Biomedical subjects

W A Dreschler

Publications and source records attributed to W A Dreschler.

At least 19 recordsLinked to original sources

PubMed2001

Efficacy of evaluation of audiometric results after stapes surgery in otosclerosis. II. A method for reporting results from individual cases.

To standardize the reporting of hearing results after middle ear surgery, the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery proposed 2 levels of guidelines: level 1 for reporting summary data and level 2 for reporting raw data. The Committee encourages the reporting of raw data from each individual case. However, in studies in which the examined population is too large, this can yield difficulties. With respect to this point, we designed a method for a simple visual presentation of hearing results in an attempt to provide data from each individually operated ear in a patient group. In this method the relation between the preoperative and postoperative bone-conduction levels is evaluated to assess overclosure and iatrogenic cochlear damage, and the relation between postoperative gain in air conduction and the preoperative air-bone gap is evaluated as a measure of technical success rate. This results in 2 plots, which we called the Amsterdam Hearing Evaluation Plots. Audiometric data from 451 stapes operations were used to demonstrate the use of the Amsterdam Hearing Evaluation Plots.

Adult↗

PubMed2001

Efficacy of evaluation of audiometric results after stapes surgery in otosclerosis. I. The effects of using different audiologic parameters and criteria on success rates.

The Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery proposed guidelines to provide more uniformity in reporting hearing results after middle ear surgery. One of the proposals was to include the hearing thresholds at 0.5, 1, 2, and 3 kHz in a 4-frequency pure-tone average (PTA) and to use post-operative bone-conduction (BC) levels rather than preoperative BC levels in describing postoperative air-bone gaps (ABGs). The hearing results of 451 stapes operations were evaluated to analyze to what extent the choice of different audiologic criteria affects success rates. It appeared that choice of PTA significantly affects postoperative gain in air-conduction thresholds and ABG levels. If one takes the improvements in speech-reception thresholds as the gold standard, the gain in air-conduction correlates best with a gain in speech-reception threshold if a higher frequency, such as 3 or 4 kHz, is included in a 4-frequency PTA. Also, choice of preoperative or postoperative BC in computing postoperative ABGs had a significant effect on the mean postoperative ABG levels, showing more favorable results with the use of preoperative BC thresholds.

Adolescent↗

PubMed1999

Long-term effect of hyperbaric oxygenation treatment on chronic distressing tinnitus.

Tinnitus is still a phenomenon with an unknown pathophysiology with few therapeutic measures. During the last two decades, hyperbaric oxygenation therapy (HBO) has been used in the treatment of sudden deafness and chronic distressing tinnitus. In this study, we prescribed HBO to 20 patients who had had severe tinnitus for more than one year and who had already had other forms of tinnitus therapy with unsatisfactory results. Four patients could not cope with the pressure gradient. The effect of HBO was assessed using subjective evaluation and VAS scores before and after HBO. Follow-up continued until one year after treatment. Six patients had a reduction of tinnitus and accompanying symptoms, eight patients did not notice any change and two patients experienced an adverse effect. Any outcome persisted with minor changes until one year after treatment. HBO may contribute to the treatment of severe tinnitus, but the negative effect on tinnitus should be weighed carefully.

Adaptation, Psychological↗

PubMed1999

Importance of temporal-envelope cues in consonant recognition.

The role of different modulation frequencies in the speech envelope were studied by means of the manipulation of vowel-consonant-vowel (VCV) syllables. The envelope of the signal was extracted from the speech and the fine-structure was replaced by speech-shaped noise. The temporal envelopes in every critical band of the speech signal were notch filtered in order to assess the relative importance of different modulation frequency regions between 0 and 20 Hz. For this purpose notch filters around three center frequencies (8, 12, and 16 Hz) with three different notch widths (4-, 8-, and 12-Hz wide) were used. These stimuli were used in a consonant-recognition task in which ten normal-hearing subjects participated, and their results were analyzed in terms of recognition scores. More qualitative information was obtained with a multidimensional scaling method (INDSCAL) and sequential information analysis (SINFA). Consonant recognition is very robust for the removal of certain modulation frequency areas. Only when a wide notch around 8 Hz is applied does the speech signal become heavily degraded. As expected, the voicing information is lost, while there are different effects on plosiveness and nasality. Even the smallest filtering has a substantial effect on the transfer of the plosiveness feature, while on the other hand, filtering out only the low-modulation frequencies has a substantial effect on the transfer of nasality cues.

Adolescent↗

PubMed1999

Evaluation of spectral enhancement in hearing aids, combined with phonemic compression.

In this study, the separate and combined effects on speech perception of compensation of the reduced dynamic range by compression and compensation of the reduced frequency resolution by spectral enhancement is investigated. The study has been designed to compare the effects of signal processing on monosyllabic consonant-vowel-consonant words for hearing-impaired listeners in conditions of quiet, fluctuating noise, and continuous noise. Speech perception of spectrally enhanced speech was compared with unprocessed speech. In addition, a comparison was made between combinations of spectrally enhanced speech and two types of phonemic compression. In the past, the definition "syllabic compressor" is often used to indicate fast compressors. However, the time constants of the fast compressors used in this study are so short that syllabic has become an inappropriate term. Moreover, intelligibility tests were performed in which scores were acquired of monosyllabic words, and their constituent "phonemic" parts. Therefore, the definitions "phoneme" and phonemic will be used throughout this paper. In one condition, spectral enhancement produced significant improvements for vowel perception. But, this was counteracted by deterioration of the consonant scores for all but one subject. In general, the best overall scores for consonant-vowel-consonant words were obtained in the unprocessed condition. After the spectral enhancement, a single-channel phonemic compressor added no improvement. There are indications that a multichannel phonemic compressor and spectral enhancement have opposite effects, because the scores for this combination are, in general, the lowest.

Adolescent↗

PubMed1999

Comparison of stapes prostheses: a retrospective analysis of individual audiometric results obtained after stapedotomy by implantation of a gold and a teflon piston.

PURPOSE: Evaluation of hearing results after implantation of a Teflon piston (type Causse; Xomed Surgical Products, Jacksonville, FL) and of a pure gold piston (K-piston; Heinz Kurz GmbH Medizintechnik, Dusslingen, Germany), both with a shaft diameter of 0.4 mm in cases of otosclerosis requiring stapedotomy. An important difference between both prostheses is the difference in mass: the gold piston is three times heavier than the Teflon piston. METHODS: Retrospective analyses were carried out of the presurgery and postsurgery audiologic results obtained after primary stapedotomy by implantation of 62 Teflon pistons and 66 gold pistons. The results were compared according to mean values of several audiometric parameters. Furthermore, individual audiometric results have been evaluated with the "Amsterdam Hearing Evaluation Plots" (AHEPs) as a method for visual presentation of hearing results from each operated ear. With this method, "unsuccessfully" and "successfully" inserted prostheses can be recognized easily and a more realistic comparison between prostheses is possible. RESULTS: It was found that in the overall group the heavier gold prosthesis gives a significantly larger gain in air-conductive hearing at 2 kHz (p < 0.05) and in the speech frequency range 0.5 to 2 kHz (p < 0.05). There were no significant intergroup differences with regard to change in bone-conduction and air-bone gaps. Analysis of the hearing results of the subgroup that included only the "successfully" implanted prostheses according to the criteria of the AHEPs had mainly consequences for improvement of air-conduction thresholds: none of the intergroup differences were statistically significant. CONCLUSIONS: For a fair comparison between prostheses, it is necessary to take only the prostheses into account that are inserted properly and that are functioning under normal conditions with regard to transmission of sound vibrations. After analysis of the hearing results of these "successfully" implanted prostheses, a trend was noticed that the heavier gold piston gives more gain in the low- and mid-frequency range and the light-weighted Teflon piston gives more gain in the high-frequency range, although none of the differences were significant.

Adolescent↗

PubMed1998

Short- and long-term results with implantable transcutaneous and percutaneous bone-conduction devices.

OBJECTIVES: To compare the percutaneous bone-anchored hearing aid (BAHA; type NBC-HC-200, Nobel Biocare, Gothenburg, Sweden) and the transcutaneous temporal bone stimulator (TBS; Xomed-Treace, Jacksonville, Fla) with conventional hearing aids and to evaluate long-term results. DESIGN: In a prospective clinical study, the new implantable bone-conduction devices were compared with the patients' previous conventional hearing aids. Speech perception in quiet and in noise were studied, and a questionnaire concerning the actual use of the device and speech recognition was administered. During follow-up that exceeded 4 1/2 years, relevant technical and medical problems were documented. PATIENTS: Forty-one successive subjects who were fitted with a BAHA and 17 subjects who were fitted with a TBS. RESULTS: In most subjects who had previously used a bone-conduction device, the new BAHA and TBS devices led to improved or comparable results on speech recognition tests and the questionnaire. However, among the subjects who had previously used air-conduction hearing aids, the results were ambiguous. In the long-term, the percentage of nonusers in the BAHA group was 5% (2/39); in the TBS group, 65% (13/20). The main reasons for not using the TBS were insufficient gain and medical and technical problems. The vulnerability of the percutaneous coupling of the BAHA to trauma or inflammation was not a major issue; only 4 implants were lost during the total follow-up of more than 250 years. CONCLUSION: Results indicate that the BAHA is the better choice.

Adolescent↗

PubMed1998

The relation between otoacoustic emissions and the broadening of the auditory filter for higher levels.

The active behaviour of outer hair cells (OHCs) is often used to explain two phenomena, namely otoacoustic emissions (OAEs) and the level dependence of auditory filters. Correlations between these two phenomena may contribute to the evidence of these hypotheses. In this study auditory filters were calculated from probe thresholds in notched-noise maskers over a range of at least 25 dB. Further. transient evoked otoacoustic emissions (TEOAEs) were measured at several stimulation levels. Ten normal-hearing and nine hearing-impaired subjects were tested. A linear increase of the width of the auditory filter with 2.2 dB/Hz was found up to a specific saturation level. The group of selected hearing-impaired subjects with mild hearing loss showed no wider than normal auditory filters. As expected, the increase of the width of the auditory filter correlated positively with the level of TEOAEs for click intensities of about 80 dB peak SPL. However, for subjects with TEOAEs wider auditory filters at a masker level of 65 dB/Hz were found for subjects with larger TEOAEs. This result cannot be explained by a model by which the cochlea shows an active behaviour for lower stimulation levels, influencing both the TEOAE levels and the filter skirts, and a passive behaviour for higher stimulation levels.

Acoustic Stimulation↗

PubMed1998

Bilateral stapedotomy in patients with otosclerosis: a disability-orientated evaluation of the benefit of second ear surgery.

This study reports the evaluation of the results of 80 stapedotomies in patients with bilateral otosclerosis. All pre- and postoperative audiological data, together with all relevant information of the operations, were stored in a database and analysed retrospectively. A new approach has been developed in order to evaluate the benefit of second ear stapes surgery in a more disability-orientated way using the AMA-criteria in the Guides to the Evaluation of Permanent Impairment. In all patients the percentage of Binaural Hearing Impairment (BHI) and the percentage of Impairment of the Whole Person (IWP) were determined according to the AMA-criteria. In patients who had both operations at the Academic Medical Centre it was found after the first operation that there was an important decrease in the BHI-percentage (from 26% to 10%) as well as for the IWP-percentage (from 9% to 4%). In addition, the percentages dropped significantly after the second operation (from 11% to 7% and from 4% to 2%, respectively). During follow-up there were no serious complications. It is concluded that bilateral stapedotomy is a safe procedure with good results.

Adolescent↗

PubMed1997

Ototoxic reactions of quinine in healthy persons and patients with Plasmodium falciparum infection.

Audiometric changes following quinine administration were studied in healthy Caucasian subjects and patients suffering from falciparum malaria disease. Quinine-dihydrochloride was administered intravenously as a single dose of 300 mg to 12 healthy subjects and as multiple doses of 600 mg in 4 h every 8 h in 10 Plasmodium falciparum malaria patients. The hearing function was monitored by conventional and high frequency audiometry. In nine healthy subjects hearing loss was documented at 2-4 h after infusion of Quinine-dihydrochloride at a mean maximal plasma quinine concentration of only 2 mg/l. In one healthy subject a persistent loss occurred of 20 dB at 14 kHz in one ear. In all malaria patients severe hearing losses and adverse effects related to ototoxicity were documented, but all the audiograms had returned to normal after 1 week and side effects disappeared. This study has shown that ototoxicity induced by quinine is almost completely reversible in healthy volunteers and in malaria patients.

Adult↗

PubMed1997

Design of two syllabic nonlinear multichannel signal processors and the results of speech tests in noise.

OBJECTIVE: Multichannel syllabic compressors have not yet shown clear advantages for speech perception. New multichannel syllabic nonlinear processors are designed and evaluated in this study to test whether they enhance speech perception scores. DESIGN: Nonsense consonant-vowel-consonant words have been processed in real time with two syllabic nonlinear methods in nine different frequency channels: 1) 30 dB of speech information is mapped into the residual dynamic range (DR) of the subjects with hearing impairment using either compression or expansion; 2) speech levels above the rms level are compressed with a ratio of 3:1, and input levels below the rms level are mapped into the reduced DR of the subjects. The overall frequency spectrum of speech is tilted with more high-frequency output for this condition. The two syllabic nonlinear processors were compared with two linear reference systems (one of them with the same spectral tilt as the second nonlinear condition) for seven hearing-impaired subjects. RESULTS: On average, the syllabic nonlinear processors show scores similar to one of the linear systems. The linear reference with tilt has, on average, 3% higher scores, mainly due to improved vowel identification. CONCLUSIONS: No negative effects were shown on average for the syllabic nonlinear processors, but no positive effects were demonstrated either. Tilting of the overall speech spectrum was advantageous.

Adult↗

PubMed1996

Compression and its effect on the speech signal.

Compression systems are often used in hearing aids to increase the wearing comfort. A patient has to readjust frequently the gain of a linear hearing aid because of the limited dynamic hearing range and the changing acoustical conditions. A great deal of attention has been given to the static parameters but very little to the dynamic parameters. We present a general method to describe the dynamic behavior of a compression system by comparing modulations at the output with modulations at the input. The use of this method resulted in a single parameter describing the temporal characteristics of a compressor, the cut-off modulation frequency. In this paper its value is compared with known properties of running speech. A limitation of this method is the use of only small modulation depths, and the consequence of this limitation is tested. The use of this method is described for an experimental digital compressor developed by the authors, and the effects of some temporal parameters such as attack and release time are studied. This method shows the rather large effects of some of the parameters on the effectiveness of a compressor on speech. This method is also used to analyze two generally accepted compression systems in hearing aids. The theoretical method is next compared to the effects of compression on the distribution of the amplitude envelope of running speech, and it could be shown that single-channel compression systems do not reduce the distribution width of speech filtered in frequency bands. This finding questions the use of compression systems for fitting the speech banana in the dynamic hearing range of impaired listeners.

Correction of Hearing Impairment↗

PubMed1995

Ototoxicity and nephrotoxicity of gentamicin vs netilmicin in patients with serious infections. A randomized clinical trial.

In the treatment of serious infection by aminoglycoside antibiotics multiple daily treatment with netilmicin is considered to be the least toxic. Studies comparing netilmicin with gentamicin using the less toxic once-daily schedule are lacking. A randomized prospective study was designed to evaluate the efficacy and toxicity of once-daily netilmicin with gentamicin treatment in patients with serious infections. Consecutive patients with serious infections were randomized between gentamicin 4 mg/kg q24h iv or netilmicin 5.5 mg/kg q24h iv. Exclusion criteria were neutropenia or severe renal failure. A good clinical response was observed in 50 of the 54 evaluable patients (92.6%) treated with gentamicin and in 48/52 (92.3%) netilmicin treated patients. Nephrotoxicity developed in 5/72 (6.9%) gentamicin patients and in 10/69 (14.5%) treated with netilmicin. Audiometry was performed with high-frequency audiometry when possible; no significant differences were found between the two aminoglycosides. We conclude that with once-daily treatment no benefit of netilmicin over gentamicin regarding nephro- or ototoxicity could be demonstrated.

Adolescent↗

PubMed1994

The effects of syllabic compression and frequency shaping on speech intelligibility in hearing impaired people.

The effect of syllabic compression on speech intelligibility is rarely positive and in those cases that positive effects have been found, the same positive results could in general be obtained by frequency shaping of the frequency response curve. We programmed a syllabic compressor on a digital processor; the compressor differed from a conventional syllabic compressor by incorporating a delay in the signal path to suppress overshoots and thus minimize transient distortion. Furthermore, the time constants were short: attack time of 5 msec and release time of 15 msec. The compressor was only active in the high-frequency band. An essentially linear signal was added to deliver the low-frequency speech components. The processing resulted in a frequency response that mirrored the hearing loss near threshold and became much flatter for higher level input signals. Speech intelligibility scores for nonsense consonant-vowel-consonant words embedded in carrier phrases were determined for hearing-impaired persons with sloping audiograms and discrimination losses for speech. Results showed little additional effect of frequency shaping to the existing improved speech score for compressed speech. Optimum results were found for a compression ratio 2 with lower speech scores for linear amplification and for compression ratio 8. We next determined the effect of providing high-frequency emphasis to the speech signal and/or to the compression control signal to compensate for the upward spread of masking. The frequency response at the root-mean-square level was adjusted according to the half-gain rule. The positive effects of moderate compression could be found again; the high-frequency emphasis, however, was positive for the vowels but made consonant recognition poorer.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1994

Frequency-resolution measurements with notched noises for clinical purposes.

Knowledge of the frequency resolving power of the pathological ear can be helpful for good hearing-aid prescription. In particular, the slope of the low-frequency edge of the auditory filter will determine the extent of upward spread of masking. The most precise method for measuring this filter is the "notched-noise" procedure developed in the early 1980s. However, at this moment, the notched-noise protocol is too time consuming for clinical use. In this paper we developed a protocol that is applicable in the clinic. In the first part of the study we investigated the minimum number of threshold measurements necessary for a reliable estimation of the filter parameters. For this purpose we analyzed 99 filters originally obtained with 13 threshold measurements. The influence of reducing the number of notch widths used to obtain filter shapes on the variability of filter parameters was investigated. Subsets of seven and five notch widths gave about the same standard deviations of the differences between the parameters obtained with the subset and the parameters obtained with the full set of 13 thresholds, while subsets of four and three notch widths gave significantly higher variability. However, because small deviations of one threshold determination can give rise to a large change in filter parameters, especially for filters with flatter skirts, it is strongly recommended to reduce the variability by measuring thresholds twice (test and retest). In the second part of the study we investigated a faster method for measuring thresholds. The forced-choice paradigm normally used in notched-noise procedures was replaced by a Békésy paradigm. The Békésy paradigm did not significantly increase intra-individual standard deviations, but did reduce the measuring time by more than 50%. In conclusion, the new procedures reduce the measurement time needed to obtain reliable estimates of auditory-filter parameters by a factor of about 5. The new protocol lasts about 15 min for each filter measurement, which appears to be acceptable for clinical use, at least for difficult-to-fit hearing aid users.

Acoustic Stimulation↗

PubMed1993

First clinical experiences with an implantable bone conduction hearing aid at the University of Amsterdam.

A transcutaneous bone-conduction hearing aid was implanted in 11 patients who were not suitable for transcranial sound amplification. Audiological and surgical selection criteria were followed strictly. One device had to be explanted and minor revision surgery was needed in two cases for skin irritation and scarring. In general the aids were well tolerated but the amplification power of the external device proved to be insufficient in some patients, in whom bone conduction levels were on the borderline of the selection limits.

Adolescent↗

PubMed1993

Syllabic compression and speech intelligibility in hearing impaired listeners.

Syllabic compression has not been shown unequivocally to improve speech intelligibility in hearing-impaired listeners. This paper attempts to explain the poor results by introducing the concept of minimum overshoots. The concept was tested with a digital signal processor on hearing-impaired subjects. The results show that moderate syllabic compression may raise speech intelligibility, as long as overshoots are minimized and relatively short time constants are used. Frequency equalization also contributes to speech intelligibility.

Acoustic Stimulation↗

PubMed1992

Late effects of radiotherapy on hearing.

The effect of radiotherapy on hearing was studied in 30 patients who were treated by surgery and radiotherapy for a parotid neoplasm. Functions of the irradiated ear were compared with those of the non-irradiated ear in the same patient. Tympanometry showed a small but significant reduction of static compliance on the irradiated side when compared with the non-irradiated side. Audiometry showed a significant increase in hearing loss in the 1-2, 4-8 and 10-20 kHz ranges that increased with frequency. This hearing loss was mainly sensorineural in contrast to hearing loss at 250-500 Hz, where it was more of a conductive type. There appeared to be a significant dose-effect relation in sound perception at 4-8 kHz. Doses to the cochlea of less than 55 Gy seldom caused a hearing loss, in contrast to doses exceeding 65 Gy. Overall, radiotherapy was found to cause significant, mainly sensorineural hearing losses, which were partly dose-dependent.

Acoustic Impedance Tests↗