ABSTRACT
Hearing thresholds were estimated in normal-hearing term and preterm neonates of <35 weeks of age using multiple-stimulus auditory steady-state responses (ASSRs). The tresholds, expressed in decibel sound pressure level, at signal frequencies of 500, 1000, 2000 and 4000 Hz were 44.30 +/- 9.88, 27.80 +/- 6.79, 26.77 +/- 6.09 and 32.87 +/- 6.12 for the term group and 49.11 +/- 9.44, 26.38 +/- 6.59, 26.74 +/- 7.57 and 35.90 +/- 8.23 for the preterm group. Significant threshold differences were measured between the groups at 500 and 4000 Hz, while the thresholds at 1000 and 2000 Hz were similar. The signal and noise levels as well as signal-to-noise ratio of responses were also measured and found to be similar. These results indicate that ASSRs can be effectively measured with a similar signal-to-noise ratio in both groups, but that there is a significant maturational effect occurring during gestation at the level of structures which participate in the formation of the ASSR at 500 and 4000 Hz.
Subject(s)
Audiometry, Evoked Response/methods , Deafness/diagnosis , Deafness/physiopathology , Evoked Potentials, Auditory/physiology , Infant, Premature, Diseases/physiopathology , Neonatal Screening , Acoustic Stimulation , Auditory Threshold/physiology , Deafness/congenital , Female , Gestational Age , Humans , Infant, Newborn , Intensive Care Units, Neonatal , Male , Otoacoustic Emissions, Spontaneous , Reference Values , Signal Processing, Computer-Assisted , Sound SpectrographyABSTRACT
This study was designed to investigate the feasibility of applying tone-ABRs in the nursery and neonatal intensive care unit (NICU), and to provide normative tone-ABR data from neonates. Normative tone-ABR latency data were determined. The study obtained intensity series of tone-ABRs from thirty preterm neonates and twenty full-term neonates who had confirmed normal peripheral auditory function after passing both an OAE and ABR screening examination. ABRs were collected in response to 500, 1500, and 4000 Hz tone bursts at 70, 50, 30, and 20 dB nHL. Mean wave V latencies were compared between groups, ears, and by gender. Responses to tone bursts of 20 and 30 dB nHL were detected in 97% and 100% of all ears respectively, in addition to responses to the higher-intensity stimuli. Preterm neonates' ABRs showed significantly longer latencies than those of the full-term infants. Tone-ABR evaluation was found to be both feasible and reliable as a measure of auditory function in neonates.
