Wendell Nakamura
LEARNING OBJECTIVES:
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Deafness, Hearing Loss, & the Auditory System
Hearing loss is a widely common condition that affects people of all ages, from neonates to the elderly (Anastasiadou & Khalili, 2023) and is often overlooked as a part of overall health and well-being (Hearing Loss Association of America [HLAA], n.d.). Hearing loss can affect one or both ears and is categorized by the HLAA (n.d.) into four different levels: mild, moderate, severe, and profound. Deaf people mostly have profound hearing loss, implying very little to no hearing (World Health Organization [WHO], 2024).
While it is commonly understood that hearing loss significantly impacts communication, it is also widely noted that hearing loss is significantly associated with increased risk of falls (HLAA, n.d.; Lin & Ferrucci, 2012), lower educational attainment, lower rates of employment, cognitive decline, and emotional effects leading to diminished social interactions (Chang et al., 2021; Haile et al., 2021; WHO, 2024).
Epidemiology of Hearing Loss
The National Institute on Deafness and Other Communication Disorders (NIDCD; 2024) estimates that approximately 37.5 million Americans over the age of 18 years (15%) report some trouble with hearing and that about 1.9 million children in the U.S. (3%) are born with some detectable hearing loss. While most neonatal hearing loss is genetic, most school-aged children and adolescents have hearing loss that is acquired (Anastasiadou & Khalili, 2023). Acquired hearing loss is closely associated with aging, exposure to noise, and comorbidities such as hypertension, high blood glucose, and smoking history (Anastasiadou & Khalili, 2023). Age is the strongest predictor of hearing loss among adults and the greatest amount of hearing loss occurs with the 60-69 age group (NIDCD, 2024).
Global Burden of Disease of Hearing Loss
During the 1999-2000 school year, the Center for Disease Control and Prevention (CDC; 2025) estimated that the cost of providing special education services to children who were hard of hearing or deaf totaled approximately $11,000 per child ($652 million total). The total lifetime educational cost of hearing loss is estimated to be approximately $115,000 per child (CDC, 2025). The total lifetime cost for all individuals in the U.S. with hearing impairment in 2000 is estimated to be $2.1 billion, 6% of which were attributed to direct medical costs (doctor visits, prescription medications, and hospital stays), 30% were attributed to direct non-medical costs (home modifications and special education services), and 63% were attributed to indirect costs (lost wages) (CDC, 2025).
Health Disparities of Hearing Loss
Adults who have been identified as having hearing loss are more likely to smoke tobacco products, consume more alcohol, engage in more sedentary behaviors, and sleep six hours or less, compared to hearing individuals (Schoeborn & Heyman, 2008). Additionally, Schuh & Bush (2020) noted that people who are members of the deaf community have significantly poorer situations in the social determinants of health. These include healthcare access and quality, education access and quality, social and community context, economic stability, and safe neighborhoods and access to community resources (Schuh & Bush, 2020).
In a 2000-2015 review of the literature on access to healthcare services, Kuenburg et al. (2015) noted that people who were deaf or had hearing impairments experienced significant barriers to accessing services compared to hearing individuals. In particular, they experienced fear, mistrust, and frustration due to challenges in communication with their providers. Furthermore, the authors suggest that members of the deaf community present with lower health literacy, even if the individual is highly educated. This may be due to lifelong challenges with accessing health information that is presented to the public in ways that are difficult for members of the deaf community to receive. There is a paucity of qualified sign language interpreters for the deaf community, especially those who understand medical terminology.
Clinical Presentation of Hearing Loss
Early signs and symptoms of hearing loss may include (Cleveland Clinic, n.d.d; Mayo Clinic, 2023):
- Difficulty understanding words, especially in crowded or noisy environments
- Often asking others to speak more slowly, clearly, or loudly
- Turning up the volume on the television or radio
- Avoiding social settings, especially loud or crowded spaces
- Presence of tinnitus, or ringing in the ears
While there are many causes of hearing loss, the most common reasons include (Mayo Clinic, 2023):
- Structural damage to the inner ear
- Build-up of cerumen, or ear wax
- Ear infection
- Ruptured ear drum, or tympanic membrane perforation
There are four primary types of hearing loss (Anastasiadou & Khalili, 2023):
- Conductive hearing loss: Involves the outer or middle ear, in which sound waves are mechanically prevented from passing through the outer or middle ear to the inner ear. Common causes for this include abnormal formation of the auricle, or outer ear; impaction of cerumen or fluid in the ear canal; infection of the middle ear (otitis media); or structural damage to the middle ear. Individuals with conductive hearing loss may perceive sounds to be diminished in volume.
- Sensorineural hearing loss: Involves the inner ear, in which includes the vestibulocochlear nerve (CN-VIII). It is the most common type of hearing loss and may be a result of aging (known as presbycusis), prolonged exposure to loud noises, head injury, bacterial or fungal infections, presence of tumors, or certain medications. Individuals with sensorineural hearing loss may perceive sounds to be diminished in volume and distorted.
- Mixed hearing loss: Involves either the outer or middle ear, AND the inner ear. Presents as a combination of both conductive hearing loss and sensorineural hearing loss. Individuals with mixed hearing loss may perceive sounds to be both diminished in volume and distorted.
- Central hearing loss: Involves the central auditory system, including the vestibulocochlear nerve and related pathways to the auditory cortex in the temporal lobe.
The Auditory System & Neuropathophysiology of Hearing Loss
There are four parts of the auditory system that we’ll explore: the outer ear, the middle ear, the inner ear, and the auditory pathway.
- The outer ear is the part of the auditory system that is visible. It is comprised of the auricle (also called the pinna, plural = pinnae) and the external acoustic meatus (also colloquially called the ear canal), terminating at the tympanic membrane (also known colloquially as the ear drum). The function of the outer ear is to channel sound waves to the tympanic membrane,
- The middle ear (also called the tympanic cavity) is an air-filled cavity in the temporal bone of the cranium that extends from the tympanic membrane to the inner ear. When sound waves travel through the external acoustic meatus, the vibrations of the tympanic membrane produce mechanical energy to three ossicles, or bones, within the middle ear: the malleus (hammer), the incus (anvil), and the stapes (stirrup). It is within the middle ear that ear infections occur, due to access through the eustachian tubes, which connect to the nasopharynx. The purpose of the eustachian tubes is to equalize air pressure in the middle ear. The stapes contacts with the inner ear through the oval window. The primary function of the ossicles, therefore, is to transmit and amplify the vibrations from the tympanic membrane to the oval window at the inner ear (George et al., 2024).
- The inner ear is a fluid-filled chamber that serves two primary functions: transmitting mechanical energy to the cochlea for hearing in the auditory system and to the vestibular apparatus, which is responsible for maintaining balance in the vestibular system. The cochlea contains hair cells, which are the afferent (sensory) mechanoreceptor cells that transform fluid energy into electrical energy going to the auditory branch of the vestibulocochlear nerve, CN-VIII.
- The electrical impulses from the vestibulocochlear nerve ascend through the auditory pathway, involving the inferior colliculus of the tectum in the mesencephalon, the thalamus, and the primary (A1) and secondary (A2) auditory cortices in the superior temporal gyrus of the temporal lobe (Augustine et al., 2024). You will recall that the inferior colliculus of the tectum (part of the mesencephalon) processes and integrates auditory information. The medial geniculate nucleus is the part of the thalamus that relays auditory information to the auditory cortex. The primary and secondary auditory cortices are located in the superior temporal gyrus of the temporal lobe of the telencephalon process auditory stimulation and distinguishes different sounds and speech (Anastasiadou & Khalili, 2024).
Medical Management & Alternative Therapies for Hearing Loss
Conductive hearing loss is managed differently, depending on the cause. It may be managed through the removal of a foreign body, removal of cerumen (ear wax) impaction, or the administration of antibiotics and placement of grommets in the middle ear (drainage tubes).
The most common cause of sensorineural hearing loss in older adults is age-related hearing loss {ARHL), also known as presbycusis, when hair cells in the inner ear die, resulting in the loss of detection of high-pitched sounds (NIDCD, 2023). There is emerging research on some pharmacologic agents that target hair cell death (Crowson et al., 2017). Damage to the inner ear structures that result in sensorineural hearing loss is most often managed through assistive devices designed for amplification, such as hearing aids, personal amplification devices (e.g., pocket talkers), or cochlear implants. While hearing aids are the mainstay devices to compensate for hearing impairment, compliance has been low (Chang, 2021), mostly due to cost.
Impact of Hearing Loss on Occupational Performance
About 40% of young adults who were identified with hearing loss during childhood reported experiencing at least one limitation in occupational performance and only about 71% of young adults with hearing loss and who didn’t have other associated conditions (such as cerebral palsy, intellectual disabilities, vision loss, and epileptic disorders) were employed (CDC, 2025). The NICDC (2024) reports that approximately 28% of adults over the age of 52 years with moderate to severe hearing loss experience difficulty with daily activities, compared to 7.3% of comparable adults without hearing loss. The vast majority of older adults have sensorineural hearing loss or mixed type (Blaylock & Bewernitz, 2024).
Some of the more significant age-related changes in hearing include pitch discrimination, auditory reaction time, and speech perception (Blaylock & Bewernitz, 2024). Untreated hearing loss may result in increased risk of falls, depression, dementia, hospitalization, social isolation, paranoia, and reduced quality of life (Blaylock & Bewernitz, 2024; Chang, 2021). Hearing loss is also associated with decreased ADL and IADL performance in the elderly (Chang, 2021). Occupational therapists can help clients with hearing loss discover ways to improve independence with ADL and IADL through the use of assistive technologies. For example, devices that provide haptic feedback (such as vibration) or visual feedback (such as lights blinking or screen displays) may alert clients with hearing loss (Chang, 2021). Other environmental modifications such as dampening background noise in living spaces through the use of sound absorbing material, may improve sound quality for people with hearing loss (Chang, 2021).
Vestibular Disorders & the Vestibular System
Vestibular disorders encompass a wide range of health conditions that affect an individual’s balance. They can be broadly classified into two categories.
- Peripheral vestibular disorders, which are a result of damage to the structures of the inner ear or the vestibular branch of the vestibulocochlear nerve
- Central vestibular disorders, which are a result of damage to the structures of the central nervous system that are related to the vestibulospinal tract (cerebellum, medulla oblongata, pons, thalamus, basal ganglia, and vestibular cortex in the parietal lobe)
Epidemiology of Vestibular Disorders
Agrawal et al. (2013) estimated that 35% of adults in the U.S. over the age of 40 years experienced balance disorders and the prevalence increased with age; 85% of individuals over the age of 80 years experienced balance disorders. Moreover, the authors found that the prevalence of balance disorders among adults with diabetes mellitus increased by 70% and more if they also had complications of diabetes, such as peripheral neuropathy or diabetic retinopathy.
Global Burden of Disease of Vestibular Disorders
It is estimated that for individuals in the U.S, who are over the age of 60 years, the total economic burden for vestibular dysfunction is approximately &227 billion for direct medical costs (Agrawal et al., 2017). In a systematic review of 16 articles on the economic burden of vestibular dysfunction, Kowacs et al. (2019) noted a significant reduction of workplace productivity and absenteeism among individuals with vestibular dysfunction who continued to work, although overall rates of work-related costs were not provided.
Health Disparities of Vestibular Disorders
In a survey of 33,047 individuals in the U.S. who were enrolled in the National Health Interview Survey (NHIS) in 2016, Youn et al. (2023) found that there were statistically significant differences between people with and without vestibular disorders, in regards to age group, sex, educational attainment, race, income level, and insurance coverage. People who were over 60 years of age, female, had lower educational attainment, white, lower income, or on public medical insurance or were uninsured had higher rates of vestibular dysfunction. Moreover, the authors found that of people with vestibular dysfunction, African Americans, people of lower income brackets, or people who were uninsured were more likely to delay access to treatment services due to lack of transportation.
Clinical Presentation of Vestibular Disorders
Commonly experienced symptoms of vestibular disorder include vertigo (a sense of spinning), accompanied by blurred vision, disorientation, nausea, vomiting, and increased heart rate (Cleveland Clinic, n.d.b). While vestibular disorders may occur at any age, they are most common in older adults and may be due to cell death, tumors, exposure to environmental toxins, inflammation secondary to viral or bacterial infections, or acquired neurological conditions such as head injury or stroke (Cleveland Clinic, n.d.b; Kashouty, n.d.). Two of the most common vestibular disorders on which we will focus include benign paroxysmal positional vertigo (BPPV) and Ménière’s Disease.
- Benign paroxysmal positional Vertigo (BPPV) is a vestibular condition that occurs when calcium carbonate crystals (called otoliths, oto- = “ear”, lithos = “stone”; or otoconia, oto- = “ear”, konia = “dust”) that normally are located in the utricle are mislocated to the semi-circular canals and push against the hair cells located there (Cleveland Clinic, n.d.b; Kashouty, n.d.). The result is that an individual with BPPV feels vertigo (the sensation of the room spinning) when they tilt their head in specific directions. While the condition itself is not serious and usually resolves within a few days to weeks, BPPV is most often experienced by people who are 50 years or older and may lead to falls. A test for BPPV is the Dix Hallpike maneuver. A specific set of exercises, the Epley maneuver may be performed by a therapist who is trained and certified to reposition the otoliths back to the utricles. The Dix Hallpike is performed to diagnose BPPV and the Epley is used to treat BPPV. A brief video demonstrating the Epley maneuver may be viewed by following this link.
- Ménière’s Disease is a vestibular condition where a build-up of endolymph, a fluid in the semi-circular canals, occurs due to viral infection, head trauma, or allergies (Cleveland Clinic, n.d.b; Kashouty, n.d.). Like with BPPV, people with Ménière’s Disease experience vertigo, but may also experience tinnitus, hearing loss, and inner ear pressure. Due to the vertigo, people with Ménière’s Disease are at higher risk of falls. The condition is usually permanent and, left untreated, may result in permanent hearing loss (Cleveland Clinic, n.d.b; Kashouty, n.d.). Treatment may involve behavioral changes (reduce alcohol, caffeine, and sodium intake), medications (diuretics and/or anti-emetics [anti-nausea]), vestibular rehabilitation, hearing aids, cochlear implants, or cognitive behavioral therapy (Cleveland Clinic, n.d.b).
The Vestibular System & Neuropathophysiology of Vestibular Disorders
The vestibular system is a complex set of sensory structures and neural pathways that functions to coordinate eye movements and maintain head position, spatial orientation, equilibrium, balance, and posture (Casale et al., 2023; Yoo & Mihaila, 2022).
- The utricle and saccule are two organs located in the cochlear vestibule that detect linear movement of the head (Augustine et al., 2024; Betts et al., 2022; Nichols-Larsen & Kloos, 2024): the utricle detects horizontal movement (like being in a moving vehicle) and the saccule detects vertical movement (like being in an elevator). The utricles and saccules contain otoliths, which stimulate hair cells during linear movement, sending electrical impulses to the vestibular branch of the vestibulocochlear nerve (CN-VIII).
- There are three semi-circular canals in the inner ear that detect rotational movement of the head (Augustine et al., 2024; Betts et al., 2022; Nichols-Larsen & Kloos, 2024). As previously mentioned, they are filled with endolymph, which push against the hair cells when the head is moved. The hair cells in the semi-circular canals then send electrical impulses to the vestibular branch of the vestibulocochlear nerve to indicate rotational movement.
- From the vestibulocochlear nerve (CN-VIII), impulses travel up the spinal cord along the vestibular tract to the pons and cerebellum in the metencephalon (Casale et al., 2023; Yoo & Mihaila, 2022)
- You will recall from Section 8.1 of the Course Manual that the cerebellum’s primary function is to coordinate and refine movements and posture; it constantly receives sensory feedback from the sensory cortex in the parietal lobe and is the error correction part of the brain.
- You will also recall that the pons’s function is to relay information between the cerebral cortices and the cerebellum and contributes to the maintenance of equilibrium and balance.
- The vestibular pathway also projects to the oculomotor nuclei (CN-III, CN-IV, and CN-VI) and to the vestibulospinal tract, which coordinate eye movements and postural corrections respectively.
The Role of Vision in Maintaining Balance
As previously mentioned, the vestibular tract has projections to the oculomotor nuclei (CN-III, CN-IV, and CN-VI) and the vestibulo-spinal tract to coordinate eye movement and postural corrections. There are two quick-acting reflexes that make this possible: the vestibulo-ocular reflex and the vestibulo-spinal reflex (Pritt, n.d.).
- The vestibulo-ocular reflex (VOR) is the involuntary quick motor response to somatosensory input that includes touch, proprioception, kinesthesia, and vestibular sensations (Somisetti & Das, 2023). Efferent information regarding body position, linear and angular movement, and head position relative to gravity is sent to the pons and cerebellum for processing and results in oculomotor response. You will recall that the extraocular muscles are innervated by the oculomotor nerve (CN-III), trochlear nerve (CN-IV), and abducens nerve (CN-VI). When the vestibular organs detect changes, the eyes move to maintain visual stability on the retina during head movement.
- The vestibulo-spinal reflex (VSR) is the involuntary quick motor response to somatosensory input that also involves touch, proprioception, kinesthesia, and vestibular sensations (Nichols-Larsen & Kloos, 2024). Consider, for example, when walking on icy surfaces. Your body takes in all kinds of sensations and makes postural corrections to keep you upright.
Medical Management & Alternative Therapies for Vestibular Disorders
Depending on the underlying cause of vestibular disorder, a number of treatment options are available.
- Antibiotics for bacterial or fungal infections.
- Lifestyle changes, including smoking cessation.
- Epley maneuver, a specialized series of positional maneuvers that aim to reposition canalith particles in the semi-circular canals.
- Vestibular rehabilitation therapy is a specialized branch of rehabilitation designed to stabilize one’s vision, reduce symptoms of dizziness, reducing reaction time during falls, and reduce risk of falls (Cleveland Clinic, n.d.c).
Impact of Vestibular Disorders on Occupational Performance
Vestibular dysfunction can cause diminished balance, unsteady vision, and an increased risk of falls. As such, vestibular dysfunction report challenges with ADL and IADL performance, especially in areas of functional and household mobility (including ascending and descending stairs) and driving (Agrawal et al., 2017). To avoid provoking symptoms, people with vestibular dysfunction may avoid leaving the house and restrict their activities, such as shopping, working, socializing, and attending worship (AOTA, 2017).
In addition to providing vestibular rehab services to remediate the effects of vestibular dysfunction, occupational therapists may modify or adapt the environment in which an activity is performed or adapting how the occupation is performed (AOTA, 2017). Entry-level practitioners have the qualifications and skills to evaluate and analyze vestibular functioning and how it impacts occupational performance (AOTA, 2017).
Summary
The auditory and vestibular systems play an integral part of everyday activities. It allows us to engage in all kinds of movement patterns, interact with the environment around us, and participate in favored occupations. When parts of the auditory or vestibular systems are damaged, occupational performance may be significantly impaired. To limited extent, occupational therapists may remediate the performance skills of people with auditory or vestibular system deficits. By far, however, occupational therapists are well-equipped to provide clients with education and training in modifying the environment or the method in which an occupation is performed, or in the selection and use of adaptive equipment.
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