An ideal clinical outcome is when a diagnosis of hearing loss agrees with the patient's self-perceived hearing problems and he or she proceeds with appropriate treatment. Not all patients, however, perceive a hearing problem in the face of a diagnosis of sensorineural hearing loss. The same situation can occur in the diagnosis of normal hearing. A patient may perceive clinically significant hearing problems despite presenting with normal pure tone detection thresholds.1 Figure 1 shows the potential relationships between a patient's self-perception and test results. In instances of disconnect between patient perception and pure tone threshold results, is it appropriate to rely solely on a single assessment of auditory detection ability to define an individual's full range of hearing and communication abilities?
Anecdotal clinical evidence is mounting regarding a population of adults with normal pure-tone detection thresholds who present with substantial hearing-related complaints in audiology clinics. Similarly, a growing body of research supports the categorization of a population that exhibits suprathreshold auditory processing deficits in the presence of normal pure tone thresholds or subjective hearing difficulties.2-6 These difficulties have been reported for middle-aged7,8 and older adults9,10 and for adults with a history of brain pathology (central auditory nervous system lesions,11,12 traumatic brain injury [TBI],13-14 history of noise exposure,15 etc.). Co-morbidities such as depression5 and emotional distress16 have both been associated with subjective hearing difficulties, potentially having a negative impact on a patient's quality of life. Accurate identification and diagnosis of adults with subjective hearing difficulties are therefore essential for the recommendation of appropriate treatment options that can improve a patient's quality of life.
The assessment of adults with subjective hearing difficulties should include:
- a careful case history;
- an authentic subjective assessment;
- a standard audiometric assessment; and
- an extensive suprathreshold audiologic processing assessment.
A careful case history, the first step in any assessment protocol, is particularly important for adults who present with subjective hearing difficulties. The case history should include questions about specific situations where hearing difficulties arise, whether symptoms are new or long-standing, and if the patient has a history of concussion or TBI. For patients with a history of noise exposure, gathering further details about the type and duration of exposure is warranted (i.e., potential presence of hidden hearing loss17). Taking extra time to complete a patient's case history may help identify a potential etiology, and more importantly, ensure that the patient's concerns are being heard.
An authentic subjective assessment is used to further elucidate the symptoms experienced by adults with subjective hearing difficulties. Standardized questionnaires are a straight-forward and time-efficient means of detailing specific situations that patients consider problematic. For example, the Hearing Handicap Questionnaire for Adults18 and the Abbreviated Profile of Hearing Aid Benefit19 are quick and easy to administer and provide extensive normative data. The assessment should also consider the patient's cognitive status. Processing of auditory information is known to be affected by cognitive factors (e.g., working memory) and can be negatively impacted by cognitive impairment. Completing a cognitive screening measure such as the Montreal Cognitive Assessment20 (MoCA) is therefore warranted. The MoCA is a 30-item assessment of visuospatial and executive function, naming, memory, attention, language, abstraction, delayed recall, and orientation. It is also quick and easy to administer, and provides immediate information about the patient's cognitive status (scores <26 indicate cognitive impairment).
The standard audiometric assessment, including pure tone audiometry and word recognition performance in quiet, is important, but it should not conclude the assessment process. According to Erber's hierarchy of auditory skills (Fig. 2), detecting pure tones is the easiest task used in clinical audiology,21 and many adults with subjective hearing difficulties will report being told that “The audiogram says I have normal hearing” or “I have been told I have perfect hearing.” Therefore, assessment of suprathreshold abilities using measures that specifically address the patient's complaints and tax the auditory system are essential to the diagnosis of subjective hearing difficulties. At a minimum, a suprathreshold audiologic assessment should include speech-in-noise testing (i.e., the primary complaint of most patients with hearing difficulties). Many speech-in-noise tests designed for clinical use are commercially available, including the Quick Speech in Noise22 (QSIN) test, Hearing in Noise Test23 (HINT), and Words-in-Noise test24 (WIN).
In addition to speech-in-noise testing, suprathreshold audiologic assessment should include clinical measures of binaural speech recognition, such as dichotic listening (e.g., dichotic digits) or spatial benefit (e.g., Listening in Spatialized Noise test), and a measure of temporal processing, such as gap detection (e.g., Gaps-in-Noise test12) or release from masking (e.g., 500-Hz masking level difference26). Interpretation of the suprathreshold assessment is based on a comparison of the results to published norms. A finding of abnormal performance on one or more tests serves as a confirmation of the patient's complaints and provides the basis for consideration of audiologic treatment.
The sensitivity and specificity of the test battery described above are unknown. Several studies2,13,14 and clinical experience suggest that a majority of patients presenting with subjective hearing difficulties will exhibit abnormal performance on one or more tests. However, not all patients with hearing complaints will exhibit abnormal suprathreshold performance. One possibility for a lack of poor performance may reflect the fact that current tests are not sensitive to the subtle nature of subjective hearing difficulties, and new measures need to be developed. It is also important to acknowledge that subjective hearing difficulties may simply be the manifestation of a deficit in another domain, such as cognition (e.g., working memory, attention, etc.).
Multiple treatment options are available for adults with subjective hearing difficulties. These can be categorized into bottom-up or top-down options. Bottom-up treatment strategies aim to provide patients with the best possible auditory signal by improving audibility of soft speech and the signal-to-noise ratio (SNR) and managing competing sounds. Examples include the use of hearing technology (e.g., mild-gain hearing aids and/or digital modulation systems) and traditional audiologic rehabilitation training (e.g., environmental management and communication strategies). Top-down strategies target the function of underlying auditory skills and enhance cognitive abilities by creating a highly redundant listening and learning environment. Examples of top-down auditory training programs include Listening and Communication Enhancement 27 (LACE; www.lacelistening.com/), Read My Quips (http://www.sensesynergy.com/readmyquips), clEAR 28 (www.clearworks4ears.com), and Angel Sound (angelsound.tigerspeech.com).
The use of hearing technology to treat subjective hearing difficulties is gaining traction in clinical audiology. Mild-gain hearing aids enhance the audibility of soft speech and improve the SNR through adaptive directionality and noise reduction algorithms. Promising results for patients with subjective hearing difficulties have been reported in trials at The Ohio State University29 and the Walter Reed National Military Medical Center.30 Significant improvements in speech-in-noise performance and self-perceived hearing handicap have been seen in patients who used mild-gain hearing aids,29 suggesting that the use of amplification is a viable treatment option with this population.
Understanding that auditory complaints and suprathreshold auditory deficits can co-exist in the presence of normal pure tone thresholds is the first step in providing appropriate clinical care for adults with subjective hearing difficulties. An assessment protocol that incorporates standardized questionnaires and clinically validated suprathreshold measures enables audiologists to promptly verify patient complaints. If audiologists are to be essential in the lives of patients, going beyond the statement, “The audiogram says your hearing is normal,” is key. It is critical to listen to patient concerns, assess those concerns clinically, and provide support for treatment. Our own clinical experience and a growing body of research have established an evidence-based rationale for the use of audiological rehabilitation for these patients, including the use of technology such as mild-gain amplification.
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