Auditory Neuropathy Spectrum Disorder (ANSD)

Auditory Neuropathy Spectrum Disorder (ANSD) is defined as a hearing condition in which sound enters the inner ear normally, but the transmission of the signal to the brain is impaired. The characteristics of ANSD are highly variable and can manifest as any degree of hearing loss and functional ability. Some individuals with ANSD have minimal auditory complaints and do not know of their condition until adulthood. Others can have a complete lack of sound awareness, localization and auditory-based language ability (Berlin et al., 2010). However, most individuals fall in between these two extremes and typically complain of fluctuating hearing loss and difficulty understanding speech in noise. These vast individual differences in perception led
Speech perception problems are a common feature of ANSD. The ability to perceive individual phonemes and understand speech in the presence of background noise is analogous to psychoacoustic measures, such as temporal processing. Researchers hypothesize that an abnormality of the inner hair cells, the auditory nerve, or the synapse between them are the causes of signal disruption and poor temporal resolution in individuals with ANSD. For example, Zeng, Oba, Garde, Sininger, and Starr (1999) observed that children with ANSD performed poorly in tests of gap detection and temporal modulation transfer function (TMTF). Gap detection involves the ability to detect a small silence in between a burst of noise, while TMTF involves the identification of a change in amplitude in noise. The researchers found that there was a correlation between these temporal findings and speech perception. The participants who had more difficulty perceiving small changes in stimuli over time, also experienced greater difficulty perceiving speech. This difficulty is exacerbated in the presence of background noise. Zeng & Liu (2006) observed that participants with ANSD performed significantly worse in sentence recognition tasks than those with normal hearing and sensorineural hearing loss (SNHL) across various signal to noise ratios (SNR). Even in a condition of +15 dB SNR, the participants yielded
(2007) examined the receptive language and speech production abilities in children with ANSD managed with hearing aids. These participants were compared to children with SNHL who were also amplified. Receptive language was measured using the Peabody Picture Vocabulary Test and speech production was measured using the Diagnostic Evaluation of Articulation and Phonology. The study revealed delays in receptive language and speech production in those with ANSD in comparison to the norms established with typically hearing children. However, there were no significant differences between the children with ANSD and SNHL. The researchers concluded that children with ANSD could benefit from standard hearing aids and can do as well as their peers with