ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTThe acoustic stapedius reflex (ASR) is the sound-evoked contraction of the stapedius muscle. The ASR is mediated by a neural network, receiving its afferent input from the VIIIth cranial (auditory) nerve and sending its efferent output to the VIIth cranial (facial) nerve. Several centers in the brain stem comprise the central portion of the reflex pathway. The stapedius muscle in each ear responds to ipsilateral, contralateral, and binaural stimulation. The normal ASR threshold is 90 to 95 dB SPL for tones and 70 to 75 dB SPL for wideband noise. In ears with sensori-neural hearing loss, ASR thresholds are elevated more for wideband noise than for tones. These bandwidth-related changes form the basis for detection of hearing loss from ASR data. A number of methods have been proposed which differ in the nature of the outcome. Some try to quantitatively estimate hearing loss, whereas others categorize outcomes as pass or fail. In general, methods that attempt quantitative estimation of hearing loss do so at the expense of higher error rates. With adequate recording techniques, the ASR has been shown to effectively detect hearing losses exceeding 30 dB in adult subjects. Although ASR recording in newborns requires a higher probe frequency than the commonly used 226 Hz, ASR thresholds in newborns appear to be similar to those in adults. Limited information exists on the use of the ASR for detection of hearing loss in the infant population. With adequate attention to methodological requirements of testing infants, the ASR may offer a cost-effective method for the early detection of hearing loss.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTOtoacoustic emissions have great promise for use in clinical tests of the functional status of outer hair cells, which represent cochlear structures that make a major contribution to the hearing process. A substantial literature is available concerning the evaluation of outer hair cell function by transiently evoked otoacoustic emissions. However, relatively little attention has been focused on the benefits of testing with distortion-product otoacoustic emissions. The purpose of this presentation is to provide knowledge of the principal advantages offered by distortion-product emissions testing.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTThe auditory brain stem response (ABR) is felt to be an objective technique for predicting hearing thresholds because a voluntary response is not required from the subject. However, determination of ABR threshold can be a subjective process. This article discusses a technique, termed Fsp, which adds objectivity to ABR threshold detection by creating a ratio of signal plus averaged background noise over an estimate of the averaged background noise for any given averaged ABR. Fsp, values have an F distribution. Consequently, the confidence of true detection for a given ABR can be determined by comparing its calculated Fsp, value to statistical tables. Using a technique such as Fsp, not only adds objectivity to ABR threshold detection, but also optimizes test time by allowing the averaging process to stop as soon as the background noise has been reduced and the true neural potential can be judged to be present. The estimate of the background noise can be used as a weighting factor to reduce the influence of noisy segments during the averaging process as well. Using this technique, we have found ABR threshold to be within 5 or 6 dB of psycho-physical threshold for like (click) stimuli and, in our pediatric clinic, ABR click thresholds are within 10 dB of pure-tone average for children with losses ranging from mild to profound.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTEvoked potential threshold estimation can be made truly objective by using statistically based methods. In general, time domain analysis is preferable for responses which are impulsive (temporally narrow, spectrally broad), whereas frequency-domain analysis is more appropriate for tonal responses (spectrally narrow, temporally broad). In both time and frequency domains, methods comparing evoked potential power to noise models are robust and powerful. For spectrally narrow responses such as steady-state evoked potentials, the performance of magnitude-squared coherence, the ratio of grand average power to mean subaverage power, is superior to that of other methods for objective response detection.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTClinical use of the middle latency response (MLR) has been limited by the variability of the response during sleep in young children. Theoretically, this variability can be explained by the differential maturation of the primary and nonprimary components of the MLR generating system. The model is supported by animal neurophysiological data. Applied to the human system, the model predicts that, in children, MLR generators are active only' during certain stages of sleep. From a clinical standpoint, this has led to a procedure for signaling the clinician when a child is in a sleep state favorable for recording the MLR.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTThis article deals with the limitations of infant behavioral audiometry, which have led us to seek objective methods of audiometry for determining hearing sensitivity in infants. It describes efforts to add objectivity to (or reduce the subjectivity of) behavioral methods of infant audiometry. Several aspects of visual reinforcement audiometry (VRA), including the head turn response, the use of control trials, and adherence to the principles of operant conditioning, serve to reduce the subjectivity inherent in behavior observation audiometry. In addition, computer control of VRA procedures can relieve the examiner of potentially subjective decision-making during the course of evaluation and can facilitate testing with sophisticated algorithms that could not be done manually by a single examiner. Computer simulations to determine the best VRA test parameters are described.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTVarious objective electrophysiological techniques have been used to supplement the behavioral measurements for cochlear implant patients. This report summarizes various studies of these measurements, including stimulus artifact, averaged electrode voltages, electrical stapedius reflexes, electrical auditory brain stem responses, electrical middle latency responses, and cortical auditory responses. These techniques have been shown to provide valuable information in the evaluation of device and electrode integrity in addition to correlated values to behavioral thresholds and comfort levels.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

ABSTRACTTransient evoked otoacoustic emissions (TEOAEs) occur after presentation of brief acoustic stimuli such as clicks and tone pips. They represent physiological activity from within the cochlea, specifically from normal functioning outer hair cells. TEOAEs are frequency specific in that their spectra are determined by the spectra of the evoking stimulus and the audiometric configuration. TEOAEs are sensitive to mild to moderate degrees of cochlear hearing loss up to about 40 to 50 dB HL. They can be measured rapidly and noninvasively in infants and children. Among the potential applications in pediatric audiology are screening for hearing impairment in neonates, separating peripheral hearing loss and central auditory dysfunction, and monitoring cochlear status in children receiving oto-toxic drugs.

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:1993

数据来源: OVID