Letters to the Editor
Beth Prieve, in her article in the special issue on newborn hearing screening [November 2000], restates a popular misconception: “Detection of low-frequency hearing loss using ABR is also poor.”
Normal newborn hearing sensitivity is similar to normal adult hearing sensitivity for low frequencies. Normal newborn sensitivity for high frequencies is poorer than that of adults. Refer to Chapter 11 in Evoked Potential Audiometry: Fundamentals and Applications by Goldstein and Aldrich (Allyn & Bacon, 1999) for documentation for this contention.
When you examine the hearing of newborns, you are dealing mainly with their low-frequency sensitivity. Also, refer back to studies of the so-called “derived response” in adults. You will note that low frequencies contribute more energy to the ABR to clicks than do the high frequencies. If one lowers the high-pass end of the band-pass filter to 1-3 Hz and extends the analysis window beyond the typical 10 ms, one can see even clearer evidence of the major contribution to the ABR in adults made by the low-frequency components of the click.
ROBERT GOLDSTEIN, PhD
Dr. Prieve responds
I agree with Dr. Goldstein, as is stated in my article, that neural responses to the low-frequency energy of the click contribute to ABRs. Despite this known finding, it has been shown repeatedly that correlations between click-evoked ABR thresholds and audiometric thresholds at and below 1000 Hz are not strong.1-3 Some researchers have found a relatively strong agreement between audiometric thresholds at 1000 Hz and click ABR thresholds, but with standard deviations on the order of 20 dB.4
Recent research does not support the notion that ABRs in newborns reflect mainly low-frequency sensitivity. Norton et al. found that click-evoked ABRs measured in the newborn period identify hearing loss at 8-to-12 months corrected age equally well at 1000 Hz, 2000 Hz, and 4000 Hz.5 In sum, there is not strong evidence that lower-frequency audiometric thresholds can be accurately predicted from click-evoked ABR.
One explanation is that neurons responding to the low-frequency energy of the click are dispersed over a longer portion of the basilar membrane, and, given a particular point in time, are not firing synchronously with neurons innervating more basal regions of the cochlea.4,6 It has also been documented on many occasions that click stimuli do not detect isolated low-frequency hearing loss because the neurons innervating the normal, basal regions of the cochlea dominate the response to the click.7,8
Because of these findings, diagnostic ABR protocols include low-frequency tone bursts to predict low-frequency audiometric thresholds. For screening purposes, clicks are the stimulus of choice, and clinicians must be aware that infants having isolated, low-frequency hearing loss most likely will pass ABR screening protocols.
1. Coats A, Martin J: Human auditory nerve action potentials and brainstem evoked responses. Effects of audiogram shape and lesion location. Arch Otolaryngol
2. Jerger J, Mauldin L: Prediction of sensorineural hearing level from the brain stem evoked response. Arch Otolaryngol
3. Moller K, Blegvad B: Brainstem responses in patients with sensorineural losses. Scand Audiol
4. Gorga M, Worthington D, Reiland J, et al.: Some comparisons between auditory brain stem response thresholds, latencies and the pure-tone audiogram. Ear Hear
5. Norton S, Gorga M, Widen J, et al.: Identification of neonatal hearing impairment: Evaluation of transient evoked otoacoustic emission, distortion product otoacoustic emission and auditory brain stem response test performance. Ear Hear
6. Fowler C, Durrant J: The effects of peripheral hearing loss on the auditory brainstem response. In Jacobson J, ed., Principles and Applications of Auditory Evoked Potentials
. Needham Heights, MA: Allyn and Bacon, 1994.
7. Stapells D, Oates P: Estimation of the pure-tone audiogram by the auditory brainstem response: A review. Audiol Neuro-otol
8. Oates P, Stapells D: Auditory brainstem response estimates of the pure-tone audiogram: Current status. Sem Hear
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