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At least 1,063 records · Page 59Linked to original sources
PubMed1991

Click evoked otoacoustic emissions in adult subjects: standard indices and test-retest reliability.

The present study was designed to evaluate transiently evoked otoacoustic emissions in an otologically normal adult population. Using the ILO 88 Otodynamic Analyzer, the recorded otoacoustic emission responses were analyzed for five parameters. Considering the variability of instrumentation and technique in otoacoustic emission testing, we have defined a normative data pool using standard commercially available testing equipment. These data should facilitate comparison with data acquired in various pathologic states. The test-retest validity of this procedure also was evaluated and was found to be high. Use of click evoked otoacoustic emissions, with some caveats, appears to be a promising technique for further research into the assessment of normal/abnormal cochlear function.

Acoustic Stimulation↗
PubMedDate not supplied

[Evoked oto-acoustic emissions in patients with retinitis pigmentosa].

Evoked otoacoustic emissions (EOE) offer a unique opportunity to measure objectively the function of outer hair cells in human beings. In this paper the Authors report a study carried out employing EOE evaluation on cochlear function in subjects with retinitis pigmentosa. Nine patients with retinitis pigmentosa with normal hearing in both ears upon traditional audiometric evaluation were studied. The frequency spectrum of the EOE was taken into consideration, evaluated in frequency bands of 50 Hz, in order to ascertain the presence or absence of the emissions and, when present, their amplitude. These data were compared statistically, using the Student's T Test, to those obtained in a homogeneous control group of normal subjects. In subjects with retinitis pigmentosa, average EOE intensity values were statistically lower than those found in normal subjects. In fact, the Student's T Test evaluation revealed significant differences in EOE intensity in 64 of the 127 frequency bands examined. Moreover, the distribution of the EOE in patients with retinitis pigmentosa proved to be more discontinuous than that observed in the normal subjects. These data appear to indicate authentic alterations in the cochlear mechanics in patients with retinitis pigmentosa. Such alterations may well be related to outer hair cell lesions. It seems likely that the auditory system is involved in retinitis pigmentosa degenerative processes more frequently than traditional audiometric tests have been able to show.

Adolescent↗
PubMed1991

[Otoacoustic emissions].

Otoacoustic emissions provide a new method for objective assessment of peripheral auditory function. Emissions have been recorded in 80 patients and comparisons made with subjective hearing tests and brain stem response audiometry. Our experiences confirm that this procedure is rapid and easy to perform, and that the presence of emissions is a reliable indication of normal function in the middle ear and cochlea. This is particularly useful in neonates, young children and adults whose inability to cooperate prevents the use of behavioural audiometry. Recording of otoacoustic emissions can replace brain stem response audiometry as the primary objective assessment of auditory function in these groups.

Audiometry, Pure-Tone↗
PubMed1990

[Effects of endotoxin on the cochlear electrophysiology and Na(+)-K(+)-ATPase activity].

Hemophilus influenzae (type B) endotoxin 10 micrograms was put in the niche of the round window in guinea pigs. The CAP thresholds and N1 latencies were measured before and 12, 24 and 72 hours after experiments. The 10 kHz and 8 kHz CAP thresholds after experiments were significantly higher (P less than 0.01), the N1 latencies were prolonged (P less than 0.05). There were minute changes in 4kHz CAP thresholds and N1 latencies (P greater than 0.05). In all time groups, the Na(+)-K(+)-ATPase activity was outstandingly weakened. It suggested that: (1) endotoxin put in the niche of the round window is responsible for the cochlear function disturbances in high frequencies, and (2) the decrease of the Na(+)-K(+)-ATPase activity is an important factor for the electrophysiological disturbances in the inner ear.

Animals↗
PubMed1991

[Evoked otoacoustic emissions in normal and hearing impaired adults and children].

In adults and children, 203 normal ears, 124 cars with hearing-impairment and 37 ears with middle ear problems were studied concerning click-evoked oto-acoustic emissions. According to the results, this method by high specifity and sensitivity renders possible the recognition of low sensory hearing losses. Complete middle ear effusions too make themselves conspicuous by preventing the reception of these responses. The recording of click-evoked oto-acoustic emissions is a most promising auditory screening-method. A general use could essentially improve the early detection of hearing losses in infants. Additionally, in the pedaudiologic practice possibilities are indicated to employ this technique as a topodiagnostic instrument.

Adolescent↗
PubMed1991

[Transitory evoked otoacoustic emissions in isolated high frequency, low frequency and middle frequency hearing].

Transient evoked otoacoustic emissions (TEOAE) of 153 patients of various ages with normal or nearly normal hearing in the low, high or middle frequency ranges (different aetiologies) have been recorded. We found that the rate of detection of otoacoustic emissions depends on the width of the frequency range of preserved hearing. Single cases of narrow bands of hearing in the middle frequency region showed this region's significance for the high detectability of TEOAE. Although the investigated population consists mainly of adults, conclusions for the use of the TEOAE method for infant screening are drawn.

Audiometry, Pure-Tone↗
PubMed1990

Distortion product emissions in humans. II. Relations to acoustic immittance and stimulus frequency and spontaneous otoacoustic emissions in normally hearing subjects.

Multifrequency and multicomponent evaluations of aural acoustic immittance, including tympanometry and acoustic reflex testing, were performed on 44 normal ears to examine the influence of middle ear functioning on the generation and detection of distortion product otoacoustic emissions (DPEs). In the same ears, the prevalence and parametric features of spontaneous and stimulus frequency emissions were also assessed so that their relationship to the detection "thresholds" and amplitudes of corresponding DPEs could be determined. The general outcome was that none of the examined features of acoustic immittance provided an explanation for the discrete, low-amplitude DPE regions observed in about one third of normal ears. Moreover, the presence of typical spontaneous and stimulus frequency emissions in these same "irregular" ears indicated that emission generation and reverse cochlear transmission were also operating normally within these regions of reduced DPEs. Consequently, other, as yet undetermined influences appear to contribute to the DPE variability noted in some ears. Finally, the simultaneous presence of stimulus frequency emissions, but not spontaneous emissions, appeared to reduce the detection "thresholds" and increase the amplitudes of low-frequency DPEs.

Acoustic Impedance Tests↗
PubMed1990

Distortion product emissions in humans. I. Basic properties in normally hearing subjects.

Distortion product otoacoustic emissions (DPEs) at the 2f1-f2 frequency were recorded from 44 normal ears in response to equilevel primary tones. Detailed testing included the recording of DPE "audiograms" in 100-Hz steps from 1 to 8 kHz at three primary-tone levels (65, 75, and 85 dB sound pressure level [SPL]). In addition, response-growth or input-output (I/O) functions depicting the relationship of the amplitudes of DPEs to primary-tone levels, ranging from 25 to 85 dB SPL in 5-dB steps, were also tested for 11 frequencies distributed at quarter-octave intervals over the identical frequency range. The average DPE "audiogram" illustrating the frequency response of these emissions demonstrated a bilobed contour having a low-frequency maximum at approximately 1.5 kHz and a high-frequency peak that plateaued at about 5.5 kHz. The two maximum regions were separated by a minimum around 2.5 kHz. Depending on the frequency region, the average I/O functions exhibited detection "thresholds" at 3 dB above the noise floor at primary levels between 35 and 45 dB sound pressure level. The dynamic range of the emitted response between detection "threshold" and maximum amplitude varied over a 40-dB extent of the stimulus-level dimension. Approximately one third of the ears exhibited irregular DPE "audiograms" in which emitted responses were significantly reduced in restricted regions tested by low, medium, or high frequencies. When the 44 ears were separated into two groups representing more-normal and less-normal responses, the irregular "normal" ears demonstrated increased variability, especially in high-frequency regions. Mean age did not explain the differences noted between the two types of normally hearing subjects. However, across ears, DPE amplitudes and "thresholds" for the highest frequencies tested were correlated significantly with age in that the oldest individuals showed higher "thresholds" and lower amplitudes.

Acoustic Impedance Tests↗
PubMed1990

[Evoked acoustic oto-emissions: effects of atropine].

The Evoked Otoacoustic Emissions (EOE) are a sinusoidal wave complex coming from the contractile properties of the cochlea and particularly of the outer hair cells. This activity is influenced by the centrifugal pathways whose transmitter is acetylcholine. In order to study the effects of the functional block of the cochlea, ten young normal subjects were examined recording the EOE before and ten mins after the i.v. infusion of 1 mg of atropine. The statistical analysis of the results has shown a significant decrease only in EOE appearance threshold in absence of modifications of the saturation level. These data have led us to believe that atropine blocking of the centrifugal pathways causes a disfunction of the outer hair cells that accept less energy to be transduced into a neural stimulus and on the other hand more energy as EOEs.

Adolescent↗
PubMed1989

[Effect of kanamycin on the cochleas in guinea pigs].

Kanamycin (400 mg/kg) was injected daily for 5 days in guinea pigs, the changes in CM and AP responses were recorded. The CM threshold was elevated in 34.5% of the animals and the CM amplitude was reduced when compared with normal animals (P less than 0.005). The AP threshold was elevated in 13.8%. The latency of N1 was increased (P less than 0.001) and the amplitude of N1 reduced at 80 dB (S-L) (P less than 0.001).cAMP and cGMP levels in the organ of Corti and stria vascularis spiral ligament decreased, and the decrease correlated with the changes in auditory function. We consider the reduction of cyclic nucleotides in the cochlea may be important in kanamycin ototoxicity.

Animals↗
PubMed1989

[A case report of spontaneous otoacoustic emissions].

A case with audible spontaneous oto-acoustic emissions (SOAE) in an infant aged four months is presented. The frequency was determined to be approximately 6,100 Hz and the volume to 27 dB sound pressure level (SPL). The mechanism involved in SOAE is summarized.

Acoustic Stimulation↗