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At least 973 records · Page 54Linked to original sources
PubMed1991

Measurement of human cochlear blood flow.

Cochlear blood flow (CBF) was measured with a laser-Doppler (L-D) flowmeter (Periflux PR2-B) in four unanesthetized human subjects with chronic tympanic membrane perforations and nine anesthetized human subjects undergoing middle ear operations. The L-D recordings were made over the promontory and/or the round window membrane during carbogen breathing and direct electrical stimulation of the cochlea in both groups and with warm water irrigation of the external ear canal in the anesthetized subjects. Carbogen led to little or no change in CBF as monitored with either measurement approach in either subject group. Electrical stimulation yielded an increase (15% to 25%) in CBF as recorded from the promontory in seven of the nine subjects tested. Warm (44 degrees C to 49 degrees C) water irrigation produced changes of 20% to 60% in CBF that were partially recoverable in the 10 minutes available for study. This study demonstrated the feasibility of direct CBF measurement in humans with the L-D method. Moreover, the data indicate that carbogen has little influence on CBF and that electrical stimulation at relatively safe levels and warm water irrigation of the ear canal produce increases in human CBF.

Aged↗
PubMed2000

A case of barotrauma-induced pneumolabyrinth secondary to perilymphatic fistula.

We report the case of a 62-year-old woman who experienced pneumolabyrinth associated with a perilymphatic fistula. Her condition was diagnosed with the help of computed tomography, which detected the presence of an air bubble in the labyrinth, and middle ear exploration, which revealed that clear fluid was emanating from the round window niche in a manner consistent with the presence of a perilymphatic fistula. The niche was repaired with tragal perichondrium and bolstered with Gelfoam.

Barotrauma↗
PubMed1982

Fluctuating hearing loss and recurrent vertigo in otosclerosis. An audiologic and temporal bone study.

This report summarizes audiologic and temporal bone findings in a 47-year-old white female with recurrent attacks of vertigo, tinnitus, and bilateral hearing loss. A series of audiograms, obtained over a 15-year period, showed a fluctuating mixed (sensorineural and conductive) hearing loss with a relatively flat configuration in the left ear and a relatively stable, mild sensorineural loss with a sloping contour in the right ear. Temporal bone studies revealed the existence of otosclerotic foci bilaterally. In the left ear, the otosclerotic focus has grown close to the utricular and lateral ampullary nerves, displaced and ankylosed the stapedial footplate, invaded the endosteal zone (1,000-2,000 Hz area), and deformed the lateral cochlear wall. In the right ear, the otosclerotic invasion was limited to the inferior portion on the promontory (vestibular cecum) and round window niche.

Audiometry↗
PubMed2001

[Contralateral suppression of latency during distortion product otoacoustic emissions detection in guinea pigs].

OBJECTIVE: To investigate the cochlear micromechanics and the function of cochlear efferent system by detecting the distortion product otoacoustic emissions (DPOAE) with or without contralateral acoustic stimulation. METHODS: The DPOAE amplitude and latency of the cubic DPOAE (2f1-f2) were measured at f2 = 2, 4 and 6 kHz with or without 70 dB SPL broad-band noise contralateral stimulation in ears of 12 healthy pigmented guinea pigs, which were divided into two groups(A and B) and tested with different primary intensity level combinations. On the next day, an operation was made to open the acoustic bulla of right ear in Group A. Kainic Acid (KA, 1 microL of 60 mmol/L) was applied onto the round window membrane and wiped up carefully after three hours. The amplitude and latency of the cubic DPOAE from the left ear were measured after 6 hours of KA administration, with or without contralateral noise stimulation. RESULTS: Before the KA treatment, the amplitude of DPOAE induced by primaries of equal levels (L1 = L2) presented no significant change and the latency prolonged significantly during contralateral acoustic stimulation (Group A). But the amplitude at 2, 4 kHz of DPOAE induced by primaries of different levels (L1 > L2) decreased significantly and the latency also prolonged significantly (Group B). After KA administration in the contralateral ear of Group A, the contralateral acoustic stimulation had no significant effect on either amplitude or latency of DPOAE measured ipsilaterally. CONCLUSION: The result demonstrates that the latency is a sensitive index for the cochlear contralateral suppression. The efferent system may act as a negative feedback during the cochlear transduction.

Acoustic Stimulation↗
PubMed1991

Structure of the endolymphatic sac after instillation of hyaluronan in the middle ear.

Hyaluronan (HA) 0.5, 1, 1.9 and 4% was instilled into the round window niche in mice. Six hours after the 1.9% HA and 4, 6 and 8 h after the 4% HA deposition there was a significant increase in the proportion of granule-containing light epithelial cells in the endolymphatic sac. This indicated an increase in secretory activity. This activity could be a response to lowered intralabyrinthine pressure due to the osmotic capacity of HA. Secretion of high molecular substances can serve to keep the sac lumen patent and/or to regulate labyrinthine volume and pressure.

Animals↗
PubMed1986

Deafness after treatment with ear drops containing neomycin, gramicidin and dexamethasone. A case report.

We describe a patient with a polyethylene tube to the middle ear who developed severe deafness and vertigo after treatment with ear drops where neomycin B was considered to be the most likely offending agent. High concentration of this antibiotic in the ear drops and access of the solution to the round window membrane in the absence of inflammatory edema and secretion may have been significant factors contributing to this serious side effect. Less ototoxic preparations should be used in patients with perforated tympanic membranes or grommets.

Deafness↗
PubMed1989

[Electric stimulation of auditory nerve fibers. Experimental study].

The authors tested in animal experiments the effectiveness of electrical stimulation of acoustic nerve fibres. To guinea pigs platinum-iridium electrodes were implanted in the round window of the cochlea. The receptors of the inner ear were functionally eliminated by the local application of the ototoxic antibiotic gentamicin. Cortical responses produced by electric stimulation of the contralateral ear and acoustic stimulation of the ipsilateral intact ear were recorded. The threshold for producing a cortical response by the electric stimulus was lowest at the frequency of 0.5 kHz and rose with the rising frequency. This relationship was the same for extracochlear and intracochlear stimulation, the absolute threshold values of the current in the same animal were, however, as a rule lower on intracochlear stimulation. The dynamic range of responses to electrical stimulation (difference between threshold intensity of the current and the intensity which produces a painful response of the animal) was 6-20 dB, as compared with 80-100 dB of the dynamic range for acoustic stimulation. The results of the experiments were used in the preparation of the Czechoslovak cochlear neuroprosthesis and serve as a basis for the further development of the implant.

Animals↗
PubMed1994

Middle-ear development. VI: Structural maturation of the rat conducting apparatus.

BACKGROUND: The contribution of middle-ear development to the overall development of hearing has not been explored in great detail. This presentation describes the maturation of conductive elements in the rat middle ear, and provides the basis on which future studies of middle-ear functional development will follow. METHODS: The middle-ear apparatus was examined at nine different ages (between 1 and 80 days postpartum) in Long Evans rats. At each age elements of the conducting apparatus was observed with either light or scanning electron microscopy (SEM), and quantitative measurements were made from video enhanced photomicrographs. Tympanic membrane area and cone depth, the length of the malleus and incus arms, ossicular weight, stapes foot plate and oval window areas, and bulla volume were all measured. Development of the area and lever ratios were derived from these measurements. The data were fitted to exponential equations and the time in days required to reach 90% of the adult level determined. RESULTS: The pars tensa achieved 90% of total area by 17 days. The oval window achieved the 90% criterion by 13 days, while the area ratio was within 10% of its adult size by 8 days. The ossicles took between 26 and 34 days, while bulla volume took 59 days to reach the 90% level. CONCLUSIONS: Middle-ear growth was very orderly and systematic in the data reported. When maturation of the area ratio was considered against development of the endocochlear potential or the round window compound action potential, it was clear that the growth of this important aspect of the middle ear preceded the onset of cochlear function.

Aging↗
PubMed1994

Alterations of auditory nerve responses by hypoxia in normal and hydropic ears of awake guinea pigs.

Total interruption of blood or oxygen supply to the inner ear produces very rapid and drastic effects, whereas moderate decreases can be well tolerated by normal ears. In experimental endolymphatic hydrops some moderate alterations of cochlear vasculature have been described which might affect cochlear adaptation to moderate blood or oxygen deficiencies. In order to test this hypothesis an hypoxia at 5% oxygen was imposed for 30 min in normal and hydropic ears of awake guinea pigs and cochlear function was monitored with an electrode at the round window. Electrophysiological recordings used measures of compound action potential (CAP) amplitudes evoked by high-intensity tones, and of CAP thresholds. In normal ears hypoxia induced threshold elevations at all frequencies and decreases of CAP amplitude only for high frequencies. Hydropic ears presented similar or smaller threshold elevations but showed CAP amplitude decreases extending to lower frequencies and showed a much slower recovery both for CAP thresholds and amplitudes. The data indicate that hypoxia had different effects on auditory nerve responses evoked by high versus low intensity tones. The deleterious effects of hypoxia were increased in hydropic ears. Hypoxia-induced alterations were measured twice at one week intervals during which an anti-ischemic drug was administered to the animals; some beneficial effects of the drug treatment were observed on normal but not on hydropic ears.

Acoustic Stimulation↗
PubMedDate not supplied

Chronic effects of phasic middle ear pressure changes.

In an attempt to better define the mechanisms of barotrauma, middle and inner ear pathology was studied in guinea pigs three weeks following exposure to a brief, sudden middle ear pressure change. Findings included tympanic membrane perforations (particularly dependent upon high negative pressure exposures), vascular hemorrhage (primarily dependent upon high positive pressure exposures), serosanguineous effusions (predominantly dependent upon infection) and serous effusion (dependent upon negative pressure exposure). Round window perforations were common in high pressure animals with infection. Other inner ear membrane changes were infrequent or minimal. Lymphatic hemorrhage was observed as a function of exposure. The clinical implications of these findings and possible mechanisms underlying these changes are discussed in terms of our previously reported study of the immediate effects of such pressure change.

Animals↗
PubMed1977

Temporal bone pathology in an active case of glue ear.

A child aged 3 1/2 died from a cardiac condition after many and prolonged antibiotic courses: bilateral glue ear had been treated for the previous 18 months. Histopathology showed cholesterol granulomata in the mastoid air cells, with evidence of old hemorrhage, and of former inflammation of bone. The exudate was histiocytic with some giant cells. An 'orange spot' on the tympanic membrane was hyperaemic middle-ear mucosa, heavily infiltrated by plasma cells, lymphocytes and histiocytes. There was no evidence of hypersecretion. Some of the most abnormal areas were around the stapedial niche and the round window.

Child, Preschool↗
PubMed1997

Effects of ionomer cement on guinea pig cochleas.

The inner ear toxicity of ionomeric cement (Ionocem) when used as a reconstructive material in ear surgery was evaluated in 47 guinea pigs used in a morphological study. The cement was implanted on either the promontory, the round window membrane or the stapes. There was no significant hair cell loss compared with the control ear at three weeks, two months or three months after implantation. Using electrocochleography, the hearing thresholds before, and three weeks, two and three months after the implantation were compared in an additional seven animals. No evident hearing loss was observed in any animal during the study period. No morphological or functional evidence for an ototoxic effect of the ionomeric cement was found in this study.

Aluminum Silicates↗
PubMed1983

Magnitude and phase-frequency response to single tones in the auditory nerve.

In this paper we describe magnitude and phase measurements obtained from primary single unit recordings in the cat auditory nerve. Levels range from threshold to 100 dB SPL, with frequencies from 0.1-30.0 kHz. The upper limit on the phase measurements was limited by the loss of neural phase locking at 4-5 kHz. For each unit, the frequency tuning curve (FTC) was measured by the method of Kiang and Moxon [M.C. Liberman, J. Acoust. Soc. Am. 63, 442-445 (1978)] to establish the threshold frequency response of the unit. Data from several selected animals, organized by characteristic frequency (CF), are presented showing phase response, group delay, frequency tuning, and tuning slope for each CF range. The major emphasis in this paper is on the "linear" aspects of the data as characterized by the filter properties of the single unit response, however a number of nonlinear (level-dependent) effects are described. Data are presented showing the phase response normalized by the cochlear microphonic (CM) recorded at the round window membrane. This normalization simplifies the phase data since it produces a constant phase slope with respect to frequency (constant group delay) for high CF units (f CF greater than 1 kHz) for frequencies more than one octave below their characteristic frequencies. A model of CM, as measured at the round window (RW), is presented and compared to experimental CM measurements. The CM model gives a reasonable fit to the experimental data above 500 Hz. Our interpretation of the CM normalization is that it removes driver and middle ear effects. In the model we assume that the CM is generated by the displacement of the basilar membrane near the round window recording site.

Animals↗
PubMed1994

Otopathology in a case of multichannel cochlear implantation.

The histopathology of the temporal bones of a patient who died of unrelated causes 10 weeks following cochlear implantation using a Richards Ineraid device is presented. Deafness was caused by a prolonged course of intravenous gentamycin therapy 5 years prior to implantation. The electrode array of the cochlear implant was left in situ throughout histologic preparation and sectioning. Despite displacement and disruption of supporting structures of the inner ear, particularly in the 6-to-15-mm range as measured from the round window, there was no significant difference in the mean densities of spiral ganglion cells in the implanted and unimplanted sides. This case is presented as evidence that despite significant disruption of supporting elements of the inner ear, which is common during cochlear implantation, there appears to be little effect on the residual spiral ganglion cell count, at least in the short term.

Cell Count↗
PubMedDate not supplied

[Sound sensations produced by electric stimulation of the structures of the middle ear and the tympanic chord].

Certain facts must be clearly understood before any attempt is made to analyse the sensations produced by electrical stimulation of the structures of the middle ear. Firstly, when the current passes from an electrode to the skin or to any polarised structure whatsoever, the point at which the electrode is applied and the skin behave like the two plates of a condenser microphone. Electrical vibrations are transformed into ordinary acoustic resonances which can travel through air or bone. These acoustic resonances are fairly pure in comparison with electrical vibrations, judged by the standards under investigation. If a continuous polarisation potential, which gives better distribution of the electrical charges, is added, the capacity of the microphone is increased and greater purity obtained. Consequently, the quality of sound heard in this way depends not only on the quality of this electro-physiological microphone but also on the quality of the internal ear. The acoustic effect produced in this way is called an electrophonic effect. Stevens, Jones and Flottorp described this. Therefore an internal ear which has lost the ability to hear high-pitched sound cannot hear them by means of this electrophonic effect any more than it can by ordinary auditory stimulation. Stimulation of the skin of the mastoid and of the external auditory meatus can be sensed by means of this electrophonic effect. Next, sensations recorded by means of direct stimulation of the acoustic nerve (DJOURNO and EYRIES) or by implantation of intra-cochlear electrodes (SIMMONS, DOYLE, MICHELSON) were studied. Sounds heard through stimulation of the structures of the middle ear should be analysed in the light of these findings and bearing in mind that very strong stimulation of the promontory or of the auditory meatus always causes an auditory sensation without frequency awareness due to global stimulation of the acoustic nerve (faciaestations appeared when experiments, the results of which are described, were carried out, although there is a possibility of episode vestibular irritation. These stimulations were in fact always very weak. Our results were analysed in relation to the quality of the internal ear: completely deaf, serious condition, internal ear normal. The impulses were provided by a direct current battery: these were square with a frequency of between 50 and 900 Hertz, a tension of 0 to 8 volts per 1/10 volt. The electrode was bipolar. The experiments were monitored from time to time by oscilloscope. Mention should be made of the technical and psychological precautions to be observed when stimulation of this kind is carried out if results of any value are to be obtained: a relaxed, sensible patient with whom one can communicate easily. Not much can be gathered from a person deaf in both ears. With the ear opened, the posterior part of the tympanum pulled forward, stimulation of the round window always results in production of a sound at a threshold of 0.5 to 2.5 volts.

Acoustic Stimulation↗
PubMed2000

Pharmacological protection of auditory function against noise and hypoxia with MK 801

INTRODUCTION: Pharmacological protection of cochlear function is one of the most exciting goals of inner ear medicine. The selective glutamate antagonist MK 801 may be neuro-protective to the cochlea.1 This study aims to investigate whether round window administration of MK 801 protects cochlear function against a combination of noise and atmostpheric hypoxia. METHODS: Eight guinea-pigs were studied. Round Window E. Catheters (Durect Inc., USA) were implanted through a trans-bulla approach and EcoG thresholds determined at 8, 16, 24 and 30 kHz. Artificial perilymph (n = 4) or 10 mM MK 801 (n = 4) was then perfused onto the round window membrane. After 15 min the anaesthetized animals were exposed to 100 dB white noise in 11.5-12. 5% atmospheric oxygen. Thresholds were determined before and 15 min after exposure. RESULTS: The mean threshold shifts from pre-perfusion at 8, 16, 24 and 30 kHz were 40, 33, 35 and 17 dB, respectively (in control animals) and 29, 28, 33 and 41 dB, respectively (in treated animals). A marginal protective effect was demonstrated at 8 kHz (P = 0.06). The 30-kHz thresholds in the treated group fell by 61 dB before noise exposure compared to < 1 dB in the controls (P = 0.0007), suggesting that at high frequencies, 10 mM MK 801 may itself be ototoxic. CONCLUSIONS: These results partially support existing data suggesting that pharmacological protection against noise/hypoxia is possible. Administration of round window NMDA antagonists may affect normal auditory threshold making detailed evaluation of the toxicity of potential inner ear therapies essential before clinical use is contemplated.

Journal Article↗