Tone burst-evoked otoacoustic emissions in neonates: normative data

Neonatal otoacoustic emission screening and sudden infant death syndrome

OBJECTIVE

Exploratory research findings have suggested that otoacoustic emission (OAE) recordings may be predictive for infants at risk of sudden infant death syndrome (SIDS). The present study aimed to investigate whether an actual SIDS prevalence rate was comparable to OAE-determined rates for "at risk" status.

METHODS

Previously collected OAE results from 521 infants in Hong Kong were used for analyses and OAE-determined "at risk" rate compared to the prevalence rate for SIDS in Hong Kong infants.

RESULTS

Results indicated that the OAE-determined rates were very much greater than the actual prevalence of SIDS in Hong Kong.

CONCLUSION

The use of OAE screening to identify infants at risk for SIDS is therefore not advisable, using present criteria, as false alarm rates would be very high and this may cause unnecessary parental anxiety and a considerable additional burden to the health care system.

Otoacoustic emissions evoked by 0.5 kHz tone bursts

The aim of this research is to extend previous studies of the time-frequency features of otoacoustic emissions (OAEs) using information about the properties of the signals at low frequencies. Responses to 0.5 kHz tone bursts were compared to OAEs that were evoked by click stimuli and by 1, 2, and 4 kHz tone burst stimuli. The OAEs were measured using 20 and 30 ms intervals between stimuli. The analysis revealed no differences in the time-frequency properties of 1, 2, and 4 kHz bursts measured using these two different acquisition windows. However, at 0.5 kHz the latency of the response was affected significantly if a shorter time window was used. This was caused by the fact that the response reached a maximum after an average time of 15.4 ms, and lasted a few milliseconds longer. Therefore, for this particular stimulus, the use of a 30 ms time window seems more appropriate. In addition, as an example of the possible application of low-frequency OAEs, signals were measured in patients suffering from partial deafness, characterized by steep audiograms with normal thresholds up to 0.5 kHz and almost total deafness above this frequency. Although no response to clicks was observed in these subjects, the use of 0.5 kHz tone bursts did produce OAEs.