Single-sided deafness: working together to improve research into treatments

Patients and other experts have worked together to identify the most important things to measure in research studies about treatments for single-sided deafness. Roulla Katiri, chief audiologist at the Mater Hospital in Dublin, and Lewis Williams, who developed single-sided deafness in 2018, explain how.

Take-home points Research studies testing treatments measure various effects (known as ‘outcomes’). Studies of treatments for unilateral hearing loss, also known as single-sided deadness (SSD), have used 520 different outcomes. This makes it difficult to compare results across studies and work out which SSD treatment works best and for whom. We can make it easier to compare results across studies by asking researchers to measure the same outcomes. These outcomes form the core outcome set. They are the very minimum that must be measured when testing treatments for a condition. The Core Rehabilitation Outcome Set for Single-Sided Deafness (CROSSSD) initiative worked closely with international experts in SSD (healthcare users and professionals) to develop a core outcome set. Adoption of the three outcomes (spatial orientation, group conversations in noisy social situations, and impact on social situations) in the core outcome set will improve the future of research into SSD treatments.


It was just a normal Friday at work for me when I suddenly felt very dizzy and was struggling to hear in one ear. I was treated for labyrinthitis, an inner ear infection. But I was left with constant intrusive tinnitus and SSD. There was a wait to try a CROS hearing device, which reroutes sounds from the poor ear to the better hearing ear. I eventually got a cochlear implant in Germany, which I hoped would help me manage my tinnitus. There were times before my implant, I could have been surrounded by all my best friends in a pub and I would feel so lonely, because I couldn’t keep up. I didn’t know what was happening. I wouldn’t know where the conversation was going. I’d just be looking left and right. And it was quite sad…


What is single-sided deafness?

Single-sided deafness (SSD), also called unilateral hearing loss, is defined as normal or near-normal hearing in one ear and a severe-to-profound hearing loss in the other ear.

What causes single-sided deafness?

Common causes of SSD in adulthood include acoustic neuroma (a type of benign tumour on the nerve leading from the inner ear to the brain), inner ear infections like labyrinthitis, and Ménière’s disease (a disorder of the inner ear). In some cases, the cause is not known, for example in sudden onset sensorineural hearing loss.

What is the impact of single-sided deafness?


Difficulties in daily life as a result of SSD vary considerably from person to person. They may include difficulties in understanding speech in noisy environments and knowing which direction sounds are coming from. People’s psychological well-being and quality of life can also be affected. For example, reduced confidence and increased anxiety about taking part in work meetings and social situations.


Everything that was effortless suddenly became challenging. Each day felt like extra time but with no final whistle in sight. There was no plaster cast or crutches to point at, so there was an assumption that I looked fine, so I must be fine. Listening and concentrating on conversations suddenly took up so much more energy, which eventually took its toll and I was exhausted.

By trait I am a social character and my friends would describe me as a bouncy ball, joking around reacting and having fun. This is where I had so much fun and spent such happy times adventuring with my buddies at festivals, out and about dancing and cycling. Just overnight my favourite amusements were taken from me, from meeting in our usual haunts and from the exhaustion I was feeling.

With the new controlling noise in my head, tinnitus, I was overcome with emotion, and this is when I started to drift away. The more I was exhausted the more I floated away. When I was out I would just zone off because I couldn’t keep up with the conversations. I might laugh at the wrong time, or I would go to the toilet for a break, and I would just realise I was alone, but the worst was when new people thought I was ignoring them and being rude.


What can we do about single-sided deafness?

Devices like the Contralateral Routing of Signals (CROS) hearing aid, Bone Anchored Hearing Aids (BAHA) or middle ear implants are often trialled in the NHS. They can help with the hearing difficulties caused by SSD by rerouting sounds from the poor ear to the better-hearing ear. In some countries, like Germany, Belgium, France, North America and Australia, people may be offered a cochlear implant, which restores hearing on the poor side.

What is the problem?

Different researchers have been testing different effects (known as outcomes) of available treatments for SSD. Examples of the many outcomes that have been used in SSD studies include how well an individual can hear speech above noise, how easily they can locate a sound, or how a device affects their quality of life. In our recent systematic review, we found that 96 studies conducted in the field of SSD used a total of 520 different measures to assess the various devices. This makes it difficult to compare results between studies, and work out which treatment is best for a given individual.

How do we address the problem?

The CROSSSD study set out to address the difficulty of comparing results between SSD studies by developing a ‘core outcome set’ for SSD. We involved a large international group of healthcare users with experience in SSD treatments, as well as audiologists, ENT surgeons, clinical researchers, and industry representatives. They rated the importance of a list of outcomes by completing a series of surveys. Then a smaller group of experts had a web-based consensus meeting to discuss the important outcomes further.

Lewis took part in the CROSSSD study surveys and web-based consensus meeting. It was really important that we included people who are experts by experience of having SSD. It was vital that they helped us shape the study and decide what is most important to measure in research studies about SSD treatments.


For me personally it is amazing that the CROSSSD study is happening. I am glad the information about SSD treatments will be there, easily found in one place, because when I was looking I couldn’t really find it. It was hard to collect this information. I think now, in the future, when it is easily found, so the doctors can hear and have the information there – that is an amazing thing.

It is great that the study was funded to be able to get all the different groups to sit down and talk about what was important, and looking at this subject in the bigger picture. For me it was so quick, from the event of going deaf and getting surgery, only five months, and being connected to the community was an emotional experience, finding out there where others out there.


The core outcome set

We found agreement on three outcomes that should always be measured and reported in SSD treatment studies. These outcomes are: (1) Spatial orientation, (2) Group conversations in noisy social situations, and (3) Impact on social situations. Our short video provides a summary of the study outcomes.

Video created by


The CROSSSD study team have created a ruler which can be used to measure the effect hearing devices can have on a person’s life like mine. It has been a fun experience taking part, and great to meet other people like myself. Most importantly, moving forward, there is a suitable way to easily review the information, and find the most appropriate solution, without getting lost in all the available the data. I was lucky to be able to find the correct solution for me, which restored normality to my life, and my friends remark on seeing that cheeky smile I have, which they had missed.


The future

Further research is currently underway to determine ‘how’ these core outcomes can best be measured. If you would like to take part in future hearing research, please register your interest by signing up to the Nottingham Biomedical Research Centre participant database.

Lewis Williams
Lewis is a keen cyclist who likes to go to music festivals and is creative day-to-day. In November 2018 he had an ear infection following which he ended up with unilateral hearing loss and intrusive tinnitus. In May 2019 he travelled to Germany where he got assessed and underwent surgery to have a cochlear implant.


The main body of work for this project is funded by the National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre (BRC), funding reference number BRC-1215-20003. 

Find out more:

Roulla and Lewis have nothing to disclose.

References (pdf)


Single-sided deafness: working together to improve research into treatments by Roulla Katiri

is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International

2 Comments on this post

  1. Great work you two. So glad you’re smiling again Lewis

    Paul James / Reply

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