countries and this proportion will increase in future, given present demographic trends. In developing regions, amplification and other hearing health needs may differ from those in industrialized nations, for cultural, health, or economic reasons. World Health Organization estimates indicate that at present only a small percentage of individuals in developing countries who are in need of amplification have access to hearing aid provision. New technologies, such as trainable hearing aids, advanced noise reduction algorithms, feedback reduction circuitry, nano coatings for hearing aid components, and innovative power options, may offer considerable potential benefits, both for individuals with hearing impairment in developing countries and for those who provide hearing health care services in these regions. This article considers the possible supporting role of innovative hearing instrument technologies in the provision of affordable hearing health care services in developing countries and highlights the need for research that considers the requirements of the majority of the world population in need of hearing instrument provision.

Implantable hearing aids

The aim of this article is to give readers a general overview of the concepts involved in the latest generation of implantable hearing aids. A section on ear biomechanics has also been included to familiarize readers with the basic concepts involved. These devices have been developed over the last 20 years, driven by problems with conventional hearing aids and by advances in the understanding of middle-ear mechanics. The use of technology borrowed from cochlear implants has enabled the first generation of fully implantable aids to be trialled. The author examines the theoretical advantages and disadvantages of implantable hearing aids over conventional aids and then reviews the technology and clinical results of a range of devices that have been trialled.

Recent advances in hearing restoration

This review is based on Pubmed, Medline and Internet literature searches, supplemented by knowledge from textbooks, conference presentations, and personal communications with experts in the field of hearing restoration and patients. We have not specifically selected a time limit for our literature searches; however, the majority are articles from the past 5 years.

[The conventional hearing aid]

The conventional hearing aid has benefited from the progress made in electronic miniaturization and digital signal processing. The prescriber should be familiar with these improvements, the anatomic and acoustic limitations related to hearing aids, the possibilities of surgical rehabilitation, as well as the indications for other auditive rehabilitation techniques (bone conduction hearing, middle ear implant, and cochlear implant). A hearing aid should be prescribed within a precise context taking into account patient history, clinical examination, audiometric testing, and choice of the device. Optimal management of a hearing device for a child should be conducted within an adapted network including a specialized ENT physician, audiophonology, a qualified hearing prosthetist, a speech therapist, etc.).