ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Outer hair cell electromotility is a rapid, force generating, length change in response to electrical stimulation. DC electrical pulses either elongate or shorten the cell and sinusoidal electrical stimulation results in mechanical oscillations at acoustic frequencies. The mechanism underlying outer hair cell electromotility is thought to be the origin of spontaneous Otoacoustic emissions. The ability of the cell to change its length requires that it be mechanically flexible. At the same time the structural integrity of the organ of Corti requires that the cell possess considerable compressive rigidity along its major axis. Evolution appears to have arrived at novel solutions to the mechanical requirements imposed on the outer hair cell. Segregation of cytoskeletal elements in specific intracellular domains facilitates the rapid movements. Compressive strength is provided by a unique hydraulic skeleton in which a positive hydrostatic pressure in the cytoplasm stabilizes a flexible elastic cortex with circumferential tensile strength. Cell turgor is required in order that the pressure gradients associated with the electromotile response can be communicated to the ends of the cell. A loss in turgor leads to loss of outer hair cell electromotility. Concentrations of salicylate equivalent to those that abolish spontaneous Otoacoustic emissions in patients weaken the outer hair cell's hydraulic skeleton. There is a significant diminution in the electromotile response associated with the loss in cell turgor. Aspirin's effect on outer hair cell electromotility attests to the role of the outer hair cell in generating Otoacoustic emissions and demonstrates how their physiology can influence the propagation of Otoacoustic emissions.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Otoacoustic emission test instruments are now entering routine audiological practice. Two general classes of technique are in use in laboratory work—those employing spectrum analysers to observe the continuous generation of OAEs, both stimulated or unstimulated, and those using transient stimulation and waveform averaging to extract a delayed OAE or “cochlear echo” waveform from ear canal sound. Both methods have particular advantages in clinical applications. The transient OAE type of method has proved very effective in screening applications, particularly in neonates. It is possible to perform noninvasive screening acoustic cochleography in about a minute. The technique is also useful for characterizing cochlear mechanical status prior to long term monitoring. Achieving routinely reliable OAE test performance in clinical and screening applications under nonideal conditions makes special demands on the instrumental design and the response evaluation procedures. The essential requirements are reviewed and discussed in a general and specific context. We have tried to meet these requirements in a transient evoked Otoacoustic emission system (the ILO88) which we designed to operate with a personal computer. We report on our design of probe, and our use of evaluation procedures for probe fit, and response qualty. Signal processing methods have been developed to reject noncochlear acoustic responses, and to optimise the rejection of patient noise. Examples of its clinical use, and the practical problems typically encountered are given here.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Otoacoustic emissions can be separated into two interrelated classes according to the type of eliciting stimulus. On the basis of this categorization, four discrete subtypes can be recognized that include spontaneous, transiently evoked, stimulus-frequency, and distortion-product Otoacoustic emissions. Methods of recording and findings in the ears of normally hearing humans are reviewed for each emission type.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Evoked otoacoustic emissions (EOAEs) are a promising tool for evaluating cochlear status in children. Preliminary data from normal-hearing subjects ranging from birth to 29.9 years old are discussed. EOAEs are present and robust in infant ears. However, there is a statistically significant decrease in EOAE amplitude for a fixed stimulus level with increasing age even in a carefully screened sample. At the present time it is unclear if these ageassociated changes are due to normal developmental changes in the external and/or middle ear acoustics, normal developmental changes in cochlear mechanics and/or everyday cochlear wear and tear. Issues related to further application of evoked emissions to pediatrie populations are discussed.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Seven hundred and twenty-three neonates under intensive care have been tested by evoked Otoacoustic emissions (EOAE) and the auditory brain stem response (ABR) to investigate the use of EOAE as a test for hearing impairment. Three hundred and thirty-one have had follow-up tests to the age of at least 2 years. The EOAE test has been found to be practical and quick to perform. The proportion of NICU infants producing a recordable EOAE is 80%, and the sensitivity and selectivity to the ABR result in the period up to 3 months post due date is 93 and 84%, respectively. These figures are high enough and the reduction in time compared to ABR is sufficient for the EOAE to be considered as the primary screen. The follow-up data show mixed results with both false positives and false negatives present. The incidence of severe hearing impairment is close to that expected from retrospective studies at 2 in 331 (1 bilateral, 1 unilateral). Firm conclusions on the sensitivity of EOAE to long-term hearing impairment await the results from larger numbers of infants and further follow up data.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

This study was performed for the purpose of determining whether or not evoked Otoacoustic emissions are useful as a clinical test. Two hundred and twenty-six sequences of the emission in response to stimulus tone bursts were averaged. The detection threshold of the emission was elevated in ears of inner ear impairment with profound sensorineural hearing loss, such as inner ear anomaly, mumps deafness, or sudden deafness, but it was not observed in ears of functional deafness. The mean interaural differences of emission threshold were near 35 dB in unilateral inner ear impairments with profound hearing loss. There was a positive correlation between the interaural difference of audiometrie threshold and that of emission threshold in sudden deafness ears with various degrees of hearing loss. The incidence of continuous emission, whose duration was longer than 6 msec, was 30% in normal hearing ears and it was close to 90% in ears with bilateral or unilateral dip type hearing loss. The result was verified in a survey of a junior high school brass band. The conclusion is that there is clinical usefulness for the evoked Otoacoustic emissions in evaluating cochlear function and in predicting noise susceptibility.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Otoacoustic emissions permit, for the first time, an unbiased means of examining the preneural elements of the peripheral auditory pathway that make the initial contribution to the perception of acoustic stimuli. Distortionproduct Otoacoustic emissions (DPOAEs) represent one type of evoked emission that has significant potential for becoming an important test in the audiometrie evaluation of hearing capacity. In the present review, selected examples of several forms of sensorineural hearing loss demonstrate that DPOAEs have the ability to act as objective indicators of the frequency/level configuration of the conventional audiogram in cases in which hearing impairment results primarily from damage to the outer hair cells. In contrast, normal DPOAE functioning, in the presence of a significant hearing loss, indicates a locus of damage central to the region of the outer hair cells. Like the other emitted responses, DPOAEs can be measured noninvasively, are highly repeatable, under test-retest conditions, and are simple and rapid to detect using microcomputerbased instrumentation. Further, DPOAEs test both the “threshold” and suprathreshold levels of outer hair-cell activity in the form of response/growth functions, over a 30− to 40-dB stimulus range. In combination, these attributes indicate that DPOAEs can provide an objective and comprehensive assessment of the cochlear reserve of a given ear.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The aim of this paper is to review the properties of otoacoustic emissions from a clinical point of view and to discuss the perspective interest of this test. In adults, the clinical significance of evoked Otoacoustic emissions seems to be limited either in endocochlear hearing losses or for detecting retrocochlear diseases. In infants, evoked Otoacoustic emissions seem to be a reliable, simple, non-invasive, and precise method for estimating auditory sensitivity for midfrequencies (1–4 kHz). Then, EOEs could be considered as an interesting way for screening auditory dysfunction in infants.

ISSN:0196-0202    

出版商:OVID    

年代:1990

数据来源: OVID