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At least 667 records · Page 37Linked to original sources
PubMed2001

[Rupture of the round window--detection with fluorescence endoscopy].

Rupture of the round window membrane as a special cause of inner ear deafness is widely accepted after changing pressure levels, e.g. in diving. However, even without a barotrauma before, the spontaneous rupture of the round window membrane is suspected occasionally in patients with sudden hearing loss and/or vertigo and tinnitus. To carry through the tympanotomy is decided by ENT surgeons often in cases of progressive hearing loss despite infusion therapy. Perilymph fistulas have been detected relatively seldom, compared to the number of reported operations by several authors. However, covering the round niche with connective tissue leads to the improvement of symptoms sometimes even in cases without microscopical evidence of fistula. Within the last 3 years 14 patients suffering sudden hearing loss of one ear underwent tympanotomy in our department. Of these patients 8 reached restitution of the hearing ability. Especially 2 patients with sudden deafness caused by spontaneous rupture of the round window membrane are reported in the following article. Perilymph fistulas were detected in these cases by IV-application of fluorescein and fluorescence endoscopy of the middle ear. Both patients obtained a normal hearing curve within 1 week after surgical intervention and obliteration of the round niche.

Adolescent↗
PubMed1998

Round window atresia in association with congenital stapes fixation.

OBJECTIVE: To document an association of round window atresia with congenital stapes fixation, discuss the diagnostic role of computed tomography, and implicate the clinical significance of these anomalies. STUDY DESIGN: Retrospective chart review and review of the literature. RESULTS: The authors report three pediatric cases of round window atresia. All cases presented with hearing loss of a conductive nature (two cases bilateral, one unilateral). Two patients underwent middle ear exploration, demonstrating stapes fixation and the absence of a round window. Stapedectomy was performed in both cases without postoperative hearing improvement. Subsequent revision stapedectomy was also unsuccessful in one of these cases. The unoperated case represents the fraternal twin of one patient. In all cases, computed tomography scanning demonstrated findings consistent with atresia of the round window niche without cochlear anomaly. CONCLUSIONS: An association of round window atresia and congenital stapes fixation is apparent. The mechanism of the conductive hearing loss following stapedectomy remains poorly understood. Computed tomography imaging and surgical confirmation are probably both necessary to establish the diagnosis of round window atresia.

Child↗
PubMed2004

The biology of intratympanic drug administration and pharmacodynamics of round window drug absorption.

The application of therapeutic agents to the round window holds great promise in the treatment of inner ear disease. The primary benefit of this route of administration is the ability to achieve high inner ear concentrations of drugs without systemic side effects. Recent research has elucidated the anatomy and physiology of the round window and provided important information on the inner ear pharmacokinetics and the pharmacodynamics of drugs administered intratympanically. Although amino-glycosides and steroids have been most thoroughly studied, many other classes of pharmaceuticals, including otoprotective agents, other antibiotics,and topical anesthetics, have therapeutic potential in the inner ear and will probably be the subject of future studies. The authors believe that direct delivery approaches other than through the round window, perhaps with slow or sustained release formulations, may hold the key to the future treatment of inner ear disorders.

Administration, Topical↗
PubMedDate not supplied

Staphylococcus aureus exotoxin has limited and transient effects on cochlear electrophysiology.

Seven ears of Sprague-Dawley rats were exposed to 20 microliters Staphylococcus aureus exotoxin suspension by injection via the tympanic membrane into the round window niche. Another 6 ears were exposed to 20 microliters broth as controls. ABR was performed in the interval 2-31.5 kHz immediately before and 1, 2, 5, 7 and 10 days after the exposure. Although threshold changes could be found in the toxin-exposed group but not the control group in the frequency range 10-20 kHz, there were only statistically significant threshold changes--at 31.5 kHz--on the 1st, 2nd, 5th, and 7th days after the exotoxin injection. S. aureus exotoxin has minor transient but reversible effects on the inner ear, causing chiefly high-frequency threshold and latency changes.

Animals↗
PubMedDate not supplied

Ototoxicity of ethanol in the tympanic cleft in animals.

This work was undertaken to study the ototoxicity of topically applied ethanol in quantitative terms. Using guinea pigs, ethanol was administered (1) on the round window for 10 min, (2) instilled in the middle ear cavity for 24 hours, and (3) perfused into the cochlear canal (into the scala tympani) at the rat of 10 microliter/min for 10 min. Cochlear microphonics from the electrode on the round window were recorded. The critical concentration (the maximum dilution ratio) of the ethanol that appears to be ototoxic in the experimental condition mentioned above was determined to be (1) 50%, (2) 10%, (3) 0.1% respectively. Using chinchillas, the effect of ethanol with round window application on the Endocochlear Potential (EP) was studied. Simultaneous recording of EP from the 1st and 3rd turn of the cochlea showed a more marked decline in EP in the 1st turn. 70% ethanol caused an irreversible, plateauing decline in EPO, while 35% ethanol caused a reversible decline in EP.

Action Potentials↗
PubMed1989

Experimental herpes simplex virus and cytomegalovirus labyrinthitis.

Herpes simplex virus (HSV) and guinea pig cytomegalovirus (GPCMV) were inoculated into the middle ear of guinea pigs. The routes of passage of middle ear infection to the inner ear are hematogenous and/or via the cochlear windows. The presence of GPCMV inclusion body-bearing cells within the cochlea strongly suggests the hematogenous route, as in some animals the inner ear does not show cell infiltration and precipitate. When viral infection approaches the cochlear windows, the first morphological changes observed are the presence of precipitate in the inner ear fluids and the appearance of macrophages. These changes are particularly marked near the windows. Direct invasion of the infection into the inner ear after rupture of the round window membrane results in hemorrhage and marked cell infiltration. Inclusion body-bearing cells are found scattered within the exudate. Possible emperipolesis is frequently observed. No cells or tissues can escape involvement in viral labyrinthitis. Fibrosis and ossification eventually occur. Anomaly of the cochlea, the mirror image of the organ of Corti, was observed in the offspring of a guinea pig in whom cytomegalovirus was inoculated into the inner ear.

Animals↗
PubMedDate not supplied

Effect of a middle ear immune response on inner ear antibody levels.

The effect of a middle ear immune response upon antibody levels in the perilymphatic compartment of the inner ear was investigated in the guinea pig. Animals were systemically sensitized with keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA) until high circulating levels were achieved. The middle ear cavity was then challenged with KLH, resulting in a vigorous immune response with effusion and mucosal inflammation. Antibody levels against KLH and BSA were then compared in serum, middle ear effusions, and perilymph. Anti-KLH levels in perilymph were found to increase substantially during middle ear response to challenge, while the anti-BSA levels did not, indicating a local origin for the anti-KLH antibody. The most likely explanations for these findings are inner ear antibody originated in the middle ear and diffused across the round window membrane, or antigen diffused across the round window membrane and evoked local production of antibody within the inner ear.

Animals↗
PubMedDate not supplied

[Inner ear injuries in breath-holding divers].

Five breath-hold divers with inner ear barotrauma due to the diving to 10 meters of depth have been treated at the Department of Otorhinolaryngology, Pula Medical Centre during 1990. Because of eustachian tube dysfunction, a negative middle ear pressure is transmitted into the inner ear over the round and oval window causing a lower hydrostatic pressure of the inner ear fluids and consequent delay in microcirculation of the inner auditory artery. Together with a hypoxia in apnea the oxygen demand is increased and the inner ear neuroepithelium damage is more severe. All treated divers had irreversible sensorineural hearing loss of the attacked ear on frequency range higher than 2000 Hz to 70-80 dB.

Adult↗
PubMed1989

Electrical tinnitus suppression (ETS) with a single channel cochlear implant.

Patients with intractable tinnitus in a dead ear were selected for electrical tinnitus suppression (ETS) first with a round window electrode inserted via the ear canal. Three patients have been selected for implantation with a UCH/RNID single channel extracochlear device to use with a sinusoidal tinnitus suppressor. We have also examined the effect of sinusoids on deafened implantees with tinnitus and conclude that tinnitus can be suppressed in some individuals with low frequency sine waves. Two patients are presented who have used cochlear implants to suppress their tinnitus for more than 18 months.

Acoustic Stimulation↗
PubMed1984

Cochlear effects of locally applied inhibitors.

The round window has been used as a route for introducing ototoxic substances into the inner ear in order to bypass barriers between the systemic circulation and the inner ear. We have used this method to administer locally sodium potassium-ATPase inhibitors and chloride transport inhibitors to the inner ear of the chinchilla. Drugs dissolved in saline solution were applied on the round window membrane. Endocochlear potential (EP) was recorded from the basal turn using the round window approach. The EP was not altered following application of saline solution as a control. Following application of ouabain (1 mM), the EP steadily declined. After vanadate (27 mM), the EP initially increased, and subsequently declined. Sanguiarine did not alter the EP. The loop diuretics furosemide and piretanide caused a marked decline in the EP after local application. However, the stilbene derivative DIDS did not alter the EP after topical application. These findings raise questions about whether the loop diuretics have any effect on chloride transport in the cochlea and make appear unlikely that active chloride transport contributes to the normal EP.

Administration, Topical↗
PubMedDate not supplied

Experimental study of nystagmus induced by injecting various solutions into the middle ear cavity.

Injecting of various solutions into the middle ear cavity of cats and rabbits provoked certain characteristic types of nystagmus which resembled caloric nystagmus or clinical cases of peripheral vestibular disorders. Solutions with different degrees of specific gravity, osmotic effect and ion composition were used in this study. Direction-changing positional nystagmus, irritative nystagmus, and paralytic nystagmus were elicited according to the physical or chemical properties of each solution. Histological findings showed mild changes in the perilymphatic space and/or in the endolymphatic space in the period with some characteristic types of nystagmus. Infiltration of the substances into the inner ear fluids from the middle ear cavity via a round window membrane were probably responsible for these types of nystagmus.

Animals↗
PubMed2000

Intratympanic immunosuppressives for prevention of immune-mediated sensorineural hearing loss.

HYPOTHESIS: Round window membrane application of immunosuppressives reduces cochlear inflammation and hearing loss in a guinea pig model of sterile labyrinthitis. BACKGROUND: Systemic immunosuppressives are used to treat sensorineural hearing loss due to inflammation (autoimmune, bacterial, viral), which in animal models causes hearing loss. Transtympanic application of drugs is an attractive and possibly efficacious method of treatment that avoids systemic toxicities. METHODS: Sterile labyrinthitis was created using keyhole limpet hemocyanin (KLH). Dexamethasone (0.048 mg/day and 0.288 mg/day), cyclosporine (0.5%), prednisolone acetate (1%), fluorouracil, (5%), and FK506 (0.01%) were delivered to the round window membrane with one injection (filling middle ear space) or osmotic minipumps. Efficacy was evaluated by auditory brainstem response and histology. RESULTS: No drug was effective at reducing hearing loss or inflammation. CONCLUSION: Local application of immunosuppressives did not suppress inner ear inflammatory infiltrates and hearing loss in KLH-induced labyrinthitis in a guinea pig model.

Animals↗
PubMedDate not supplied

Hearing loss in relation to round window membrane morphology in experimental chronic otitis media.

The present study was performed to test the effect of single and repeated Pseudomonas aeruginosa exotoxin A (PaExoA) instillations in the middle ear of the rat. The hearing level was examined by the ABR technique, round window membrane (RWM) thickness was measured and morphology was studied by light microscopy. The results showed both reversible and permanent hearing loss (HL). In animals that received a single dose of PaExoA, the RWM thickness doubled initially and remained thickened during the observation period. When PaExoA was instilled on several occasions, RWM thickness doubled, before decreasing to near-control levels. This study confirms the toxicity of PaExoA and the partially reversible HL occurring after a single application of the toxin. The diminished effect of repeated toxin instillations--despite the decreasing thickness of the RWM--is discussed.

ADP Ribose Transferases↗
PubMedDate not supplied

Electrical stimulation of the ear: experimental studies.

The possibility of stimulating the ear by way of an electrode on the round window in order to relieve tinnitus or to produce auditory sensations has been investigated experimentally in guinea pigs. The deleterious effects of DC currents applied to a normal cochlea clearly demonstrate that this means is unsuitable for use in relieving tinnitus in hearing patients. Although AC currents do not cause further damage in ears with the organ of Corti already destroyed by aminoglycosides, the effects of DC currents in such cases have still to be investigated before they can be recommended for the relief of tinnitus in totally deaf patients. Electrical stimulation of the round window combined with masking has made it possible to record responses of auditory neural elements from the eighth nerve to the auditory cortex. This technique could be promising for the basic study of the central auditory nervous system, both experimentally and clinically, and could lead to a more accurate evaluation of candidates for cochlear prostheses.

Animals↗
PubMed1992

Permeability of arachidonic acid metabolites through the round window membrane in chinchillas.

Our previous studies showed that samples of middle ear effusion contain high concentrations of arachidonic acid metabolites (AAMs); both prostaglandins (PGs) and leukotrienes (LTs). Since abnormal levels of AAMs in the perilymph seem to be associated with salicylate ototoxicity and the round window membrane (RWM) is the most likely route of entry from the middle ear to the inner ear, it would be important to know the permeability of AAMs through the RWM. Permeability of AAMs was determined by applying labeled and standard representatives AAMs on the RWM and counting radioactivity or measuring concentrations of AAMs in perilymph at different time intervals. Using chinchillas as experimental animals, samples of perilymph were obtained through a fenestration made at the helicotrema of the cochlea after 0.5, 1, 2, and 4, hours from placing tritiated or standard PGE2, 6-keto-PGF1 alpha, LTB4, LTC4 and 15-hydroxyeicosatetraenoic acid (HETE) over RWMs. Radioactivity in the perilymph was determined by a scintillation counter and concentrations of AAMs were measured by reverse phase high performance liquid chromatography (RP-HPLC) and radioimmunoassay. AAMs, which are twenty carbon fatty acids, were found to cross the RWM readily. Radioactivity and concentrations of AAMs in perilymph were detected in 30 minutes and peaked by one hour from the application of AAMs on the RWM. The results of this study suggest that AAMs such as PGs and LTs present in the middle ear fluid can cross the RWM readily and enter into the perilymphatic space of the cochlea. Sensorineural hearing loss observed in chronic otitis media could be mediated by PGs and LTs in the middle ear effusion crossing over to the inner ear through the RWM.

Adrenal Cortex Hormones↗
PubMed1978

Action potentials in the cat at low sound intensities: thresholds, latencies, and rates of change.

The interpretation of whole-nerve action potentials is a topic of increasing importance in both clinical and research settings. This effort has been hampered by a lack of data on the action potential that are theoretically interpretable and systematically measured over a wide range of frequencies and at low sound intensities. Therefore, the present study was designed to measure the thresholds, latencies, and rates of change in the whole-nerve action potential in response to constant-spectral-width tone pips at eight frequencies between 0.5 and 20 kHz in the cat ear. These quantities were calculated by a linear regression technique from round-window potentials in 28 normal ears. They were found to be consistently within approximately 18 dB of previously published behavioral measures, a difference attributable to temporal integration. The interanimal variability had a standard deviation of about 5 dB and the intra-animal variability was extremely low. The growth of amplitude across frequencies, the rate of change of latency with intensity changes, and the latency at threshold all demonstrated orderly relationships which are presented. The data were all consistent with contention that the potentials were being produced by a single population of cells located at a place consistent with the frequency of the eliciting tone. The methods used provide exceedingly stable measures and should be applicable in both clinical and research settings.

Acoustic Stimulation↗
PubMed1985

Frequency characteristics of the middle ear.

For 68 temporal bones, frequency curves for the round window volume displacement have been measured for a constant sound pressure at the eardrum. Phase curves were measured for 33 of the specimens. The levels averaged amplitude curve is approximately flat below 1 kHz, where the round window volume displacement per unit sound pressure at the eardrum is 6.8 X 10(-5) mm3/Pa, and falls off by about 15 dB/oct at higher frequencies. For the 20 ears having the largest sound transmission magnitude at low frequencies, the corresponding amplitude curve is displaced about 5 dB towards higher levels. The phase of the round window volume displacement lags the eardrum sound pressure phase. In average for 33 temporal bones, the phase lag increases from zero at the lowest frequencies to pi near 2 kHz and to about 1.5 pi at 10 kHz.

Acoustics↗