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  • Writer's pictureKoorosh Nejad

What are CROS and BiCROS hearing aids?

Updated: Oct 4, 2023

SSD or single-sided deafness refers to a condition when a patient has profound hearing loss in one ear only. Continue reading to learn more about this type of hearing loss and learn how CROS or Bi-CROS hearing aids can help.


In this article you will learn about:

  1. What is single-sided deafness (SSD)?

  2. What could cause single-sided deafness (SSD)?

  3. What does the audiogram look like for patients using CROS and BiCROS?

  4. How can single-sided deafness be managed?

  5. What are CROS and BiCROS hearing aids?

  6. How are CROS hearing aids different from other hearing aids?

  7. What benefits can CROS and BiCROS hearing aids bring to the patient?

  8. What are the shortfalls of a CROS or BiCROS hearing aid?

  9. What to consider when selecting a CROS or BiCROS hearing aid?

  10. Is a manufacturer's CROS hearing aid different from the other? What about BiCROS?

  11. What can I do to improve my chance of adjusting well with a CROS hearing aid?

  12. I used CROS hearing aids for a while but now hearing on my better side has declined, do I need to purchase a BiCROS?



What is single-sided deafness (SSD)?

A unilateral hearing loss may also be called a one-sided hearing loss or a single-sided hearing loss.


If a unilateral hearing loss is severe or profound, it is often called single-sided deafness (SSD), as there is practically no hearing left. Single-sided deafness is defined as a hearing loss with normal or near-to-normal hearing in one ear (“the good ear”) and severe to profound hearing loss in the other. If the unilateral hearing loss is severe or profound, the person affected more or less only hears with one ear (monoaural hearing). Single-sided deafness may also be called unilateral deafness.


A unilateral hearing loss can both be a sensorineural hearing loss and a conductive hearing loss. A unilateral hearing loss can occur in both adults and children.


Children with unilateral deafness may have sensorineural deafness which is caused by a fault in the inner ear (cochlea) or conductive deafness, which is often caused by microtia and/or atresia. The deafness may be permanent or temporary.


What could cause single-sided deafness (SSD)?


A unilateral hearing loss can occur as a result of many causes.

  • It can be inherited (as other types of genetic hearing loss).

  • It can occur as a result of trauma or injury to the head.

  • An acoustic neuroma often results in unilateral hearing loss.

  • It can be a result of viral or bacterial infections.

  • It can also be caused by maternal illnesses, microtia, Ménière’s disease and mastoiditis.





What does the audiogram look like for patients using CROS and BiCROS?

The audiogram for a person with single-sided deafness would be something similar to the below sample. As you can see the left side has normal hearing thresholds (lower than 20 dB) while the hearing on the right side is almost or completely deaf. It is a poor chance that an Ultra-Power (UP) hearing aid can have a meaningful benefit to the hearing on the right side of this patient but s/he may want to try it first before considering CROS hearing aids.

single sided deafness - cros and bicros hearing aids on hearingnow

The audiogram for a patient that could benefit from BiCROS would be similar to the below image. As you can see the hearing on the right side (in red) is deaf, but the left side (in blue) also has mild to moderate sloping sensorineural hearing loss (SNHL).

single sided deafness - cros and bicros hearing aids on hearingnow


How can single-sided deafness be managed?

The hearing loss of a patient with single-sided deafness can be managed or improved through an operation, by hearing aids (CROS and BICROS hearing aids), bone-anchored hearing aids (BAHA), or with a cochlea implant. The management plan depends on the severity of the hearing loss, and more importantly, if the hearing loss is conductive (due to damage or disorder with the middle ear), or damage or disorder of the cochlea (in the inner ear).


What are CROS and BiCROS hearing aids?

CROS stands for Contralateral Routing of Sound. A CROS hearing aid is a special type of hearing aid for people who are deaf in one ear and have normal hearing in the other ear. A BiCROS hearing aid is similar to a CROS hearing aid but is for people who are deaf in one ear but also hearing impaired in their better ear. With CROS or BiCROS hearing aids, the sound is wirelessly transmitted from the deaf ear into the better ear. What looks like a conventional hearing aid is worn on the deaf ear, but this is a microphone only. This microphone picks up sound from your deaf side and sends it via a wireless connection to a conventional hearing aid on your better ear. The sound can also be amplified if you have a hearing impairment in your better ear (BiCROS).


single sided deafness - cros and bicros hearing aids on hearingnow

“You are now hearing signals on both sides of your head all in one ear,” said Dr. Catherine Palmer, Director of Audiology and Hearing Aids at the University of Pittsburgh Medical Center and the President of the American Academy of Audiology.


How are CROS hearing aids different from other hearing aids?

Traditional hearing aids amplify the sound into the ear they are sitting on. With a CROS set-up, the device on the non-hearing ear looks like a usual hearing aid. But it is really a microphone and transmitter and is picking up the sound to send it to the device on the hearing ear.





What benefits can CROS and BiCROS hearing aids bring to the patient?

  • To be able to hear sounds from both sides without turning your head

  • This can mean you are less likely to miss someone speaking to you from your poor side

  • This can make you feel less cut off on your bad hearing side

  • If you have your good ear towards noise and there is speech coming from the bad side then the CROS might help you to hear the speech, although background noise will always be challenging


What are the shortfalls of a CROS or BiCROS hearing aid?

  • These hearing aids cannot improve your ability to tell where a sound is coming from (sound localisation)

  • Background noise and poor acoustic environments are always challenging for hearing aid users

  • If you have your bad ear towards noise the CROS may make it harder to hear than if you didn't have the aid in

  • CROS/BiCROS aids may take longer than standard hearing aids to get used to





What to consider when selecting a CROS or BiCROS hearing aid?

Obtaining CROS/BiCROS hearing aids is easy. You need to contact your local audiologist to discuss your options. While sound processing and the hired technologies in a pair of hearing aids for binaural hearing loss may take the patient time to try a few different models and brands, choosing CROS hearing aids is quite straightforward as the unit on the better ear does not make much processing on the sound, but only works as a receiver. So my advice is to go for the lowest level of technology for the CROS hearing aids when you need one. On the flip side when considering a BiCROS hearing aid the unit on the better side also does sound processing, so my advice is to go for the highest tech level that you can afford if you are in the market for a BiCROS hearing aid.


Is a manufacturer's CROS hearing aid different from the other? What about BiCROS?

The answer is yes, but not that much for the CROS hearing aids. The unit that goes on the better side in CROS and BiCROS hearing aids may sound different from manufacturer A versus B.


What can I do to improve my chance of adjusting well with a CROS hearing aid?

While getting used to CROS hearing aids can be challenging, the most important thing a person can do is wear their CROS aid as much as possible, my advice is not to give up too quickly. Use the device full time—all waking hours—in order to get used to this listening arrangement. It is very different from what anyone is used to and it will take time to adjust.





I used CROS hearing aids for a while but now hearing on my better side has declined, do I need to purchase a BiCROS?

No, the good news is that your CROS hearing aids can be programmed to work as BICROS. In a CROS hearing aid, the unit on your good side is a normal hearing aid. Later on in life if the hearing in your better side starts to decline and you need some amplification your audiologist will be able to program your CROS to work as BiC|ROS and provide a prescribed level of amplification to the better side.





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