Clinical Value of Acoustic Reflex Decay Testing

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Answer

Well, first, I have your answer (with a little bit of history thrown in as well) and then I have a few words of caution.

First, the answer. If you examine the early literature on impedance testing, much of the work was done using contralateral testing, because of technical problems associated with the early impedance bridges;specifically, ipsilateral tests resulted in many more false positives because of the artifact associated with delivering the stimulus to and measuring the response from the same ear (Green & Margolis, 1984;Wilber, 1976). Initially, impedance equipment allowed for contralateral presentation only;however, technological improvements of impedance equipment allowed for both ipsilateral and contralateral presentation by the late 1970s (Green & Margolis, 1984). In the words of Stach and Jerger (1991), this advancement resulted in "the understanding of the substantial diagnostic power of crossed versus uncrossed reflex patterns (p. 115)." However, comparing ipsilateral and contralateral responses is done for acoustic reflex threshold (ART) testing, not acoustic reflex decay (ARD) testing, so it is not necessary to do both for ARD testing.

Current admittance meters are much improved in their ability to reduce artifact;however, artifact can still occur. It is more likely to occur during ipsilateral testing versus contralateral testing, especially when high intensity stimuli are used or the ear canal is very small (see Gelfand (2002) or Green & Margolis (1984) for a review). This is most likely why the ARD protocol described in audiology textbooks specifies that the ARD is usually tested contralaterally.

As to the part of your question that asks if ipsilateral ARD testing is being used by clinicians, one of my former doctoral students, Dr. Olivia Hensen, surveyed audiologists for her 2009 doctoral thesis (400 surveys mailed to a random sample of AAA members;93 surveys completed) and found that 54% of respondents indicated they do ARD testing "never", "rarely", or "only with medical recommendation." The remaining 46% indicated they do ARD testing "sometimes", "almost always", or "always." These findings represent a decrease in the percentage of audiologists doing ARD testing compared with a study done 11 years earlier (i.e., in Martin, Champlin, & Chambers (1998), 62% of audiologists reported that they conducted ARD testing). Respondents who indicated they "always", "almost always" or "sometimes" completed ARD testing were asked if they presented stimuli ipsilaterally, contralaterally or both. Her results indicated 53.8% selected contra, 34.6% selected ipsilateral and 11.6% selected both. In summary, less than half of the audiologists surveyed are reportedly doing ARD testing, and the majority of those who do perform ARD testing are using contralateral stimulation. Further (although you didn't ask about this part), the survey asked which frequencies were tested and 44.4%, 71.1%, 26.7%, and 6.7% reported testing at 500, 1000, 2000, and 4000 Hz, respectively;this is surprising considering higher frequencies very often result in false positive responses.

Now, on to the caution. In a 2004 AudiologyOnline Ask the Expert column by Dr. Gerald Church, it was pointed out that ARDs are often absent or normal in the case of acoustic neuromas and he stated: "If there is a strong suspicion of the presence of an acoustic tumor, then ABR would be the diagnostic procedure of choice." I agree with his statement and would add that in 1999, Lisa Hunter and her colleagues published an article in Ear and Hearing that discussed one clinical case in detail and briefly summarized 11 others (some were from studies published between1980 to 1999) in which permanent threshold shift (PTS) resulted from acoustic reflex testing or other single-time exposure to high-intensity sound. They found that pure tone threshold (PTT) asymmetry had better sensitivity and specificity for identification of acoustic neuromas than acoustic reflex testing and they suggested a PTT asymmetry of 15 dB or more (PTA 1k, 2k, 4k, and 8k Hz) was a better indicator of the need for referral for ABR or neuroimaging studies compared with acoustic reflex testing. They also suggested using the 90th percentile normative data values to guide ART testing to limit the intensity of exposure. For example, they suggested that for a patient with a moderate loss, when testing ART at 1000 Hz, a response of 100-105 dB HL would be classified as elevated and no response at 105 would be classified as absent, with no further need to test higher levels.

I do not suggest that the use of ARTs should be eliminated, because, as Brad Stach and James Jerger (1991) have pointed out so eloquently, crossed ART responses have substantial diagnostic power. ARTs (also known as MEMRs or middle ear muscle reflexes) are also an important part of the test battery for differential diagnosis of auditory neuropathy spectrum disorder (ANSD). However, because ARD is tested at 10 dB above the ART, which potentially subjects patients to very high sound intensity pure tones, and there are far better diagnostic tools available, I would say that the potential for causing harm outweighs the benefit of the test. While it is true that current admittance meters are not capable of producing levels as loud as the earlier bridges and there is a warning signal on many systems, I no longer do ARD testing because, like Hunter and colleagues (1991), a colleague of mine had a patient who developed tinnitus as a result of ARD testing. This case was the inspiration for Dr. Henson's study. Further, in addition to the previously mentioned statistics on ARD test protocols, the study asked respondents to report cases of tinnitus and hearing loss. Respondents reported 1 case of permanent tinnitus, 7 cases of temporary tinnitus, 1 case of documented hearing loss, and 12 cases of suspected hearing loss as a result of acoustic reflex testing. Recall that there were only 93 respondents, so these numbers are concerning.

In summary, think carefully about the use of ARDs, if you choose to administer ARDs then be careful of the intensity levels and, in response to your question, using a contralateral presentation paradigm appears to be the most popular and should result in less artifact than ipsilateral presentation.

References

Church, G. (2004). Ask the expert: Reflex decay testing. Available from: www.audiologyonline.com/askexpert/display_question.asp?question_id=245

Gelfand, S. A. (2002). The acoustic reflex. In J. Katz (Ed.), Handbook of clinical audiology (5th ed.) (205-232). Baltimore: Lippincott, Williams & Wilkins.

Green, K. W., & Margolis, R. H. (1984). The ipsilateral acoustic reflex. In S. Silman (Ed.), The acoustic reflex: Basic principles and clinical applications (275-299). Ontario: Academic Press, Inc.

Henson, O. (2009). Prevalence of noise-induced tinnitus and hearing threshold shift following acoustic reflex testing. (Unpublished doctoral thesis). Towson University, Towson, MD.

Hunter, L. L., Ries, D. T., Schlauch, R. S., Levine, S. C., & Ward, W. D. (1999). Safety and clinical performance of the acoustic reflex tests. Ear & Hearing, 20(6), 506-514.

Martin, F. N., Champlin, C. A., & Chambers, J. A. (1998). Seventh survey of audiometric practices in the United States. Journal of the American Academy of Audiology, 9(2), 95-104.

Stach, B. A., & Jerger, J. F. (1991). Immittance measures in auditory disorders. In J. T. Jacobson & J. L. Northern (eds.). Diagnostic audiology (113-139). Austin, TX: Pro-ed.

Wilber, L. A. (1976). Acoustic reflex measurements: Procedures, interpretations and variables. In A. S. Feldman & L. A. Wilber (Eds.), Acoustic impedance & admittance: The measurement of middle ear function (197-216). Baltimore: The Williams & Wilkins Company.

Diana C. Emanuel, Ph.D. is a professor and the program director for the Doctor of Audiology (Au.D.) program at Towson University. She earned her bachelor's degree from Towson State University (1988) and her M.S. (1990) and Ph.D. (1993) from Penn State. She teaches in the areas of hearing science, audiology diagnostics, and anatomy and physiology of the auditory system. Her research interests include behavioral auditory processing assessment, hearing science, and pedagogy in Communication Sciences and Disorders. Dr. Emanuel is the co-author of Hearing Science (2009), which provides a student/instructor-friendly approach to learning and teaching hearing science. For more information, go to www.towson.edu/asld.