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At least 217 records · Page 12Linked to original sources
PubMed2004

Preservation of basal inner ear structures in cochlear implantation.

The aim of this report was to examine basal trauma in implanted human temporal bones and discuss modified approaches to the basal cochlear turn to avoid destruction of basal cochlear structures. Thirty-three human temporal bones were implanted with four different cochlear implant electrode arrays manufactured by MED-EL using either a caudal approach cochleostomy or round window membrane insertions. All specimens were processed with a special histological technique that allows sectioning of undecalcified bone with the electrode in situ. All bones were evaluated histologically in terms of basal cochlear trauma. Two pathomechanisms of basal trauma could be distinguished and were evaluated separately, buckling of the basal end of the array and trauma by drilling. Using the caudal approach cochleostomy, the total percentage of destructive basal trauma was 48% compared to less than 15% when performing round window membrane insertions. Although it is still unclear whether basal cochlear trauma influences apical cochlear function or not, adapted surgical procedures and no forceful insertion maneuvers should be used when performing cochlear implantations with hearing preservation.

Cochlea↗
PubMed1997

Increased secretory capacity of the middle ear mucosa after acute otitis media caused by Haemophilus influenzae type B.

Secretory otitis media is associated with a highly increased goblet cell density of the middle ear mucosa. Previous studies have shown that a single episode of experimental acute otitis media caused by Streptococcus pneumoniae or nontypeable Haemophilus influenzae is followed by increased goblet cell density for a period of at least 6 months. This condition may create a predisposition for subsequent development of secretory otitis media. We inoculated the middle ears of 25 rats with type B H. influenzae to determine the effect of the bacteria on mucosal secretory capacity. Five rats were euthanized 4, 8, 16, 60, and 180 days after inoculation, followed by dissection, staining, and whole-mount embedding of the middle ear mucosa. The goblet cell density was determined in 24 well-defined localities. Compared with that of 25 normal middle ears, the goblet cell density was significantly increased in almost all counting localities on all days of euthanasia. Thus increased goblet cell density and enlargement of mucosal areas containing goblet cells persisted for 6 months after the acute incident. Inoculation of type B H. influenzae induced an increase of goblet cell density that was higher than the increase after inoculation of S. pneumoniae or nontypeable H. influenzae. We conclude that experimental acute otitis media caused by type B H. influenzae is followed by a longstanding increase of mucosal secretory capacity, which is likely to induce a subsequent development of secretory otitis media.

Acute Disease↗
PubMed1996

Erythrocyte removal and blood clearance in the endolymphatic sac. An experimental and TEM study.

The endolymphatic sac (ES) appears to serve as an immunologic/phagocytic defence organ. This may involve both specific and unspecific cell reactions for removal of both endogenous waste products and debris and foreign material. The present study was carried out in order to investigate whether the ES is involved in the removal of blood from the inner ear. The round window was exposed and the stapedial artery experimentally lesioned to cause bleeding. The ES was taken out after various time intervals and analyzed by TEM and LM, care being taken to maintain the structural integrity at all levels. This was done in order to see if the endolymphatic sac is involved in the removal of blood from the inner ear. The results indicate that the ES possesses hitherto unknown specific cellular properties for the disposal of blood and blood corpuscles. It is believed that this system may represent an important physiological function for regulation of homeostatic equilibrium around the inner ear sensory structures. The results also offer further support for the existence of a longitudinal "flow" of endolymph from the cochlea into the ES. Judging from the time it takes for erythrocytes to appear in the duct and sac, this flow would seem to take about 1-2 h in the mouse.

Animals↗
PubMed2002

Loud sound-induced changes in cochlear mechanics.

To investigate the inner ear response to intense sound and the mechanisms behind temporary threshold shifts, anesthetized guinea pigs were exposed to tones at 100-112 dB SPL. Basilar membrane vibration was measured using laser velocimetry, and the cochlear microphonic potential, compound action potential of the auditory nerve, and local electric AC potentials in the organ of Corti were used as additional indicators of cochlear function. After exposure to a 12-kHz intense tone, basilar membrane vibrations in response to probe tones at the characteristic frequency of the recording location (17 kHz) were transiently reduced. This reduction recovered over the course of 50 ms in most cases. Organ of Corti AC potentials were also reduced and recovered with a time course similar to the basilar membrane. When using a probe tone at either 1 or 4 kHz, organ of Corti AC potentials were unaffected by loud sound, indicating that transducer channels remained intact. In most experiments, both the basilar membrane and the cochlear microphonic response to the 12-kHz overstimulation was constant throughout the duration of the intense stimulus, despite a large loss of cochlear sensitivity. It is concluded that the reduction of basilar membrane velocity that followed loud sound was caused by changes in cochlear amplification and that the cochlear response to intense stimulation is determined by the passive mechanical properties of the inner ear structures.

Acoustic Stimulation↗
PubMed2004

[1D-and 3D- computer simulation for experimental planning and interpretation of pharmacokinetic studies in the inner ear after local drug delivery].

The local delivery of drugs to the cochlea is a promising alternative to systemic treatment of inner ear disorders. Whilst new drugs are being developed for this purpose, it is important to determine the time course and total dose required for the various target regions within the inner ear. Due to the small fluid spaces of the inner ear and the resulting experimental and analytical difficulties, many animal studies have only obtained one sample per animal. This results in limited information about drug time courses at specific locations in the inner ear. We show here how computer models considering general pharmacokinetic principles and inner ear geometry are used for application of the 3R-principle in animal research while avoiding experimental sampling artefacts. This can be achieved by: (1) careful planning and interpretation of experiments to study pharmacokinetics in the inner ear, (2) optimising volume sampling techniques, (3) facilitating the use of advantageous, continuous sampling methods like microdialysis and (4) developing a 3D-model that will permit consideration of the complex geometry of the inner ear when transferring results from one species to another.

Animal Testing Alternatives↗
PubMed1997

Preoperative assessment of the implantable middle ear pump system using CT scans and conventional X-rays of the temporal bone.

A completely implantable micropump system for drug delivery has recently been developed. After implantation in the temporal bone, this microdosage system enables application of drugs into the middle ear and round window area. Successful application of this new technology depends upon a suitable fit of the micropump within the patient's temporal bone. To obtain information about the fit before surgery, we analyzed 50 cadaver temporal bone specimens before total mastoidectomy, using conventional X-ray and spiral CT scans for water volume determination. Spiral CT is a feasible method for preoperative planning of the surgical implantation of the implantable middle ear micropump system (TI-DDS). The best parameter for a preoperative judgment is the volume of the mastoid cavity, as determined by CT. Implantation may be recommended when the mastoid volume, as measured by CT, is greater than 6.6 ml. To be certain that the implantable drug delivery system will be implantable, a cut-off value of 9.3 ml seems to be advisable. Spiral CT imaging is of great value as a tool for testing implantation preoperatively. The imaging is accomplished in approximately 30 seconds. Our preliminary results with cadaveric temporal bones are encouraging. Further studies are needed in order to transfer the results to a clinical implantation situation.

Ear, Middle↗
PubMed1984

Histological considerations in implant patients.

The selection of patients for cochlear implantation requires consideration of a variety of anatomical and histological facts. Mechanical impediments to cochlear implantation, including the consequences of chronic otitis media, bony obliteration of the membranous labyrinth, or labyrinthitis ossificans, following bacterial labyrinthitis or vascular compromise of the inner ear, obliterative otosclerosis, and middle-ear dysplasias may present difficulties in access to the inner ear and placement of electrodes. Consideration of the histopathological features of known causes of profound deafness will help predict the presence or absence of inner ear structures essential for successful implantation. The identity of these critical structures and the histopathologic characteristics of bacterial labyrinthitis, fungal meningitis, syphilis of the inner ear, otosclerosis, presbycusis, genetically determined degenerations, trauma, intoxications, inflammatory, autoimmune and idiopathic disorders are presented in terms of their relevance for cochlear implantation.

Adult↗
PubMed1985

Treatment of endolymphatic hydrops with cochleosacculotomy. Clinical results and experimental findings.

Cochleosacculotomy was performed on 25 patients with Meniere's syndrome. Long-term relief of vertigo was obtained in 19 out of 23 (82%). Postoperatively dead ears occurred in three cases. The same operation was performed on 12 guinea pigs in which hydrops had been surgically induced by blockage of the endolymphatic duct and sac. All fistulas were healed and cochleosacculotomy did not decrease or prevent the induced endolymphatic hydrops in these animals. Although histologic confirmation of persistent fistulas in human ears is lacking, the relief of vertigo in patients may not be caused by "drainage" but, rather, by a nonspecific effect on the inner ear. Cochleosacculotomy gives results comparable with other nondestructive surgical procedures performed to suppress vertigo in Meniere's syndrome.

Adult↗
PubMed2006

Alternatives to systemic steroid therapy for refractory immune-mediated inner ear disease: A physiopathologic approach.

Immune-mediated inner ear disease (IMIED) is one of the few forms of reversible sensorineural hearing loss. Corticosteroids-responsive patients are usually associated with hearing improvement. Due to the long clinical course of IMIED that frequently present recurrences (hearing loss and vertigo), alternatives to corticosteroids such as methotrexate and recently TNF-alpha blockers have been proposed. Likewise new procedures for delivering corticosteroids to the inner ear have been developed. The aim of this article is to assess the efficacy of methotrexate and transtympanic 6-methylprednisolone in refractory IMIED. From a database of 200 patients affected by IMIED, 16 selected patients with refractory disease were included in the present study. Five patients were treated with methotrexate and 11 by means of transtympanic injection of 6-methylprednisolone. All patients treated with methotrexate had an improvement in their vestibular symptoms. However, hearing loss did not improve. Most patients treated with local 6-methylprednisolone (68.75%) showed an improvement in hearing loss and vestibular symptoms. Methotrexate has been shown to be ineffective in maintaining long-term remissions of hearing relapses although patients presented an improvement in vestibular symptoms. However, transtympanic 6-methylprednisolone has been shown to be a safe, easy and useful therapy in refractory IMIED and it may actually become the first-line treatment for these patients based on the existence of glucocorticoid receptors and the possible targets of immune-mediated damage within the inner ear.

Administration, Oral↗
PubMed2006

Local perfusion of the tumor necrosis factor alpha blocker infliximab to the inner ear improves autoimmune neurosensory hearing loss.

OBJECTIVE: To evaluate the effect of transtympanic administration of tumor necrosis factor alpha (TNF-alpha) blockers to patients suffering from autoimmune inner ear disease (AIED). STUDY DESIGN: Nonrandomized, prospective pilot study. SETTING: Tertiary referral center. PATIENTS: 9 patients (4 men and 5 women; aged 51.22 +/- 13.11 years) presenting with autoimmune sensorineural hearing loss who responded to oral steroid treatment. Two groups of patients were treated. Group A consisted of 5 patients with AIED who could not be tapered off steroids. Group B consisted of 4 patients who were treated with intratympanic anti-TNF-alpha antibody therapy alone after a relapse of hearing loss following discontinuation of steroids. INTERVENTION: A Silverstein MicroWick local delivery system was placed in the round window niche and the patients were treated for 4 weeks with a weekly infusion of infliximab, a monoclonal antibody against TNF-alpha. MAIN OUTCOME MEASURE(S): Evaluation of hearing thresholds at 250-8000 Hz was performed before and after implantation of the Silverstein MicroWick and local delivery of the TNF-alpha blocker. RESULTS: Local administration of the TNF-alpha blocker allowed methylprednisolone to be tapered off without loss of hearing function in 4/5 steroid-dependent patients. Four additional patients were treated only with anti-TNF-alpha perfusion to the round window membrane without concomitant systemic administration of methylprednisolone. In 3 of these 4 patients, the pure tone average improved to 22.6 +/- 15.7 dB, resulting in hearing recovery comparable to treatment with systemic methylprednisolone. The 7 responding patients showed a significant reduction of recurrence of hearing loss to 0.028 +/- 0.072 episodes per month over the 4.3 +/- 2.4 months of the post-treatment period compared to 0.84 +/- 0.4 recurrences per week seen in the pretreatment period. CONCLUSIONS: The results of this pilot trial demonstrate that in patients with AIED, transtympanic delivery of the TNF-alpha blocker infliximab once weekly for 4 weeks allowed steroids to be tapered off, resulted in hearing improvement and reduced disease relapses. These preliminary efficacy and safety results appear encouraging enough to warrant further follow-up and studies for better determination of the potential clinical utility of local administration of infliximab for autoimmune hearing loss.

Adult↗
PubMed1997

Anatomy of the normal human cochlear aqueduct with functional implications.

There is great variation in published descriptions of the shape, size, and patency of the human cochlear aqueduct. The first part of this paper describes the anatomy of the normal human cochlear aqueduct as determined from a study of 101 temporal bones. Nineteen bones aged 0-1 years and approximately 10 bones per decade of life until age 100 years were examined. The aqueduct was found to have a funnel shaped aperture at the cranial end with a dural sheath extending into it for a varying distance. The rest of the aqueduct was filled with a meshwork of loose connective tissue, often with a central lumen within it. Four types of patencies were noted: central lumen patent throughout length of aqueduct (34%), lumen filled with loose connective tissue (59%), lumen occluded by bone (4%), and obliteration of the aqueduct (3%). The mean value (+/- SD) of the narrowest portion was 138 (+/- 58) microns which occurred 200-300 microns from the cochlear end of the aqueduct. There was no correlation between age and narrowest diameter, or between age and category of patency. In the second part of this paper, we propose quantitative models of aqueduct function, based on measurements of ductal dimensions and known acoustical properties of the inner ear. Our model analyses suggest that in normal ears, the aqueduct (1) cannot support fluid flows large enough to explain stapedectomy gushers, (2) does filter out cardiac- and respiration-induced pulses in CSF and prevents them from affecting cochlear function, and (3) has little effect on normal ossicular transmission of sound for frequencies above 20 Hz. In pathological ears, such as those with ossicular disruption or after a type IV tympanoplasty, a patent aqueduct might affect hearing for frequencies below 150 Hz.

Acoustics↗
PubMedDate not supplied

Effect of ototopic application of a corticosteroid preparation on cochlear function.

The ototoxicity of the corticosteroid triamcinolone diacetate was investigated using the compound action potential (CAP) of the auditory nerve as a parameter when the drug was applied to the middle ear cavity of the chinchilla. Comparison with the contralateral ear, instilled with Ringer's solution, demonstrated no significant difference in the threshold, amplitude, and latency of the CAP responses at the overall frequencies tested. In addition, the side difference of the CAP threshold in individual animals showed that this corticosteroid did not induce cochlear dysfunction in any case.

Administration, Topical↗
PubMed1992

[Investigations of the ototoxicity of dicortinef (ear drops)].

The authors investigated the ototoxic influence of Dicortinef in laboratory animals. Their examinations were performed on 15 guinea pigs (weighing 210-380 g.) after application of this medicine to the fenestra rotunda. The harmful effect of Dicortinef was expressed by the characteristic fall in the microphonic potential (PM) and potential of the acoustic nerve (AP).

Animals↗
PubMed1992

Transmission of change in the atmospheric pressure of the external ear to the perilymph.

In experiments using guinea pigs, the middle ear and perilymphatic pressures were simultaneously registered in response to pressure change in the external ear canal. In the first experiment, pressure was slowly loaded in the ear canal in the range of 200 mm H2O to -200 mm H2O. Pressure transmission to the perilymph was smaller when the bulla was open to the outside than when it was closed. It was significantly impaired by disruption of the ossicular chain and especially by closure of the round window. The data indicate that air volume in the middle ear cavity plays an important role in transmission of slowly changing atmospheric pressures. In the second experiment, the eustachian tube was closed and the pressure was changed in the range of 1000 mm H2O to -1000 mm H2O. The middle ear and perilymphatic pressures increased or decreased corresponding to the loading pressure in the range of 400 mm H2O and -200 mm H2O. Beyond these levels, response rate of the middle ear pressure decreased and perilymphatic pressure declined in spite of further increase in loading pressure. The increase in pressure difference between the middle ear and the inner ear might cause disruption of the round and/or oval windows.

Animals↗
PubMedDate not supplied

Limits of normal for pressure sensitivity in the fistula test.

In patients with perilymphatic fistula (PLF), nystagmus may sometimes be elicited by application of pressure to the external ear canal. The extent to which the normal population also exhibits such 'pressure sensitivity' is presently unknown. Our goal was to determine the limits of normal pressure sensitivity and to quantify the performance of the fistula test. Our subjects consisted of 13 normal controls and 7 patients with a history of pressure sensitivity who later underwent exploratory tympanotomy. We measured nystagmus prior to and following pressurization of the external ear canal. Pressure was applied manually over 60 s with a pneumatic otoscope bulb. In normal subjects, change in nystagmus between prepressure and postpressure tests ranged from -1.3 to 0.9%s. In patients, change in nystagmus greater than the 95th percentile limits of normal was not a reliable indication of PLF.

Acoustic Impedance Tests↗
PubMed2004

Intratympanic treatment of hearing loss with novel and traditional agents.

As knowledge of the cellular and molecular pathophysiology behind otopathologies expands, the possibility exists of preventing sensorineural hearing loss and perhaps reversing the loss. Cellular and molecular mechanisms seem to be similar in hearing loss secondary to aging, drug ototoxicity, noise, or other mechanisms. A final common pathway may hinge upon apoptosis. It is likely that anti-apoptotic factors will increasingly be realized as an important intervention strategy for sensorineural hearing loss. Furthermore, it is also possible that mounting a staged attack at the various regions in the pathway leading to cellular damage using a combination of several protective substances such as steroids, antioxidants, neurotrophic factors, anti-apoptotic compounds, and mitochondrial enhancers may prevent hearing loss and even reverse it in some situations. This article has presented some of the molecular and cellular mechanisms for hearing loss and potential ways of treating them. In theory, the delivery of these medications to the inner ear transtympanically would decrease systemic side effects and be more target specific. Because most of the studies conducted to date have been animal studies, randomized, double-blind, placebo-controlled clinical trials would be necessary before the use of these therapies becomes common practice.

Administration, Topical↗