Djourno, Eyries, and the first implanted electrical neural stimulator to restore hearing

Minimum intraoperative testing battery for cochlear implantation: the international practice trend

PURPOSE

In cochlear implantation (CI) surgery, there are a wide variety of intraoperative tests available. However, no clear guide exists on which tests must be performed as the minimum intraoperative testing battery. Toward this end, we studied the usage patterns, recommendations, and attitudes of practitioners toward intraoperative testing.

METHODS

This study is a multicentric international survey of tertiary referral CI centers. A survey was developed and administered to a group of CI practitioners (n = 34) including otologists, audiologists and biomedical engineers. Thirty six participants were invited to participate in this study based on a their scientific outputs to the literature on the intraoperative testing in CI field and based on their high load of CI surgeries. Thirty four, from 15 countries have accepted the invitation to participate. The participants were asked to indicate the usage trends, perceived value, influence on decision making and duration of each intraoperative test. They were also asked to indicate which tests they believe should be included in a minimum test battery for routine cases.

RESULTS

Thirty-two (94%) experts provided responses. The most frequently recommended tests for a minimum battery were facial nerve monitoring, electrode impedance measurements, and measurements of electrically evoked compound action potentials (ECAPs). The perceived value and influence on surgical decision-making also varied, with high-resolution CT being rated the highest on both measures.

CONCLUSION

Facial nerve monitoring, electrode impedance measurements, and ECAP measurements are currently the core tests of the intraoperative test battery for CI surgery.

En route to sound coding strategies for optical cochlear implants

Hearing loss is the most common human sensory deficit. Severe-to-complete sensorineural hearing loss is often treated by electrical cochlear implants (eCIs) bypassing dysfunctional or lost hair cells by direct stimulation of the auditory nerve. The wide current spread from each intracochlear electrode array contact activates large sets of tonotopically organized neurons limiting spectral selectivity of sound coding. Despite many efforts, an increase in the number of independent eCI stimulation channels seems impossible to achieve. Light, which can be better confined in space than electric current may help optical cochlear implants (oCIs) to overcome eCI shortcomings. In this review, we present the current state of the optogenetic sound encoding. We highlight optical sound coding strategy development capitalizing on the optical stimulation that requires fine-grained, fast, and power-efficient real-time sound processing controlling dozens of microscale optical emitters as an emerging research area.

Current perspectives on the safe electrical stimulation of peripheral nerves with platinum electrodes

This review details some peripheral nervous system (PNS) targets and electrode designs used for electrical stimulation. It investigates limitations in current knowledge of safe electrical stimulation and possible future electrode developments. Current PNS targets are large, leading to poor resolution and off-target side-effects. Most clinical devices are platinum or platinum/iridium embedded in an insulation material. Their safety is usually guided by the Shannon plot, which is not valid for the PNS. New electrode designs are needed to target smaller nerve fibers, enabling higher resolution electrical therapies with fewer off-target side-effects. Damage can occur through biological and electrochemical mechanisms. Greater mechanistic understanding is required to ensure safe and efficacious, long-term electrical stimulation with new electrode materials, geometries and stimulation waveforms.

Age Dependent Cost-Effectiveness of Cochlear Implantation in Adults. Is There an Age Related Cut-off?

OBJECTIVE

To analyze the impact of age at implantation on the cost-effectiveness of cochlear implantation (CI).

STUDY DESIGN

Cost-utility analysis in an adapted Markov model.

SETTING

Adults with profound postlingual hearing loss in a "high income" country.

INTERVENTION

Unilateral and sequential CI were compared with hearing aids (HA).

MAIN OUTCOME MEASURE

Incremental cost-effectiveness ratio (ICER), calculated as costs per quality adjusted life year (QALY) gained (in CHF/QALY), for individual age and sex combinations in relation to two different willingness to pay thresholds. 1 CHF (Swiss franc) is equivalent to 1.01 USD.

RESULTS

When a threshold of 50,000 CHF per QALY is applied, unilateral CI in comparison to HA is cost-effective up to an age of 91 for women and 89 for men. Sequential CI in comparison to HA is cost-effective up to an age of 87 for women and 85 for men. If a more contemporary threshold of 100,000 CHF per QALY is applied, sequential CI in comparison to unilateral CI is cost-effective up to an age of 80 for women and 78 for men.

CONCLUSIONS

Performing both sequential and unilateral CI is cost-effective up to very advanced ages when compared with hearing aids.

Concepts in Neural Stimulation: Electrical and Optical Modulation of the Auditory Pathways

Understanding the mechanisms of neural stimulation is necessary to improve the management of sensory disorders. Neurons can be artificially stimulated using electrical current, or with newer stimulation modalities, including optogenetics. Electrical stimulation forms the basis for all neuroprosthetic devices that are used clinically. Off-target stimulation and poor implant performance remain concerns for patients with electrically based neuroprosthetic devices. Optogenetic techniques may improve cranial nerve stimulation strategies used by various neuroprostheses and result in better patient outcomes. This article reviews the fundamentals of neural stimulation and provides an overview of recent major advancements in light-based neuromodulation."

The Connection Between the Nervous System and Machines: Commentary

Decades of technological developments have populated the field of brain-machine interfaces and neuroprosthetics with several replacement strategies, neural modulation treatments, and rehabilitation techniques to improve the quality of life for patients affected by sensory and motor disabilities. This field is now quickly expanding thanks to advances in neural interfaces, machine learning techniques, and robotics. Despite many clinical successes, and multiple innovations in animal models, brain-machine interfaces remain mainly confined to sophisticated laboratory environments indicating a necessary step forward in the used technology. Interestingly, Elon Musk and Neuralink have recently presented a new brain-machine interface platform with thousands of channels, fast implantation, and advanced signal processing. Here, how their work takes part in the context of the restoration of sensory-motor functions through neuroprostheses is commented.

Cochlear Implant

Cochlear implant is the first approved cranial nerve stimulator that works by directly stimulating the cochlear nerve. The medical and societal impact of this revolutionary device cannot be understated. This article reviews the evolving indications for cochlear implant, patient assessment, surgical approach, and outcomes for pediatric and adult cochlear implant that demonstrate its impact. Future concepts in cochlear implant are introduced briefly. This article covers a breadth of information; however, it is not intended be entirely comprehensive. Rather, it should serve as a foundation for understanding cochlear implant.

Simulation of visual perception and learning with a retinal prosthesis

OBJECTIVE

The nature of artificial vision with a retinal prosthesis, and the degree to which the brain can adapt to the unnatural input from such a device, are poorly understood. Therefore, the development of current and future devices may be aided by theory and simulations that help to infer and understand what prosthesis patients see.

APPROACH

A biologically-informed, extensible computational framework is presented here to predict visual perception and the potential effect of learning with a subretinal prosthesis. The framework relies on optimal linear reconstruction of the stimulus from retinal responses to infer the visual information available to the patient. A simulation of the physiological optics of the eye and light responses of the major retinal neurons was used to calculate the optimal linear transformation for reconstructing natural images from retinal activity. The result was then used to reconstruct the visual stimulus during the artificial activation expected from a subretinal prosthesis in a degenerated retina, as a proxy for inferred visual perception.

MAIN RESULTS

Several simple observations reveal the potential utility of such a simulation framework. The inferred perception obtained with prosthesis activation was substantially degraded compared to the inferred perception obtained with normal retinal responses, as expected given the limited resolution and lack of cell type specificity of the prosthesis. Consistent with clinical findings and the importance of cell type specificity, reconstruction using only ON cells, and not OFF cells, was substantially more accurate. Finally, when reconstruction was re-optimized for prosthesis stimulation, simulating the greatest potential for learning by the patient, the accuracy of inferred perception was much closer to that of healthy vision.

SIGNIFICANCE

The reconstruction approach thus provides a more complete method for exploring the potential for treating blindness with retinal prostheses than has been available previously. It may also be useful for interpreting patient data in clinical trials, and for improving prosthesis design.

Paediatric auditory brainstem implantation: The South Asian experience

INTRODUCTION

Paediatric Auditory Brainstem Implantation (ABI) is indicated for children with congenital cochlear aplasia, absent/hypoplastic vestibulocochlear nerve, for whom cochlear implantation is not possible. Knowledge of the anatomical landmarks and variants in anatomy of the brainstem is vital for ABI surgery.

METHOD

Study was done at Auditory implant centre in Madras ENT research foundation, which includes 24 children who had undergone ABI surgery and are being followed up for 1 year, post operatively. Aims were to study the anatomical variants and the outcomes of ABI implantation. To determine if different anatomical variants effect placement of ABI electrode. To assess the patient outcomes by Categories of auditory Performance (CAP) scores and Speech Intelligibility Ratings (SIR) scores.

RESULTS

All the candidates showed gradual improvement in audiological and verbal outcomes after the ABI. The mean CAP and SIR scores after 6 months of AVHT were 2.07 and 1.37 respectively. After 1 year of auditory verbal rehabilitation therapy CAP was 3.42 and SIR was 2.33. Flocculus of the cerebellum can be of different grades. Though, there was difficulty in insertion of the electrode in subjects with anatomical variants, the outcomes were comparable with other subjects.

CONCLUSION

ABI surgery involves frequent anatomical variations surrounding the lateral recess which makes the positioning of the auditory prosthesis difficult. Variants during the surgery can make the placement of ABI electrodes difficult, but promising results were seen all the implantees.

Learning to see again: biological constraints on cortical plasticity and the implications for sight restoration technologies

The 'bionic eye'-so long a dream of the future-is finally becoming a reality with retinal prostheses available to patients in both the US and Europe. However, clinical experience with these implants has made it apparent that the visual information provided by these devices differs substantially from normal sight. Consequently, the ability of patients to learn to make use of this abnormal retinal input plays a critical role in whether or not some functional vision is successfully regained. The goal of the present review is to summarize the vast basic science literature on developmental and adult cortical plasticity with an emphasis on how this literature might relate to the field of prosthetic vision. We begin with describing the distortion and information loss likely to be experienced by visual prosthesis users. We then define cortical plasticity and perceptual learning, and describe what is known, and what is unknown, about visual plasticity across the hierarchy of brain regions involved in visual processing, and across different stages of life. We close by discussing what is known about brain plasticity in sight restoration patients and discuss biological mechanisms that might eventually be harnessed to improve visual learning in these patients.

Does cerebellar flocculus size affect subjective outcomes in pediatric auditory brainstem implantation

OBJECTIVES

The objectives of study was to 1) Describe relevant surgical anatomy in defining and accessing the lateral recess for placement of electrode, 2) Propose a working classification for grades of Flocculus; 3) To determine if different grades of cerebellar flocculus effects placement of ABI electrode and subjective outcomes in implantees.

METHODS

Our study was a prospective study, and comprised of cohort of 12 patients who underwent ABI surgery via retrosigmoid approach between 1 Jan 2012 to 31 Dec 2014. All children with congenital profound sensorineural hearing loss with either absent cochlea or cochlear nerve were included in the study. Relevant anatomy was noted. We also noted down the difficulty encountered during the placement of ABI electrode. Auditory perception and speech intelligibility was scored post operatively for 1 year.

RESULTS

Cerebellar flocculus was divided into 4 grades depending on the morphology of cerebellar flocculus. It was noted that Grade 3 & 4 flocculus (Group B) had difficult ABI electrode placement in comparison to Grade 1 & 2 flocculus (Group A). The subjective outcomes of Group A was better than Group B. However the p value was not statistically significant.

CONCLUSION

Cerebellar flocculus can be graded depending on morphology and size. Flocculus of higher grades can make the placement of ABI electrodes difficult and adversely effects the postoperative subjective outcomes.

[The history of cochlear implantation]

The creation of cochlear implants has become possible owing to the collaboration in the field of neurophysiology, otorhinolaryngology, audiology, engineering, and psychoacoustics. The experiments carried out in the 1930s were not directly associated with the electrical stimulation of the auditory nerve but had a significant influence on the development of cochlear implants. The first attempt at direct electrical stimulation of the auditory nerve was performed in 1957 using a device that consisted of an active electrode and an implantable induction coil. A good discrimination of intensity but poor frequency discrimination of the acoustic stimuli in a deaf patient was achieved. In 1985, the cochlear implants were approved for the treatment of the adult patients and in 1990 for the children at the age under 2 years. Multi-channel cochlear implantation has been carried out in Russia since 1991 although the efforts to introduce singe-channel implantation were made in the 1980s. Nowadays, there are more than 8000 cochlear implant users in the Russian Federation. Cochlear implantation is performed in a number of clinical centres in several regions of the country funded from the federal budget.

On the Horizon: Cochlear Implant Technology

Cochlear implantation and cochlear implants (CIs) have a long history filled with innovations that have resulted in the high-performing device's currently available. Several promising technologies have been reviewed in this article, which hold the promise to drive performance even higher. Remote CI programming, totally implanted devices, improved neural health and survival through targeted drug therapy and delivery, intraneural electrode placement, electroacoustical stimulation and hybrid CIs, and methods to enhance the neural-prosthesis interface are evolving areas of innovation reviewed in this article.

Cochlear Nerve Stimulation in the Internal Auditory Canal in Ossified Cochlea: A Case Study

OBJECTIVE

To present the first reported case of intraneural direct cochlear nerve stimulation in a human being.

STUDY DESIGN

This is a case report.

RESULTS

A 23-year-old patient with bilateral progressive hearing loss associated with bilateral complete semicircular canal aplasia and ossified cochleas underwent cochlear implantation. During surgery, a patent cochlear lumen could not be found, and the array was positioned in the internal auditory canal adjacent to the cochlear nerve. Against our expectations, an assiduous rehabilitation and frequent fitting adjustments have led to a word recognition score, in open set speech with lip reading, of 18/25 and acceptable frequency discrimination.

CONCLUSIONS

We are aware that this was an anomalous use of the cochlear implant, and it is not our aim to suggest a new indication for cochlear array positioning. However, this case shows that auditory perception, to some degree, can be obtained with intraneural direct cochlear nerve stimulation.

Auditory implant research at the House Ear Institute 1989-2013

The House Ear Institute (HEI) had a long and distinguished history of auditory implant innovation and development. Early clinical innovations include being one of the first cochlear implant (CI) centers, being the first center to implant a child with a cochlear implant in the US, developing the auditory brainstem implant, and developing multiple surgical approaches and tools for Otology. This paper reviews the second stage of auditory implant research at House - in-depth basic research on perceptual capabilities and signal processing for both cochlear implants and auditory brainstem implants. Psychophysical studies characterized the loudness and temporal perceptual properties of electrical stimulation as a function of electrical parameters. Speech studies with the noise-band vocoder showed that only four bands of tonotopically arrayed information were sufficient for speech recognition, and that most implant users were receiving the equivalent of 8-10 bands of information. The noise-band vocoder allowed us to evaluate the effects of the manipulation of the number of bands, the alignment of the bands with the original tonotopic map, and distortions in the tonotopic mapping, including holes in the neural representation. Stimulation pulse rate was shown to have only a small effect on speech recognition. Electric fields were manipulated in position and sharpness, showing the potential benefit of improved tonotopic selectivity. Auditory training shows great promise for improving speech recognition for all patients. And the Auditory Brainstem Implant was developed and improved and its application expanded to new populations. Overall, the last 25 years of research at HEI helped increase the basic scientific understanding of electrical stimulation of hearing and contributed to the improved outcomes for patients with the CI and ABI devices. This article is part of a Special Issue entitled .

Electrical stimuli in the central nervous system microenvironment

Electrical stimulation to manipulate the central nervous system (CNS) has been applied as early as the 1750s to produce visual sensations of light. Deep brain stimulation (DBS), cochlear implants, visual prosthetics, and functional electrical stimulation (FES) are being applied in the clinic to treat a wide array of neurological diseases, disorders, and injuries. This review describes the history of electrical stimulation of the CNS microenvironment; recent advances in electrical stimulation of the CNS, including DBS to treat essential tremor, Parkinson's disease, and depression; FES for the treatment of spinal cord injuries; and alternative electrical devices to restore vision and hearing via neuroprosthetics (retinal and cochlear implants). It also discusses the role of electrical cues during development and following injury and, importantly, manipulation of these endogenous cues to support regeneration of neural tissue.

The contributions of William F. House to the field of implantable auditory devices

William F. House was a pioneer in the evolving field of cochlear implants and auditory brainstem implants. Because of his vision, innovation and perseverance, the way was paved for future clinicians and researchers to carry on the work and advance a field that has been dedicated to serving adults and children with severe to profound hearing loss. Several of William House's contributions are highlighted in this prestigious volume to honor the recipients of the 2013 Lasker-Debakey Clinical Medical Research Award. Discussed are the early inventive years, clinical trials with the single-channel cochlear implant, the team approach, pediatric cochlear implantation, and the auditory brainstem implant. Readers may be surprised to learn that those early contributions continue to have relevance today. This article is part of a Special Issue entitled <Lasker Award>.

Cochlear implantation in a patient with combined renal and liver transplantation

OBJECTIVE AND IMPORTANCE

Patients who have undergone solid organ transplantation and continuing immunosuppressant medication are at a higher risk of wound problems and infections following cochlear implantation. This risk is theoretically even further increased in multi-organ transplant recipients due to the increased doses of immunosuppressive medications that these patients are administered.

CLINICAL PRESENTATION AND INTERVENTION

Here, we present the first reported case of successful cochlear implantation in a patient who had previously undergone successful combined liver and kidney transplant. She had no significant complications from the surgery and had good audiological outcomes 3 months post-operatively.

CONCLUSION

As we continue our advances in the use of cochlear implant technology, our report adds to the growing evidence of its benefits in transplant recipients. However, there are important pre- and peri-operative considerations in this group of patients which can improve safety and outcome.

New strategies for the restoration of hearing loss: challenges and opportunities

INTRODUCTION

For most types of hearing impairments, a definitive therapy would rest on the ability to restore hair cells and the spiral ganglion neurons. The only established technique to treat deafness is based on the functional replacement of hair cells with a cochlear implant, but this still has important limitations.

SOURCES OF DATA

A systematic revision of the relevant literature is presented.

AREAS OF AGREEMENT

New curative strategies, ranging from stem cells to gene and molecular therapy, are under development.

AREAS OF CONTROVERSY

Although still experimental, they have delivered some initial promissory results that allow us to look at them with cautious optimism.

GROWING POINTS

The isolation of human auditory cells, the generation of protocols to control their differentiation into sensory lineages, their promising application in vivo and the identification of key genes to target molecularly offer an exciting landscape.

AREAS TIMELY FOR DEVELOPING RESEARCH

In this chapter, I discuss the latest advances in the field and how they are being translated into a clinical application.

Advances in auditory prostheses

PURPOSE OF REVIEW

Auditory prostheses use electric currents on multiple electrodes to stimulate auditory neurons and recreate auditory sensations in deaf people. Cochlear implants have restored hearing in more than 200  000 deaf adults and children to a level that allows most to understand speech. Here we review the reasons underlying these results and describe new directions in restoring hearing to additional patient populations and the design of new devices.

RECENT FINDINGS

From their early development about 50 years ago, cochlear implants have been well received and beneficial to people who had lost their hearing. Although those first implants did not allow high levels of speech understanding, they provided auditory information that worked synergistically with lip reading to improve communication. Present day cochlear implants provide excellent speech understanding in children and in postlingually deafened adults. Research is focused on improved signal processing and new electrode designs. Electric stimulation of the auditory brainstem can also produce excellent hearing in some children and adults.

SUMMARY

Auditory prostheses, both at the level of the sensory nerve and at the brainstem, can restore patterns of neural activation that are sufficient for high levels of speech understanding. These prostheses are not only clinically successful but also important tools for understanding sensory processing in the brain.

Ethical issues in the development of a vestibular prosthesis

During the development of a neural prosthesis, various ethical aspects have to be considered. These range from the basic design of the prosthesis and manufacturing of the various components and the system using biocompatible materials to extensive in vitro and in vivo testing and investigations in the animal model, before taking the final step and going to human trials. As medical systems, neural prostheses have to be proven absolutely safe before considering any clinical study. In this work, the various steps accompanying the development are described taking the example of a vestibular prosthesis currently developed within the European project CLONS.

Automated stimulus-response mapping of high-electrode-count neural implants

Over the past decade, research in the field of functional electrical stimulation (FES) has led to a new generation of high-electrode-count (HEC) devices that offer increasingly selective access to neural populations. Incorporation of these devices into research and clinical applications, however, has been hampered by the lack of hardware and software platforms capable of taking full advantage of them. In this paper, we present the first generation of a closed-loop FES platform built specifically for HEC neural interface devices. The platform was designed to support a wide range of stimulus-response mapping and feedback-based control routines. It includes a central control module, a 1100-channel stimulator, an array of biometric devices, and a 160-channel data recording module. To demonstrate the unique capabilities of this platform, two automated software routines for mapping stimulus-response properties of implanted HEC devices were implemented and tested. The first routine determines stimulation levels that produce perithreshold muscle activity, and the second generates recruitment curves (as measured by peak impulse response). Both routines were tested on 100-electrode Utah Slanted Electrode Arrays (USEAs) implanted in cat hindlimb nerves using joint torque or emg as muscle output metric. Mean time to map perithreshold stimulus level was 16.4 s for electrodes that evoked responses (n = 3200), and 3.6 s for electrodes that did not evoke responses (n = 1800). Mean time to locate recruitment curve asymptote for an electrode (n = 155) was 9.6 s , and each point in the recruitment curve required 0.87 s. These results demonstrate the utility of our FES platform by showing that it can be used to completely automate a typically time- and effort-intensive procedure associated with using HEC devices.