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Biomedical subjects

R Dauman

Publications and source records attributed to R Dauman.

At least 55 records · Page 3Linked to original sources
PubMed1985

Effects of glycerol on cochlear frequency selectivity in patients with Menière's disease.

During transtympanic electrocochleography, action potential (AP) tuning curves were derived as a measure of cochlear frequency selectivity. In 18 out of 21 patients with symptoms of Menière's disease, a poor frequency selectivity was observed. In 12 subjects the effects on frequency selectivity of oral glycerol were measured, and in 5 patients AP tuning curves indicated an improvement in sharpness of tuning by a factor of 1.5-2.5. These changes started approximately 30 min after oral glycerol administration. In 2 subjects there was a deterioration in AP tuning. In 5 patients no significant changes were observed.

Action Potentials↗
PubMed1985

(Treatment of sudden deafness: first results of a comparative study).

A comparative study is undertaken in 36 cases of sudden deafness in order to appreciate the efficiency of three therapies: vaso-active drug and steroid administered through continuous perfusions, normovolemic hemodilution, and hyperbaric oxygen therapy. Groups are homogeneous with respect to age, time elapsed between onset of deafness and treatment, occurrence of vertigo, degree of hearing loss, and audiometric pattern. Results are expressed in terms of pure tone threshold improvement (dB), audiometric ratio recovery taking into account initial hearing loss, and effects upon tinnitus. These data are complemented with electrophysiological measures (click-evoked electrocochleography and auditory brainstem responses). Analysis of variance does not show significant differences among the three procedures. Mechanisms and possible usefulness are discussed, keeping in mind the difficulty of ascertaining the real efficiency of therapies with respect to spontaneous recovery.

Adrenal Cortex Hormones↗
PubMed1984

Low frequency thresholds assessed with 40 Hz MLR in adults with impaired hearing.

In a group of 30 adults with impaired hearing, objective thresholds defined with 40 Hz middle latency responses (MLR) were compared with subjective audiometric measures. Frequencies of 0.25, 0.5, and 1 kHz were studied. In order to guarantee a good frequency specificity, subjects presenting large high-frequency hearing loss were particularly chosen. The 40-Hz MLR thresholds were generally worse than the audiometric measures. The average difference was around 12 dB, but in about one-third of the cases it was between 20 and 30 dB. Although not perfect, 40-Hz MLR estimates on low frequencies can be very helpful and deserve further consideration, especially in children.

Adult↗
PubMed1984

40 Hz middle latency responses to low frequency tone pips in normally hearing adults.

Middle latency auditory evoked potentials can be rapidly obtained using a 40/second stimulous rate, taking advantage of response periodicity to accelerate the averaging procedure. This technique was used in 31 normally hearing adults for low frequency response evaluation. Tone pips at 250, 500, and 1000 Hz were employed. The average difference between the middle latency evoked potential threshold and the subjective threshold was 17.9 dB at 250 Hz, 14.5 dB at 500 Hz, and 13 dB at 1000 Hz. The waveform of the response and the latency and amplitude of its main peaks were also analyzed. Thresholds at 500 and 1000 Hz were also determined using brainstem evoked responses in 15 of the subjects. These differed, on average, by 30 dB from subjective thresholds. The 40 Hz MLR paradigm thus appears to be an accurate and rapid method for low frequency threshold evaluation in adults, but it is greatly influenced by the state of arousal. During sleep, response amplitude decreases and threshold increases by about 15 dB. This may be of great concern when interpreting the results in children, in whom low frequency threshold evaluation is of primary importance.

Adolescent↗
PubMed1983

Hemodilution in sudden deafness: first results.

The technique of hemodilution was assessed in 12 cases of sudden hearing loss as it is known to improve peripheral circulation. Good results were obtained in nine patients. The immediacy of the effects suggests the real efficacy of hemodilution as opposed to spontaneous recovery. Hemodilution is supposed to improve oxygenation in the cochlea. This technique is very simple and quick to perform.

Adult↗
PubMed1981

[Rapid derived auditory evoked potentials].

Brain stem auditory-evoked responses to a 70 dB SL click masked by high-passed noises were recorded in 12 normal hearing subjects. By applying the technique of derived potentials, the contribution of one-octave-wide frequency bands are assessed. Summation of these derived potentials gives a pattern similar to the unmasked-response waveform. Waves I and III show a strong predominance of high-frequency responses, whereas wave V is discernible down to low-frequency responses.

Adult↗
PubMedDate not supplied

Summating potential and water balance in Meniere's disease.

The summating potentials (SP) to free-field 1-, 2-, 4-, and 8-kHz, 90-dB HL tone bursts were recorded by means of transtympanic electrocochleography in 45 patients divided into three groups: those with Meniere's disease, those whose diagnosis was uncertain, and control subjects. The similarities across frequencies between the human SP (promontory) and the experimental SP (DIF component from basal turn) suggest that the SP recorded in electrocochleography originates mostly from the base of the cochlea; negative values were observed at low frequencies (1 to 2 kHz), positive values at high frequencies (8 kHz). Patients with Meniere's disease showed significantly larger SP values than control subjects. The effect of orally administered glycerol on the SP and action potential amplitudes was evaluated by means of automated recordings repeated every 5 minutes. Summating potential values were remarkably constant in the control group. A decrease in SP absolute amplitude was observed in most patients with Meniere's disease and some subjects with uncertain diagnoses, specifically at low frequencies. These changes were frequently associated with action potential amplitude and auditory threshold improvements at low frequencies. It is assumed that the glycerol-induced SP changes at low frequencies are related to modifications in the low frequency mechanical response of the basilar membrane at the basal turn.

Adult↗
PubMedDate not supplied

Electrocochleographic measures of cochlear frequency selectivity in hearing loss of cochlear origin.

One of the basic functions of the cochlea is to separate out the frequency components which are present in complex sounds. This frequency selectivity can be measured objectively in the clinic from the compound action potential (AP) during transtympanic electrocochleography, using a two-tone masking paradigm. An AP is evoked by a test tone near to threshold, and a measure is made of the frequency bandwidth over which this AP can be suppressed by a continuous pure tone masker. In normal-hearing subjects, this frequency range is 0.17-0.39 octaves (test tone pip at 4 or 8 kHz). In patients with cochlear deafness, this bandwidth is greatly enlarged, ranging from 0.42-2.2 octaves. Some observations suggest that a deterioration in frequency selectivity can occur before any important threshold elevation. The early detection of this could be a warning sign of potential cochlear susceptibility. In the clinic the measure is already of use: a deterioration is a positive indication of cochlear involvement in a hearing loss.

Audiometry↗
PubMedDate not supplied

Audiometric and electrophysiological correlations in sudden deafness.

Electrophysiological measures were collected over 3 years in 61 cases of sudden deafness. Electrocochleography (ECochG) and Auditory Brainstem Responses (ABR) using click stimuli were recorded down to threshold and compared with pure-tone and speech audiometry data. This study was intended to precise 1) localization of the disorder, 2) prognosis, 3) analysis of the contribution of different frequencies in click-evoked responses. The following results are: 1) In most cases the observations indicated that the inner ear was affected. 2) However, in 19 cases electrophysiological measures revealed a retrocochlear involvement. Four acoustic neuromas were evidenced by CT scan. In 3 of these, audiometric and electrophysiological thresholds returned merely to normal levels after medical treatment, while brainstem responses remained delayed. Thus in these cases recovery would seem to be related to release of vascular compression in the auditory internal meatus. 3) When the latencies of the VII nerve potential (N1) and wave V (PV) were short, and the therapy undertaken early, a good recovery was often obtained. 4) When recovery occurred on low frequencies only, the electrophysiological responses to the click showed slight latency increases.

Adolescent↗