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Biomedical subjects

R Dauman

Publications and source records attributed to R Dauman.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1987

Stapedius reflex and cerebellopontine angle tumours.

The stapedius reflex was investigated in 61 patients with cerebellopontine angle tumours, in order to evaluate the reliability of the reflex-decay test in VIIIth nerve disorders. The reflex was completely normal in 11% of the patients. The 2 most frequently observed abnormalities were (1) an absence of the reflex when stimulating the ear on the side of the tumour, and (2) the conjunction of pathological reflex-decay at 0.5 kHz with a unilateral threshold elevation and/or absence of the reflex at other frequencies. The decay test was normal in one-third of the patients with a preserved reflex.

Acoustic Impedance Tests↗
PubMed1987

Electrophysiological prognosis in facial paralysis.

Electrical prognosis was evaluated in 79 patients with facial paralysis, of spontaneous (n = 43) or post-traumatic origin (n = 36). Three electrophysiological tests were employed jointly: detection, stimulation and stimulodetection. The patients were reviewed at least 1 year later, in order to appreciate the agreement between the electrical prognosis and the clinical outcome (satisfactory or not). Those patients with a favourable prognosis on electrical testing had in the majority of cases a satisfactory outcome. The accuracy of the prognosis was also better in cases of early examination (within 15 days) and partial paralysis.

Adolescent↗
PubMed1987

[Responses evoked in "steady state" in man by means of a sinusoidal frequency modulation].

The response of the human auditory system to a 40 Hz sinusoidal modulation of the frequency of a tone can be reliably recorded from the human scalp using Fourier analysis. With increasing intensity the amplitude of the response becomes larger and its phase delay shorter. The response amplitude is larger and the phase delay longer for lower carrier frequencies. The response may possibly become useful in the objective evaluation of frequency discrimination.

Adult↗
PubMed1986

[Normovolemic hemodilution in the treatment of sudden deafness].

After the apparition of a sudden deafness, 45 patients (22 men and 23 women, with a mean age of 44 +/- 14.9 years) were treated with normovolaemic haemodilution performed with dextran 60. They were placed into 4 groups depending on their hearing loss: total loss: 10 cases; severe loss: 90 to 70 db. 13 cases; moderates loss: 65 to 40 db, 14 cases, slight loss: less than or equal to 35 db, 8 cases. The mean time between the onset of the hearing loss and treatment was 9.3 +/- 12.4 days. The initial mean haematocrit was 44.8 +/- 3.8% and mean haematocrit after haemodilution was 33.1 +/- 2.8%. For 51% of the patients, an almost total recovery was obtained. In 15.5% of cases, recovery was between 25 to 50% of the hearing loss, and in 33.3% of the patients recovery was negligible. We did not find any relationship between hearing recovery and initial haematocrit. The best results were obtained in the group of patients treated early. Hearing gain was significatively better if delay in starting treatment was less than 7 days. There was a relationship between the initial hearing loss and the final recuperation. These results suggested that haemodilution increased labyrinth microcirculation and oxygenation of the cochlear sensory cells, reversing the ischaemic insult to these cells.

Adult↗
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↗