OBJECTIVE: To review the literature on auditory dyssynchrony (AD) or neuropathy which is characterized by absent auditory brainstem. Braz J Otorhinolaryngol. Jul-Aug;77(4) Auditory neuropathy/Auditory dyssynchrony in children with Cochlear Implants. [Article in English. Auditory neuropathy (AN)/auditory dyssynchrony (AD) is a very often missed diagnosis, hence an underdiagnosed condition in clinical practice.

Author: Zululmaran Daijas
Country: Turks & Caicos Islands
Language: English (Spanish)
Genre: History
Published (Last): 15 December 2007
Pages: 331
PDF File Size: 17.57 Mb
ePub File Size: 1.9 Mb
ISBN: 487-8-37096-335-4
Downloads: 66875
Price: Free* [*Free Regsitration Required]
Uploader: Shakajar

Outcomes of cochlear implantation in children with auditory neuropathy.

In such cases, the cochlear microphonic would also be expected to dyssynchfony absent. A comparison of hair-cell and nerve-fiber responses in the alligator lizard.

Auditory Neuropathy/Dys-synchrony and Its Perceptual Consequences

Two-way analysis of variance was applied to evaluate correlations between age at surgery, duration of cochlear implant use, and speech perception results. Zhonghua Dyssybchrony Xue Za Zhi ; Otolaryngol Head Neck Surg ; In both children, similar poor open-set speech perception scores on the Cantonese Speech Discrimination Test were obtained in both the unaided and aided conditions.

Methodologic differences between studies—some, for example, have used cochlear microphonic testing whereas others have used otoacoustic emissions as their measures of preneural function—make direct comparison difficult. Although neurons that are not entirely myelinated are capable of conducting action potentials, they do so with prolonged refractory periods and an impaired ability to transmit high-frequency pulse trains McDonald and Sears, ; Rasminsky and Sears, ; Pender and Sears, However, if they do represent a similar level of neural disruption, one might expect the early-onset patients to cope better because they grow up with an impaired but reasonably consistent neural signal.


Experience with statewide hearing screening. Axonal damage can occur in isolation as a result of specific disease processes or can occur in conjunction with or as a consequence of demyelinating conditions. Mechanical preprocessing in the mammalian cochlea. The impaired ability to accurately encode even low-rate 10 Hz amplitude changes seen in some cases does, however, point to neural disruption of the order of tens of milliseconds and may suggest a different pathologic mechanism.

Similarities in neural response characteristic at stimulus frequencies of 35 and 80 Hz suggests that the auditory system in the study population retrieved the temporal properties in coded information, following electrical stimulation, irrespective of the stimulus frequency.

Second, in addition to this normal effect of level, subjects with cochlear hearing loss often show a further reduction in resolution ability that is thought to be the result of a loss of outer hair cell function, and hence, a disruption of the active process Sellick et al. Click-evoked otoacoustic emissions and hearing threshold in sensorineural hearing loss.

Auditory neuropathy/Auditory dyssynchrony in children with Cochlear Implants.

The effects of hearing loss and age of intervention on some language metrics in young hearing impaired children. Sininger YS, Trautwein P.

Journal List Trends Amplif v. Frequency selectivity and temporal processing in Friedreich’s ataxia.

Auditory neuropathy/auditory dyssynchrony in children with cochlear implants

J Am Acad Audiol 1: The mechanism underlying this phenomenon has been a matter of some conjecture, but recent reports have shown that nonacoustic middle-ear muscle reflexes can be elicited in auditory neuropathy patients by tactile stimulation to the face, suggesting that the efferent components of the reflex arc facial nerve and stapedius muscle are intact Gorga et al.


This active process, which is thought to enhance both the threshold sensitivity and frequency tuning of the inner ear transduction system, is considered to reside in the outer hair cells Davis, Journal of the American Academy of Audiology It examines how outer, middle, and inner ear dysfunction; auditory neuropathy; and brainstem dysfunction influence the auditorh of the ABR and other auditory tests by a basic review of clinical cases.

However, the other 8 children did show a significant aided benefit, with a mean PBK-phoneme score of Excessive amounts of bilirubin a byproduct of red-blood cell metabolismwhich is often associated with liver immaturity in the newborn, can be toxic to the central nervous system and can result in significant neurologic insult known as kernicterus Shapiro, Physiological and Psychophysical Bases of Auditory Function.

These fluctuations, although not as dramatic as those reported by Gorga et al. See Figure 10 for details. Partial or complete loss of myelin can have profound effects on the generation and propagation of action potentials within auditory nerve fibers. Mechanisms by which synaptic disruption might occur in the auditory pathway in human subjects are yet to be determined. A high degree of intersubject variability has been reported, but overall, the findings indicate that discrimination ability is degraded by cochlear damage.

Autoimmune inner ear disease: Hearing loss due to auditory neuropathy.