Are Auditory Steady-State Responses Useful to Evaluate Severe-to-Profound Hearing Loss in Children?

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As universal newborn hearing screening programs are established in numerous countries, more children will be diagnosed in early childhoodwith some degree of hearing loss. Early detection and intervention during the critical
period for language and cognitive development can improve individual performance [1].

Children with severe-to-profound bilateral hearing loss are candidates for cochlear implantation (CI) and require
specific audiologic evaluation prior to intervention. As early age of indication and presence of residual hearing are important factors for postimplant speech perception and language development, this has resulted in further decrease of minimum age of surgery [2–7].

In these very young children, behavioral audiologic evaluation can be challenging, may not be obtained in children
younger than 6 months, and usually does not assess each ear separately.Thus the audiologic evaluation of pediatric cochlear implant candidates reliesmore andmore on electrophysiological measures. The most widely used electrophysiological procedure for estimating hearing thresholds in young children is click and tone burst auditory brainstem responses (ABR). Due to the transient nature of the stimuli used to evokeABR,maximum output levels are 95 dB hearing level (HL). In view of that, the possibility of residual hearing at severe-to-profound levels
cannot be investigated with ABR [8]. Hearing assessment of children, using the Auditory Steady-State Responses (ASSR), is made by frequency specific continuous modulated tones and allows increased levels of stimulation intensity. Therefore, ASSR can provide ear and frequency specific threshold information at elevated intensity
Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 579206, 7 pages 2 BioMed Research International levels up to 120 dB HL and higher, providing better and more reliable investigation of ears with minimal residual hearing [9]. Furthermore, ASSR thresholds may be used for hearing aid fitting prior to cochlear implantation.

For such reasons, ASSR is a unique tool for auditory assessment of young cochlear implant candidates. Some authors [10, 11] have investigated the use of ASSR to evaluate patients with severe-to-profound hearing loss. They showed that spurious responses might occur during high stimulus intensities, especially in 500 and 1000Hz. Solutions have been implemented by themanufacturer to reduce artifacts at high-intensity stimulation [12].

Few papers have been published since 2004. One report evaluated 15 childrenwith severe-to-profound hearing loss by
ASSR, but behavioral thresholds were obtained for only one subject [13]. As cochlear implant is the first choice, especially, for the young child with severe-to-profound hearing loss, it is quite important to obtain more data in the pediatric population.

Previously, we performed two studies at the University of S˜ao Paulo. One of them evaluated adults with severe-toprofound hearing loss. The responses of pure tone audiometry (PTA) and ASSR were compared. Patients’ subjective
perception of ASSR stimuli was also evaluated and compared to PTA test results, and no systematic extra-auditory ASSR responses at high intensities were observed [14]. The other study evaluated children with severe-toprofound
hearing loss from 6 to 65 months. Most ASSR responses (48%) were found at 500Hz [15].

The aim of this study was to evaluate Auditory Steady- State Responses (ASSR) at high intensities in pediatric cochlear implant candidates and to compare the results to behavioral test responses.