Bone conduction hearing implant (BCHI) devices: An interview with Nicola Guderley

The Interacoustics Academy welcomed Nicola Guderley, Deputy Lead Audiologist / Lead for Implantable Acoustics Device Services at Great Ormond Street Hospital, London, to discuss bone conduction hearing implant (BCHI) devices.

The interview covers:

1. Hearing aids vs BCHIs
2. Which patients that can benefit from BCHIs
3. Criteria for BCHI implantation
4. Precursors to BCHI implantation
5. Important information when considering a BCHI implant
6. Likely patient outcomes with BCHI implantation

You can read the full transcript below.

Hearing aids vs BCHIs

So I think it's important to remember that the any decision is made with the family in conjunction with the audiologists with their medical professionals. It's not a unilateral decision. So everything is a discussion. And it's about thinking about what's most appropriate.

So, with any patient who has a conductive hearing loss, I would expect them to see a medical professional, at least, hopefully an ENT doctor if not an audiovestibular medic or audiovestibular physician, whatever you call them, and to offer them that as an option if it's appropriate.

So at least that's on the table for them to accept or reject. If they want the medical intervention, and that's appropriate for them, they can go down that path. If for any reason they can't have a medical or surgical intervention, they can consider aiding.

I would expect patients, who are able, to try an air conduction device before being referred or considering a BCHI (which stands for bone conduction hearing implant) because it's a non-surgical option, and it might do really well for them.

If a patient doesn't get on well with their air conduction hearing aid for any reason, or they are physically unable to trial an air conduction device, I would then start thinking about whether or not a BCHI is appropriate for that patient.

Once you get to that point, you then can then think about whether or not they meet the fitting criteria, or at least the referral criteria. So that would be: Do they have a permanent mixed or conductive hearing loss, that cannot be managed by an air conduction device?

Do they have a structural abnormality such as microtia or atresia which prevents them from having an air conduction device? Do they have recurrent ear infections? Do they have single sided deafness? And then you can start to think actually, if they meet those criteria, are they BCHI appropriate?

Which patients can benefit from BCHIs?

Yeah, absolutely. So there's definitely a vast array of syndromes which makes you sort of BCHI applicable. Most of our patients who have BCHI are microtia and atresia patients who have outer or middle ear abnormalities, structurally. Many of these conditions... ...an example of these conditions would be Goldenhar syndrome, hemifacial microsomia, CHARGE, Treacher Collins, Nager's. Many more.

And with these patients, they usually have some sort of outer ear abnormality which is preventing them from being able to wear an air conduction device. CHARGE is a really interesting one because these patients often have a mixed and conductive hearing loss mixed or conductive rather.

But then on the other side, they might also have eighth nerve hyperplasia, which means that they might be wearing a BAHA programmed to a mixed conductive hearing loss on one side, and then have a BAHA set to single sided deafness on the other side. Single sided deafness is another cohort of patients who would be suitable for BAHAs as well.

You have other interesting conditions that are much less common like ichthyosis, where the ear canal is patent, but they can't tolerate a BTE or air conduction device because the condition is a skin shedding condition that's all over their body, and that includes the ear canal. So they might have a lot of debris and skin cells in their ear canal, which prevents them from wearing an air conduction device.

Patients who have recurrent ear infections as well would be very suitable for BCHI.

Which patients are not suited for BCHIs?

Things that would steer me away from a bone conduction device or a bone conduction implant are patients who have fluctuating hearing loss to the point where their hearing thresholds either normal or near normal at some, in some stage in their in their progression.

That's because when you're offering a BCHI, you want to be sure that your patient is going to have a permanent hearing loss. So you're offering a soft band to a patient on the understanding that they are going to be or probably going to be implanted.

You don't want to implant a patient who's later going to have normal hearing and think well, I've now got this implant that I don't need.

Criteria for BCHI implantation

So when people refer in for a BCHI implant, I think they forget that there is more than one type of implant option available. They often refer in saying 'Please can this patient have a BAHA implant?' and that's not the end of the story. So each of the implants will have different criteria to fulfill.

The implants we offer here at GOSH are a percutaneous sort of abutment device, a magnet option, and then you also have the active implants and also middle ear implants, and they sort of all fall within our BCHI service.

So, audiologically, the criteria for those are slightly different. So, a patient could have bone conduction values up to around 55 for example, the Cochlear BAHA 6 Max the Oticon Ponto, or the Osseo, which is an active implant.

But for patients who have a greater degree of underlying hearing loss up to 65 dB, you've got the superpower devices from various companies. The middle ear implant that we offer at Great Ormond Street is the Vibrant Soundbridge from Med-el. And that one has...the fitting range is slightly greater, so from about 60 to 80, depending on what frequency you're looking at.

So when you refer in, a patient could have quite a broad range of bone conduction thresholds, and they might still be suitable for an implant. Really important though, those bone conduction thresholds should be stable. If you've got a patient who has deteriorating bone conduction thresholds, do you really want to be implanting with them with a device which later might become not suitable for them?

Also, patients with single sided deafness as well can be referred in but before they have surgery, it's really important to give them a trial of an air conduction CROS device. That is very much a trial though, and many of our patients decide they prefer the BCHI and will still go down that road. But I want them to trial a CROS aid for at least a few months, just to see how they get on with it, because that is a non-surgical option that then becomes available to them through that trial.

In terms of surgical considerations, the main consideration is bone quality and thickness. So that will be determined by a CT scan. Generally, you want the bone to be around or greater than three millimeters in thickness and have a sufficient quality that can support the implant.

This is generally around five years old but will vary from patient to patient. But because that's generally the age, that's roughly the age we'll say, Okay, you're coming up to five years old, we can make that referral.

Another really important surgical consideration is hygiene as well: Can the patient keep the implant site clean and maintain it? And that might influence the decision to what type of implant they get as well.

And also do they have the family support in place is really important, both from a medical perspective of maintaining their surgical site, but also will they carry on using their implant after they've been implanted? Do they have that support and structure in place to support usage?

Precursors to BCHI implantation

So there are many predefined areas that you need to consider does the patient fulfill and you assess those to determine if they are suitable to go down the surgical route because it's quite an important decision.

So first of all, you need to know their audiometric information, be that behaviorally or from the ABR, to determine if they meet criteria for an implant and also determining which type of implant they might receive.

Second is having a soft band trial on a BAHA type device to determine how much benefit they're getting from the device. For pediatrics, the trial might be a lot longer than you'd expect with an adult. So a lot of our patients will come in at a very young age and be on their soft band for years.

And they can have the option to be referred for surgical intervention at the age of five, but they might stay on their soft band for longer because they're not ready. So the trial can be years... we call it a trial, it's actually just soft band aiding, whereas an adult might only trial it for three months.

Another important element is usage. So you might have heard this referred to as data logging, where we count up the hours of usage to check that the child is actually using their device because you don't want to implant a child who is then not going to use this implant and just have an implant in their head. And it will differ from service to service. There's no standard in terms of usage. So, it is just to show a minimum level of usage that is acceptable for that department to proceed with implantation.

Another important aspect is verification of the device as well. So you would perform a hearing test through the device on the software and it's literally performed like an audiogram in the same way you would perform an audiogram to determine how much gain is required for that device to provide good benefit to the patient.

We look at those thresholds to determine is the patient getting sufficient benefit from this device? Do they need to try something more powerful? Do they need to think about a different type of implant?

Also really important is validation. So performing outcome measures such as speech testing and aided outcomes as aided thresholds as well, to determine is this patient getting sufficient benefit from the device that they currently have? Or do we need to think about implanting them with something different.

Aided thresholds are not typically used for, for example, hearing aid fittings, it's deemed outdated, but you now have REMs and those types of tests that you can do. But you don't have the equivalency with bone conduction devices. So we still utilize that to some extent.

Also, really important is thinking about do they have the family support in place, as I mentioned earlier, to support their journey with the implant. We know that if they have really good family support that outcomes are likely to be better.

Important information when considering a BCHI implant

As much information as possible. So I think our biggest battle with referrals is they are often very basic and say, "Please, can you consider this child for a BCHI?" And we have no other information. So in an ideal world, I would have audiometric information via from either an ABR or behavioral testing.

I would have a history of if they trialed any other hearing devices and what their usage was like with that. And a diagnosis information. Is this because of a structural abnormality, is it single sided deafness, is it ear infections? That would be the minimum information I would want.

In terms of nice extras, I would also want to know have their etiology been done. I would like to know the outcome of any scans... is there cochlear nerve hyperplasia, that kind of thing. Speech testing results, even if it's just unaided, that can be really useful.

In terms of as well, we'll sometimes get referrals for patients who just come for surgery. And for those patients, I would say that's the biggest battle because we've had a referral saying, "Please, can you implant this patient who already has a device with a soft band?", and we don't get any other information.

And we can't make the decision at the MDT unless we have all the prerequisite information. So in a referral for surgery only, I would like to see the audiogram, the verification, the validation, the usage, everything that we'd need to decide.

Likely patient outcomes with BCHI implantation

So outcomes for patients, post surgery, should be similar to or better than what they have had for their soft band device. They're best predictors of the outcomes are those that we look at the MDT. And that's exactly why we look at them at the MDT.

So that will be things like their usage, their audiogram, their verification and validation outcomes. So those are the best predictors for those patients’ outcomes.

Patients who don't do quite so well, there could be a number of reasons. It could be that their devices become infected, so a more surgical medical issue, and they need to have the device ex-planted. A lot of these patients might go on to be re-implanted with something else.

Another reason for poor outcomes is low usage, low compliance. And this is why we look at the usage pre implant and it's really, really important. And, but even so, even with looking at that beforehand, our patients grow up and they become teenagers.

And we face the same problems that all departments see with hearing aid patients that when you get to teenage years, the usage can drop off. And that's why I think it's really important to look at the family support as an indicator as well. Does the family think that their BAHA is essential you know, what their perspective and attitudes towards it and that is a really powerful indicator as well.