*** UPDATED*** What is Auditory Neuropathy Spectrum Disorder (ANSD)? *** UPDATED***
NOTE to PROFESSIONALS
As a wise lady once said: “Don’t forget underneath the puzzling science, there is a child and a family hoping for answers”
In my own words and, most importantly, those of a parent and layman (you may, like me, need to refer to the glossary page for clarification on some of the many acronyms):
Auditory Neuropathy Spectrum Disorder (ANSD) is a long-winded misnomer. It is the latest in a long line of long-winded misnomers which, thus far, takes the prize for being the longest and, in my opinion, the biggest misnomer.
I am sure there are plenty of experts out there rolling their eyes at me for saying this and I have, time and again, been reassured that given the ambiguities of the condition, it is the best name they can come up with at present (until the next one that is). The definition was coined at a conference 2008 where a consensus was reached on how to refer to the idiosyncratic symptoms which define the condition. Previously, patients have been given the diagnosis of hair-cell dys-synchrony, auditory neuropathy, auditory mismatch, auditory de-synchrony, neural hearing loss, per-synaptic hearing loss, AN/AD and a whole host of other names. They are all covered in ANSD.
Herein lies the crux of the problem – ANSD is not a condition per se – it is a description of an anomalous set of symptoms and test results which define this type of hearing loss apart from more common sensoneural or conductive hearing losses.
Children with near normal hearing and children with nerve issues are all lumped together under the umbrella, despite the very obvious differences in their ears.
So, ANSD – what does it mean? – it means that your child is not a ‘typical’ deaf child, your child could go on to hear and develop speech and language (regardless of what their testing tells you) or it could mean your child is like Alice or Oliver and can’t hear anything useful.
Make no mistake, a child with ANSD may be able to hear in windows, they may have good days and bad days, moments of hearing and moments of not. As a parent we missed Alice’s hearing disability because we thought she could hear. You are not mad, this condition is designed to confuse and confound. Equally, it is now understood that certain types of ANSD are temperature sensitive and can even get worse with a fever; frustrating does not explain it.
So, with some help from proper scientists (thank you so much to Kai from the University of Manchester) we are trying to put their words into words that parents can understand. We freely admit there will be holes in our explanation, feel free to comment, as we are learning, we are our own great science project. The experts are learning as much as we are, let’s try and help each other.
ANSD is diagnosed by a number of tests. We have described these tests in the glossary, but essentially, the diagnosis of ANSD is a time-consuming process, unless you know what you are looking for. Alice was diagnosed at 16 months, Oliver at 16 hours. Their results are the same, but that is the issue with being a well baby with an unusual hearing condition. But we digress. The table below summarises the various tests that can be performed on adults and children and a comment on how ANSD would show itself.
|‘Typical’ Hearing Loss Results||ANSD Results|
|OAE||Absent / Poor / reflects level of hearing loss||Usually present, can disappear over time (at the age of 4 Alice still had hers). Oliver has both. Essentially this demonstrates that the outer hair cells are behaving normally|
|VRA||Testing levels reflect patient’s hearing levels||Booth tests can be inconsistent and may not reflect patient’s ability to understand speech, especially in noise. Alice could test profound to moderate in the same session.|
|ABR||Reflects hearing loss||Absent or abnormal regardless of the audiogram|
|Cochlear microphonics||Reflects hearing loss||Usually present, Alice and Oliver both have beautiful CMs.|
|CAEP||Present / reflect hearing loss||Can be absent or present and not necessarily an indicator of level of loss, may reflect speech perception abilities|
This is the joy of ANSD.
In children with ANSD there can be normal OAEs, but completely absent or abnormal ABRs. In the UK, this means that ANSD is not picked up in the normal Universal Newborn Hearing Screen, for well babies. This suggests that the problem in transmitting sound from the ear to the brain lies either in the innermost workings of the ear itself or in an abnormality (or in rare cases complete absence) of the auditory nerves. Hence the name ANSD. But, and this is the crux of the issue from a management perspective, the TEST RESULTS WILL NOT REFLECT THE PATIENT’S ABILITY TO HEAR SPEECH . For whatever reason, you can present as a classic case of ANSD and go on to develop speech alongside hearing peers.
What seems to be consistent in ANSD patients is that they can ‘hear’ at certain levels (this may be moderate, profound etc.) but what they hear is largely distorted. I read somewhere that it is best described as like listening to a badly tuned radio. There is speech in there somewhere, but the white noise makes it very difficult to decipher. There is a simulation of this through the link at the bottom of this page.
Like many conditions, children (or adults) with ANSD sit somewhere on a normal distribution curve. Some have a reasonable grasp of speech and in situations where there isn’t too much background noise, can learn and use speech quite well. They may grow up in the mainstream without any assistance and, in some cases, go undetected. Some children (like Alice and Oliver) exist at the other end of the spectrum and have no useful sound and hence develop no speech or language – everything to them is distorted. The majority sit somewhere in between.
So as we have seen there are a number of tests within the audiologist’s kitbag which may enable them to say you have / your child has ANSD. We then run into the confusing world of definable causes and the actual site of the ‘lesion’. Whilst this is scientifically interesting and knowing the cause can help pinpoint the site, or knowing the site may help to understand the cause, arguably neither ultimately matters if getting the best out of your hearing is your aim. Most commonly:
- Hereditary conditions (Charcot Marie Tooth disease, Friedreich’s ataxia, general nervous system diseases)
- Acquired conditions (diabetes mellitus, HIV)
- Low birth weight
- Hyperbilirubinaemia (Jaundice or Kernicterus)
- Anoxia / hypoxia
- Specific genetic causes (Otoferlin, DFNB59)
- No specific causes (freak occurrence)
- Site of the Lesion:
- Inner Hair Cells
- Inner hair Cell Synapse to the afferent nerve fibers
- Auditory neurons in the spiral ganglion.
- Auditory Nerve
- Brain Stem Auditory Nuclei
- Any combination of the above
In as much as this makes any sense at all, this sounds to me like any number of different conditions, rather than just one and herein lies the problem. Audiologists can’t get a decent look inside to tell you definitively.
If you are very, very lucky, you will find out, for sure, the root cause of your child’s ANSD. If not, you are left with a best guess. Our working assumption with Alice, was ‘freak occurrence’, whilst it now seems clear, because of Oliver, that somewhere we have wonky genes.
Well babies with ANSD are rare. This is why in the UK only OAEs are performed as standard as part of the Universal Newborn Hearing Screening Programme. Oliver is almost unique in that he is a early diagnosed well baby in the UK. In a 2001 paper Sininger & Oba identified 25 babies with ANSD,the majority were not viewed as being at risk. We understand that the possibility of ANSD with a well baby is somewhere between 1:5700 and 1:500,000 depending on the research you read. For an at-risk baby the odds are higher (0.2%-4%). We always want to know how unlucky we were – someone cleverer than me can work it out, but in a 2008 study of the Spanish population showed that 4.4% of cases of isolated hearing loss were down to otoferlin.
So, in a manner of speaking, that is what ANSD is. So what can you do about it?
This is where ANSD converges with ‘typical’ deafness insomuch as the choices available to parents are limited to three things.
- Embrace your child’s deafness and the opportunities and challenges this will bring and immerse them in the deaf world using sign or lip-reading (or other non-sound-based modes of communication) as their primary tool to communicate with the rest of the world.
- Conventional hearing aids (of which there are various types which I have neither the inclination nor expertise to describe here). In ‘typical’ deaf children, simple amplification, so long as the loss isn’t too profound, can solve the problem. The evidence seems to suggest that some ANSD children benefit from hearing aids as it brings the spoken language to the audible range. Equally, in the classroom an FM system may be all that is required.
- Cochlear implantation. Evidence suggests that success with a CI in ANSD patients is in line with that of ‘typically’ deaf children, although it does seem to be those ANSD children at the profound end of the scale who benefit most.
Beyond these ‘interventions’ what is most important is giving your child access to language. Be that through signing or, as is often recommended for children with ANSD, Cued Speech, which helps clarify the spoken word, rather than replacing it.
How to make the decision which pathway you are on is the biggest issue facing families and professionals alike.
There are a couple of overriding issues that make the decisions for an ANSD child harder than for a ‘typically’ deaf child. Firstly there is, as we describe it, the mythical maturity issue. Then will an implant even work and the overriding parental requirement to do no harm. Surgery always brings risks The answer to any of these questions is ultimately to do what feels right for your family and to ask lots and lots of questions. However, some points we do feel are pertinent and should be put into everyone’s decision making.
- Maturation – This can happen (believe it or not – we recently heard the amazing news in our little world) – which is terrifying. However, things to bear in mind: it more likely to happen to prems or those with jaundice. Watch your child carefully for any changes and get good regular audiology and teacher of the deaf monitoring. Have one eye on the windows of cochlear implantation if you want to go oral.
- Will the implant work? Again this boils down to getting some good research. There are a number of research papers on the issue, that you can find on this site. Additionally, the age of the child when implanted has a big impact due to the elasticity of the brain. If you’re lucky, get additional testing. We considered it, but ultimately we realised that Alice had no speech, hearing aids weren’t working and it was essentially implant or visual language. We chose to implant, with our fingers firmly crossed. Fortunately our faith has been repaid.
- Do no harm. A cochlear implant is an astonishing piece of medical kit but the surgery, albeit relatively safe, is still surgery. Trial hearing aids, try an FM system, try everything and see if anything makes that difference. The key here is regular audiology, regular checks to see if they are keeping up with hearing peers if oral communication is your choice.
It’s not easy, the best things in life are sometimes hard-fought, but if you are well-informed and well supported by your therapists and audiologists, you will do the best for your child. This blog is just the starting point, do your own research, tell us where ours is bad (do try to be polite – we are trying our best) and hopefully the pool of knowledge will grow.
Some useful links: