ANSD Flashcards
Berlin et al. (2003)
The ABR reflects the synchronous neural response to acoustic stimuli
Starr et al. (1996)
Evaluated patients with ANSD and determined that nine out of every ten patients had absent ABRs, while the 10th patient had grossly abnormal ABRs characterized by the presence of only wave V responses to high-intensity stimuli.
Berlin et al. (2003)
To diagnose ANSD accurately using an ABR, responses obtained from rarefaction and condensation clicks should be evaluated to distinguish the cochlear microphonic from neural responses
Collet et al. (1989)/Starr, Sininger, & Pratt (2000)
Since OAEs reflect the functional integrity of the outer hair cells of the cochlea/OAEs are typically present despite absent or abnormal ABRs for patients with ANSD
Collet et al. (1989)
Established that for patients with sensorineural hearing loss, OAEs are generally absent when hearing loss reaches a moderate degree or worse and that presence of OAEs drops as a function of hearing loss.
Talaat et al. (2013)
However, while present OAEs may support the presence of ANSD, OAEs can disappear over time
Santarelli et al. (2008)
As a crosscheck to the ABR and OAE evaluations for suspected ANSD, electrocochleography (ECochG) may be used to obtain further information about cochlear nerve and hair cell activities.
Berlin et al. (2005); Gelfand et al. (1990)
Patients with ANSD have absent or elevated ASR responses. whereas ASR responses will be present in the normative range for cochlear hearing loss of up to moderately-severe degree
Amos & Humes (2007)
For patients with high-frequency sensorineural (cochlear) hearing loss, speech understanding is expected to be correlated to the degree of hearing loss
Zeng et al. (2004) #1
In fact, the perceptual consequences of ANSD are approximately the opposite of what is observed in cochlear-impaired subjects // As such, it is expected that patients with cochlear impairment experience impaired frequency resolution, but relatively normal temporal processing after taking into account the person’s audibility // The disrupted neural activity does impact timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, signal detection in noise, and sound localization using interaural time differences
Zeng et al. (1999)
Poor temporal resolution will limit a person’s access to temporal cues, such as those needed for the gap detection test
Zeng et al. (2004) #2
The differences in perceptual consequences for ANSD and cochlear hearing loss suggest the use of different neural codes in auditory perception: a synchronized spike code for temporal processing and a duplex code for frequency processing.
Berlin et al. (1993); Starr et al. (1996)
For children with ANSD, hearing levels can fluctuate over time and can range from normal to a profound hearing loss
Breneman, Gifford, & DeJong (2012)
Some evidence suggests that cochlear implantation is a viable solution for children with ANSD who are not making auditory progress independent of their behavioral hearing thresholds
He et al. (2016)
Yet, at the level of the auditory nerve, some aspects of temporal response properties have been shown to differ between implanted children with ANSD and implanted children with cochlear hearing loss
Rance & Barker (2008)
While outcomes of cochlear implants may exceed those with hearing aids in this patient population, these children still may not perform like their peers with cochlear hearing loss who receive cochlear implants
Walker et al. (2016)
Parents can be counseled that children with ANSD in the mild-severe hearing loss range may achieve function outcomes that are similar to those from children with cochlear hearing loss when fit with appropriate amplification
American Academy of Audiology (2013)
Based on this information and recommendations from the AAA Pediatric Amplification Guidelines, children with ANSD should receive hearing aids first if their behavioral thresholds are significant enough to impede speech/language development and speech understanding at conversational levels.
Speech understanding differences between ANSD and Cochlear HL
Both cochlear hearing loss and ANSD will affect a person’s ability to understand speech. However, they do so in different ways. In cases of ANSD, speech recognition performance is highly variable for both quiet and noise conditions. Notably, speech understanding in ipsilateral competing noise is generally poorer for patients with ANSD than with cochlear hearing loss. For patients with high-frequency sensorineural (cochlear) hearing loss, speech understanding is expected to be correlated to the degree of hearing loss (Amos & Humes, 2007).
Temporal and Spectral Cues as reflected in ANSD versus Cochlear HL
Cochlear hearing loss and ANSD will also affect an individual’s ability to access spectral and temporal cues differently. In fact, the perceptual consequences of ANSD are approximately the opposite of what is observed in cochlear-impaired subjects (Zeng et al., 2004). At a global level, cochlear hearing loss implies disrupted frequency processing with normal temporal processing, while ANSD implies normal processing of frequency cues but abnormal processing of temporal cues. Spectral processing for frequency resolution occurs at the level of the cochlea and is dependent on good cochlear function. As such, it is expected that patients with cochlear impairment experience impaired frequency resolution, but relatively normal temporal processing after taking into account the person’s audibility (Zeng et al., 2004). On the other hand, patients with ANSD likely experience normal cochlear processing. Psychophysical measures show that disrupted neural activity minimally effects pitch discrimination at high frequencies and sound localization using interaural level differences. The disrupted neural activity does impact timing related perception, such as pitch discrimination at low frequencies, temporal integration, gap detection, signal detection in noise, and sound localization using interaural time differences (Zeng et al., 2004). Poor temporal resolution will limit a person’s access to temporal cues, such as those needed for the gap detection test (Zeng et al., 1999). The differences in perceptual consequences for ANSD and cochlear hearing loss suggest the use of different neural codes in auditory perception: a synchronized spike code for temporal processing and a duplex code for frequency processing (Zeng et al., 2004).
