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At least 127 records · Page 7Linked to original sources
PubMed2005

[Temporal bone histopathology in a patient suspected of inner ear extension of otitis media].

We report the histopathological findings in the temporal bone of a 30-year-old female who died of cervical esophageal carcinoma. The temporal bone sections revealed severe bilateral suppurative labyrinthitis and otitis media that presumably occurred immediately before her death. Many inflammatory cells were present in the middle ear, particularly around the stapes and the round window niche. They had also infiltrated the inner ear via the annular ligament of the stapes and the round window membrane. Inflammatory cell accumulation was also observed in the peri- and endolymphatic spaces, and it was most severe in the basal turn. Most of the inner and outer hair cells were preserved, but some had degenerated or were missing. Numerous round cells were observed in the modiolus, and some of the spiral ganglion cells had degenerated. On the basis of these findings, we concluded that bacterial otitis media had extended in to the inner ear via the oval window and round window membrane and had resulted in suppurative labyrinthitis. These findings are consistent with those of stage II suppurative labyrinthitis according to the classification of Schuknecht.

Adult↗
PubMedDate not supplied

Predictors of cochlear implant performance.

Open set speech understanding with cochlear implants, without speechreading, is nowadays a common finding. However, there is a large variation in speech understanding between cochlear implant users. We tried to find pre-operative parameters which predicted the post-operative results. Thirty-seven adult post-lingually deafened Nucleus cochlear implant users with a mean age of 46 years (range 16 68) and a mean duration of deafness of 15 years (range 1.5-47) were studied. Pre-operatively, we performed pure-tone audiometry, round window and ear canal electrical stimulation, psychological tests and imaging. Additionally, we measured pre-operatively speech understanding in the auditory, the visual and the audiovisual conditions with several tests which were also administered after 6 and 12 months' implant experience. Correlation analysis between the pre-operative variables and the post-operative factors showed that duration of deafness and residual hearing are the most important predictors. The temporal difference limen in pre-operative round window electrical stimulation is a secondary predictor.

Adolescent↗
PubMed2004

Drug delivery to the inner ear using gene therapy.

The last 10 years have seen the development of numerous strategies for the delivery of genes to the inner ear. Besides being a useful research tool,gene therapy has significant promise as a potential clinical treatment. The human inner ear is easily accessible through either the round window or the stapes footplate. It is now possible to choose a variety of vectors to target a variety of different tissues. Modification of promoters yields different expression patterns as well as differences in degree of expression. Several animal studies have also demonstrated that expression of exogenous genes in the cochlea does not result in loss of hearing function. A variety of potential clinical applications are already evident from these early studies. Protective strategies such as prevention of neuronal degeneration and protection of auditory hair cells from oxidative stress are potential examples where gene therapy may be useful. As the understanding of gene therapy improves, investigators will be able to move toward targeted single-gene replacement to treat disorders such as connexin mutations and applying gene therapy to sensory cell replacement.

Administration, Topical↗
PubMedDate not supplied

Cochlear implantation: strategies to protect the implanted cochlea from middle ear infection.

A cochlear implant for use in children must take into account the high incidence of middle ear infection in this age group. A scala tympani electrode that traverses the middle ear and round window will likely act as a conduit by which infection can spread to the inner ear and potentially to the CNS. In this study an attempt was made to reestablish a separation of the cochlea from the middle ear by developing a seal around the implant at the level of the round window. A series of cats were implanted with simulated cochlear prostheses consisting of either a plain Silastic cylinder, a Silastic cylinder wrapped with autogenous fascia, or a Silastic cylinder with a cuff of bioactive ceramic. Middle ear infection was induced, followed by histologic examination. Bioactive ceramic appears to have some merit as a round window sealing material, while fascia was shown to be of no value. Intracochlear infection, when it did occur, was limited to the basal regions of the cochlea.

Animals↗
PubMed2004

Round window gentamicin application: an inner ear hair cell damage protocol for the mouse.

It is important to develop an inner ear damage protocol for mice that avoids systemic toxicity and produces damage in a relatively rapid fashion, allowing for study of early cellular and molecular mechanisms responsible for hair cell death and those that underlie the lack of hair cell regeneration in mammals. Ideally, this damage protocol would reliably produce both partial and complete lesions of the sensory epithelium. We present a method for in vivo induction of hair cell damage in the mouse via placement of gentamicin-soaked Gelfoam in the round window niche of the inner ear, an adaptation of a method developed to study hair cell regeneration in chicks. A total of 82 subjects underwent the procedure. Variable doses of gentamicin were used (25, 50, 100 and 200 microg). Saline-soaked Gelfoam, sham-operations and the contralateral, non-operated cochlea were used as controls. Survival periods were 1, 3 and 14 days. Damage was assessed on scanning electron microscopy. We found that this method produces relatively rapid hair cell damage that varies with dose and can extend the entire length of the sensory epithelium. In addition, this protocol produces no systemic toxicity and preserves the contralateral ear as a control.

Animals↗
PubMed1992

Round window membrane rupture and inner ear damage due to barotrauma.

We investigated inner ear barotrauma in humans and in guinea pigs. The shapes of audiograms in patients with inner ear barotrauma were varied, such as high-tone hearing loss, profound loss, low-tone hearing loss, dip type, etc. In inner ear barotrauma in guinea pigs, damage to the organ of Corti was observed in various parts of the cochlear turns in varying severity. Some animals showed rupture of the round window membrane and/or reduction of endocochlear potential following the barotrauma but the rupture healed and EP recovered spontaneously within one week. We consider that irreversible hearing loss in patients with inner ear barotrauma depends on the extent of damage to the organ of Corti.

Animals↗
PubMed1993

Classification of congenital middle ear anomalies. Report on 144 ears.

The surgical findings in 144 successive ears operated on for congenital conductive hearing loss were analyzed, and the results were evaluated in terms of hearing gain. All the patients underwent middle ear surgery at the University Hospital Nijmegen between 1964 and 1990. A classification system was developed to analyze the findings. Class 1 comprises ears with congenital isolated stapes ankylosis. Class 2 comprises ears with congenital stapes ankylosis in combination with a congenital anomaly of the ossicular chain. Class 3 comprises ears with congenital anomalies of the ossicular chain and at least a mobile stapes footplate. Class 4 comprises ears with aplasia or severe dysplasia of the oval window or round window.

Child↗
PubMed2005

Standardized computed tomographic imaging and dimensions of the round-window niche.

Both the increasing usage of intratympanic medication to the inner ear through the round window and the popularity of cochlear implantation have raised interest in the anatomy of the round-window niche (RWN). The objectives of this study were to measure the RWN and to standardize a computed tomographic projection for measuring it. We included patients of all ages who underwent computed tomography for various reasons. We measured computed tomographic images acquired from 214 patients aged 4-85 years and included 414 ears and excluded 14 inflamed "wet" ears. We measured depth, width, and shape of the RWN and skull width. The RWN dimensions did not change with age, whereas the skull width increased with age in both genders throughout the patients' entire life. Folds and soft tissue could not be demonstrated in computed tomographic imaging. In conclusion, a special oblique projection that clearly demonstrates the RWN was reconstructed, and this reconstruction allows for standardized measuring.

Adolescent↗
PubMed1993

[Development of a cochlear input-impedance measuring device and its application in the temporal bones of dogs].

Cochlear input impedance was measured in 6 temporal bones taken from 3 dogs by use of a newly developed ceramic device. The device was composed of two ceramic bimorph elements, one for activation of the stapes and the other to pick-up vibration of the former element in the form of an electric output, which varies in accordance with the magnitude of cochlear impedance. Average impedance in the dogs was 2.3 Mohm at 2 kHz, 6.3 Mohm at 4 kHz and 17.8 Mohm at 6 kHz. Effect of closure of the round window was also investigated by placing dental cement on the window. In 3 ears, the impedance increased mainly below 4 kHz, while in the remaining 3 ears no such change occurred. This was probably because the closure was complete in the former but not in the latter.

Acoustic Impedance Tests↗
PubMed2004

[Use of the round window micro cath for inner ear therapy - results of a placebo-controlled, prospective study on chronic tinnitus].

BACKGROUND: The local therapy of inner ear diseases provides a means of directly applying pharmacological substances and delivering electrical stimulation to inner ear structures. Problems relating to dosage, systemic effects and the blood-cochlear barrier are thus avoided, which is not the case with systemic therapy. The preferred access point is the membrane of the round window. PATIENTS AND METHODS: An appropriately shaped catheter (DURECT Corporation, Cupertino, CA, USA), whose double-lumen passage system permits the variation of concentration and flow, is inserted into the round window niche. In a prospective, placebo-controlled clinical study, this application system was tested in 20 patients with chronic tinnitus. Following implantation the substances lidocaine, glutamate, glutamic acid and caroverine were applied via an attached external micropump. RESULTS: The values for tinnitus loudness, level of irritation caused by the tinnitus and subjective effectiveness of the therapy - measured by means of the visual analog scale (VAS) - showed no significant change, although the most marked improvement was indicated for caroverine. CONCLUSIONS: These results indicate that a positive effect was observable only in a proportion of the patients. Continuous therapy of tinnitus and inner ear diseases will only be possible once a totally implantable microdosage system has been developed.

Administration, Topical↗
PubMed1992

Inner ear damage and passage through the round window membrane of Pseudomonas aeruginosa exotoxin A in a chinchilla model.

By the use of computer-assisted morphometric analysis of the organ of Corti and/or measurements of action potential threshold changes, inner ear changes in chinchillas were evaluated 4 weeks after application on the round window membrane of a Pseudomonas aeruginosa exotoxin A solution. Severe inner ear damage was detected after application of 50 ng (5 microL at a concentration of 10 micrograms/mL) exotoxin A, whereas application of 5 ng exotoxin did not cause measurable inner ear damage. Perilymph concentrations of exotoxin A were measured with an enzyme-linked immunosorbent assay 1.5 to 19 hours after 50 ng, 0.5 micrograms, or 5 micrograms of exotoxin A was applied on the round window membrane. Only the highest concentration produced measurable levels of exotoxin in the inner ear fluids. It is concluded that exotoxin A present on the round window membrane of the chinchilla has the ability to penetrate into the inner ear and cause irreversible inner ear changes.

ADP Ribose Transferases↗
PubMed1995

Posterior canal-activated excitatory vestibuloocular relay neurons participate in the vestibulocortical pathways in cats.

We have previously reported that axon collaterals of posterior canal-activated excitatory vestibular (PC) neurons project to the contralateral oculomotor nucleus, and rostrally to the thalamus. To elucidate the vestibulothalamocortical pathways we investigated the synaptic connections of the PC neurons with the thalamic neurons by post-spike averaging of compound potentials triggered by spikes of the PC neuron in anesthetized cats. The averaged field potential evoked in the ventrobasal complex (VBC) revealed a spike followed by a negative wave. Latencies of the wave ranged from 0.8 to 1.5 ms. Next, we examined the location and axonal projection of 36 thalamic neurons which were activated by nose-up head rotation and by contralateral labyrinth stimulation. Most of them were located in the VBC and some in the medial geniculate body. Thirteen of the 36 neurons were antidromically activated from the anterior suprasylvian sulcus or postcruciate dimple of the cortex. These results suggest that the PC neurons participate, at least in part, in the vestibulocortical pathways contributing to spatial orientation.

Animals↗
PubMed1988

Pressure transmission properties from the externa ear canal to the inner ear. An experimental study using guinea pigs.

The inner ear pressure (PIE) in response to pressure changes in the external ear canal was measured in guinea pigs while alternatively opening and closing the perforation of the otic bulla. When the bulla was opened, only a transient degree of applied pressure was transmitted to the inner ear and the amplitude of the PIE was smaller than that of the corresponding PIE when the bulla was closed. This was because the applied pressure was exclusively transmitted to the inner ear via the ossicular chain. When the otic bulla was closed, the pressure was transmitted not only via the ossicular chain but also via the round window (RW) through the middle ear cavity. When the bulla was closed, the amplitude of PIE was larger by a positive pressure load than by the corresponding negative one. The amplitude of PIE showed a linear relationship to ear canal pressure of at least within the +/- 200 mmH2O range, as long as pressure was slowly applied to the ear canal. When the loading pressure was abruptly changed, a bouncing response, possibly reflecting elasticity of the RW, was evoked, which diminished or disappeared when the round window was artificially ruptured.

Acoustic Impedance Tests↗
PubMed1997

Inner ear perfusion and the role of round window patency.

OBJECTIVE: The goal of this investigation was to evaluate the degree of round window membrane obstruction in the native state. The implications for the perfusion of the inner ear via the intratympanic instillation of medications are addressed. STUDY DESIGN: This was a retrospective chart review and a prospective intraoperative observation in the setting of an outpatient office. PATIENTS: The study population was composed of 41 patients who were undergoing middle ear endoscopy before perfusion of the inner ear with medication for the treatment of Meniere's disease, sudden sensorineural hearing loss, or tinnitus. INTERVENTION: Office-based laser-assisted tympanostomy and middle ear endoscopy was carried out in each case. Lysis of adhesions overlying the round window membrane was undertaken when the underlying round window membrane could not be visualized. MAIN OUTCOME MEASURES: Evaluation of the round window niche with regard to accessibility of the round window membrane was recorded for each patient studied. RESULTS: Of the 41 cases examined, 29 of the round windows were judged to be unobstructed, 7 were obstructed partially, and 5 were obstructed completely. CONCLUSION: A significant rate of round window obstruction exists among patients who have no history of manipulation to this area. Although, intuitively, we would expect prior middle ear surgery to increase the likelihood of obstruction, this is not uniformly the outcome. If intratympanic instillation of a medication is contemplated for the treatment of an inner ear disorder, considerations for the evaluation of the round window should be made to enhance adequate diffusion into the perilymph.

Aged↗
PubMed1992

Middle-ear phenomenology: the view from the three windows.

To provide a common ground for the comparison between theory and experiment, this paper presents a framework for the phenomenological description of middle-ear mechanics. The framework defines those measurements sufficient to characterize the transduction properties of the middle ear and its components. Phenomenological equations are represented in the form of an equivalent electrical circuit that can be used to deduce testable relations among measurable quantities. Two applications are then discussed. First, the classical concept of the middle-ear transformer ratio is generalized to include any effects of eardrum flexion or nonrotational ossicular motion. Middle-ear models predict that the resulting transformer ratios vary considerably with frequency. Second, the conditions under which the topology of existing circuit analogs satisfactorily approximates middle-ear mechanics are given. Most middle-ear models cannot be used to correctly predict the absolute pressures in the cochlea.

Animals↗