KidsAudiologist

Archive for the ‘single-sided deafness SSD’ Category

At a recent NDCS Family Weekend for families of newly diagnosed children I was reminded of a question I’m asked alot – is the newborn hearing screen accurate? And the parents most likely to ask are those whose child passed newborn hearing screening but was later diagnosed with a hearing loss. So is it? Or have these children been misdiagnosed?

I believe that there is an issue here but that it might not be what is immediately thought!

The goal of newborn hearing screening is to enable the identification of as many newborns as possible who do have a hearing loss (high sensitivity) but also exclude as many newborns as possible who do not have a hearing loss (high specificity). Depending on the type of screen carried out, around 15% of babies who are tested using otoacoustic emissions (OAE), and 3% of babies tested using automated auditory brainstem response (AABR) will be referred for further testing. Between one to two babies in every 1000 are born with some level of hearing loss in one or both ears, so we know that it is much more likely that a baby is referred from screening and found to have normal hearing than the other way round. But there is a real issue with information sharing between professionals, as well as between professionals and parents…

Only half the children with permanent childhood hearing loss are born deaf. The other half develop deafness during the first few months/years. There are therefore young children who passed newborn screening and diagnosed as deaf early in life that can look like an inaccurate or late diagnosis but may have actually developed the deafness post-screening. There are some common causes of childhood deafness that cause this, such as CMV infection and genetics, that are commonly believed to be congenital (from birth) but are actually progressive early in life. One of the reasons we test for unilateral (one-sided) hearing loss in newborns in this country is because we know that a proportion go on to develop bilateral hearing loss soon after so it’s important to monitor these babies and young children. Another issue is that the screen is designed to pick up moderate or greater deafness but this isn’t explicitly laid out to parents and therefore again parents feel misled if later their child is diagnosed with mild deafness (or maybe was born with mild deafness that progressed early). Some of this we have only begun to understand better in the last few years and since universal screening was implemented – in the past children were always diagnosed later and therefore assumed to have been deaf from birth.

Although the information leaflet that is provided with newborn screening clearly says that deafness can happen at any age, most people’s perception is that a passed screen = normal hearing. Parents continue to express concerns that they have problems accessing an audiology assessment for their child. A GP may fail to refer concerned parents because everything must be OK as ‘they passed their newborn test’ and Health Visitors who used to test babies at 8 months may now assume that there’s no need to be concerned because of the early screen.

Having said all this, there is of course always the chance of error or mis-diagnosis within the system, or a false report of passing the screen. In which case any concerns of the parents should be treated seriously and investigated fully. For other families it can be helpful to discuss the ‘aetiology’ or cause of their child’s deafness and that may help to understand how and why the hearing loss happened/progressed. NDCS publishes a great booklet that is free to download called Understanding your child’s hearing tests that includes a section ‘Medical tests used to help diagnose the cause of
permanent deafness’ with more information.

More than 9 out of every 10 chldren born with a hearing loss have hearing parents. It’s therefore entirely natural that early on they are going to ask “What can my child actually hear, what does it sound like for them?” They share a need to try and get to grips with this as part of the process of understanding what they need to do to help their child. It is a very difficult question to answer. Some of the things we know at this stage include the degree and type of deafness: we know how much volume is lacking for a mild (20-40dB), moderate (41-70dB), severe (71-95dB) or profound (95+dB) hearing loss, and we know that loss of hair cells in sensorineural hearing loss means that some natural processing that happens within the cochlea is lost – including the cochlea amplifier, pitch discrimination and the ability to recognise different sound levels (reduced dynamic range). We also know a good amount about the benefits and limitations of various types of hearing technologies that are used. Now more than any time in history, we know that almost all deaf children can perceive the full range of speech sounds with their hearing aids or cochlear implants. But we also know that they can’t do this as easily as hearing children and that no hearing technology can replace normal levels or quality of hearing.

So it’s relatively easy to mock up some simulations of what a hearing loss might sound like using some software to reduce the overall level of sound and filter out some of the frequencies that make up speech sounds. There are some good ones available online and my favourite is the Better Hearing Institute which has mild and moderate hearing loss in different situations. The NDCS also have a couple of examples that are specific to children in classrooms.

But there is a health warning about these simulations and that is that we don’t know, especially in the early days following diagnosis in young babies, what is happening beyond the ear and how well they can make sense of the sound they hear. Hearing, listening and understanding are sophisticated processes that are determined by a complex interaction between the physical properties of the ear as well as attention, memory and auditory processing (what happens when your brain recognises and interprets sound so that it becomes meaningful). The brain has the incredible power of plasticity in the early years and is continually moulding and learning from new experiences and sounds. As adults the brain is much less plastic and it takes much longer to adapt. This means that the experience of hearing and listening is hugely variable between individuals and is influenced by whether someone is born deaf or what age they became deaf, how long it was between developing a hearing loss and being fitted with hearing aids, their listening experience, and their cognitive and auditory processing abilities. Children born deaf and those who become deaf early in life experience deafness as the norm. Older children, teenagers and adults who become deaf have a very different experience of deafness to which they need to psychologically and physically adapt to. Much of what we understand hearing loss to sound like comes from adults who have previously experienced normal hearing levels. This is a particular issue when parents are considering a cochlear implant for their child for example. It is commonly reported that cochlear implants sound electronic, that they aren’t natural, and that voices sound like ‘a Dalek underwater’. This can be a devastating idea for parents considering this option but in fact when you speak to these same implanted adults later on they describe their implants as sounding very natural as their brain has acclimatised to the new sound. I recently chatted with a group of teenagers who all used cochlear implants and they agreed – “people think they sound like robots, but they don’t”. Just from listening to the voice quality of the thousands of implanted children, we can be certain that they do not experience this kind of ‘electronic’ sound. But to listen to this type of electronic simulation the best one I’ve found is Scientific American Frontiers.

Auditory Neuropathy Spectrum Disorder (ANSD) affects approximately one in 10 deaf children and causes distortion of sound and difficulty discriminating speech over and above what we would expect from the hearing loss alone. The level of distortion is highly variable from very slight to very severe and it is not measurable. So in young children we do not know early on how it will affect their speech and language development. Simulations of ANSD from mild to profound neuropathies can be heard here and make scary listening but again we know that with the right intervention children with ANSD are successfully using their hearing and using spoken language.

There are 10 million people in the UK have some degree of hearing loss and the majority of these people experience age-related deterioration of hearing. At the other end of the age spectrum there are just 45,000 under 18’s with a permanent hearing loss. Inbetween there are those adults who grew up with a hearing loss as well as those who have lost their hearing as an adult. My experience is that individuals (and their parents or family) use a wide variety of terms to describe their hearing level – deaf, hearing loss, partially hearing, hearing impaired, hard of hearing – and they rarely relate to their audiogram level. There are those people who associate themselves culturally with the Deaf community who we may traditionally think of as those who are profoundly deaf sign-language users. But there are also people who have developed a mild hearing loss for the first time who may tell their audiologist they are ‘stone deaf’ or ‘can’t hear a thing’ and this is their perception compared with their normal experience.

Every child’s hearing levels and hearing experience is unique and it is impossible for these types of simulations to represent how all deaf people process and experience sounds heard. But they are useful in giving the listener an understanding of the difficulties encountered and I particularly like those that can highlight the big differences experienced between listening in quiet and noisy environments and which are an important reminder of how much easier we can make life for children by improving their listening environments in school and elsewhere.

This weekend I had the priviledge to be invited to the final residential weekend for the current NDCS Youth Advisory Board (YAB) cohort. Wow, I mean just wow, what an amazing bunch of teenagers! I was doing some filming with them on retubing earmoulds, using radio aids with other equipment, and their experiences with cochlear implants, and the films will appear on the NDCS Buzz website soon. I had the chance to have a chat with some of them and had a read through their memory books of their year but you can have a read of their new blog for more details of the weekend.

But my main memory of the weekend will be about communication. These teenagers had a range of hearing losses from mild to profound; most were using a range of technology including hearing aids, cochlear implants and radio aids; and most had identified themselves as using one main communication preference prior to joining the YAB. In the last 20 years or so I have often walked into a room full of deaf kids signing with one another and this was no different. But some of these kids hadn’t signed a year ago at all – they had learnt it so that they could all communicate easier with one another. At the same time they almost all used spoken language and effortlessly switched depending on who they were chatting to. They were so flexible – it was much less about their own communication needs, as them adjusting to others communication needs! One of the teenagers had taken her mock oral GCSE in German last week, and another had passed both GCSE Japenese and BSL Stage II in the same year.

None of these kids are ‘mine’ or had been seen in my clinic but they all made me very proud to be an audiologist. There has never been a time in history when deaf children and young people had as many options, choices and opportunities available to them, thanks in part to the technology they’re using.

Following on from my earlier post “Don’t worry about it, the other ear will compensate” about unilateral hearing loss, the next myth is “hearing aids won’t help”.  The importance of providing hearing aids to children with deafness in both ears as early as possible is widely recognised. If you have a hearing loss in both ears then your audiologist is likely to recommend that you have a hearing aid in both ears. This is going to help keep the hearing balanced and help provide the brain with the binaural information it needs to distinguish direction of sound as well as effectively filtering out unwanted background noise. Hearing aids aren’t always helpful for every child with a unilateral hearing loss – a careful assessment should be done on an individual basis and will depend on their type and level of hearing loss as well as their particular needs. But if a child does need the support of a hearing aid then there are lots of options to think about:

Hearing aids

Conventional hearing aids work by amplifying (making louder) sounds going into the ear. Hearing aids come in a range of styles. Good-quality digital hearing aids are available free of charge for all children on the NHS. If there is some hearing in the poor ear then a hearing aid may help to balance the hearing in both ears.

CROS hearing aids

Children who have very little or no hearing in one ear may benefit from a special type of hearing aid known as a CROS aid. Although it is described as a hearing aid, a CROS aid does not amplify sound. It is simply designed to transfer sound from the ear with deafness to the ear with hearing. The main advantage of using a CROS aid is that it can help the child to hear sounds from all directions. A CROS aid includes two units which both look like ordinary behind the ear hearing aids. However, the unit worn on the ear with deafness just contains a microphone. It is connected to the other unit, sometimes with a lead and sometimes by a wireless radio link e.g. Unitron or Phonak.

Bone anchored hearing aids

A bone anchored hearing aid consists of a sound processor that clips on to a fixture, known as an ‘abutment’, attached to a small titanium screw that has been implanted in the skull just behind the ear. This allows sound to be conducted through the bone rather than through the ear canal and middle ear as it would normally. Through the abutment, the sound processor is directly connected to the skull bone, of which the cochlea (inner ear) is part. This allows sound to be transmitted more directly to the inner ear. The implant surgery cannot be done until the child has sufficient bone thickness and quality of the skull bone. In very young children, the skull bone may be too thin to firmly hold the fixture the sound processor attaches to. Younger children and children undergoing assessment before surgery are therefore offered a bone anchored hearing aid that is worn on a soft headband. Bone anchored hearing aids have recently been used for people who have unilateral hearing loss. The sound processor is worn on the poor hearing side and the sound vibrations will vibrate through the skull bone and be picked up by the cochlea on the better hearing side. This can help with understanding directionality of sound, as well as improving hearing of speech and other sounds that come from the poor side.

FM Systems

Children with unilateral hearing loss may benefit from using an FM system. FM systems help overcome problems of listening when

  • there is unwanted background noise;
  • sounds are echoing around the room (reverberation); and
  • there is a distance between the person who is speaking and the deaf child.

FM systems can be used with or without hearing aids. They consist of a transmitter, worn by a teacher, and either a receiver worn by your child or speakers. A system using a receiver (ear piece) worn by the child is known as the Phonak iSense. A system using speakers is known as a soundfield system. Both systems work by making the teacher’s voice clearer in relation to other unwanted noise. Children with unilateral deafness are likely to benefit from an FM system because it provides a consistent sound quality around the classroom enabling them to hear the teacher clearly in their good ear even if the teacher is moving around the classroom.

Classroom soundfield systems are increasingly popular and may already be fitted in your child’s classroom. They are designed to improve listening conditions for all children in the classroom as well as reducing vocal strain for the teacher.


So a child has been diagnosed with a unilateral hearing loss (often known as one-sided or single-sided deafness). Should you be concerned? After all the other ear hears completely normally doesn’t it?

Well yes, the hearing in the other ear is fine and this is great. It means that most children will hear well enough in their early years to make good progress in their speech and language development. However, there is a large body of evidence now that suggests that although not all, a significant proportion of children with unilateral hearing loss fall behind with language development, require additional educational assistance and suffer perceived behavioural issues in the classroom. Why might this be?

Well, the ears might be doing the hearing, but it’s our brains that are doing the listening. It’s the brain that identifies sounds by analyzing their pitch, loudness, and duration. It then searches for and maps this information onto existing stored information. When a match occurs, we understand what is being said, or we recognise sounds that have meaning to us, such as words or the telephone ringing. And basically our brains are ‘wired’ to hear sounds from both ears. Hearing with both ears is known as binaural hearing. When the brain receives sounds binaurally it is able to filter out a lot of unwanted background noise and concentrate just on what we want to listen to. It is also able to distinguish the direction and distance of where sounds have come from (localisation). Being able to filter out background noise is a skill we use a lot of the time because the majority of the speech we listen to is not in perfectly quiet situations. Being able to localise sound means we can tell which direction important sounds come from, whether this is being called by a friend when playing or hearing a car approaching. It is also important in being able to follow a conversation in groups. Binaural cues that the brain uses include the effect of ‘head shadow’ (where the head physically blocks some sound that comes from the affected side so that the good side hears it at a reduced level), and intra-aural level and timing differences (where the brain is able to perceive differences in location of sound based on which ear gave it the information quickest and loudest). So a child with unilateral deafness is likely to have problems listening in some situations because their ability to use binaural listening cues are reduced.

So the situations where a child with unilateral deafness will find it more difficult to hear well include:

  • hearing sounds or speech on the side with the deafness because of the ‘head shadow’ effect
  • identifying the source of a sound, the direction a sound is coming from, or judging the distance the sound is coming from
  • understanding speech when there is background noise.

Incidental learning is learning that takes place informally and is not taught in formal situations such as school. Children learn language incidentally through play and by hearing things going on around them. A child with unilateral deafness may not naturally overhear what people are saying or events that are happening. This means that a child may appear ‘out of it’, as though they don’t know what is happening or appear unconnected to their environment. Some children may need to be taught directly skills that other children learn incidentally.

Unilateral deafness may therefore cause or contribute to speech or language delay, and difficulties learning and reading. Unilateral deafness may impact on any co-existing conditions or additional needs. such as:

  • children with learning difficulties
  • children with speech or language disorders
  • children with attention deficit disorder
  • children who use English as a second language.

Additionally, children with unilateral deafness may be using more energy concentrating on listening, particularly in noisy environments, and as a result may experience problems in concentrating, tiredness and frustration that affects their behaviour. They may prefer to play alone and experience more difficulties than other children in reading and learning.

There are a couple of other things that are important to mention with unilateral hearing loss. Firstly that it is important to teach your child to take extra care when crossing the road because they can’t tell which direction a sound is coming from and older children/adults will have difficulty judging speed from the sound alone. Secondly, remember that the other ear is hearing well but may not always be if it is damaged by infection or noise. If a child has an ear infection they should be seen by their GP as soon as possible. And like all children, make sure they aren’t exposed to very loud sounds over long periods (for example at pop concerts or listening to music with headphones at high volumes). Provide ear protectors where appropriate, for example during noisy leisure activities such as motor racing.

Next time I’ll write something about the different styles of hearing aid that can be used to help children with unilateral hearing loss in “Hearing aids won’t help”.

References:

Lieu, J.E.C. (2004) Speech-Language and Educational Consequences of Unilateral Hearing Loss in Children, Arch Otolaryngol Head Neck Surg. 2004;130:524-530

Lieu, J.E.C., Tye-Murray, N., Karzon, R.K., Piccirillo, J.F. (2010) Unilateral hearing loss is associated with worse speech-language scores in children. Pediatrics. June 2010;125(6).

Most, T. (2004) The effects of degree and type of hearing loss on children’s performance in class, Deafness and Education International, 6(3), 2004.

Priwin, C., Jonsson, R., Magnusson, L., Hultcrantz, M., Granstrom, G. (2007) Audiological evaluation and self-assessed hearing problems with single-sided congenital external ear malformations and associated hearing loss, Int J of Audiology 2007; 46:162-171


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