The Auditory Steady-State Response (ASSR) issimilar to auditory brainstem response (ABR) in many ways. However, there aresome differences. When comparing the ASSR and ABR some issues should beconsidered: frequency specificity, response generators, the effects of hearingloss, and the automatic detection algorithms. The following table compares ASSRand ABR in theses aspects:ASSR overcome thislimitation; due to that the response is evoked by a pure tone that are amplitudeand/or frequency modulated.Lack of frequency specificity Measurement of the response phase spectrum is used to estimateresponse latency.
Phase is used to characterize the latency range of theresponse.dominated by evokedpotential neural generators responsible for the late cortical evoked potential.Measures of phasecoherence, magnitude squared coherence or the fast Fourier transform of theresponse subjected to a variance ratio test.Correlation, templatematching, or estimating the signal-to-noise ratio (SNR) from the variance of asingle point. Two studies werereported in which the threshold estimates from auditory responsive tests; theASSR in compression to the ABR. The first study was a retrospective reviewcomparing ASSR and ABR results in fifty-one cases of infants and children, demonstratedboth the click-ABR and the ASSR by using either visual reinforcement audiometryor play audiometry. Then, comparing between the ABR threshold with eachaudiometric threshold (both in dB HL) and between ASSR thresholds andaudiometric thresholds (both in dB HL). The results show that both click-ABRand ASSR have strong and statistically significant correlations with thepure-tone audiogram in infants and children with various degrees of hearingloss.
The second study was a prospective review of ten normal hearing adultfemales, demonstrated tone burst-ABR and modulated tone ASSR. The results showthat tone-burst ABR and ASSR could both be used to estimate hearing thresholdbut that the stimulus used and detection method the threshold determination.1- Infants and children were tested using age appropriateprotocols.2-All testing was carried out in double-walled, sound-attenuatedrooms.3- This study contains correlation between,ASSR, ABR, and the behavioral threshold.1-Excluding any intervals between the ABR, ASSR, and behavioralthreshold tests if greater than 24 months.
2- Variation in hearing loss types.3- Variation in age range.4- This study suggests that both c-ABR and ASSRthreshold estimates can be used to predict pure-tone threshold for infants andchildren with variate normal hearing and hearing loss ranges.
1-ASSR determination of residual hearing for those with severe to profoundand profound hearing losses.2-This study includes findings for modulated frequency (MF) at 41Hz, as well as for high MFs, depending on the test tone frequency.3- The location of the study where the study is doneisn’t mentioned.1-The majority of the participants were awake at the end of thesession.2- Only one ear was tested.
3-No U.S. Food and Drug Administration approvedon the ASSR technique.