1 We're always hearing and reading about auditory processing disorders (APD) in children. Are you suggesting that APD can also occur in adults?
It certainly can. As a matter of fact, the first recognized cases of APD were probably adults, even if they weren't labeled that at the time. Virtually all our sensitivity and specificity data for tests of central auditory function (when available) were obtained from adults with known lesions of the central auditory nervous system (CANS). That's how we learned which types of patterns on central auditory tests correlate with dysfunction in specific brain regions.
Moreover, for decades we've been dealing with adults who come to the clinic complaining of decreasing ability to hear or understand speech, especially in noisy environments, yet exhibit completely normal peripheral hearing sensitivity. Even when we scratched our heads and said, “Gee, I don't know…” we still knew something wasn't quite right. However, at the time, audiologists weren't trained to evaluate the entire hearing system, from ear to brain. Instead, we tended to focus on the peripheral system alone.
You'll find references in the literature to adults with “obscure auditory dysfunction” (OAD), a term that really meant “folks who have distinct auditory symptoms and complaints that don't show up on our standard audiologic testing.” We didn't start identifying the condition in adults as APD until after the term was being applied to children.
2 Couldn't some of these adults just be kids with APD all grown up?
That's a reasonable assumption. Anyone who works with children with APD knows that, very often, their parents report having had similar difficulties when they were kids—and many of them still do. That's why we're pretty sure there's frequently some type of familial or inherited component to APD.
On the other hand, we don't automatically assume that kids with APD will have it all of their lives. With appropriate management and remediation, along with the healing salve of time that may resolve many childhood APDs that result from delayed neuromaturation, children with APD may not grow up to be adults with APD.
But there are also cases of adult-onset APD that occur in persons with no history of the disorder. The condition may be the result of neurologic disease, such as tumors or stroke. It may be iatrogenic, resulting from surgical intervention for brain disorders. It can be the result of head injury, such as might occur in an auto accident. And there is increasing evidence that some cases of adult-onset APD are a result of the normal aging process—a condition that is sometimes called “central presbycusis” or “central effects of biological aging.”1
3 Do adults with APD have the same symptoms and presenting complaints as children with APD?
Many of the auditory-specific symptoms are quite similar, including difficulty understanding speech in noisy or reverberant environments or with rapid talkers, difficulty following spoken directions or understanding verbally presented information, and frequent “mishearing” involving substitutions of similar-sounding phonemes (e.g., “time” for “dime”).2-5
Where children and adults tend to differ is in the impact of the disorder on daily life. With children, we focus largely on the language and learning implications of the disorder, as APD is suspected to be associated with a host of educational difficulties.2-7 With adults, who have presumably acquired language and, usually, completed their education, the impact of APD on daily life is more likely to manifest itself in social communication and in the workplace. However, when adults with APD return to school to pursue a degree, they often encounter learning-related difficulties remarkably similar to those of school children with APD.3, 8
4 Do adults with APD closely resemble adults with hearing loss?
They certainly can. That's why so many of them come to us for audiologic testing, convinced that they are losing their hearing. But many of them don't exhibit any peripheral hearing loss at all. Others may have auditory difficulties that are disproportionate to the degree of hearing loss they do exhibit, or they may have difficulty achieving satisfaction with binaural amplification.
We should be careful not to over-generalize, though. Some persons with APD (both adults and children) do not exhibit any of the typical symptoms of hearing loss. Instead, they may have other types of auditory difficulties that don't involve clarity of sound, per se, but relate instead to perceiving the subtler aspects of spoken communication, such as prosodic aspects of speech (rhythm, stress, and intonation) that convey what a person means in relation to what he or she says.2-4 These individuals may not complain of difficulty hearing in noise or the other “typical” symptoms of APD and hearing loss. Instead, they may report having a hard time picking up on sarcasm, humor, and tone-of-voice cues that carry important information to the listener. In fact, recent evidence suggests there may be gender difference in the normal central auditory aging process and that men and women may exhibit very different auditory complaints at specific points in the adult life-span.9
5 That's intriguing. What types of gender differences?
Well, the evidence suggests that interhemispheric function (and related binaural listening skills) declines with aging in adults.9-12 The timeline for this decline seems to differ by gender, with men exhibiting decline by age 40 or so and women exhibiting preserved interhemispheric function until after menopause, at which time they show a pretty rapid decrease in function. By their 70s, men and women don't seem to differ in this regard. These behavioral findings also mirror the timeline of gender-based anatomic changes that occur in the corpus callosum during those same adult years.13
The really interesting thing is that women in the immediate post-menopausal years also seem to exhibit right-hemisphere-based auditory processing symptoms related to perception of prosody (or tone-of-voice) cues of speech.9 This does seem to resolve later on, and we're currently investigating the effect of estrogen supplementation on this function. Anyway, this may provide a physiologic basis for the common complaint by women that their husbands can't “hear them when the water's running” by the time they're in their 40s. It may also explain why husbands complain that their wives “take everything the wrong way” during the immediate post-menopausal years.
6 So, men really are from Mars and women from Venus. Does that provide an automatic excuse for a man in his 40s or a woman in her 50s?
Don't count on it. I certainly don't excuse my husband's listening behavior on that basis alone! Also, we need to recognize that the aging process is highly individualized, so not everyone will exhibit these patterns. Furthermore, there are so many other psychosocial and related factors that shape listening and communicative behavior in aging, along with a variety of additional health and body changes (not the least of which is the onset of hearing loss in many individuals), that we must be careful not to attribute all of the difficulties to a single underlying cause. Much more research is needed to determine the functional implications of these findings.
7 Well, it was worth a try. So, how does the screening and diagnostic process for APD differ in adults from that of kids?
From a central auditory diagnostic perspective, it really doesn't. We use the same behavioral and electrophysiologic tests for diagnosing APD in children as in adults. Where the difference lies is in the other, ancillary information we consider. With children, we include multidisciplinary information focusing on learning, language, cognitive, and academic function in the overall assessment and management/treatment picture. With adults, we often do not have this information, nor is this type of testing typically indicated.
While we may have neuropsychologic data, particularly if the adult in question is being evaluated following a head trauma or other neurologic disease or insult, the amount and variety of formal, multidisciplinary test results from other disciplines are substantially less. Also, with adults, we tend to focus mostly on workplace and social (including home) communication sequelae, whereas with children we focus much more on educational implications.
8 Even if we can diagnose APD in adults, is there any point? What's the clinical utility of the diagnosis for an adult?
The functional impact of APD in adults can be every bit as marked as in children. APD can interfere with success at work, satisfaction in social situations, and in many other aspects of life. However, just as with children, it is critical that the APD be diagnosed appropriately (not just the presence of disorder, but an analysis of the nature of the disorder) for the development of a deficit-specific management and treatment plan. Only through careful diagnostics can we appropriately address the difficulties an individual adult is experiencing in daily life.
9 You mentioned possible effects of APD on binaural hearing aid success. Can you be more specific?
In recent years, there have been reports of dichotic listening deficits coinciding with dissatisfaction with binaural hearing aids.14,15 Some patients report (and functional evaluation bears them out) that they do far better with one hearing aid (usually the right one) than with two. Although this seems to fly in the face of conventional wisdom, it makes sense if you consider that dichotic listening tests directly assess an individual's binaural integration and/or separation skills and binaural amplification recruits those skills for daily employment in listening situations. If a person has an inherent deficit in listening with two ears, the “binaural is better” argument may not apply to them.
To be sure, binaural amplification has many benefits: elimination of the head shadow effect, binaural summation, improved localization, etc. However, many of these benefits rely, at least in part, on adequate binaural processing. If a person exhibits an APD that affects binaural processing, the relative benefit he or she derives from binaural amplification (and the person's satisfaction with two hearing aids) may, likewise, be compromised. This is an area that deserves much additional research and scrutiny, and may help explain, at least in part, why some adults do so much better with binaural amplification than others.
10 Does this mean that some type of behavioral central auditory test should be a part of routine hearing tests for elderly individuals?
Although it may be premature, I really think that's not a bad idea. If we added one dichotic listening measure, for example, we might get an idea of the patient's auditory processing capability. That would help guide us on what recommendations we should ultimately make, whether those recommendations involve amplification, additional testing, communicative strategies, or all of the above. However, we must recognize that adding just one test would not give us a full picture of a person's auditory processing abilities. Only a comprehensive central auditory diagnostic evaluation performed by an audiologist can give us that. But, the addition of one test might indicate the need for follow-up in this area.
11 Would this give us more information than the tests we might already use, e.g., word recognition in quiet?
We should always analyze the task demands of any measure. What does word recognition in quiet really tell us? It tells us how well this person can repeat a list of words (words devoid of context, I might add) in a nice, non-competing listening environment that often does not represent real-world listening in any way. Even if we look at word recognition in noise, we should realize there are many factors—hearing, auditory processing, and language, among others—that can affect the ability to understand speech in noise.
Moreover, while many other tests may give us a better idea of a person's speech-understanding abilities, do they look specifically at how the two ears work together, or at left-, right-, and inter-hemispheric functioning? Typically, they don't, even though they may be affected by dysfunction in any of these areas.
Dichotic tests, on the other hand, give us a quick, focused look at something that's very important to ultimate listening success (especially in competing environments) and that we can get through no other test.
12 So, are you saying if an adult's performance on a dichotic task is poor, we shouldn't aid binaurally?
I wouldn't go that far. We should be very careful not to draw definite conclusions from dichotic listening results at present, as the data are not all in. Even when they are, I think this will (and should) continue to be a highly individualized decision.
On the other hand, when we do see an adult with significant dichotic listening difficulties, we should consider that information when we are developing our own expectations for our clients. All too often, I have seen audiologists contend, simply on general principles, that binaural is better—even when the client insists that he or she performs far better with one hearing aid.
It's this “We know what's best for you better than you do” approach that I object to. We should recognize that, while binaural may be better in the vast majority of situations, it may not be better for every patient. And, we need to understand that binaural listening deficits may be one factor that influences the degree of benefit from binaural amplification.
I always counsel clients during the trial period to use their hearing aids together and then one at a time in a variety of listening situations to determine for themselves which aided condition is most beneficial. When clients exhibit significant dichotic listening difficulties, I still recommend binaural amplification, but I am probably better prepared for them to report at the end of the trial period that they prefer listening with just one aid. As a result, they may end up deciding on monaural amplification. Or, at the very least, they may require more time and more intensive counseling than other patients to accommodate to binaural amplification.
13 Which specific dichotic test(s) do you recommend for an adult audiologic battery, and why?
I tend to be partial to the Dichotic Digits test,16 as it is only lightly linguistically loaded, takes just a few minutes to administer, and, most importantly, is relatively resistant to peripheral hearing loss. Recently, some test modifications have been suggested that involve administering the stimuli in directed listening conditions so as to deal with the possible ceiling effects of the test.17 There are other tests, but I think this one gives me the most bang for the buck.
Here again, we should recognize that one isolated test is no substitute for a complete diagnostic auditory processing evaluation. Such an evaluation is likely to include various other behavioral tests along with electrophysiologic measures and other steps to ensure that any central auditory findings are not due to a problem that might require medical or surgical intervention.
14 Okay, let's say we have diagnosed an adult patient with APD. Aside from the hearing aid issue, what can we do about it? Would our management strategies or remediation activities really differ from those we would use with adults who simply have hearing loss?
The management and treatment of APD patients should be highly individualized and must be based upon accurate diagnosis of the presence and nature of the disorder. As such, although some environment-based techniques (e.g., making good use of visual cues, choosing listener-friendly places to sit in a room) may be recommended for some types of APD, these are only the beginning. Remember, not all cases of APD manifest themselves as hearing loss. Moreover, APD treatment focuses on directed, deficit-specific auditory training activities designed to eliminate or reduce the impairment. However, we can only know which are the “right” activities if we clearly understand the nature of an individual adult's APD.
15 Come on, we've all heard “you can't teach an old dog new tricks.” Am I really supposed to believe that auditory training will help “cure” adults with APD?
Well, “cure” is a pretty strong word, but recent research in neuroplasticity is pretty promising—even for “old dogs.” Certainly, the younger we are, the more plastic our brains are. But plasticity extends throughout our lifetime. How else could we learn new information or recover after a stroke?
Specific evidence regarding auditory training and central auditory plasticity in adulthood shows that not only do functional changes occur following auditory training, but these changes are accompanied by alterations in neurophysiologic responses. For example, adults can be trained to discriminate phonemic contrasts not found in their native language, and the event-related potentials recorded also demonstrate changes that reflect this new ability.18-19 Granted, the whole area of treatment efficacy needs a great deal more research, both in children and adults. But, age alone is no reason not to employ deficit-specific therapeutic interventions.
16 Can you give me some examples of management and treatment activities you'd use with adults with APD?
Whether the patient is a child or an adult, any APD management and treatment program has three basic components: (1) environmental modifications, designed to improve access to auditory input; (2) compensatory strategies to strengthen higher-order central resources (e.g., memory, attention, language) that individuals with APD may draw upon to assist in overcoming auditory deficits; and (3) direct remediation activities, targeted toward reducing or eliminating the auditory impairment itself.2–4,20
Beyond those, I really don't like to offer specific suggestions, as any management/treatment program needs to be designed specifically for the person (and the deficit) in question. I discourage at all costs any cookie-cutter approach or the use of general lists of recommendations that imply that certain intervention approaches are appropriate for everyone with APD.
17 Point taken. But, what about just a few environmental modifications?
If you insist. Some adults with APD will benefit from the same types of modifications used for those with hearing loss, such as using assistive listening devices (ALDs) at work. However, ALDs are not appropriate for everyone with APD, as some forms of APD do not affect signal clarity or acoustic access, per se, and thus require different environmental interventions.2-4
Other environmental modifications that may be appropriate include requesting information in writing, frequently checking for understanding of oral instructions, ensuring that seating is optimal in any conversational situation, and analysis (and modification, if necessary) of the acoustic characteristics of the communicative environment.
Remember, the key is access to information. Therefore, adults with APD need help in understanding their disorder, problem-solving their particular work- and social-related communication difficulties, and coming up with reasonable solutions. In addition, I include family members in this process so that a game plan can be developed that identifies and implements communication strategies that work in the unique home communication characteristics of the family.
18 What about compensatory strategies?
Again, individualization is critical. However, the types of activities we may wish to consider here include methods of improving metacognitive and metalinguistic skills so that greater effort can be allocated to receiving the information in the first place. Thus, we may focus on: memory strategies (chunking, mnemonics, etc.); recoding information into pictorial form (especially if visualization skills are a strength); and using schema induction (analysis of the conversational or linguistic context to fill in missing pieces of the message, derive meaning, and make predictions) and methods of enhancing auditory vigilance.2–5,20–21
Above all, motivation and belief in outcomes need to be addressed, since people with APD often become relatively passive listeners and may develop secondary motivational deficits because of their disorders.
19 What about direct remediation or therapy activities?
It is critical to match the therapy to the disorder so, again, accurate diagnosis is an integral part of developing a treatment plan. Direct therapy activities may focus on teaching discrimination skills, enhancing localization abilities, interhemispheric training activities, binaural separation or integration (i.e., dichotic listening) training, speech-in-noise skills, and similar interventions.2–5,20,22–24
The key is to maximize neuroplasticity through frequent, challenging, and intense activities focusing on the specific auditory deficit(s) identified during diagnostic testing. I have found that many adults are particularly well-suited to home-based programs, which are also more convenient for them than going to a clinic for regular therapy sessions. Therefore, I often use computer-based and other auditory training activities that can be implemented nightly in the home setting, and I monitor progress from a distance.
20 For many adults, APD seems like an inevitable consequence of getting older. Is there any way to prevent it?
Ah, that's the $65,000 question, isn't it? I don't really have an answer for you. Much has been written in the popular literature lately of methods of keeping the brain “sharp” during adulthood. It is entirely possible that engaging regularly in activities that require discrimination, localization, binaural separation or integration, interhemispheric transfer of information, and similar skills may help preserve auditory and related function, just as auditory stimulation may partially counteract the impact of presbycusic hearing loss.25
However, we have no empirical evidence to support this contention in the case of auditory processing disorders in adults. I would like to see longitudinal studies that examine the long-term effects on aging adults of engaging in these types of activities. Until we have these, logic suggests that the old dictum, “Use it or lose it,” may apply to preserving auditory processing skills in aging adults.
What kind of person would devote her career to the study of auditory processing disorders (APD)? A professional model? A professional actress? A massage therapist? A first-degree Reiki healer? A tarot card reader? These are just a few of the many “qualifications” that Teri Bellis, PhD, this month's guest author, brings to Page Ten.
Dr. Bellis is an associate professor of audiology at the University of South Dakota in Vermillion. You've no doubt seen her presentations at professional meetings, and are familiar with her popular textbook, Assessment and Management of CAPD in the Education Setting. Dr. Bellis's literary talents are perhaps even better known to people outside our discipline, as her book When the Brain Can't Hear: Unraveling the Mystery of Auditory Processing made it to #38 on Amazon's top 100 bestseller list! Teri recently received the honors of the South Dakota Speech and Hearing Association, and she is president-elect of that organization.
When we think of APD, we often think of the child who is having problems in school. In fact, last year Bob Keith joined us on Page Ten to talk about this population. But, what about adults? Don't they also have communication problems associated with APD? Of course, they do. Are they simply kids with APD who have gotten bigger? Sometimes, but not always. Do APD problems require medical or surgical intervention? Usually not, but we need to make sure of this with a good diagnostic work-up. Does adult APD have an impact on hearing aid use and audiologic rehabilitation? Absolutely, which is another reason it's important to identify these patients.
I find it puzzling that most clinicians are very interested in observing the results of monosyllabic word-recognition tests, even though they are usually predictable from the audiogram, whereas very few clinicians are interested in the results of APD speech tests, which are rarely predictable from the audiogram. In her excellent overview of APD in adults, Dr. Bellis tells us why it may be worthwhile to think more about how our patients are processing speech, and maybe even add an APD speech test to our clinical battery. And of course, we always must consider the impact of APD when we counsel patients on the benefits of amplification.
As a Reiki healer, Teri is a specialist in non-invasive, hands-on energy transfer. I'm betting she'd be very pleased if you took some of the energy that she used in writing this article and transferred it to some “hands-on” APD assessment!
Page Ten Editor