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You can have a hearing loss of equal severity in both your ears or, more frequently, hearing loss that differs in severity between each ear. We describe the latter as asymmetrical hearing loss.
This article explains the ins and outs of asymmetrical hearing loss.
What Is Asymmetrical Hearing Loss?
Asymmetric hearing loss is when a hearing loss is greater in one ear than it is in the other. This is very common as hearing loss is very rarely exactly the same in both ears.
To be diagnosed with this type of hearing loss, there must be a certain difference in severity between the two ears in a number of frequencies. There must also be a bilateral hearing loss (hearing loss in both ears).
Specifically, asymmetrical sensorineural hearing loss (ASNHL) is defined as a binaural difference in bone conduction thresholds of >10 dB at two consecutive frequencies or >15 dB at one frequency.
Like hearing loss in general, it is common amongst the older population and can be a symptom of various underlying conditions such as an immune disorder or demyelinating disease.
Is Asymmetrical Hearing Loss the Same as One Ear Hearing Loss?
Asymmetrical hearing loss is not quite the same as one ear or unilateral hearing loss.
When we talk about one ear hearing loss, we assume that hearing loss occurs in one ear but that the other ear is unaffected. With asymmetrical hearing loss, there is a degree of hearing loss in both ears, although one ear can be a lot worse than the other. One ear might only be mildly affected, but some degree of hearing loss is still detected through a hearing test and experienced by the sufferer.
It is easy to think of it in terms of one ear hearing loss is a unilateral hearing loss, whereas asymmetrical hearing loss must be a bilateral hearing loss.
If you have asymmetric hearing loss it can be a sensorineural hearing loss (ASNHL), a conductive hearing loss, or a mixed hearing loss.
What Causes Asymmetrical Hearing Loss?
If you’re aware of some of the causes of hearing loss in general, or bilateral sensorineural hearing loss, you’ll know some contributing factors to asymmetrical hearing loss.
Common causes include:
- Loud noise (this can be an asymmetrical exposure, for example, if you have frequently used noisy equipment and tools on one side of your body)
- Aging
- Genetic causes
- Injuries to the head or the ear
- Certain ototoxic drugs
- Acoustic neuroma or other tumors (pushing on the hearing nerve which will cause a faster decline in hearing in the affected ear)
- Surgery
- Repeated infections
- Viral infection on the hearing nerve
- Ménière's disease
ASNHL might be the only noticeable symptom of an intracranial tumor or a vestibular schwannoma.
Keep in mind that dual pathology is common in instances of sensorineural hearing loss, and any asymmetry might be evidence of another factor or condition that has caused a greater loss in the worse ear. Your audiologist should be aware of this and conduct thorough tests to ensure nothing is missed.
It is important to report all other symptoms such as tinnitus, aural fullness, vertigo, imbalance, otalgia, and otorrhoea as well as your history of ear problems, surgeries, medication use (particularly aminoglycosides, nonsteroidal anti-inflammatory agents, salicylates, and chemotherapy drugs). Knowing your family's history of hearing loss can also be useful.
How Do You Know if You Have Asymmetrical Hearing Loss?
Hearing loss is a change in physiology, and while much of your hearing loss might show up on an audiogram, a lot of it may not.
To diagnose your hearing loss, a hearing health professional or audiologist will need to conduct a thorough medical examination.
They will check the auricle (skin lesions, preauricular sinuses, oedema, erythema, and tragal tenderness), external auditory canals (mass lesion, discharge), and tympanic membranes (color, thickness, scarring, effusion).
The head and neck, cranial nerves, and postnasal space might also be examined.
An audiology investigation might also be necessary. This includes detailed diagnostic imaging (MRI) to determine aetiology, and in some cases, blood tests will be required.
You should be referred to a specialist ear, nose, and throat doctor (ENT) for more assessments, as there could be multiple factors at play. This referral will definitely happen, and fast, if you have any neurological symptoms.
How your asymmetrical hearing loss is treated will depend on the results from these tests.
How to Treat Asymmetrical Hearing Loss
Even after a diagnosis of ASNHL you should still try to minimize your exposure to loud noise as much as possible to prevent further hearing decline.
Your audiologist might advise the use of hearing aids to improve your hearing capacity. This might take some trial and error if health care professionals are still unsure about exactly what’s going on in your case. It will also be your decision as to whether you want to use two hearing aids or just one. Although some people think that they can cope if their hearing is considerably better in one ear, if you have hearing loss in both ears, it is recommended to get hearing aids for both ears.
Just as your ears are designed to work together to allow your brain to combine input from both sides, many hearing aids are designed to work together too. If the cost of two hearing aids (which admittedly, can be a lot) is putting you off, do remember that your hearing will probably be much better with two hearing aids, and the hearing in your ‘better’ ear will be more effectively preserved with the use of a hearing aid.
You can also consider serial fittings which are when one hearing aid is fitted first and then the second hearing aid is added later. This helps you to determine which ear is benefitting from the amplification and whether both are.
Some hearing aids use advanced features such as binaural communication to ‘talk’ to each other which can be useful in improving localization. This is another thing to consider when deciding whether to get one or two hearing aids.
Everyone’s hearing loss is different, so it’s difficult to say what will be the best course of treatment for you within the scope of this article. It’s always best to listen to your audiologist's expert advice as they have years of experience in dealing with the tricky nuances of hearing loss and its treatment.
To learn more about the different types of hearing loss, check out our other blog articles.
The information in this guide has been written using the following reliable sources:
https://www.audiologyonline.com/articles/asymmetrical-sensorineural-hearing-loss-fitting-12222
https://www.racgp.org.au/afpbackissues/2008/200805/200805prasad.pdf
https://www.hear-it.org/asymmetric-hearing-loss
https://www.dallasear.com/conditions-asymmetrical-hearing-loss.html
