"Most people with single-sided hearing loss, meaning it is limited to one ear, compensate very well. The perception of sounds through the healthy ear becomes stronger. However, the brain cannot perform a magic trick: determining where the sound comes from. This is called sound localization. If you know someone who suffers from single-sided hearing loss, or if this is your case, it is essential to remain very aware of your surroundings. You can hear the car coming, but without knowing where it is coming from.” - Drew Sutton, MD, board-certified otolaryngologist
We don't think much about the mechanics of hearing, yet it is an essential process that provides a lot of information to our body. Information such as distance or direction reaches us through binaural cues.
The brain uses the tiny differences between the signals received by each ear to locate a sound source in space. Even with closed eyes, it is easy to determine where a sound is coming from, provided you have two fully functional ears.
Hearing impairment can have multiple causes: exposure to loud noises, head trauma, genetics, or external factors. The causes of hearing loss are numerous, and hearing loss also varies from person to person.
Symptoms and signs to watch out for include earwax buildup, inflammation, and swelling.
While typical hearing loss has its drawbacks, single-sided hearing loss can be particularly difficult to live with. The brain must adapt to a hearing discrepancy between the two ears and cope with distorted binaural cues.
Asymmetrical hearing loss, also known as single-sided deafness, can have many causes, from a simple ear infection to more serious problems such as meningitis or mumps. Here is a more detailed look at three causes of single-sided hearing loss and their possible treatments, as well as other information about single-sided deafness.
Ménière's Disease
Ménière's disease is a complex disorder related to the balance of inner ear fluids. The inner ear has two distinct fluid-filled cavities, and in Ménière's disease, one of these cavities swells, causing tinnitus, hearing loss, and a feeling of fullness in the ear. In extreme cases, the ear can trigger a vertigo attack that then requires time to properly recover.
Ménière's disease usually appears in later life and affects only one ear. As its progression is usually slow, the impact on binaural cues is less, but it still affects your ability to hear well.
Treatments for Ménière's Disease
Ménière's disease causes a particular form of hearing loss that usually affects only one ear. The cause of this hearing loss is an abnormal accumulation of fluid in the inner ear, at the level of the cochlea.
Treatments for Ménière's disease aim to reduce vertigo symptoms and prevent fluid accumulation in the cochlea. Medications for nausea and motion sickness may be part of the management to alleviate vertigo during an attack. To prevent fluid accumulation in the cochlea, a diuretic may be prescribed, in addition to a low-sodium diet.
Hearing loss associated with Ménière's disease can be permanent. Assistive devices such as hearing aids are then recommended to limit its effects. However, many prescription hearing aids are expensive and can cost over a thousand dollars. Over-the-counter hearing aids, on the other hand, are much more economical and offer many of the same features as those sold by an audiologist.
Ear Infections
As a child, you most likely had at least one ear infection. Children are more susceptible to them due to a narrower Eustachian tube, which clogs much more easily than in adulthood. The Eustachian tube connects the middle ear to the back of the throat, near a structure called the adenoids.
When a child gets sick, the adenoids can become inflamed and obstruct the Eustachian tubes. Combined with the entry of bacteria or viruses, this can lead to otitis media.
In reality, otitis media is just one way that bacteria and viruses can infect the ears. These unwelcome guests can also reach the inner ear and cause lasting hearing loss. Cochlear infection is rarer, but when it occurs, it is one of the rare forms of sudden sensorineural hearing loss.
Treatments for Ear Infections
Generally, ear infections heal on their own, but sometimes an antibiotic is needed when a bacterial infection does not resolve on its own. In cases of chronic ear infections, a child may need a procedure called tympanostomy, which involves placing a tympanostomy tube (drain) in the eardrum.
This drain allows fluid to drain from the middle ear and effectively limits pressure differences between the middle and outer ear. It also significantly reduces the risk of recurrent ear infections.
Unfortunately, there is no treatment for a viral inner ear infection. All that can be done is to provide supportive care during the infection and look for ways to recover lost functions. As this can result in sudden hearing loss, the beginning is often difficult, with the ears and brain having little time to adapt.
Eardrum Injuries
Physical trauma can affect you in many ways, and one of them concerns the ears.
The tympanic membrane, in particular, is vulnerable, and its injury can lead to hearing loss. The tympanic membrane, better known as the eardrum, is a thin membrane that separates the outer ear from the middle ear. Its role is to transmit sound waves by vibrating the ossicles of the middle ear, so that the cochlea can perceive sounds.
Certain activities increase the risk of eardrum perforation: flying with a cold, deep-sea diving, being near extreme noise levels, or any activity involving a large pressure difference.
Eardrum injuries can affect both ears, but they often affect only one side. A tympanic injury to one ear can cause unilateral conductive hearing loss. If your single-sided hearing loss is sudden and severe after a particular activity, consult a doctor to rule out any more serious underlying conditions. In some cases, an infection and skin can develop behind the eardrum and form a benign skin tumor called a cholesteatoma. Cholesteatomas evolve slowly, and the skin can release enzymes capable of damaging the structures of the middle and inner ear. Hearing loss can result, but hearing can also be improved by surgery in most cases. Artificial ossicles can replace those destroyed by the lesions.
Treatments for Eardrum Injuries
While a torn eardrum may seem dramatic, tympanic injuries actually heal on their own in most cases. Recovery from a perforated eardrum varies, but healing usually occurs in about three months.
If you suspect a perforated eardrum, consult a doctor to rule out other possible problems and get the right information and medications needed to prevent infection. An ENT should determine if it is solely an eardrum perforation or if there is another condition, such as a cholesteatoma.
Ear drops may be prescribed to prevent infection, and you may be advised to wear earplugs for swimming or showering. Furthermore, some perforations require surgery; during the consultation, a qualified healthcare professional can support you in your recovery and advise you on the best course of action.
How is asymmetrical hearing loss diagnosed?
While classic bilateral hearing loss is fairly easy to spot, unilateral deafness is more difficult to identify and less likely to prompt people to seek help. Unlike people with bilateral hearing loss, those with single-sided hearing loss generally retain the ability to hear their interlocutors, but they exhibit very specific signs and symptoms.
Symptoms of asymmetrical hearing loss
A characteristic manifestation of unilateral deafness is the head shadow effect. Specifically, when a sound comes from the side of the affected ear, the person is unlikely to hear it, since the healthy ear does not receive these sound signals. The head then blocks the sound and casts a symbolic "shadow" that prevents the good ear from perceiving it.
To hear this sound, a person with unilateral deafness usually has to turn their head to direct their healthy ear towards the speaker.
People who find themselves frequently turning their head during a conversation to hear better should consider taking a hearing test to ensure their hearing acuity is intact: this reflex can indicate the onset of hearing loss.
Other symptoms of unilateral deafness may appear: vertigo, increased difficulty following a conversation in a noisy environment, difficulty hearing whispers, etc. Getting tested sooner rather than later allows for a faster return to quality of life.
Diagnosing asymmetrical hearing loss
The best way to identify unilateral deafness is to perform a pure-tone audiometry test. This examination is part of a standard hearing assessment and aims to determine at what relative volume you perceive different frequencies.
The test is performed with isolating headphones connected to a device that allows the audiologist to vary the frequency, intensity, and ear in which the sound is played. The professional emits a sound and asks the patient to raise the hand on the side where they heard it. If the sound is not perceived, they repeat at a slightly higher volume.
The result is called an audiogram: it is a graph that shows how well you hear each frequency. It shows the performance of both ears, and if one of them performs significantly worse, it indicates unilateral hearing loss.
Treatment for asymmetrical hearing loss
If you suffer from hearing loss or single-sided deafness, several solutions can help: cochlear implants, oral or injectable corticosteroids, hearing aids, and sign language.
Conclusion
In summary, single-sided hearing loss can have multiple underlying causes, from physical trauma to biological conditions. While the three causes presented above can cause unilateral deafness, there are many others. If you experience symptoms of unilateral deafness, make an appointment with your audiologist to get tested and find the best solution for your case.
Sources:
Binaural cue | APA Dictionary of Psychology
Tympanostomy Tubes | Columbia University Medical Center Department of Otolaryngology Head and Neck Surgery
Role of viral infection in sudden hearing loss | NCBI
