Listening devices

• Listening devices and UHL - the evidence
• Options for intervention
• Unaided children
• Wearable devices - hearing aids, remote microphone and FM systems
• Implantable devices - bone anchored devices, middle ear implants and cochlear implants
• Whole room devices - sound field systems

There are a number of listening devices, which may enhance your child’s listening experience. These include hearing aids, Remote Microphone or FM systems, implantable devices and sound field amplification systems.

Listening devices may provide listening benefits but they will not ‘fix’ your child’s hearing loss. Even when UHL is identified at an early age and treatment in terms of device fitting is offered, it is important to remember that the difficulties arising from the presence of UHL cannot be compensated for entirely by fitting of personal hearing devices.  The use of these devices enables sounds on the affected side to be audible, but does not restore normal hearing to the affected ear. 

Listening devices and UHL – the evidence

There is currently no high-quality evidence on how best to manage unilateral hearing loss in children.¹⁴

Hearing loss and brain development 
In recent years, we have learnt a lot about the development of the human brain and there is evidence about the importance of building good neurological pathways in the early months and years.

There is also evidence that most babies with hearing loss in both ears (bilateral hearing loss) who are diagnosed early and provided with hearing aids and good early intervention will develop age-appropriate language skills by the time they start school.¹⁵

It seems logical that doing the same for babies with UHL would support the development of their binaural neurological pathway. However, high-quality scientific evidence is lacking to guide clinical decisions on the management of unilateral hearing loss in children. 

How effective is amplification? 
Some studies have looked at the effectiveness of amplification in mild and unilateral hearing loss and show that the use and benefit of amplification varies amongst individuals.¹⁶ 

Device benefit cannot be predicted by the degree of hearing loss, age or gender. No study shows consistently high success rates of amplification.^17,18

One small study at Children's Hospital of Philadelphia concluded that it was worth trialling a hearing aid with children who had a unilateral hearing loss.  The study found that approximately 65% of the client group aged 2-17 liked or loved their hearing aids. Hearing loss in the impaired ear ranged from mild to moderately severe. While many clients showed an improvement in listening related tasks there was more variability as to whether the children also benefitted from the aid in psychosocial areas such as confidence, general disposition and frustration level.¹⁹ 

Another study on mild and unilateral hearing loss in children found that 26% of children with a unilateral hearing loss wore their hearing aid all the time while 50% of the children never wore their aid. ²⁰ 

An Australian study found the success of hearing aids may be linked to parents’ and teachers’ estimates of the difficulty caused by the child’s hearing loss and parental attitude towards hearing loss and hearing aids.¹⁷

CROS aids have been reported to be more successful if there is some slight degree of loss in the better hearing ear.²¹

A survey of teenagers and young adults by Australian Hearing in 2006 included data from 472 clients with normal hearing or a mild hearing loss in the better ear.  These clients showed much greater variability in aid use, aid benefit and satisfaction with their device than clients with greater degrees of hearing loss.

• 21% of these clients did not wear their device at all
• 33% wore it for less than an hour per day 
• 21.5% of these clients indicated that the main reason for not wearing their aid/s was that they either didn’t need help with their hearing or that the hearing aid/s did not help them.²²

Careful monitoring of personal FM fittings is also required to ensure that optimal use continues with time. A study by Australian Hearing found that use of personal FM systems decreases over time. Only 50% were still being used 12-18 months after being provided.²³

Language development 
Recent research on an Australian population of children with bilateral hearing loss revealed that maternal education, degree of hearing loss and cognitive ability were significant predictors of early language development.²⁴ The evidence on effectiveness of early amplification for early language development of children with UHL is lacking.  

Children with UHL have normal hearing in their better ear.  Many of them develop normal speech and language and perform well in preschool settings. By school age, current literature suggests that approximately 25% of them may experience academic difficulties in formal schooling and require support services.²⁵  

The effect of age of fitting on language development of children with hearing loss in both ears suggests that deferring device fitting from 6 months to 24 months of age is estimated to reduce standardised language scores by only 1.1 points for a child with 30 dB hearing loss; and 4.6 points for a child with 50 dB HL in the better ear.²⁶  

As an example, if a child who has 30 dB hearing loss in their better ear and was fitted with hearing aids at 24 months of age obtained a score of 89 in a language assessment, that same child is estimated to have obtained a score of 90 had the hearing aids been fitted at 6 months of age. 

As children with unilateral hearing loss have hearing within the normal range in their better ear, the research suggests that for most children with unilateral hearing loss, delaying hearing aid fitting from 6 months to 2 years is not expected to result in a significant delay in language development. 

Knowing early about the presence of hearing loss may create time for the family to get used to things, make plans, prepare for work ahead, and know their child has a hearing loss in one ear right from the start.²⁷

In light of the limited scientific evidence available, the Clinical Practice Guidelines, published by the American Academy of Audiology Task Force on Pediatric Amplification in 2013, have made the following recommendations/statements: 

• For a child with unilateral deafness, an FM system with the wireless remote microphone receiver coupled to the open, good ear may be preferable to a CROS configuration in classroom situations. 
• Use of a bone conducted signal may be considered an option with children who have unilateral hearing loss. ²⁸

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Options for intervention

The following table summarises available options that may be suitable for your child.  There is currently a lack of high-quality evidence to guide best practice management of children with unilateral hearing loss.  Therefore, the audiologist at Australian Hearing will provide you with information on possible technology solutions for your baby, consider your child's listening needs and difficulties, and guide and support you in whatever decision you make about fitting.

Table:  Summary of management options for children with unilateral hearing loss

* The applicability of Remote Microphone/FM and sound field systems will vary depending upon the child’s lifestyle and pre-school setting.  Sound Field systems are most useful for activities that involve group instruction and are likely to have greater benefits in school settings.

If you decide against a hearing aid now, you can always review your child’s needs with Australian Hearing in the future. And vice versa: you may decide to trial a hearing aid but feel there are no noticeable advantages for your child, and discontinue its use.  Keep in mind that you can revisit options in the future as the listening demands of your child changes with age or type or degree of hearing loss.

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UNAIDED CHILDREN

If you decide against fitting a device, your child with unilateral hearing loss will be reviewed by Australian Hearing at around 10 months of age, around 4 years of age and again prior to starting high school. Functional tests can be undertaken to determine if the hearing loss is affecting your child's listening in everyday situations and whether any listening device may be of some benefit. 

It is recommended that you -

• Have your child’s hearing tested once a year – talk to your Australian Hearing audiologist about your options.
• Monitor your child’s language and other developmental milestones and seek advice from your GP if you are concerned.
• Create a language rich home environment – talking, singing, reading
• Create a good listening environment at home – quiet spaces and times where background noise is minimal
• Contact Australian Hearing if you are concerned that your child is experiencing listening difficulties in everyday situations. 

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WEARABLE DEVICES

Hearing aids

Hearing aids amplify sound but they do not provide perfect hearing.  A hearing aid may be helpful in the ear with the hearing loss.

Hearing aids today are digital. They can be adjusted by an audiologist using custom software to: 

• set a specific amount of amplification at each frequency to suit the hearing level of the user
• control feedback
• reduce potential discomfort arising from amplifying loud noises and
• suppress background noises.

In Australia, children with a permanent hearing loss who use a hearing aid receive free audiological care through Australian Hearing which is funded by the Australian Government. 

Types of hearing aids
There are broadly three types of hearing aids available for children with UHL.

• Air Conduction hearing aids
  Air conduction aids send amplified sound into the ear canal via an ear mould.  There are two styles available, only one of which is suitable for infants.
  • Behind-the-ear hearing aid (BTE)
    This aid fits behind the ear and is attached to an ear mould which sits in the ear canal and transmits sound from the hearing aid into the ear. This hearing aid will provide greatest benefit to children with a moderate to severe unilateral hearing loss. It is fully subsidised and available from Hearing Australia. These hearing aids can also be used with an FM system at school.
  • Custom Aids, such as “In-the-Ear (ITE), In-the-Canal (ITC) or Completely-in-the-Canal (CIC) aids 
    For these types of hearing aid, the sound amplifier sits into a customised shell that is made to fit the child’s ear canal. These aids are not suitable for infants, but are an option for children in primary school and above, when the growth of the ear canal has slowed and the child is not at risk of swallowing the aid or batteries.  Custom aids are available fully subsidised from Hearing Australia and many can be used with an FM system at school.
     
• CROS (Contralateral Routing of Sound) hearing aids
  CROS aids have two parts and look like conventional hearing aids. A microphone in the hearing aid on the deaf side transmits sound to the hearing aid in the hearing ear. The CROS aid can be beneficial when speech is on the deaf side.  CROS aids are fully subsidised and available through Hearing Australia.
   
• Bone conduction hearing aid
  In certain circumstances, a child cannot wear or benefit from the use of a behind-the-ear hearing aid. This includes children with a profound hearing loss (also called single-sided deafness) and those with microtia and atresia. Bone conduction hearing aids transmit sound through the bone of the skull directly to the cochlea, bypassing the outer and middle ear. Bone conduction is not as efficient as hearing through the air but it is an alternative for children who cannot use a traditional hearing aid. A number of bone conduction hearing aids are available but not all are fully subsidised by Hearing Australia.

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How much do hearing aids cost?

The cost depends on the type of hearing device and whether it is available through Hearing Australia or not.

• Some hearing aids and wireless technology such as FM systems are fully government-subsidised and are provided at no cost to children under 26 years of age through Hearing Australia.
• Some hearing aids have more features or improved technology and, while they are available through Hearing Australia, you will need to contribute to the cost of the device. 
• Some hearing aids are not available through Hearing Australia and parents will need to organise their purchase independently. Technology is changing rapidly and the list of available aids through Australian Hearing does change so it is always worth checking with your audiologist at Hearing Australia first.
• Hearing Australia currently covers the cost of maintenance of the hearing devices used by children with UHL.

What to expect from a hearing aid

Because babies with a UHL have normal hearing in one ear and are most likely responding to a wide variety of sounds, it can be difficult to observe changes related to hearing aid fitting.  Depending upon the degree of unilateral hearing loss the most obvious change is likely to be an improvement in the baby’s ability to correctly identify the source of a sound. Remember, though that the responses of very young babies are subtle, even with normal hearing in both ears.

The responses of older children are also varied. Children diagnosed with unilateral hearing loss when they are older are not always compliant with hearing aid use. Their brain may need time to adapt to the new sounds and you may need to show some patience and perseverance with them. Encourage them to use the hearing aid at home first, in a quiet environment, and build up the amount of time they wear the hearing aid. Wearing the hearing aid when watching television is often a good place to start.

Older children also tend to worry about the cosmetic appeal of the hearing aid. Your response to the hearing aid will impact on how your child feels about wearing it. If you fuss about hiding the hearing aid with their hair, or remove it for photos or special occasions, you may be giving them the message that the hearing aid is something they should hide and this can result in an unwillingness to wear it.
The most successful hearing aid users understand why they need a hearing aid and are able to tell other people about their hearing loss. Teach your child to confidently explain why they need a hearing aid. 

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Babies and hearing aids

If you decide on a hearing aid for your baby, the two main challenges are:

• stopping it whistling, and
• keeping it on!

Ear moulds sit in the ear canal and transmit sound from the hearing aid into the ear canal. When ear moulds are loose, they cause the hearing aid to whistle which is uncomfortable for everybody. Babies' ear canals grow quickly and the ear moulds will need to be replaced frequently in the early months. This involves the audiologist taking an impression of the ear canal and sending this off to the ear mould manufacturers. The ear mould will take a couple of weeks to be made and can be posted to you which is usually more convenient. The ear mould comes with longer tubing than is necessary and you will need to carefully trim the tubing to the right length for your baby. Ask the audiologist to show you how to do this the first time. Rubbing some ear mould lubricant (available from Australian Hearing) around the mould may also stop the whistling. The lubricant creates a better seal and reduces the amount of feedback which causes the whistling.

The second challenge is keeping the hearing aid on as the baby grows. They tend to pull them out and this can be frustrating, particularly when you are not around to see where it has disappeared. Babies tend also to put the aids in their mouths. The hearing aids have small batteries and although the battery case door is tamper-proof, it is best to avoid the possibility of your baby accidentally swallowing a battery or an ear mould.

There are a couple of solutions here and the most popular one with mums appears to be using pilot caps on the baby for a time. They are made from soft fabric and fit snugly over the ears and tie under the chin. These make it more difficult for a young child to pull off the hearing aid. They can be purchased at a number of the early intervention services. The baby soon grows out of this phase and it is worth persisting if you have decided on using a hearing aid.

Remote Microphone and FM systems

Wireless technology such as personal FM systems is improving rapidly with the widespread use of smartphones and other mobile digital devices. Wireless technologies help to eliminate the difficulties caused by background noise, distance and acoustics and are particularly helpful in the classroom. This is the most effective listening device for children with UHL in the classroom. An FM or other wireless system provides the best available access to the teacher's voice.

A wireless system consists of a transmitter and a receiver. In the classroom situation, the teacher wears a small lapel microphone which is attached to the transmitter. The transmitter sends the sound via a wireless connection to the receiver, which is usually attached to the hearing aid.

If a child does not wear a hearing aid, there are other wireless options available through Hearing Australia. Some are fully subsidised and others require a contribution from the family. Maintenance for all devices is covered by Hearing Australia.

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IMPLANTABLE DEVICES

Implantable devices may be a solution for a child with total deafness in one ear, or children who are unable to wear other hearing devices. These devices all have an implanted part and an external sound processor which is worn much like a hearing aid. 

Implantable devices require surgery and there are a number of regulatory and surgical guidelines which specify a minimum age for undertaking various types of implant surgery.  The minimum age varies according to the type of device. 

The cost of the surgery and the device may be refundable under some private health funds.  Some sound processors for implantable devices other than cochlear implants are provided fully subsidised through Hearing Australia for children who meet clinical candidacy criteria.  Hearing Australia covers the cost of maintenance of implantable devices used with UHL at their centres for both fully subsidised and privately purchased devices.

Implantable devices can be broadly categorised into three types:

• Bone anchored devices transmit the sound through the bones of the skull to one or both cochleas. Different devices have different ways of attaching the sound processor to the implant in the skull.
  • Bone anchored device with an abutment that protrudes slightly from the skull. The sound processor attaches to the abutment. 
  • Bone anchored device where the implant sits under the skin of the skull. The processor attaches to the implant by magnet.
• Middle ear implants deliver sound to the cochlea on the side of the implant using mechanical vibrations. The implanted device sits under the skin. 
• Cochlear implants provide the sensation of hearing by directly stimulating the auditory nerve using electrical signals.  The internal receiver is implanted surgically. 

There is limited scientific evidence for the benefits or otherwise of implantable devices in children with UHL. Most studies have been done on adults and often on those who have lost their hearing later in life. Some studies report improvement in speech perception in noise and sound localisation while others find less consistent results.^29-34 

Due to the paucity of scientific evidence, the decision to implant remains a very individual one for each family.  To implant or not will be a big decision for your family and it must be one that is right for you and your child.  The section  “Making informed choices” may help as you look at the options and work through what will be best for your child in the long-term. 

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WHOLE ROOM SYSTEMS 

Sound field amplification systems
Sound field amplification systems are an option for children when they start school. A large part of the school day is spent listening. Children listen differently to adults. They lack the experience and knowledge to interpret what is being said in a noisy environment. Children need a quieter environment and a louder signal-to-noise ratio than adults in order to learn. The better a child can hear, the more he will learn.

The goal of sound field amplification is for every child in the classroom to hear the teacher's voice, no matter where they are sitting and where the teacher is facing. Sound field amplification systems overcome adverse classroom conditions, such as poor acoustics and high ambient noise levels and make it easier for all children to hear the teacher. The advantage of a sound field system is that individual children are not singled out as requiring assistance.

Several sound field systems are available using different technologies. However, all increase the signal-to-noise ratio in the classroom and consist of a transmitter microphone, receiver/amplifier and speakers. The systems with four speakers mounted around the classroom will provide the best quality sound. There are also portable devices, which are less costly, and parents and teachers report good results.

If your child uses a personal FM system, then using a sound field system as well provides little or no additional benefit.  If the personal FM system will be used in a class that also uses a sound field system, talk to your audiologist about the best way to combine use of the two technologies so that your child can continue to get the full benefit of their personal device.

Funding for sound field systems
There are a variety of options for funding of sound field systems:

• The school may fund the sound field system for the classroom - discuss this option with the school principal.
• Some parents have chosen to purchase a portable system for their child's classroom.
• Lions Hearing Dogs supply a limited number of sound field systems to primary schools each year. The application form is available at http://www.hearingdogs.asn.au/about-us/school-sounds-system

Last but not least, remember that whatever decision you make about the management of your child’s unilateral hearing loss, every child will benefit from living in a home environment that promotes a love of language and learning.

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