How to Diagnose Mild to Moderate Hearing Loss in Children

In this short course excerpt, you will learn how to efficiently diagnose mild to moderate hearing losses in pediatric cases. The course is presented by Jack Bennett, International Clinical Trainer at the Interacoustics Academy. It features Constantina Georga from The Royal Berkshire Hospital who discusses how she uses ASSR in her clinic.

You can read the full transcript below.

Classification of hearing loss

Jack Bennett: In this next section, we will discuss how we can efficiently diagnose mild to moderate hearing losses. Generally, in the literature, hearing losses are classified in this way:

• Mild hearing losses are seen as 21 to 40 dB HL
• Moderate hearing losses are 41 to 70 dB HL

Generally, this will be a pure tone average of 0.5 kilohertz, 1 kilohertz, 2 kilohertz, and 4 kilohertz. However, of course, configurations of hearing loss like this, which are normal at 0.5 five kilohertz and 1 kilohertz wouldn't be described as mild to moderate using the classification we've just described.

So, often, the literature will also include air conduction thresholds greater than 25 dB HL at two or more frequencies above two kilohertz. Brief inspection of this audiogram may lead some people to describe this hearing loss as insignificant or not important for the normal development of speech.

However, if we consider the SII of an ISTS signal presented at 65 decibels, the SII will only be 76% for that particular hearing loss compared to normal hearing where the SII would be at or approaching 100%.

Delayed confirmation of hearing impairment

You may now agree with me that that hearing loss that we've looked at, will actually pose a significant impact on a child's speech development. In the previous presentation, we looked at this study from the British Medical Journal. In it, we looked at the fact that the prevalence of hearing loss mild to moderate hearing loss appears to increase as age increases.

In the paper, they state some children acquire impairment postnatally, impairments that are acquired as distinct from progressive or of late onset account for 4 to 9% of overall prevalence and 7% in the present study, thus, they explain only a small proportion of the rise.

That is to say hearing losses that are acquired or progress do not adequately explain the increase in prevalence as age increases. In this paper, they also say confirmation of impairment is delayed in some children.

This paper was published in 2001. This was immediately before the newborn hearing screening program was implemented nationally in the UK. At the time, newborn screening programs varied across the country. And diagnostic testing also varied.

It can be argued that a hearing loss like this would be missed in a healthcare system that has a newborn hearing screening program that is not sensitive enough to pick up this hearing loss or diagnostic practices that would miss a hearing loss like this. That is to say if they were not using frequency specific ABRs or ASSRs, to diagnose the hearing loss.

Click stimulus vs CE-Chirp

If we use a click stimulus for ASSR or ABR testing, all or much of the basilar membrane is stimulated when we present the stimulus. This means a hearing loss like this may actually mask the presence of a hearing loss as the low frequencies would be significantly represented in the trace that's analyzed. The high frequency component of the hearing loss would be missed if using a click stimulus.

Therefore, there are also frequency specific stimuli for this kind of testing. Shown here is the narrowband CE-chirp. Where stimuli at key frequencies are presented in a tight enough band to show frequency specific information but allowing enough neural stimulation to be adequately represented on an ABR trace or an ASSR recording.

The Eclipse ASSR system uses the narrowband CE-chirp as its primary stimulus.

I'd now like to introduce you to Constantina Georga, a Clinical Scientist at the Royal Berkshire NHS Foundation Trust in the UK. She's going to use a recent case of hers to illustrate how she uses narrowband CE-Chirps and ASSR testing in her clinical practice.

ASSR case study

So the first case is a baby that were referred from the newborn hearing screening program. They failed both on automated otoacoustic omissions and automated ABR. They were born at 42 weeks of gestation. We saw them a on two occasions at three weeks and at five weeks.

We first tested with ABR for 4 kilohertz and 1 kilohertz on both sides. And then on the second occasion, we went on to carry out ASSR testing. The results, as you can see, show asymmetric hearing loss, mild on the right and moderate on the left.

The ABR results are shown in red and blue respectively, for the right and left, whereas the ASSR results are shown with black dots for the right and an "X" symbol for the left. What that shows is that both ABR and ASSR results agree within 10 dB.

Why did you choose to perform ASSR at the second appointment?

So on the first appointment, obviously, we picked up what looked like a permanent hearing loss. I should add that we carried out bone conduction testing. So testing for air conduction for two frequencies and bone conduction takes a long time. So that was more than enough on the first occasion.

And then on the second occasion, when we were actually thinking of fitting hearing aids, we needed more information and more frequencies to set up the hearing aids.

So ASSR helps you fill in the gaps around the ABR results?

Absolutely, and also to confirm because we'd like to have on permanent hearing loss and we'd like to have results from two on two separate occasions and showing a permanent hearing loss just to rule out an equipment fault for example.

Yeah, so routinely, we carry out a ASSR on all our permanent hearing losses once a hearing loss has been categorized. And then we would employ we don't necessarily need to obtain two frequencies. If a hearing loss has been categorized even with one frequency in each ear and bone conduction has been completed, then we can move to ASSR testing.

Has using ASSR reduced your testing time?

I don't have any data from local audits that we've done, but from my experience, I would say that yes this points that we regularly complete the assessments in two appointments.

Does using ASSR mean you have more time for other lings, like counseling?

Yes, in actual fact, because with once we finish the ASSR we would want to go through all the results with a family, and then we either do it on the second appointment or if there is not enough time we would book a separate appointment just to give parents the chance to for the news to settle in for them to formulate their questions and to go through all the questions and the results with them.

In this case, was CMV suspected or confirmed at this stage?

Currently, we arrange CMV locally we arranged CMV testing at the point of the referral rather than at the point of having confirmed a hearing loss. There is a bit of variability across the country. But it's well aware that it's very difficult to catch those babies with sensorineural hearing loss. And get the results before they're four weeks.

The four weeks is the cutoff for quite a few departments. The cutoff time for offering treatment. And it's an issue where we've struggled and a lot of different departments are struggling, especially as baby sometimes are referred to us when they're older.

Do you then use ASSR to monitor the progression of hearing loss?

Definitely, with CMV, yes. And we're routinely doing that because we monitor every three to six months. And obviously, as the child grows up, their sleep patterns change, and they sleep less. And we don't know how much time we're going to have.

ASSR is the first point of test when we're monitoring for any signs of progression. And definitely we've had quite a few cases of progression associated with CMV. And we were able to identify them on the first appointment and obviously book another appointment if further testing was required for the CMV cases.

Is that what's the advantage of ASSR is that is the binaural testing. So when there is a progression, you don't know which side is going to affect to what degree or what frequencies are going to be affected. So basically, you have a blank canvas, you don't know what's happening.

So being able to test both ears, for all frequencies is a bonus because you can, you can pick up a problem much faster than going one frequency at a time and one year at a time. You're thinking, Okay, this is where I need to focus on what's going on here.

Whereas with the ABR, it's because it's serial, then it's a matter of chance which side you've started with, that's the side that's been affected or not.