Page 16 - Volume 12, Issue 2 - Spring 2012

ral conduction disorders or auditory neuropa- thy/dyssynchrony in the absence of sensory dysfunction may not be detected by an OAE test.
OAE and ABR tests are recommended for identifying infants at risk for hearing impairment in the birth-admission screening (Norton et al., 2000). According to the JCIH, infants who do not pass a birth-admission screening should be rescreened within 1 month of hospital discharge, and those infants who do not pass the rescreening should receive a comprehensive audiological evaluation by age 3 months. The overall goal is that infants with confirmed hearing loss receive a medically appropriate intervention by age 6 months.
The birth-admission screening exam recommended by JCIH does not include middle-ear or acoustic-reflex testing. The audiological assessment in the one-month rescreening exam (up to 6 months) includes 1000-Hz admittance tympa- nometry, but acoustic reflex testing is not recommended until age 6 months. These recommendations were based on earlier research that found difficulties in interpreting single- frequency admittance tympanograms in newborns and that many infants with normal hearing had an absent acoustic- reflex response.
Intrinsic limitations of NHS testing include the problem of false positives, i.e., those infants with normal hearing that are referred as impaired on the NHS exam, and false nega- tives, those infants later found to have a permanent hearing loss who pass the NHS exam as having normal function. The positive predictive value, which is the proportion of infants referring on the exam who are later confirmed to have a per- manent hearing loss, of the NHS rescreening exam is only 6.7% (Thompson et al., 2001), and even less in the initial birth-admission screening. That is, most infants referred by NHS do not have a hearing loss. The most common reason for referring on NHS exams is a transient middle-ear dys- function that is present at the time of testing but that resolves thereafter. The presence of middle-ear dysfunction increases the likelihood of an absent response on an OAE or ABR test irrespective of whether the infant has normal hearing or a hearing loss. The problem of false positives, which number in the post-rescreening exam period in the many tens of thou- sands of infants every year in the U.S., increases screening and rescreening costs, generates anxiety in parents, lessens confidence in early hearing detection programs, and delays the discovery of the true hearing status.
A promising recent development in research is the fact that wideband tests of middle-ear function are feasible in newborns and can account for about 80% of the false-posi- tives in a birth-admission NHS exam using OAEs (Keefe et al., 2003). Wideband absorbance was more accurate than 1000-Hz admittance tympanometry in classifying OAE out- comes (as pass or refer) from NHS (Sanford et al., 2009; Hunter et al., 2010). In one- and two-day-old infants, an acoustic-reflex threshold was present in 97% of ears that passed the NHS exam (Keefe et al., 2010). A combination of wideband absorbance and reflex testing performed better than either test alone in predicting the outcome of the NHS exam. As described above, ABR testing is recommended in the birth-admission screening test for infants in a NICU
because of its ability to detect auditory neuropa- thy/dyssynchrony. It is of interest that an elevated or absent acoustic reflex test detected auditory neuropa- thy/dyssynchrony in 100% of adult test ears (Berlin et al., 2005). This finding suggests the hypothesis, as yet untested, that wideband reflex testing may also detect this disorder in infant ears. The results to date lend confidence that more extensive combinations of acoustical tests of middle-ear, cochlear and neural function may be beneficial for screening and diagnosing hearing loss in infants. This is an active area of current research that may improve programs dedicated to early hearing detection and intervention.AT
Acknowledgments
Research described in this article has been funded for more than two decades by grants from the National Institute on Deafness and Communication Disorders. The author is grateful for his many constructive interactions with research colleagues during this time. Walt Jesteadt provided helpful comments on this article.
References
Abdala, C. (2001). “Maturation of the human cochlear amplifier: Distortion product otoacoustic emission suppression tuning curves recorded at low and high primary tone levels,” J. Acoust. Soc. Am. 110, 1465–1476.
Abdala, C., and Keefe, D. H. (2012). “Development of the ear: mor- phology and function,” in Human Auditory Development, edited by L. Werner, A. N. Popper, and R. R. Fay, Springer Handbook of Auditory Research 42 (Springer, New York), Chap. 2, pp. 19–59.
von Békésy, G. (1989). Experiments in Hearing, translator and edi- tor, Wever, E. G. (Acoustical Society of America, New York). This book was originally published in 1960.
Berlin, C. I., Hood, L. J., Morlet, T., Wilensky, D., St. John, P., Montgomery, E., and Thibodaux, M. (2005). “Absent or elevated middle ear muscle reflexes in the presence of normal otoacoustic emissions: A universal finding in 136 cases of auditory neuropa- thy/dyssynchrony,” J. Am. Acad. Audiol. 16, 546–553.
Brass, D., and Kemp, D. T. (1993). “Suppression of stimulus fre- quency otoacoustic emissions,” J. Acoust. Soc. Am. 93, 920–939. Brown, A.M., and Kemp, D. T. (1984). “Suppressibility of the 2f1-f2 stimulated acoustic emissions in gerbil and man,” Hearing Res.
13, 29–37.
Don, M., and Kwong, B. (2009). “Auditory brainstem response:
Differential diagnosis,” in Handbook of Clinical Audiology, Sixth Edition, edited by J. Katz, L. Medwetsky, R. Burkhard, and L. Hood (Wolters Kluwer, Philadelphia), Chap. 13, pp. 265–292.
Feeney, M. P., and Keefe, D. H. (1999). “Acoustic reflex detection using wide-band acoustic reflectance, admittance, and power measurements,” J. Speech, Language, and Hearing Res. 42, 1029–1041.
Goldstein, J. L. (1967). “Auditory nonlinearity,” J. Acoust. Soc. Am. 41, 676–689.
Goldstein, J. L., and Kiang, N. Y.-S. (1968). “Neural correlates of the aural combination tone 2f1-f2,” Proceed. Inst. Electrical and Electronics Engineers 56, 981–992.
Gorga, M. P., Neely, S. T., Kopun, J., and Tan, H. (2011). “Distortion-product otoacoustic emission suppression tuning curves in humans,” J. Acoust. Soc. Am. 129, 817–827.
Holte, L., Margolis, R. H., and Cavanaugh, R. M. (1991). Middle-ear and Cochlear Functions 15