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Biomedical subjects

R Dauman

Publications and source records attributed to R Dauman.

At least 19 recordsLinked to original sources
PubMed1992

[Tinnitus: peripheral and central aspects].

Tinnitus is often related to a peripheral impairment which seems to trigger an abnormal autonomous functioning of the central auditory system. Moreover peripheral stimulations may diminish, and even suppress their perception, either through masking or through inhibition of an aberrant neuronal activity. Here we present an experimental model of peripheral deafferentation in which a decrease of neurochemical activity is observed in the brainstem auditory nuclei, followed by a progressive recovery after the peripheral destruction. This activity could represent a central morphofunctional correlate of tinnitus. Development of experimental models of tinnitus must be continued. Such models should allow the study of the basic physiological mechanisms behind tinnitus and suggest some therapeutic approaches which could be objectively evaluated.

Animals↗
PubMed1991

Electrocochleography: applications and limitations in young children.

Electrophysiological measurements of auditory function are especially indicated in children who are difficult to test by behavioral audiometry. This report is concerned with transtympanic electrocochleography (ECochG) findings in young children (0-3 years) who were examined over the last 6 years in order to extend behavioral audiometric data. On an average, 25% of the children tested with auditory brainstem responses (ABR) needed general anesthesia and were therefore also investigated with ECochG (n = 65). These ECochG children often showed developmental retardation, and behavioral audiometry was doubtful or not possible in 60% of them. ECochG thresholds were generally similar on both ears. Despite general agreement between thresholds obtained by ECochG and behavioral audiometry, differences were found in both directions, ECochG being better or worse than hearing in several children. Detection of severe threshold elevation and low frequency residual hearing remain major limitations of ECochG in the early diagnosis and rehabilitation of deafness in young children.

Audiometry↗
PubMed1991

Betahistine dihydrochloride versus flunarizine. A double-blind study on recurrent vertigo with or without cochlear syndrome typical of Menière's disease.

This study was designed to compare the efficacy and safety of betahistine dihydrochloride and flunarizine. All patients included in this multicenter, double-blind, randomized trial showed a specific pattern of vertigo, i.e. recurrent paroxysmal vertigo with or without the cochlear symptoms typical of Meniere's disease. Fifty-five patients were treated for 2 months (28 in the betahistine group and 27 in the flunarizine group). Analysis of intra-group symptom changes demonstrated a greater efficacy for betahistine. Statistically significant decreases in duration and severity of attacks, and in the presence of vegetative symptoms were seen in the betahistine group after the first and second months of treatment, whereas in the flunarizine group this was the case only at the end of the first month of treatment. Furthermore in the betahistine group, statistically significant decreases occurred for the other major criteria, including number of attacks, evidence of vestibular dysfunction, and presence of cochlear symptoms. Adverse effects were similar to those reported in previous studies of both products: stomach pains only with betahistine, and drowsiness, asthenia, and depression with flunarizine.

Betahistine↗
PubMed1990

[Clinical value of tuning curves or frequency selectivity curves].

A simplified method, useful in clinical practice, is described in order to study the frequency selectivity in various conditions. The patient is asked to indicate the levels of pure tones which are necessary to mask completely the perception of an intermittent probe. The resulting psychoacoustic tuning curves are characterized by a more or less narrow bandwidth which reflects the ability to resolve simultaneously presented sounds. Several circumstances where these tuning curves are helpful, are presented: assessment of tinnitus, Menière's disease, unclear impairment of speech intelligibility. Therefore, this technique appears as a valuable tool which can be used in addition to the usual audiometric and electrophysiological tests battery.

Humans↗
PubMed1990

[Role of electrophysiology in the current diagnosis of deaf children].

The role of electrophysiology (auditory evoked potentials) in children up to 3 years old was studied through the feasibility and results of subjective audiometry. In children over six months old, subjective tests are performed systematically or at least tried before using electrophysiology. Electrophysiology is required when audiometry is impossible, and it is often performed when audiometry is abnormal. When subjective tests were not performed first, either because the child is too young or shows a developmental retardation, and the electrophysiological tests are abnormal, it is absolutely necessary to obtain an exact level of hearing as soon as possible using subjective tests. The results of a study on 244 electrophysiologically tested children between the 0 and 3 years of age are presented briefly. In 73% of the cases, the auditory brainstem responses were sufficient for clarifying or confirming the subjective tests. In 27%, they had to be completed be an electrocochleography (ECochG) under general anesthesia. The information based on the ECochG and the comparison data between the ECochG and subjective thresholds are presented. On one hand, this study highlights the double complementarity between audiometry and electrophysiology on the other, the brainstem potentials and ECochG.

Audiometry↗
PubMed1990

The prognostic value of the stapedius reflex in peripheral facial palsy.

Stapedius reflex can provide useful prognostic information in FPs when the middle ear is normal. Its preservation may have a favorable significance in partial FP and Bell's palsy. Its loss, even though less reliable, can also have some value as an indicator for a poor prognosis in patients with total and herpes zoster FPs. Most importantly, our findings have shown that the SR alone is not sufficient to be of prognostic value, but is useful if combined with other clinical parameters and electrical responses.

Adolescent↗
PubMed1989

Auditory frequency selectivity and tinnitus.

In the majority of cases tinnitus has a high pitch and can be matched rather precisely to an objective high frequency sound. However, it is well known that tinnitus can be masked by different tones without any frequency selectivity. We wondered whether objective tones matched to tinnitus would show a more significant deterioration of frequency selectivity than could be expected from any associated hearing loss. Psychoacoustic tuning curves were obtained using simultaneous pure-tone masking and revealed a broadening of frequency selectivity. In cases of comparable bilateral hearing losses with unilateral tinnitus, the broadening associated with the tinnitus was particularly conspicuous. This broadening strongly suggests that tinnitus originates in the cochlea, although some involvement of central pathways may also occur. Tinnitus-induced broadening of frequency selectivity as a possible sign of cochlear origin deserves further consideration in future studies.

Adult↗
PubMed1989

Modern diagnostic strategy for acoustic neuromas.

We have reviewed the most recent 120 cases of acoustic neuromas operated upon in Bordeaux, France. In so doing, we have defined the strategy required to reach an accurate diagnosis as essentially comprising three stages. The first of these is to understand that the presenting symptom complex may be typical with progressive unilateral hearing loss, tinnitus, etc., or atypical with sudden hearing loss (10%), recovering facial paralysis (3.3%) or a Menière's syndrome (3.3%). Included in the first stage of diagnosis are audiovestibular investigations. An absent stapedial reflex was noted in 41% of our cases and an abnormality in vestibular testing in 95% of cases tested. These findings would be clear indicators to proceed to the second stage of the diagnostic strategy. This second stage comprises electric response audiometry consisting of auditory brainstem response (ABR) testing and electrocochleography (ECochG) employed as a filter for determining which patients should proceed to the third stage of testing. A combination of ABR and ECochG provides the clinician with results of high sensitivity and specificity. The false-negative rate for combined results in our experience has been less than 1%. The final diagnostic stage is radiological imaging, in particular using magnetic resonance imaging (MRI) with gadolinium contrast as the modality of choice. MRI is superior to CAT scanning, especially in the diagnosis of stage I intracanalicular tumors.

Audiometry, Evoked Response↗
PubMed1989

[ORL aspect of meningioma of the cerebellopontine angle].

Through 14 recent cases, the authors review the main clinical syndromes leading to the diagnosis of petrous and brain-stem meningiomas. The cochleovestibular syndrome, the most frequent amongst them, recalls the symptomatology of an acoustic neuroma. The jugular foramen syndrome is similar to that seen in jugulo-tympanic paragangliomas. The middle ear tumor syndrome is specific to primary or secondary intrapetrous tumors. The positive diagnosis of meningiomas belongs to the field of CAT scares and mainly of NMR, which define morphological characters, none of them being specific: oval shape, the closed angle sign, intratumor calcification, hyperdensity, osseous changes on the posterior aspect of the petrous bone NMR permits a very precise localization and definition of the tumor which is necessary among the per-op studies. This decreases the occurrence of once frequent surgical surprises.

Cerebellar Neoplasms↗
PubMed1988

Limits of ABR and contribution of transtympanic electrocochleography in the assessment of cerebellopontine angle tumours.

Auditory brainstem responses (ABR) and transtympanic electrocochleography (ECochG) were analysed for 63 patients with tumours of the cerebellopontine angle (CPA) and/or internal auditory meatus (IAM). ABR recordings indicated a clearly prolonged wave I-V interval (above 4.3 ms) in half of the patients, hence suggesting a retrocochlear disorder. For the remaining patients ABR alone was not sufficient for clear diagnosis and ECochG was therefore used in addition. When the latency of wave V was uncertain due to the absence of wave I, the latency of wave N1 was always measurable by ECochG. The NI-V interval evaluated in this way was always significantly prolonged (above 4.5 ms) relative to a control group of patients with a sensorineural hearing loss. In 9 of the 13 subjects without any discernible ABR, an ECochG response could be recorded and its threshold was often better than the mean pure tone audiogram. This study confirms the validity of transtympanic ECochG in the diagnosis of retrocochlear disorders. The time difference observed between wave N1 (ECochG) and wave I (ABR) in CPA tumours is discussed and a possible explanation is proposed.

Audiometry, Evoked Response↗
PubMed1988

Clinical significance of the summating potential in Menière's disease.

Transtympanic (TT) electrocochleography (ECochG) data recorded with click stimuli and tone bursts (1, 2, 4, and 8 kHz) were evaluated in 50 patients with Meniere's disease and compared with the data from control groups of 10 sensorineural hearing impaired patients and 5 subjects with normal hearing. The mean summating potential (SP) amplitude was larger in the Meniere's disease group for 1, 2, and 8 kHz. The low frequency (1 or 2 kHz) SP decreased in 59% of the Meniere's disease patients during a glycerol dehydration test, whereas subjective hearing improved in only 29%. The use of ECochG with the monitoring of SP thus improves the sensitivity of the glycerol test for the detection of endolymphatic hydrops. There appeared no clear relation between clinical observations and the ECochG data either before or after glycerol. However, the Meniere's disease patients with a large negative SP at low frequencies also had larger action potential (AP) and often had short-term symptoms. The present report confirms the usefulness of measuring the SP in the diagnosis of Meniere's disease.

Action Potentials↗