Ask the Audiologist

What’s the Latest on UHL or SSD?

Unilateral Hearing Loss vs Single Sided Deafness

By Jennifer Drohosky, Au.D.

Our knowledge and best practices for managing unilateral hearing loss (UHL) and single sided deafness (SSD) have changed significantly over the course of my career. (See sidebar for definitions). Several years ago, the field confidently accepted that having UHL with typical hearing in the other ear was “enough.”  No interventions were recommended beyond protecting the typically hearing ear from noise exposure. We found evidence later about what kids and adults with UHL knew already: one ear is inadequate for easily accessing speech and language, especially in background noise. Having a UHL increases the risk of academic struggles such as needing to repeat a grade, behavioral concerns, and delays in speech-language development. Localization skills are poor with UHL, which can lead to safety issues (think: crossing streets and riding bikes in traffic). Additionally, technologies twenty years ago paled in sophistication to technologies now.

With this knowledge, the best of intentions, and available technologies, options included fitting very powerful hearing aids on the ear with SSD.  Ears with little to no residual hearing had varied outcomes with amplification. With experience, we learned that hearing aids for SSD were not as effective as anticipated, and sometimes were even detrimental by providing distorted input. In some cases, a fitting with a powerful hearing aid is a great option, especially in a situation of UHL where there is residual hearing and good speech understanding. But for an ear with a profound sensorineural hearing loss, the benefit can be limited or even interfere with clear hearing on the other ear. Of great concern is fitting an infant who is in the critical period for language development but not yet ready for gold standard testing measures in the soundbooth that can verify a hearing aid is helping and not hurting. A scan of the inner ear is very important to ensure that a hearing nerve is present and the inner ear anatomy is normal. This is a critical component when considering all treatment options for SSD.  

Treatment Options:

The CROS (or Contralateral Routing of Signal) hearing aid: an earlier version of the CROS had a substantial size and required a wire to be worn between the two devices, which was not practical for children. Today’s CROS is much smaller and wireless, sending sounds through a small hearing device picked up on the SSD side through a microphone and received by the hearing ear. With safety concerns due to small pieces and challenges with verification, a CROS may not be a fit for very small children.

Bone conduction hearing devices (BCHD) are another technology option for sending sounds on the side of SSD to the ear with normal hearing. A sound processor is worn on a headband for younger children and sounds are sent through bone conduction and received through the better hearing ear.

The CROS and BCHDs can provide access to sounds and conversation which occur on the side with UHL or SSD. For instance, if a child is sitting at the dinner table and a parent is sitting on the side with UHL/SSD and no technology, it will be very hard for the child to hear that parent’s voice, especially if other people are talking. By using a CROS or BCHD, the child would have much better access to the conversation at that dinner table from his/her parent. Many children benefit from these technologies as well as traditional hearing aids, and they are noninvasive treatments. A trial with one or more of these options is strongly recommended, especially before pursuing something more permanent, such as a cochlear implant (CI). A potential drawback of the BCHD and CROS is that neither provides stimulation to the auditory nerve on the ear with UHL or SSD. Outcomes should be measured whenever possible to ensure that they are providing good benefit.

Cochlear Implants for SSD: We know that hearing from both ears is important for several reasons, especially to reduce listening fatigue, to improve localization, and to hear better in background noise. CIs for treatment of SSD have been in practice for the past few years across the world, starting with adults and now often with children. The advantage is that the auditory nerve is stimulated directly on the ear with SSD. Happily, patients report that the sound quality is better than anticipated, especially as they compare it to their typically hearing ear. The evidence of benefit has led to FDA approval for this procedure for children at younger ages: now five years and older for one implant manufacturer (Medel). 

Questions persist regarding cochlear implants for SSD, especially for children. What is the critical period for cochlear implant success–and is it different for SSD than bilateral deafness? We suspect younger is better. Programming the device and therapy may be more challenging with a very young child. What is the best trial period for other technologies where benefit can be a challenge to measure as language develops? However, the body of literature is growing rapidly, and many practices are re-evaluating their protocols to ensure that patients and families are well-informed and receiving the best recommendations for decision-making with their audiologist.

With our growing knowledge of early identification, intervention, and conditions like congenital cytomegalovirus (cCMV) or others where progressive hearing loss and potentially bilateral loss can be anticipated, a CI for SSD is emerging as an option for children. For these conditions, a cochlear implant may be recommended sooner in light of the possibility of hearing changes.

In summary, there are a variety of treatment options for UHL and SSD, and more evidence will present itself as we learn more from the experience of children. No matter which intervention is chosen, close monitoring of a child’s hearing levels and their speech-language development is critical. Less invasive options such as a traditional hearing aid, BCHD, and/or a CROS hearing aid should be trialed as appropriate to determine benefit.  A scan of the inner ears is crucial in the decision-making process. While the current guidelines limit a CI to children with SSD at five years and older, younger ages at implantation may show even more benefit given what we know about the critical period for language development and the auditory cortex.

As we return to our workplaces, we’ll face some uncertainty and more change ahead. We can be sure that one solution for SSD/UHL will not work for all children and we’ll have to adjust to new insights in the same way. However, we will push onwards for the most effective recommendations and outcomes possible.    ~

Editor’s note: Jennifer Drohosky is a pediatric audiologist at Children’s Hospital Colorado and a regular contributor to The Hands & Voices Communicator.