The subject of this case study is a 6-year-old child who was diagnosed with bilateral ANSD shortly after birth.
#Auditory neuropathy spectrum disorder in adults trial#
5,8,13-16 Case Study and Trial Hearing Aid Fittings For a 6–Year–Old With ANSDīackground. The enhanced amplitude difference also increases perception of speech events, such as voice onset time, burst, and transitions, and helps to maximize signal-to-noise ratios. These enhanced amplitude differences help provide salient cues for consonant and vowel perception. Adjusting the release time for compression to a slower rate allows for greater amplitude differences in the temporal modulations. Another method proposed to expand the amplitude of the temporal modulations.
One method proposed was to filter out low frequency signals or shift them to the high frequency ranges via frequency transposition. Research utilizing speech perception scores and psychophysical results supports the use of linear circuitry and other innovative signal processing schemes to improve speech understanding for patients with ANSD. Note the decrease in amplitude and increase in noise present in the “fast response” compared to the enhanced amplitudes of “slow response” for a speech sample. Spectrographs of speech sample demonstrating the effects of compression rate on the amplitude of the spectral envelope. 6,7,12-14 The impact of this reduction in the temporal cues may be more detrimental to children who rely more heavily on temporal variations during their language development. Further, it can reduce consonant and sentence intelligibility and decrease the overall signal-to-noise ratio. This reduction of the amplitude fluctuations in the spectral envelope can make it more difficult to perceive these much-needed temporal cues. Several studies have demonstrated that the use of non-linear amplitude compression hearing aid circuitry, such as WDRC, which tend to utilize fast compression attack and release times, actually reduces the amplitude fluctuation of the spectral envelope of speech (Figure 1). Current hearing aid technology doesn’t address enhancing the temporal envelope of the speech signal to compensate for temporal processing deficits associated with ANSD. 1,11 Patients with ANSD have temporal perception difficulties that can make speech difficult to understand. 10 However, research has demonstrated that the behavioral puretone thresholds for patients with ANSD can fluctuate and are less predictive of the child’s true hearing difficulties.Īccordingly, hearing aids are of limited use for patients with ANSD. Some management strategies propose fitting a child with ANSD with hearing aids “when consistent test-retest reliability” for puretone and speech detection thresholds is obtained. With hearing- impaired patients, audiologists typically address “restoring audibility” with the utilization of hearing aids by meeting prescribed targets for frequency and gain. 5-9 Treatment StrategiesĬlinical management of patients with ANSD can be difficult. Speech perception can be adversely affected due to reduced sensitivity to follow fast and slow temporal modulations, reduced ability to detect gaps in continuous sound, and reduced frequency discrimination at low frequencies. 3,4 Further studies have demonstrated poor temporal resolution associated with ANSD, which results in poor perception of changes in stimuli over time. 2 A majority of individuals with ANSD have low frequency hearing loss and/or very poor speech recognition scores for the degree of hearing loss measured through puretone assessment. The range of auditory complaints and auditory difficulties associated with AN is vast and has resulted in the acceptance of the term auditory neuropathy spectrum disorder (ANSD) to better describe the disorder. Spirakis, AuD, is clinical coordinator for audiology at All Children’s Hospital, Tampa, Fla.
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