By Marcello Cherchi, MD PhD
For patients
Hearing loss is a common problem, especially in older adults. Many people with hearing loss are helped by hearing aids, which is one of several methods of “hearing amplification.” For unusual or more complicated cases of hearing loss, you should talk with an audiologist or ENT.
For clinicians
Overview
There are many causes of hearing loss. Some common causes, such as age-related hearing loss, can often be addressed by external devices (“hearing aids”) that are more easily accessible today than previously. Forms of hearing loss that are more complex, or due to uncommon causes, warrant further evaluation through consultation with an audiologist or otologist. Despite technological advances, the currently available strategies do not restore hearing to “normal.”
Introduction
Many disorders can interfere with a person’s ability to perceive and interpret sounds. We will not present a comprehensive guide to this problem and its solutions, but examples are provided in the Table below.
|
Site of lesion |
Example pathologies |
Type of hearing loss |
Potentially useful diagnostic techniques |
Treatments |
|
External ear |
Cerumen and other foreign bodies |
Conductive |
Inspection with otoscope |
Disimpaction (for cerumen) |
|
Middle ear |
|
Conductive |
Audiometry with air and bone conduction |
Depends on underlying pathology |
|
Cochlea |
Age-related hearing loss |
Sensorineural |
|
|
|
Auditory nerve |
Auditory neuropathy Vestibular schwannoma |
Sensorineural |
|
|
|
Brainstem and higher auditory processing |
Focal neurological lesions |
Neurologic |
Central auditory processing tests |
Depends on underlying pathology |
Table : Anatomically based classification of hearing loss.
Greater availability of hearing amplification
In the United States some basic hearing amplification strategies (basically, “hearing aids”) are now more accessible than before due to several factors:
- In some states, including Illinois, the majority of adults no longer require medical clearance by a physician to get amplification.
- On 8/16/22 Congress enacted a law permitting sale of over-the-counter hearing aids
The greater availability of amplification is important, and will benefit many patients.
Continued role of audiologists and otologist
However, because of the variety of hearing disorders (many of which have different treatments), we still encourage patients suffering from hearing loss to consult an audiologist in order to secure a correct diagnosis and appropriately tailored recommendations. In cases of complex or unusual hearing loss, consultation with an otologist (otolaryngologist specializing in hearing disorders) may also be appropriate. There are various factors to consider, of which we cite two broad categories.
- Is the hearing loss sensorineural, or conductive, or mixed? Broadly, the greater the degree of conductive hearing loss, the less likely a conventional hearing aid will be helpful. If the etiology of the conductive hearing loss cannot be corrected, then there are strategies for bypassing the outer and middle ear, and delivering vibrations to the cochlea (such as with a bone anchored hearing aid).
- Is the hearing loss symmetrical, or is it predominantly/exclusively in one ear? These two scenarios are treated differently. If the etiology of unilateral hearing loss cannot be corrected, then there are several strategies to bring sounds reaching the “bad ear” to the “good ear,” thereby having the good ear do “double duty.” Examples of such strategies include BiCROS (bilateral contralateral routing of signal) hearing aids, and a bone anchored hearing aid (BAHA).
Problems not yet solved by amplification
Amplification is often helpful, though does not restore “normal” hearing (Lesica 2018). Here are two examples of problems that amplification does not solve.
The strategies used for asymmetrical hearing loss generally do not restore stereoacusis (Plauska, van der Heijden, Borst 2017; Shamma, Shen, Gopalaswamy 1989) and thus do not restore the ability of sound localization (Zheng et al. 2022).
When in an acoustically complex environment, such as one in which multiple conversations are occurring simultaneously, a human’s ability to focus on (and successfully extract information from) one conversation is said to have solved the “cocktail party effect” (Cherry 1953). Hearing loss of any type degrades this ability, and hearing amplification generally does not restore it (Stoop 2022) despite considerable research and technological advancements (Fischer, Caversaccio, Wimmer 2020).
Differences among devices
The non-invasive forms of hearing amplification vary in their conspicuity (such as whether the receiver is behind the ear, situated visibly within the pinna, or entirely within the external auditory canal) and features (e.g., programmability, ability to link to other devices such as phones and televisions, etc.). These types of hearing aids vary considerably in cost. Competition from over-the-counter hearing aids is likely to exert downward pressure on the pricing of these devices, since their efficacy for mild to moderate hearing loss appears similar (De Sousa et al. 2023).
References
Cherry EC (1953) Some Experiments on the Recognition of Speech, with One and with Two Ears. The Journal of the Acoustical Society of America 25: 975-979. doi: 10.1121/1.1907229
De Sousa KC, Manchaiah V, Moore DR, Graham MA, Swanepoel W (2023) Effectiveness of an Over-the-Counter Self-fitting Hearing Aid Compared With an Audiologist-Fitted Hearing Aid: A Randomized Clinical Trial. JAMA Otolaryngol Head Neck Surg 149: 522-530. doi: 10.1001/jamaoto.2023.0376
Fischer T, Caversaccio M, Wimmer W (2020) Multichannel acoustic source and image dataset for the cocktail party effect in hearing aid and implant users. Sci Data 7: 440. doi: 10.1038/s41597-020-00777-8
Lesica NA (2018) Why Do Hearing Aids Fail to Restore Normal Auditory Perception? Trends Neurosci 41: 174-185. doi: 10.1016/j.tins.2018.01.008
Plauska A, van der Heijden M, Borst JGG (2017) A Test of the Stereausis Hypothesis for Sound Localization in Mammals. J Neurosci 37: 7278-7289. doi: 10.1523/JNEUROSCI.0233-17.2017
Shamma SA, Shen NM, Gopalaswamy P (1989) Stereausis: binaural processing without neural delays. J Acoust Soc Am 86: 989-1006. doi: 10.1121/1.398734
Stoop R (2022) Why Hearing Aids Fail and How to Solve This. Front Netw Physiol 2: 868470. doi: 10.3389/fnetp.2022.868470
Zheng Y, Swanson J, Koehnke J, Guan J (2022) Sound Localization of Listeners With Normal Hearing, Impaired Hearing, Hearing Aids, Bone-Anchored Hearing Instruments, and Cochlear Implants: A Review. Am J Audiol 31: 819-834. doi: 10.1044/2022_AJA-22-00006
