Perspectives on Neuroaudiology: An Interview with Frank Musiek, PhD
Interview with Frank Musiek, PhD
Director of Auditory Research
University of Connecticut
By: Douglas L. Beck, AuD
Board Certified in Audiology
Web Content Editor
American Academy of Audiology
Academy/Beck: Hi, Frank. Thanks for meeting with me today.
Musiek: Hi,Doug. Thanks for the invitation.
Academy/Beck: Frank, please define “neuroaudiology.”
Musiek: Neuroaudiology is the study and clinical activity related to the diagnosis and treatment of disorders of the auditory nervous system. Neuroaudiology focuses on the auditory nerve and the central auditory nervous system and disorders that impact hearing related to these structures. It is key to understand that neuroaudiology embraces the auditory neurosciences.
As you know, Doug, neuroaudiology is not an official or recognized term, although it has a lot to do with audiology. It is an emerging area of study that is gaining some traction nationally and internationally. Clinically, neuroaudiology may involve other professionals, too, not just audiologists—but neurologists, neuroscientists, and others.
Academy/Beck: Frank, I recall about 15 years ago you had published a book, titled Neuroaudiology, that really caught my eye as I was doing a great deal of neurophysiology at that time.
Musiek: Right. That book was published in 1994. It was titled Neuroaudiology:Case Studies and it was authored by Jane Baran, Marilyn Pinheiro, and myself. That book is a good profile of the kinds of cases germane to meuroaudiology.
Academy/Beck: I remember reading and referring to that book quite a bit. It was very straightforward, using a case-by-case presentation style—sort of like a grand rounds—to explore hearing loss and related issues involving neurological and CNS etiologies and systems.
Musiek: Yes, it was an exciting project. Marilyn Pinheiro, who has since passed away, was my mentor. She was a very well-respected neuroscientist with a great clinical background. She used to say there was a large area of study related to how the central auditory system functions, beyond the periphery. I was fortunate because in the 1980s and 1990s, while at Dartmouth, we did a lot of work focusing on the brain and disorders related to the brain which affected hearing.
Academy/Beck: And that also got you involved with central auditory processing?
Musiek: Yes, in some respects, it did. In the early 1990s, I thought we needed to make a statement because some professionals working with pediatric populations and central tests were looking only at children with learning difficulties. I believed it was important to evaluate the full range of clinical populations that may present with neurological involvement and hearing difficulties. These kinds of cases are not only intriguing but extremely informative. So while at Dartmouth, as we focused on the brain as audiologists, that provided much of the inspiration for that book.
Academy/Beck: Okay, very good. And going back to the professionals involved in neuroaudiology, what about training and preparation for neuroaudiology?
Musiek: Well, that’s a discussion that would take an awfully long time. In some schools, we have excellent neuroaudiology training and in some schools, we don’t. Some audiologists are not trained regarding the central auditory nervous system. So we’re hot and cold, because it depends on where one went to school, the interests of the faculty at that time, and their particular areas of expertise. The bottom line is we need to do a better job defining and teaching neuroaudiology in our educational programs, to assure the highest quality outcomes. For instance, graduate courses in human neuroanatomy and neurophysiology, as well as pathophysiology of the CNS, electrophysiology, and psychoacoustics are also core ingredients for a solid neuroaudiology curriculum.
Academy/Beck: Very good. In my master’s program (25 years ago) we did a lot of work related to human brains and auditory processing. I didn’t realize until a year or two later how different my experience was from some of my colleagues with regard to brain anatomy, auditory processing, and other related issues.
Musiek: Yes, that’s the point, and something we’ll need to continue to focus on, as a profession. Of course we’ve got far better standards in place now, but we’re still evolving as a profession. Admittedly, it’s a challenge for the profession and for the educational programs. Nonetheless, diagnostic audiology needs a shot in the arm! Neuroaudiology could be that shot in the arm if we can get more audiologists interested in this area and get them trained appropriately. It seems to me students would be interested in disorders of the brain and how they impact various aspects of hearing and hearing rehabilitation.
Academy/Beck: Frank, what’s the Web site address for people that want to learn more about neuroaudiology?
Academy/Beck: Okay, if I may, I’d like to change the focus here a bit and get your perspectives on a few different topics related to a complete analysis of the central auditory nervous system. What can you tell me about the middle latency response (MLR) and its clinical application?
Musiek: MLR is probably the second most popular evoked potential (EP). Of course, ABR is the most common, but ABR only tells us about auditory pathways up to and including the pons. However, we need to know what happens further up the system. For example if information is needed regarding the neural integrity of the thalamo-cortical pathway, MLR may be able to provide that insight. The MLR has quite a “track record” but unfortunately has not been utilized as much as it should be.
Academy/Beck: What about P300?
Musiek: Well, P300 does deserve more study. Psychologists use this potential far more than we do. P300 tells us about exogenous and endogenous function and we really have not yet learned how to maximally use it in audiology. P300 has been shown to have some value in research with aging and Alzheimer’s. With more focus on clinical trials and research, P300 could become a powerful clinical tool for audiologists. There have already been some interesting papers on P300 and (C)APD.
Academy/Beck: It sounds to me like P300 and mis-matched negativity (MMN) are at about the same level of development with regard to their clinical application?
Musiek: Yes, that’s probably a fair statement. MMN got a lot of publicity a few years ago, but as it turns out, MMN may not be a very good clinical tool—in my opinion. It’s harder to consistently obtain the MMN than the P300 and at times the MMN can’t be recorded in the normal population. So with respect to applicability, MLR is likely the tool of choice. There are some electrophysiologic procedures such as Biomap and EPs in noise that are beginning to emerge and they might enhance this area.
Academy/Beck: What about the dichotic digits test? What are your current thoughts?
Musiek: Well, the dichotic digits test (DDT) has been around for a long time and has a pretty good track record. The DDT doesn’t take all of the language and vocabulary issues out of the interpretation—especially for kiddos but is still valuable overall. Words can be problematic as test stimuli, whereas simple low numbers, like 1 through 10, remove some vocabulary and language issues making DDT a pretty good test for people who have dysfunction of the central auditory nervous system. Of course, as we move forward and we’re able to look at more basic processes, we’re pushing toward a more electropysiologically-based test paradigm to allow direct measures of function. Of course, there are drawbacks to electrophysiologic measures, too—so we need to be careful.
Academy/Beck: Certainly, I agree. So what would your preferred central auditory nervous system (CANS) test battery include?
Musiek: That’s a bit of a loaded question! Nonetheless, it really would require more discussion than we have time for here. It seems to me that we really need to be able to do both electrophysiologic-based measures and behavioral tests to obtain a comprehensive overview of central auditory nervous system function. We need to understand the strengths and weaknesses of both EPs and behavioral tests. So we might need a combination ABR/MLR and behavioral measures such as a dichotic procedure and a temporal processing measure to assess brain-stem, hemispheric and inter-hemispheric function. But remember, as I always say—it is not the specific tests in isolation that matter most, what matters most is the person that puts together the whole picture, their knowledge and understanding of the CANS and how well they communicate that!
Academy/Beck: Very good. And what about the gaps in noise (GIN) test as the temporal processing measure?
Musiek: Well, the GIN test is based on auditory research going back into the psycho-acoustic literature for some 50 years, and as you know, it’s a gap detection test that measures temporal resolution. The problem has been that the psychoacoustic forms of gap detection are usually not clinically feasible.
Academy/Beck: Right. But in previous tests, one had to have quite a bit of lab equipment lying about and a lot of time available to actually construct and administer the test. However, now you’ve got a fairly straightforward and accurate test available on a CD?
Musiek: Yes, this version is very simple. And you can play the CD on any CD player, so it’s clinically feasible and repeatable. The GIN test measures temporal resolution and this relates to central auditory processing ability. Those with central auditory nervous system dysfunction have much less ability to perform well on this test and the language level required for the test is minimal. All the patient does is press the button when he or she perceives the gap or the silent interval. Gap durations vary from easy to extremely difficult to detect.
Academy/Beck: What is the average gap “normals” can detect?
Musiek: The average gap detection (within channel) for noise without practice is about 4 to 5 milliseconds and with practice most people might be able to detect gaps of 2 to 3 milliseconds. We also have some very nice numbers from different groups on sensitivity and specificity for the GIN test ranging from about 70 to 90 percent for various lesion types in the central auditory system.
Academy/Beck: And these sensitivity and specificity numbers are based on a gold standard?
Musiek: Yes, they’re based on people with confirmed, well-defined lesions of the central auditory nervous system. Some may argue that’s not exactly a “gold standard” but as close as we can get currently.
Academy/Beck: Okay, Frank. Thanks so much for your time. It’s always fascinating speaking with you. And if my notes are correct, we’ll speak again in the fall, addressing your thoughts on auditory neuropathy and auditory dys-synchrony (AN/AD) versus (C)APD.
Musiek: Well that will prove interesting, and I’ll look forward to chatting with you on that later this year.
Academy/Beck: Excellent. Thanks, Frank.
Musiek: My pleasure, thank you, too.