Steady-state evoked-potentials (SSEP) in infants: modulation frequency effects [Abstract]

The University of Melbourne experience shows that steady-state evoked-potentials are a sensitive indicator of hearing loss in children and adults (Rance et al., 1996). Cognizant of the effect of stimulus rate upon ABRs in early development (Lasky, 1987, Cone-Wesson et al., 1995), we investigated the effect of modulation frequency (MF) upon the detectability of the SSEP recorded from full-term (FT) neonates and those with a history of prematurity (PM). The influence of gender was also evaluated, as it has been shown to be a significant variable in ABR results (Sininger et al., 1995, Eldredge and Salamy, 1996). Ten male and 9 female FT infants were tested on the second day post partum (range 1-5 days).8-12 Jun

Towards a SSEP hearing screening test for neonates [Abstracts]

Newborn hearing screening tests utilizing evoked otoacoustic emissions (EOAEs) and/or the auditory brainstem response (ABR) recording have been recommended by the NIH(1993). The University of Melbourne experience with steady-state evoked potentials (SSEPs) in newborns suggests that they too, have potential as a screening tool (Rickards et al, 1984). In the present study, SSEPs were recorded from neonates in a pilot study of how the technology may be applied to newborn hearing screening. Eighty-eight neonates were tested using transient-and distortion product EOAEs, ABRs and SSEPs. Only those infants who had TEOAEs, DPOAEs, and ABRs that met a rigid and objective "pass" criteria were included in the study. SSEPs were evoked by amplitude modulated tones using carrier frequencies at 500, 1000, 2000, and 4000 HZ, and modulation frequencies between 75 and 95 Hz presented at levels between 40 and 80 dB SPL. Out of 324 individual SSEP tests, 12% were no-stimulus control trials. Phase-coherence statistics were used to determine when a significant or "passing" result had been obtained. Preliminary results show that a 94% pass rate is achieved for a CF of 2 KHZ, presented at 60 dB SPL, but that pass rates are lower (79% to 89%) for 500, 1KHz and 4KHZ CF's at the same stimulus levels. For lower stimulus levels, pass rates do not exceed 80% for any carrier frequency. Phase-coherence estimates were made for 32, 64, ahd 96 samples at each carrier and modulation frequency combination. We will report the phase coherence estimates for each CF, MF and level combination as a function of sample size, in order to suggest a protocol that may be efficient in newborn hearing screening applications.8-12 Jun