Biomedical subjects

S Hatzopoulos

Publications and source records attributed to S Hatzopoulos.

18 recordsLinked to original sources

PubMed2003

TEOAE recording protocols revised: data from adult subjects.

The objective of this study was the experimental re-evaluation of the current clinical transiently evoked otoacoustic emission (TEOAE) protocols, based on linear and non-linear protocol paradigms from a population of 42 adult subjects serving as a normative database. The linear and non-linear TEOAE responses were elicited by clicks with average intensities of 72 and 84 dB p.e. SPL respectively. An initial comparison between non-processed non-linear and linear recordings, at early recording segments from 3.2 to 5.2 ms, showed that the responses had highly similar contours and no statistically significant mean differences. The stimulus-induced artefact in the linear TEOAE responses was suppressed by post-processing the data with a window function (3.8-13.8 ms) and by a high-pass filter at 830 Hz. A repeated-measures model was used to evaluate the differences between post-processed linear and non-linear responses across clinical variables of interest (such as TEOAE response, noise, correlation, and signal-to-noise ratios (SNRs) at 1.0-5.0 kHz). The data indicated that the linear recordings demonstrate significantly lower levels of noise (and thus superior SNRs) and higher values of reproducibility. Normative adult scoring criteria were calculated from free distribution tolerance intervals for the TEOAE correlation and the SNRs at 2.0 and 3.0 kHz.

Acoustic Stimulation↗

PubMed2002

Hearing loss evaluation of Sjögren's syndrome using distortion product otoacoustic emissions.

Sjögren's syndrome (SS) is a cell-mediated immune disorder primarily affecting the exocrine glands and hearing loss may be the first otological manifestation of this autoimmune disease. In order to assess the degree of sensorineural hearing loss in SS, 22 female patients were examined by means of standard audiometric tests (pure-tone audiometry, acoustic reflexes and impedance testing) and using distortion product otoacoustic emissions (DPOAEs). The results indicated that only 36.3% of the patients had mild sensorineural hearing loss. Hearing level and distortion product threshold estimates were found to be significantly correlated. No relationship was found between the duration of the disease and the DPOAE and hearing threshold variables. The data suggest that SS may not directly cause sensorineural hearing loss.

Adult↗

PubMed2002

[Cisplatin and carboplatin-induced ototoxicity in children: clinical aspects and perspectives for prevention].

In 70% of the cases of malignant neoplasms in pediatric patients antiblast therapy is used. The administration of platinum compounds, Cisplatin (CDDP) or Carboplatin (CBDCA), often at high cumulative doses, necessarily implies a certain degree of toxicity which normally takes on secondary significance in the healing of the child. Among the side effects, early and delayed ototoxicity is well known and, in the child, take on particular aspects. While not abandoning the treatment of the base pathology, the therapeutic findings, increasingly comforting in terms of long-term survival, require more accurate evaluation and overall control of the quality of life of these young patients. Since initial cochlear damage can be reversible, auditory function must be carefully monitored in order to prevent the lesions from becoming permanent, in particular prior to the onset of speech. For this reason a retrospective study was made of a group of 26 children affected by malignant neoplasms all of whom had undergone a polychemotherapy protocol with the administration of CDDP in 14 cases and CBDCA in 12 cases. All these young patients were monitored with conventional audiometry. The presence of different variables (antiblastic drug administration schedule, course of the disease, general conditions) only permitted evaluation of a single correlation: between auditory function at the end of the treatment (or after a few cycles of therapy) and the overall dose of CDDP or CBDCA administered. In 16 cases (62%) typical bilateral perceptive deafness was detected progressively involving the hyperacute and acute frequencies. The finding of hearing loss was significantly greater in the patients treated with CDDP (86%) vs. those treated with CBDCA (33%). Moreover, analysis of the results showed that, within certain limits, ototoxicity can depend more on individual sensitivity to the drug than to the total dose administered. The results confirm the well-known ototoxicity of platinum compounds, in particular CDDP. As ever improved therapeutic results are achieved in the treatment of malignant neoplasms in pediatric patients, greater attention can be paid to the quality of life of these young patients after the disease has been healed. Careful monitoring of auditory function can be extremely important in the pursuit this objective; indeed, this makes it possible to adjust antiblast drug administration, particularly in the later stages of treatment, customizing the treatment schedule to individual patient sensitivity.

Adolescent↗

PubMed2001

Efficient otoacoustic emission protocols employed in a hospital-based neonatal screening program.

Within the context of a hospital-based newborn hearing screening program, we have studied the application of two OAE protocols (TEOAE and DPOAE) on a group of 250 well babies. The main goal of this study was to evaluate the performance of DPOAE protocol in a relatively large population sample. using a preset number of five tested frequencies, in comparison with a default TEOAE screening protocol. The data were collected on the second day of life and during spontaneous sleep. The TEOAE recordings were acquired with linear protocols using click stimuli of 70-75 dB SPL and were used as indicators of normal cochlear function. The cubic distortion product DPOAE responses were evoked by an asymmetrical 75-65 dB SPL protocol, with a frequency ratio of 1.22. Five frequencies (referring to F2) were tested at 1.5, 2.0, 3.0, 4.0 and 5.0 kHz. The data from the DPOAE responses show a similar pass rate (similarity = 0.98) to the linear TEOAE protocol. The data presented suggest that a DPOAE cochlear evaluation, at 5 pre-selected frequencies, has clinical potential.

Deafness↗

PubMed2001

Correlations between risk factors for hearing impairment and TEOAE screening test outcome in neonates at risk for hearing loss.

The aim of the study was to find the correlation between specific risk factors for hearing impairment as well as between risk factors and TEOAE screening results in neonates at risk for hearing impairment. Seventy-one newborns at risk for hearing impairment have been included in the study. Strong correlations between specific risk factors were found. Investigation of the relationship between specific risk factors and TEOAE signal-to-noise ratio (SNR) showed that in children with genetic risk factors, TORCH (toxoplasmosis, rubella, CMV, herpes virus, others) infections and in those treated with ototoxic drugs, the values of SNRs were significantly lower than in children at risk who did not present those factors. In case of hyperbilirubinaemic children the values of SNR were significantly higher than in the controls. In our opinion these relationships may be partially explained by the positive predictive values of these risk factors, but other intrinsic factors may also be involved.

Guidelines as Topic↗

PubMed2000

Optimization of TEOAE recording protocols: a linear protocol derived from parameters of a time-frequency analysis: a pilot study on neonatal subjects.

Linear and non-linear TEOAE protocols were compared in terms of nine parameters in order to define the protocol producing recordings with the highest signal quality (lowest noise and highest signal-to-noise ratio). The pilot project acquired data using ILO-92 apparatus from 220 neonates (397 ears) at the second/third day after birth in three European laboratories. A Gabor spectrogram time-frequency representation of the recordings showed considerable frequency dispersion in TEOAE latencies >4.0 ms. The data, analysed with a Wilcoxon test, indicated that a linear TEOAE protocol: (i) generates recordings of a lower noise and a higher signal-to-noise (S/N) ratio in the 2.0, 3.0, 4.0 kHz TEOAE bands; (ii) the increase in the S/N ratio can result in a decrement of the required number of TEOAE sweeps; (iii) the higher values of S/N can be used in the estimation of more robust pass-fail criteria, minimizing the percentage of false positives and negatives.

Acoustic Stimulation↗

PubMed2000

[Distortion product otoacoustic emission (DPOAEs) and newborn hearing screening: a feasibility and performance study].

In view of the great psychological effect deafness has on one's social life, the scientific community has long sought the best way to define the hearing function. The development of new technologies in this field has set "early intervention" as the primary target for screening. For this reason, within the contest of a program of audiological newborn hearing screening, the Authors have used data from a selected group of 1250 newborns to (a) compare the clinical feasibility and performance of three different DPOAE protocols and (b) establish the scoring criteria defining "pass" or "fail" responses. All subjects participating in this study were randomly selected and their normal hearing was verified by linear TEOAE recordings. The test was carried out, using an Otodynamics ILO92 Analyser version 5.60, on the second day of life or later (in case of extended recovery), during natural sleep and after feeding. The DPOAE recordings were elicited using asymmetric stimuli with L1 > L2 and a frequency-ratio of 1.22 following three different SPL protocols: 60-50 dB (PR1), 65-55 dB (PR2) and 75-65 dB (PR3). Five frequencies of the cubic distortion product (referring to f2) were tested with an ILO macro at 1.5 KHz, 2.0 KHz, 3.0 KHz, 4.0 KHz and 5.0 KHz. The statistical evaluation of differences in the signal-to-noise ratio (S/N) between the PR1 and PR2 protocols showed no significant differences. On the other hand significant differences were found between the PR3 and the PR2 S/N ratios, the former providing the best performance (higher values). The scoring criteria were defined by minimum free distribution tolerance intervals of the S/N ratios at the five tested frequencies. In conclusion this study confirms the feasibility of DPOAE recordings in a un iversal newborn hearing screening program and shows the appropriate pass-fail parameters to be used for this purpose. It should be noted that this approach enables acquisition of frequency-specific information which might further improve audiological diagnosis.

Cochlea↗

PubMed1999

An animal model based on the Sprague Dawley rat for the evaluation of ototoxicity.

Various methodological approaches that can be used to detect ototoxic effects caused by the administration of various substances are presented, using the Sprague-Dawley rat as an animal model. Electrophysiological data are also presented to show how the model behaves with potentially ototoxic (hyaluronic acid) and initially inert (hydroxy-propyl-methyl-cellulose) substances.

Acoustic Stimulation↗

PubMed1999

Evaluation of cisplatin ototoxicity in a rat animal model.

The ototoxic effects of cisplatin were evaluated by otoacoustic emissions and evoked auditory responses. A transient otoacoustic emissions protocol indicated no significant ototoxic effects in rats treated intravenously with 7.5 mg/kg/week for 2-weeks. A chronic 6-week treatment (2.5 mg/kg/week) monitored by 2F1-F2 distortion product emissions presented significant SNR alterations in a narrow range of frequencies (5.04-5.66 kHz). An acute treatment of 15 mg/kg, using slow 30-min intraperitoneal infusion, presented the highest DP and ABR alterations. The SNR at the 2F1-F2 frequencies 6.34, 7.13, and 7.56 kHz was found significantly decreased, and ABR latency measurements from 8-kHz burst stimuli verified these alterations.

Animals↗

PubMed1999

A TEOAE screening protocol based on linear click stimuli: performance and scoring criteria.

In order to improve the quality of current TEOAE recording methodologies, we have conducted a comparison of TEOAE neonatal recordings acquired with linear protocols using click stimuli of 68 dB SPL and non-linear protocols using the ILO default stimulus values. From a theoretical standpoint it was expected that the linear recordings would generate responses characterized by higher S/N ratios due to the fact that the stimulus sequence contains four clicks of the same intensity and polarity. The project included recordings from 1,416 neonatal ears (age 48 h). The TEOAE data were compared in terms of correlation, response amplitude, noise, corrected response and S/N ratio in the 1.0-, 2.0-, 3.0-, 4.0- and 5.0-kHz bands, using a paired t-test criterion. We found that windowed (4-14 ms) responses evoked by a linear TEOAE protocol generated superior S/N estimates in the 2.0-, 3.0-, 4.0- and 5.0-kHz TEOAE bands, in addition to superior correlation estimates, and demonstrated lower levels of noise. Clear-cut scoring criteria were established for the S/N ratios at 2.0, 3.0 and 4.0 kHz, by constructing one-sided distribution-free tolerance boundaries.

Acoustic Stimulation↗

PubMed1999

TEOAE-based estimation of the auditory threshold in the mid-octave frequencies.

The purpose of this study was to estimate the hearing levels, at the mid-frequencies, of 233 ears with sensorineural hearing loss by classifying the corresponding transiently evoked otoacoustic emissions (TEOAE) recordings into three threshold groups. A classification algorithm was based upon a discriminant analysis of fast Fourier transform (FFT) data, evoked by non-linear click stimuli of 80 (+/-2) dB SPL per ear. To validate the efficiency of the proposed methodology TEOAE recordings were initially grouped by mean hearing level values of the 1 kHz and 2 kHz octaves into three threshold ranges according to two strategy schemes: in the first, TEOAE data were assigned into 10-19 dB HL, 20-39 dB HL or > or = 40 dB HL groups. In the second, TEOAE data were assigned into 10-29 > dB H >, 30-39 dB HL or > or = 40 dB HL groups. The most accurate prediction estimates were obtained from the second strategy scheme with a 90.9% accuracy in the 10-29 dB HL group, 82% in the 30-39 dB HL group and 71.4% in the > or = 40 dB HL group.

Adult↗

PubMed1999

[Audioscan automatic audiometry: theoretical basis and normative data].

Audioscan automatic audiometry is a high resolution method to explore hearing thresholds in the 125 Hz-16 KHz range offering a resolution of 64 points per octave. This procedure makes it possible to study hearing threshold levels at intermediate frequencies which are not measured by conventional audiometry. As suggested in the literature, it is possible to identify hearing threshold notches, considered indicators of mild or subclinical cochlear pathology. In clinical practice, the use of a new audiometric technique requires affirmation of reliability, sensitivity and replicability in time. It also requires defining standard criteria for use in various otologic pathologies. The present study examined 50 normal hearing subjects with conventional audiometry and Audioscan (Essilor model) measurements. A standard acquisition protocol was followed where three Audioscan measurements were conducted per subject. Subjects with a history of acute otologic pathology and familiarity for genetic deafness were ruled out of the study. Multiple, pairwise correlation analyses of the audiometric and Audioscan responses indicate that: (1) there are no significant differences between threshold levels measured by Audioscan and conventional audiometry; (2) there are no significant variations in the hearing levels measured by three Audioscan retests. Three mean indicators of the threshold level have been defined, expressing Audioscan normality in three different frequency ranges. The data suggest that there are some difficulties in the subjectivity of the Audioscan method and some technical problems regarding the lower octave frequencies and these need to be addressed. The results obtained in this study confirmed reliability of the Audioscan in the mid and high frequencies. The definition of the standard mi criteria makes it easier to interpret the Audioscan measurements from cases presenting various otologic pathologies. Therefore, the plasticity and high detection sensitivity of hearing loss make the automatic Audioscan audiometry a useful clinical tool for diagnostic and/or preventive purposes.

Adult↗

PubMed1998

[Evaluation of a linear TEOAE protocol in hearing screening of neonates: feasibility study].

The audiological screening of newborns based on recording TEOAEs--the expression of anatomical-functional integrity of the cochlea--has unanimously gained importance. The prevalence of severe of genetic or congenital hearing loss in the healthy infant population and in the population at risk for audiological disorders, as well as the consequent psycholinguist and socialization problems such children have to deal with, have led the authors to set up a preliminary protocol for the audiological screening of neonates. The purpose of this protocol is to improve the feasibility of applying such a program. To this purpose, the preliminary protocol called for the recording of the TEOAE in both non linear (NL) and linear (L) modes. Examination was performed in 347 newborns (30% of all the children born during 1997) the second day of life and during spontaneous sleep. The ILO 92 was used for the screening. The results obtained with the two methods were statistically compared using the 9 parameters considered response indicators. Using the linear method of a function-window and improving the signal-to-noise ratio, the study showed a significant difference in the quality of the TEOAE using the linear method as compared with the non linear method, although this did not modify response reliability. This lead to the definition, through free distribution statistical analysis, of broader than normal criteria by which to evaluate the responses evoked with the L method. All this is aimed at increasing system specificity and reducing the number of false positives which feeds family anxiety.

Acoustic Stimulation↗

PubMedDate not supplied

Clinical applicability of transient evoked otoacoustic emissions: identification and classification of hearing loss.

The study aimed at the development of a clinically applicable methodology that could: (1) discriminate transient evoked otoacoustic emission (TEOAE) recordings from normal hearing or hearing impaired individuals; (2) classify the nature of the hearing loss as conductive or as cochlear, and (3) define clear-cut TEOAE clinical criteria. A classification algorithm based on a multivariate discriminant analysis of fast Fourier transform data from recordings evoked by click stimuli of 50 +/- 2, 62 +/- 2, 68 +/- 2 and 80 +/- 2 dB SPL was used to discriminate 302 normal subjects from 383 subjects suffering from mild to moderate hearing losses. The best discriminant model (QDF80) produced a sensitivity of 93.8% and a specificity of 79.4%. When extra correlation criteria were serially applied to the classification outcome, the specificity was increased to 85.3%, but the sensitivity was marginally decreased to 91.7%. The classification of the correctly identified hearing-impaired cases yielded 93.8% identification of conductive and 75.1% identification of cochlear cases. A sensitivity analysis of the misclassified hearing-impaired cases suggested that the TEOAE spectra are well correlated with the 2-kHz but poorly correlated with the 4-kHz octave frequency.

Acoustic Stimulation↗

PubMedDate not supplied

Time-frequency analyses of TEOAE recordings from normals and SNHL patients.

This study evaluated the characteristics of transient evoked otoacoustic emission (TEOAE) time-frequency (TF) representations from normal and hearing-impaired ears. Linear and non-linear TEOAE recordings from normally-hearing subjects (40) and non-linear recordings from patients with sensorineural hearing loss (SNHL) (40) were analysed using the short-time-Fourier-transform spectrogram, the Gabor spectrogram, and the adaptive spectrogram. The TF representations of the TEOAE recordings indicated a considerable dispersion of energy across frequencies and TEOAE time segments >4.0 ms. The linear and non-linear recordings from the normal subjects showed common frequency peaks. The TF representations from the patients with SNHL indicated that the significantly reduced energy in the mid-to-high TEOAE frequencies did not correlate closely with the threshold elevation. As in the recordings from the normal subjects, a high percentage of the TEOAE cumulative energy was found within a short TEOAE segment (4-14 ms).

Acoustic Stimulation↗

PubMedDate not supplied

Comparison of neonatal transient evoked otoacoustic emission responses recorded with linear and QuickScreen protocols.

Linear and QuickScreen (non-linear) transient evoked otoacoustic emission (TEOAE) protocols were compared in terms of standardized clinical parameters in order to define the protocol producing recordings with the highest signal quality. Neonatal responses (520) were obtained from three different screening sites. The linear recordings were evoked by 69 and 75-dB p.e. SPL clicks. All responses were post-windowed by a 3.5- to 12.5-ms window, chosen by time-frequency analysis as the segment representing 97.35 per cent (linear) and 95.6 per cent (quick) of the total cumulative spectral energy. Evidence from hearing loss cases and the high similarity between the profile contours of the QuickScreen and the linear normal recordings have strongly suggested that a linear response evoked by a 75-dB p.e. SPL stimulus and post-processed by a 3.5 to 12.5 window is free of stimulus artefacts. The data indicate that the 75-dB linear protocol produces higher signal to noise ratios at 2.0, 3.0, and 4.0 kHz, higher wave reproducibility, and lower TEOAE noise values than the QuickScreen protocol.

Hearing Loss, Sensorineural↗

PubMedDate not supplied

Identification of hearing loss using TEOAE descriptors: theoretical foundations and preliminary results.

It was hypothesized that the relationship between transiently evoked otoacoustic emission (TEOAE) signals and the functional status of the outer hair cells provides an opportunity to design a clinical procedure that can evaluate the normality of cochlear function. To discriminate normal subjects from subjects suffering from mild to moderate hearing loss (HL), it was assumed that every subject population has unique and discrete TEOAE signal descriptors. The main classification algorithm was based on a discriminant analysis of raw fast Fourier transform data. When it was applied to a sample set of TEOAE recordings (from 56 normal and 68 HL subjects) elicited from 68-dB SPL click stimuli, it correctly identified 90.2% of the normal and 87.5% of the HL subjects. The same algorithm yielded an 85.5% discrimination between TEOAE recordings from conductive and cochlear HL cases.

Acoustic Stimulation↗

PubMedDate not supplied

Cisplatin ototoxicity in the Sprague Dawley rat evaluated by distortion product otoacoustic emissions.

The present study has evaluated the use of distortion product otoacoustic emission (DPOAE) responses in the detection of cisplatin-induced ototoxicity in a Sprague Dawley rat animal model. The cisplatin was administered as a 16 mg/kg, dose introduced by a slow 30-min intraperitoneal infusion. Data from three DP-gram protocols, DPOAE input-output responses at 8 kHz, and auditory brainstem responses (ABRs) at 8, 12 and 16 kHz were collected before and 72 h after treatment. The post-treatment ABRs at 16 kHz showed the greatest mean threshold shift of 33.6 dB. The post-treatment DP-gram data showed significant reduction of the signal to noise ratios in the majority of the frequencies tested, across all tested protocols. The data suggest that the most sensitive DPOAE procedure for the early detection of the cisplatin-induced ototoxic damage is the DPOAE I/O protocol. Morphological analyses indicated that the inner hair cells remained intact, while several types of alterations were observed in the arrangement of the stereocilia in the outer hair cells.

Animals↗