Douglas L. Beck, AuD, speaks with Dr. Moncrieff about amblyaudia, auditory processing disorders, dichotic digits, and more.
Academy: Hi, Debbie, great to speak with you again!
Moncrieff: Hi, Doug. Thanks for the invitation.
Academy: My pleasure. Debbie, in our recent discussion you told me about the new diagnostic term you’ve created, amblyaudia. I thought it was very clever, so let’s start with that. What is it?
Moncrieff: Amblyaudia is the auditory equivalent of amblyopia, and as you know, amblyopia is a common visual problem in children, often referred to as “lazy eye.”
Academy: How does amblyaudia fit into audiology?
Moncrieff: Glad you asked! I’m starting to think about it as a new diagnostic category within auditory processing disorder (APD).
Academy: Please explain.
Moncrieff: Well, you and I and so many audiologists have gone around and around with regard to APD and in the final analysis, there are two primary areas of criticism for diagnosing APD. These criticisms are important as they have prevented us from moving forward.
The first primary area of criticism is that there’s no universally accepted definition of APD. APDs are heterogeneous and can be characterized by a number of weaknesses and failures across many auditory processes from speech-in-noise problems to temporal processing and difficulty in dichotic listening tests. The second major criticism is we all use behavioral tests that engage multiple processes such as linguistic and cognitive processes as well as attentional resources, all of which can impact APD evaluations.
Academy: Exactly! Evaluating APD while engaging secondary processes allows the APD evaluation to be corrupted or tainted by the multiple secondary processes. Of course, many tests and evaluation procedures use very simple words and numbers so as to have minimal language issues. However, when I think of the number seven versus the number one, or the number six versus four, they all have meanings that may or may not contaminate the APD evaluation.
Further, if I may…Although you mentioned the two major criticisms, a third might be that people in audiology, SLP, and education often use screening tools and they derive a diagnosis from them—which is totally nuts! And then, a fourth criticism is that we don’t have a standard pool of age-appropriate “normal” responses to compare individual APD scores to. Ferguson and Moore are actually taking the bull by the horns in the United Kingdom and gathering data across some 1,600 school-aged children with regard to their performance on a number of tests. This will help establish normative ranges and metrics, and from there, one can say, “Johnnie is performing within normal limits with regard to text ABC” or one might say, “Johnnie is two standard deviations below normal on this particular test.”
Moncrieff: Exactly. There is a lack of normative data for many of the APD tests that clinicians routinely use and this is a very significant problem. I agree, Ferguson and Moore are engaged in an excellent normative process. Their work is focused primarily on the temporal processing aspects of auditory disorders. They have chosen this important aspect of APD because it has been put forth as the underlying deficit for all kinds of APD.
Their work will be very beneficial for establishing the prevalence of temporal difficulties in children and will likely shed light on whether it is as fundamental a problem as has been proposed. I keep in touch with them and other colleagues in the Netherlands and Australia who have helped set the stage for moving forward with some aspects of APD.
Academy: I know you’ve done extensive work on APD with dichotic listening tests. So how does that fit into the discussion?
Moncrieff: Good question. Dichotic tasks with digits and words do involve language and cognitive and attentional resources. The primary deficit we see in children tested with dichotic tests is normal performance in their dominant ear (usually the right ear) with a larger than normal asymmetry evident when comparing the right to the left ear.
Academy: So in the case you described, the child serves as his/her own control, because the language and cognitive and attentional resources remain the same, but you’re evaluating how the left ear and how the right ear perform compared to each other, with everything else being held constant?
Moncrieff: Right. That’s the idea and we can only do that through dichotic listening tests because they’re the only tests that place the two ears in competition.
Academy: And which dichotic word tests do you use?
Moncrieff: It depends on the age of the child. I have used the SCAN subtest called Competing Words as a screener. For diagnostic purposes, I add a Double Dichotic Digits test or I use the Randomized Dichotic Digits Test, which is more challenging because the Double Dichotic Digits test has ceiling effects fairly early in development. I also use a new dichotic words test, which I created, and lastly I use the Dichotic CV Test from Kenneth Hugdahl.
Academy: And so the beauty of dichotic listening tests is they eliminate these same secondary issues?
Moncrieff: Yes. If the dominant ear performs well, you’ve eliminated language and attention and cognition from the equation, because if these secondary factors were compromising the test, they would do so for both ears.
Academy: And I should mention this approach appears to be well founded for children and adults with normal brain anatomy and physiology. However, if the person being tested is an adult, and he or she has a brain injury such as a stroke or trauma, depending on which structures have been impacted and the magnitude of the impact, the response could be compromised.
Moncrieff: Right, I agree. But if we limit the discussion to children without neurologic insult, I think we’re on solid ground.
Academy: I agree. So, by comparing the performance of the two ears, while holding all other secondary factors fixed, we can look at how the child performs with regard to left ear versus right ear processing.
Moncrieff: Yes. That’s exactly right. So then, for children with this specific type of APD, when the two ears are competing, the non-dominant ear can’t keep up, and this indicates that one side of the auditory pathway has a problem. It could indicate an ascending pathway problem, or it could be an inter-hemispheric transfer issue.
Academy: Very interesting, Debbie. So it could be an issue as the signal from the non-dominant side goes through the lower brain stem, or it could be the anterior commissure or the corpus callosum?
Moncrieff: Yes, all of those are possible, but I’m getting more interested in the possibility of deficits in the left-sided thalamo-cortical pathway and upper level processing.
Academy: Okay, well, we can explore that at another time as we’re running out of time, but am I correct that the children identified via the dichotic auditory tests you’ve discussed are the “lazy ear” or “amblyaudia” kiddos?
Moncrieff: Right. That’s exactly the point, and it can only be seen when the two sides are in competition, much like the visual correlate, amblyopia. Most importantly, you cannot see amblyaudia when testing one ear at a time. When competing input comes in through both pathways at the same time, the dominant pathway in children with amblyaudia takes a “winner takes all approach.”
Academy: Okay, and so the circle is complete and we’ve come back to amblyaudia. I know we’re out of time, but let me just ask one last question: So if I wanted to look for amblyaudia in a child using speech-in-noise tests, I would have to place the speech in one ear and the noise in the other? In other words, I could not test speech-in-noise in the left ear and compare that to the right ear?
Moncrieff: I don’t have an answer to that question because I haven’t specifically tested children with amblyaudia in that way. It’s likely that children with amblyaudia will have greater than normal difficulties during speech-in-noise tasks, especially when there are different signals in the two ears, but that’s for another study!
Academy: Okay, and perhaps next time we’ll discuss the specifics relating to speech-in-noise tests for amblyaudia, too. Thanks, Debbie…fascinating work!
Moncrieff: My pleasure. Thank you, too, Doug.
Debbie Moncrieff, PhD, is an assistant professor of audiology at the University of Pittsburgh.
Douglas L. Beck, AuD, Board Certified in Audiology, is the Web content editor for the American Academy of Audiology.