Overcoming Hearing Loss: From Drug Therapy to Cochlear Implant Surgery

The following sections are included:

• Foreword
• Preface
• Contents
• List of Corresponding Authors

The ear is a complex organ which is divided into the outer, middle, and inner ear, consisting of different structures such as external auditory canal, tympanic membrane, ossicles, the cochlea, and vestibular apparatus. These all work in tandem to convert mechanical sound energy into electrical impulses, which are transmitted to the central nervous system. Dissecting deeper into these structures reveals complex electrochemical gradients and molecular processes that help further elucidate the mechanism of hearing and balance function. Patients can experience various symptoms and disorders due to disruptions in the normal functioning of these structures.

For example, damage to the hair cells in the cochlea can result in hearing loss or tinnitus, while damage to the vestibular apparatus can result in dizziness, vertigo, or loss of balance. Understanding the precise mechanisms underlying these disorders is critical for developing effective treatments.

Treatments for inner ear disorders include otoprotective medications, surgical interventions, and physical and vestibular therapy. There are also a variety of devices that can be utilized and implanted to treat both conductive and sensorineural hearing loss (SNHL) such as hearing aids and cochlear implants. Balance therapy and medications can be used to manage vertigo and other balance disorders. Overall, a thorough understanding of inner ear anatomy and physiology is essential for diagnosing and treating disorders affecting this area of the body.

Hearing loss is a common disability affecting around 15% of Americans. Sensorineural hearing loss (SNHL) concerns patients presenting with inner ear or auditory nerve dysfunction. When symptoms occur, patients can feel overwhelmed and lost. This chapter aims to discuss different etiologies causing SNHL in adults and in children, as the situation is very different in both cases. Sudden SNHL will also be defined with its possible etiologies; this is a common cause of urgent care visits and requires appropriate and timely treatment or referral to an Otolaryngologist, also known as an Ear, Nose, and Throat (ENT) specialist. Diagnostic tools currently used are described, along with the differential diagnosis physicians must rule out before confirming a sensorineural disease. Treatment options and current guidelines are presented, to prepare and inform patients on the different options.

Hearing loss affects many individuals in the United States and has many negative impacts on both the health and quality of life of these individuals. With cases of hearing loss on the rise, there have been new technologies developed to aid in hearing; however, preventing hearing loss from the outset remains important. There are many different causes of hearing loss. With different causes such as genetic, infectious, age-related, or occupation-related, to name a few, there are different strategies that may be most effective in preventing hearing loss. Lifestyle adaptations, certain supplements, and several medications have proven to be particularly helpful in preventing hearing loss, and these changes can have a big impact not only on an individual’s hearing, but also on their overall well-being.

Hearing loss is a symptom of an underlying pathologic change to the auditory system. Determining the cause of hearing loss is critical for appropriate treatment for children and adults affected by this condition. Because the majority of hearing loss in children is due to a genetic cause, genetic evaluation has become a cornerstone for clinical evaluation and diagnosis. However, because there are hundreds of known hearing loss-associated genes, genetic testing for hearing loss is complex. Testing of all known hearing loss genes at once is required for effective and accurate genetic diagnosis — single gene testing is generally ineffective. Determining the etiology for hearing loss provides several important pieces of information to the patient and the clinician, including prognosis, recurrence risk, and evaluation for syndromic forms of hearing loss. Importantly, a genetic diagnosis is required for enrolment in any new and upcoming clinical trials for cellular, molecular, or gene therapies for hearing loss.

Hearing loss can be classified as sensorineural, conductive, or mixed. Sensorineural hearing loss (SNHL) is associated with a dysfunction of the inner ear, auditory nerve, or central hearing pathway. Conductive hearing loss (CHL) is usually due to outer or middle ear involvement hampering the conduction of sound energy from its source to the inner ear. Mixed hearing loss (MHL) is a combination of CHL and SNHL. Proper characterization of the type of hearing loss is the first step to better identify its underlying cause. A lot of causes, congenital or acquired, can be responsible of conductive or MHL. Depending on the cause and the degree of hearing loss, CHL or MHL can be addressed by medical therapy, surgical procedure or conventional or implanted hearing aids.

Sensorineural hearing loss (SNHL) is a symptom that may reflect a myriad of causes, and combines both cochlear (‘sensory’) and neural (nerve and/or brain) potential sites of lesion or injury. Therefore, there are several possible medical treatments for SNHL, and they are as targeted as possible to potential pathophysiological states. In this chapter, SNHL has been categorized as we often think of the clinical presentations, with treatments discussed for each, including presbycusis, noise-related hearing loss, fluctuating hearing loss, and sudden SNHL. As we learn more about correlations between untreated hearing loss and depression, isolation, and even dementia, it becomes all the more important to treat patients as best as possible to reverse the hearing loss. The reader should also keep in mind that hearing aid technology is an important part of our armamentarium and patients should be encouraged in their use if there is inadequate hearing recovery.

Tinnitus is a sound that is usually perceived within the head or ears. The current available health data suggest that roughly 10% of the US population have experienced tinnitus that lasts at least 5 minutes. Typically, a tinnitus that lasts <5 minutes is not considered as pathologic or significant. Tinnitus does not have any external source and it can be described as ringing, roaring, and static sounds or it may be perceived like a pulse. Tinnitus has been categorized as primary or secondary tinnitus. Primary tinnitus is usually associated with sensorineural hearing loss and the secondary tinnitus is frequently accompanied by other conditions such as ear infections or cardiovascular issues. Tinnitus is a pathologically heterogeneous ailment. This means that a variety of conditions can be associated with tinnitus or cause tinnitus. Tinnitus is a manageable condition and there are a variety of effective methods that are used in tinnitus centers around the world to help those who suffer from it. Providing empathic care and support to the patient from the clinician’s side and motivation and determination in getting better from the patient’s side usually result in significant reduction in the annoyance caused by tinnitus. Addressing the factors of sensation, emotion, and cognition in the management of tinnitus is essential. When tinnitus is associated with hearing loss, specific medical or surgical approach may also be used in parallel to sound or cognitive therapies.

Immune-mediated inner ear disease (IMED) represents several disease processes, all of which can be characterized by a new, asymmetric sensorineural hearing loss that may be ameliorated by timely immunosuppression. However, not all patients are responsive to corticosteroids. As a result, there is a clear clinical need to identify the mechanisms by which the hearing loss occurs, thereby identifying new potential therapeutic targets for intervention. Furthermore, within IMED, although sudden sensorineural hearing loss (SSNHL) and Meniere’s disease (MD) can be clearly characterized, autoimmune inner ear disease (AIED) is a complex entity that presents challenges for both diagnosis and management. While the pathogenesis of disease remains to be fully delineated, proposed pathological mechanisms include immunological perturbations in both the innate and adaptive immune response, vascular compromise, and disturbances in cochlear physiology. First-line treatment for all patients with suspected IMED includes high-dose oral corticosteroids and/or intratympanic steroid injections. The injection alone may provide benefit for those who cannot tolerate systemic treatment. For those who fail to respond or become resistant to steroids, biological agents such as anakinra may offer promising results. Finally, patients with IMED with profound hearing loss should be considered for early cochlear implantation for the best long-term results although their hearing may continue to fluctuate even after implantation.

Aural rehabilitation can improve quality of life for people of all ages. Devices including hearing aids, implantable hearing aids, bone-anchored hearing aids, cochlear implants, and auditory brainstem implants are some technological advancements in the otologist’s/neurotologist’s toolbox. Each device has its own set of advantages and limitations, indications and contraindications. Ultimately, the correct device choice for the patient comes down to a team decision, comprised of, but not limited to, the patient, family, audiologist, speech language pathologist, and otologist/neurotologist.

Cochlear implantation has emerged as the gold standard for severe-to-profound sensorineural hearing loss. The technological advances made in this field are continuously revolutionizing hearing rehabilitation. In this chapter, we will thoroughly discuss cochlear implantation. We will start with the pioneering discoveries that led to the cochlear implant (CI) and conclude with the current research in the field on the development of the optimal implant. We will discuss sound processing to understand the basic mechanisms of how CIs work and explain the implant characteristics and the main different types of implants available. As cochlear implantation criteria are continuously expanding, we will also focus on demographics of CIs and current implantation criteria. Pre-operative evaluation and surgical approach are also explained to give a global view of the implantation process. Finally, the post-operative stages of implantation (programming, hearing rehabilitation), which are crucial in obtaining optimal hearing outcomes, are detailed along with the outcomes of implanted patients. This chapter aims to provide a comprehensive guide to cochlear implantation.

Single-sided deafness (SSD) disrupts spatial hearing, thereby leading to a number of adverse effects for the listener. The functional losses associated with SSD includes reduced sound awareness in the impaired ear, poor speech understanding in noisy environments, and the inability to locate where sound is coming from. These negative consequences are linked to social-emotional impacts, and can result in increased listening effort and overall poorer quality of life in SSD listeners. Clinical rehabilitation of SSD remains limited in its ability to fully restore access to binaural cues to restore spatial hearing abilities. Management of SSD most often consists of rehabilitation through hearing devices and implants, which improves access to sound thus alleviating some of the hearing deficits.

Medical management of auditory disorders has proved to be a challenging area of study. Due to the various underlying causes of these disorders, individuals have a wide spectrum of symptoms, from temporary to permanent changes in hearing. In addition to this disparity in physical presentation, there are challenges in developing medications, such as understanding the clinical course of a patient’s symptoms as well as the difficulties in targeting the inner ear due to the presence of the blood labyrinth barrier, a barrier between the blood vessels and the inner ear. This chapter aims to review some of the recent advancements in developing treatment modalities for the medical management of auditory disorders such as sudden sensorineural hearing loss, idiopathic sensorineural hearing loss, noise-induced hearing loss, cisplatin ototoxicity, antibiotic ototoxicity, tinnitus, vertigo, and Meniere’s disease. Corticosteroids have been used extensively to alleviate symptoms in individuals with hearing loss and vestibular problems. Various medical combinations have been compared to and used in conjunction with corticosteroids with varied outcomes. Antioxidants also play a role in treating many conditions. The efficacy and safety of other off-label and novel medications were evaluated in preliminary studies based on animal models. The efficacy and safety of other off-label and novel medications were evaluated in preliminary studies based on animal models; results were varied. Future research should continue looking for novel drug candidates for the efficient treatment of auditory disorders due to the discrepancy in outcomes and incomplete understanding of the mechanisms of action of both disorders and treatments.

Hearing loss is a prevalent condition that affects millions globally. While hearing aids and implants alleviate the burden, personalized hearing medicine and inner ear therapeutics offer promising solutions. Gene therapies (gene replacement and gene editing) have demonstrated effectiveness in animal models, and ongoing studies continue to tackle the remaining challenges for their clinical translation. Maintaining baso-apical cochlear spatial tonotopic organization, selecting optimal vectors according to target cell types, and routes of administration for gene delivery, discovering new efficient nuclease variants, and identifying precise clinical endpoints are key considerations. The safety and efficacy of these therapies must be rigorously evaluated, particularly regarding immune responses and the overall safety of surgical procedures and gene delivery vectors. While challenges remain, ongoing research and collaborations between scientists, clinicians, audiologists, engineers, academic, private companies, patient organizations, and regulatory bodies are necessary to overcome obstacles and pave the way for effective and safe personalized inner ear therapies.

Robots have allowed for great advances in safety, efficiency, and cost-saving measures across many fields. Although robotic systems in surgery can offer similar benefits, implementation in healthcare settings is accompanied by stringent legislative and patient safety barriers. There are several types of robotic systems being used, tested, or developed for applications in ear surgery. This chapter discusses three main types of robotic surgical systems: 1 — collaborative/guide; 2 — teleoperated; and 3 — autonomous. While each of these systems has various benefits and limitations, they all offer the potential to augment or optimize various otologic surgical techniques. We focus on two clinical applications within ear surgery especially suited for robotic incorporation: surgical drilling and insertion of cochlear implant (CI) electrode arrays. Robotic systems for both drilling (minimally invasive tunneled techniques and bulk drilling applications) and CI electrode insertion have been developed to improve current techniques and are discussed throughout this chapter.

The following sections are included:

• What Is Self-Advocacy?
• Inheriting Hearing Loss
• Concept of Disability and Personal Perspectives
• Federal Role in Access for Adults and Children With Disabilities
• Owning One’s Hearing Loss
• References
• Helpful Resources

The following sections are included:

• Glossary
• Index