Sanford E. Gerber

Evoked otoacoustic emissions in preterm infants

Since Kemps discovery of the otoacoustic emissions phenomenon [7], much study has been given to understanding the nature of it and its ontogeny. Development of the evoked otoacoustic emissions (EOAE) has spurred much interest because they may used as a valid and relatively quick test to assess cochlear integrity in the very youngest patients. One thing that has been learned is that EOAE amplitudes are much larger in normal ears of infants than in normal ears of adults. We asked about the form of this development in a longitudinal, rather than cross-sectional, study in an investigation on children born before 40 weeks postconceptional age. We were able to examine reliably five ears of four preterm babies while they remained in the neonatal intensive care unit. The EOAEs of these ears were then studied to determine whether and how they changed over time. To do this, we examined both their amplitudes and their spectral properties. It turned out that there are properties of the EOAE spectrum that may be related to post-conceptional age. These are described herein. These findings are expected to have considerable clinical utility as more and more researchers are able to confirm their validity.

Degeneration of speech, language, and hearing in a patient with mucopolysaccharidosis VII

Mucopolysaccharidosis VII (MPS-VII) is probably the rarest of the mucopolysaccharidoses; literature reveals only 20 cases. We have had the opportunity to study and treat such a child in our clinic, and this paper documents his speech, language, and hearing. Results demonstrated a delay with respect to his chronological age in all cognitive, linguistic, and social domains. He had a mixed hearing loss which could have contributed to his diminishing speech and language abilities; he had chronic otitis media. After 59 h of speech and language intervention (over a period of 19 months), primarily for language treatment, standardized tests revealed that his scores had decreased over time. During this period, both his speech production and his hearing got poorer. At about the time of his 8th birthday, he underwent a permanent tracheostomy, altering further therapy. Although MPS-VII is a very rare disorder, what has been learned here may apply to other MPSs and even to other multiply handicapped patients. We hope that the presentation of our findings may assist others when confronted with complex, degenerative disorders.

Review of a high risk register for congenital or early-onset deafness.

This paper is an attempt to assess the success of a high risk register for congenital or early onset of severe to profound hearing impairment. With some years experience, and a large number of publications, it is possible to evaluate (at least in part) the extent to which such a register actually does permit us to identify these infants. To that end, an extensive review is reported here and some recommendations are made.

Early Development of the Acoustic Reflex

Acoustic reflex testing was conducted on 2-day-old and on 6-week-old infants to determine how frequently, if at all, the acoustic reflex occurs, if it can be reliably observed, and also to determine what is the mean normal acoustic reflex threshold for pure tones and broad-band noise in these populations. Twenty normal infants were tested in each group. Each infant was considered to be normal by the following criteria: full term, normal pregnancy normal pregnancy and delivery, birth weight greater than 2500 g, 5-min Apgar of 7 or greater, and considered to be not at risk for hearing loss by the absence of any high risk factors. Subjects were tested following feedings. Acoustic reflexes were obtained from subjects with normal tympanograms (+/- 50 mm H2O) for 500, 1,000, 2,000, and 4,000 Hz and broad-band noise stimuli. Behavioral responses were common, requiring quieting pauses in testing and repeated stimulation for habituation of the behavioral component. Acoustic reflexes were observed, and normative reflex threshold data were obtained. The number of reflexes obtained and the mean acoustic reflex thresholds for these age-groups are reported.

Acoustical analyses of neonates' vocalizations

Crying and other vocalizations of normal children under the age of 3 days were recorded and analyzed. The purpose was to establish a norm, in acoustical terms, to which one could compare the cry of any given newborn of the same age. One hopes that such a template may assist in the identification of such neonates who have airway obstructions and/or inadequate neuromotor control of respiration. The data reveal two things. One is that the type of vocalization (cry or non-cry) is not relevant to the analysis. The other finding is that spontaneous vocalization (as distinguished from elicited vocalization) is satisfactory for the purpose.

Developmental Norms for the Acoustic Reflex

Acoustic reflexes were observed in 45 infants between the ages of 12 and 36 weeks. As age increased, smaller ranges of signal levels were needed to elicit the reflex and less intensity was required, but a noise stimulus did not show age-related changes. Stimulus frequency was not a source of variation of response. The reflex arc has undergone maturation by 12 weeks of age and continues to mature to 36 weeks.

The limiting effect of discard interval on time-compressed speech.

Twenty subjects listened to CNC word lists compressed at a 2: 1 compression ratio using four different discard intervals, 40, 50, 60, and 70 milliseconds. The stimuli were presented to the subjects both dichotically and diotically. Results indicated a clear advantage in word intelligibility of time-compressed speech at discard intervals from 40 to 70 milliseconds when the signal was presented dichotically. Intelligibility was found to decline rapidly, however, under diotic presentation when the discard interval exceeded 50 to 60 milliseconds. Intelligibility scores for all discard intervals, dichotic presentation, remained above 90%.

The Cardiovascular Response to Acoustic Stimuli

The purposes of this investigation were to determine whether adults display alterations of cardiac rate under acoustical stimulus conditions and whether such alterations are influenced by signal level. The stimulus consisted of a narrow band of noise centered at 1 000 Hz and presented at 20, 40, 60 and 80 dB SPL. The stimulus was found to produce alterations of heart rate significantly different from variation under non-stimulus conditions, indicating that cardiovascular responses occurred. However, the responses themselves were unaffected by differences of sound pressure level.

Stimulus, response, and state variables in the testing of neonates.

This paper endeavors to answer three closely related questions:What motor behavior displayed by an infant may be considered to be a response to acoustic stimulation?What acoustic phenomena elicit such behavior?Does responsiveness vary with postconceptual age? Review of our work over the past decade reveals that we know the answers to the first two questions, but not the third. Briefly, arousal responses (eye and limb movements) are reliably elicited by wideband signals but not by narrowband signals. However, there is still confusion about whether preterm infants are more or less responsive than full term infants.

The use of noise-making toys as audiometric devices.

For a considerable period of time in the literature concerned with pediatric audiology--or, more specifically, audiometry for infants--it has been suggested that one should or should not use measurable noise-making toys as stimulus devices. Proponents of their use suggest that they are intrinsically more attractive to infants and therefore enhance responsiveness. Opponents of the use of such devices have based their claims on the idea that the signal produced by such devices are neither calibrated nor replicable. It is probably the case that both positions are correct, and this leaves the practitioner without expert advice. The study reported here is a simple electroacoustic evaluation of a set of such toys which are now commercially available. The experiment consisted of having two persons use each device 3 times according to the instructions provided with the materials. The toys consist of a bell, a horn, two rattles, and a squeaking toy. The signals produced by these several repetitions of the toys were subjected to one-third octave band analysis by a Bruel and Kjaer Model 2112 spectrometer. A result showed that the signals produced by these toys are indeed replicable, but generally have such flat spectra that they may not be selectively useful except as gross screening devices.