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PubMed1985

The conical cartilage of the cat's middle ear.

The object of this study was to investigate the anatomy, histology, and possible function of a conical structure found in the middle ear of the cat. This conical structure lies across the dorso-caudal compartment of the middle ear. It is directly related to the course of the chorda tympani nerve in the middle ear. Its base is attached by fibrous tissue to the dorso-caudal segment of the tympanic bone adjacent to the tympanic membrane. Its apex rests on the promontory just rostral to the round window niche. Histologically, it is cartilaginous tissue enveloped by a mucous membrane with no trace of bone. Portions of some conical cartilage specimens display extensive calcification. A previous hypothesis suggests that this structure conducts high frequency sounds directly from the tympanic membrane to the round window membrane. This seems unlikely because its length is shorter than the distance between the tympanic membrane and round window membrane. The conical cartilage may be a vestigial remnant of the second arch bar (Reichert's cartilage).

Animals↗
PubMed1995

Extracochlear electrically evoked otoacoustic emissions: a model for in vivo assessment of outer hair cell electromotility.

Cochlear outer hair cell (OHC) motion in response to changes in membrane potential (electromotility) has been extensively studied in vitro. Electromotility is thought to actively control the micromechanical properties of the sensory epithelium. In order to understand how OHC electromotility contributes to normal cochlear responses, its role must be assessed in vivo. We have developed a novel animal model for the study of electromotility in vivo. Alternating current is delivered by an electrode to the round window (RW) of gerbil cochlea and the electrically evoked otoacoustic emission (EEOE) is measured from the external ear canal. As much as 45 dB SPL sound could be generated by about 200 micro A RMS extracochlear current delivered to the RW. Except for the fine structure of EEOE transfer function curves, the magnitude of the EEOE has a bandpass appearance ranging from about 4 to 32 kHz and shows a positive linear relationship to the current intensity. The phase has a linear relationship with frequency and shows no significant change with current intensity. Local intracochlear perfusion of 4% paraformaldehyde caused EEOE to decrease by approximately 20 dB. These results indicate that the EEOE is probably generated by OHCs near the electrode location and propagates to the external ear canal. In addition, the force generated by OHCs in vivo is a linear function of the electrical stimulus. The major advantages of our model include: (1) non-invasive procedure and normal cochlea; (2) wide dynamic range of the measurement; (3) simple and easy preparation. With these features this model has potential applications in basic hearing research and in the diagnosis and treatment of otological patients.

Animals↗
PubMed1994

Cochlear endoscopy with preservation of hearing in guinea pigs.

Advances in fiberoptic technology have revolutionized the way many disorders are treated by otolaryngologists. We have previously described our experiences with cochlear endoscopy during cochlear implantation. However, endoscopy of the functioning cochlea has not previously been reported. To test the hypothesis that endoscopy of the guinea pig cochlea is possible without catastrophic loss of auditory function, we subjected 20 ears of 10 Hartley-strain albino guinea pigs to limited endoscopy of the cochlea through the round window with evaluation of distortion product otoacoustic emissions and auditory brain stem responses. Insertion of the endoscope caused measurable changes in auditory brain stem response latency and amplitude. Distortion product otoacoustic emission amplitudes were reduced an average of 6 dB with greater loss close to the round window. Frequencies above 18 kHz, corresponding to the region of endoscopy, were not evaluated in this preliminary study and are suspected to have sustained more damage. Results demonstrate that endoscopy of the guinea pig cochlea is possible without major loss of the above physiologic measures in the regions tested. If endoscopy of the cochlea is to become a tool with clinical and basic science applications, refinements in techniques to avoid damage are necessary.

Animals↗
PubMed2002

Changes in Ca2+-ATPase in a guinea pig endolymphatic hydrops model.

OBJECTIVE: To investigate the localization of Ca(2+)-ATPase (Ca(2+) pump) in the cochlear and its change after endolymphatic hydrops, and to study the relationship between compound action potential (CAP) threshold and the Ca(2+)-ATPase activety. METHODS: The left endolymphatic sac was ablated to induce endolymphatic hydrops in fourteen healthy guinea pigs with normal action potential thresholds measured after a sliver ball electrode placed on the round window. Ca(2+)-ATPase activity was studied cytochemically using a lead citrate reaction in control and hydropic ears. The reaction product was lead phosphate particles as an expression of Ca(2+)-ATPase activity, observed with an eletron microscope. RESULTS: Ca(2+)-ATPase activity is mainly found on the endolymphatic surface of Reis sner's membrane, the stereocilia and cuticular plate of inner and outer hair cells, and along the infolded plasma membrane of strial marginal cells. CAP thresholds of filtered click are increased and Ca(2+)-ATPase activity significantly decreased after endolymphatic hydrops in the mentioned locations. CONCLUSIONS: CAP thresholds are increased and Ca(2+)-ATPase activity are significantly decreased in the cochlea after endolymphatic hydrops. These results suggest that there is a negative correlation between them.

Action Potentials↗
PubMed1999

[Changes of Ca(2+)-ATPase in the cochlea of guinea pig during labyrinthine hydrop].

OBJECTIVE: To investigate the localization of Ca(2+)-ATPase (Ca2+ pump) in the cochlea and its change in labyrinthine hydrops. METHODS: The left endolymphatic sac was ablated to induce endolymphatic hydrops in fourteen healthy guinea pigs after the sliver ball electrode was placed on the round window. The Ca(2+)-ATPase was studied by the lead citrate reaction in the control and hydropic ears. The reaction product was lead phosphate particles as an expression of Ca(2+)-ATPase activity under the electron-microscope. RESULTS: The Ca(2+)-ATPase activity was found mainly on the endolymphatic surface of the Reissner's membrane, the stereocilia and cuticular plate of inner and outer hair cells, as well as along the infolding plasma membrane of the strial intermediate cells. The Ca(2+)-ATPase activity was significantly decreased during endolymphatic hydrops in the above-mentioned locations. CONCLUSION: The response thresholds of filtered click were increased and the Ca(2+)-ATPase significantly decreased in the cochlea during labyrinthine hydrops. These results suggest that correlation exists between the CAP threshold and the activity of Ca(2+)-ATPase in the model of labyrinthine hydrops.

Animals↗
PubMed2003

Menière's disease and gentamicin: preliminary results using the minimum effective dose and integrated therapy.

Treatment of Menière's disease is aimed at restoring a normal quality of life and preserving residual hearing, in view of the increasing frequency with which the contralateral ear is affected. Conventional medical treatment (diuretics + vasoactive drugs) leads to cure in a large percentage of patients (75-95%). In intractable cases, transtympanic (intratympanic) aminoglycoside therapy, associated with various techniques, is becoming widespread as an alternative to surgery. Progressive reduction of the dose introduced into the middle ear did not prevent the onset of anacusis in several patients; the variable, unpredictable permeability of the round window membrane, the object of fundamental studies in the past, explains this complication. The Author has used gentamicin transtympanically in Menierians since 1978, and has treated a total of 105 patients. He first prescribed transtympanic gentamicin therapy that did not follow, but was integrated with conventional medical treatment in 22 intractable Menierians, by instilling the minimum effective dose, to reduce the risk of hearing impairment. Preliminary results, related to stage of disease, may be summarised as follows: improvement in the quality of life, as evaluated by the American Academy of Ophthalmology & Otolaryngology Committee on Hearing and Equilibrium questionnaire (14 patients--63.63%--at point 1 and 8-36.36%--at point 2); disappearance of vertigo in 15 patients (68.18%); a minor vertigo attack in 3 and two minor attacks in 3 others not affecting quality of life; persistence of occasional unsteadiness in one patient. Hearing remained unchanged in 15 patients, improved slightly in 3 cases and worsened slightly in 2; decreased sensitivity to high tones was observed in 2 patients at the first insertion of gentamicin. According to the Author, employing integrated therapy and using the minimum effective dose of gentamicin, the risk of damage to the cochlear structures may be reduced, although not excluded, while restoring a good quality of life, even when repeat instillation is necessary.

Administration, Topical↗
PubMed1988

Imaging contributions to the temporal bone anatomy (high jugular fossae).

A high jugular fossa, above the lower border of the round window, sometimes with a diverticulum-like protrusion from the top, was found in 23% of an unselected material, usually associated with low pneumatization. They were more common in the right than the left temporal bone. The high jugular fossa has a varying anatomy and its topographic relationship has been evaluated. The laterally situated fossa could be dehiscent to the tympanic cavity and intrude upon the round window or the ossicles. The high, medial fossa encroached in some cases upon structures in the inner ear, such as the vestibule, the cochlear and vestibular aqueducts, the posterior semicircular canal, the cochlea or the mastoid portion of the facial canal and this was considered in relation to the symptoms in a clinical material.

Humans↗
PubMedDate not supplied

Suppressed sneezing as a cause of hearing loss and vertigo.

Two cases of inner ear injury caused by suppressed sneezing are described. One patient experienced vestibular symptoms in the form of reflexogenic vertigo that was relieved by surgical section of the tensor tympani tendon. The other patient had a sudden severe permanent sensorineural hearing loss. It is proposed that the aerodynamic pressure increase associated with suppressed sneezing is transmitted via the eustachian tube to cause an implosive fistula of either the round or oval window with injury to the membranous labyrinth.

Adult↗
PubMed1993

[Intracochlear placement of cochlear implant electrodes in soft surgery technique].

It is commonly accepted that the intracochlear placement of the cochlear implant electrode is potentially damaging to the hearing rests which may exist. Consequently, cochlear implants have been recommended for totally deaf ears only. The question has been raised whether or not it is possible to preserve residual hearing during intracochlear implantation through extremely careful surgical techniques. Experience has shown, that the cochleotomy of the scala tympani anterior to the round window niche, careful preservation of the fibrine endost layer and the use of Healon are amongst the surgical procedures described which may assist in retaining the rest function of the inner ear. These observations which are discussed in detail suggest that the experienced surgeon can effect preservation of residual hearing for patients who cannot derive significant benefits from conventional acoustic amplifiers.

Adult↗
PubMedDate not supplied

Labyrinthitis ossificans.

Three cases with postinflammatory inner ear sequelae are presented to illustrate unusual histopathologic changes. Endolymphatic hydrops without changes in the perilymphatic system was present in one ear following "influenza" meningitis and labyrinthitis ossificans in the contralateral ear. The characteristic histopathological changes of the temporal bones with hematogenic bacterial infection were an extensive labyrinthine ossification associated with a generalized sclerotic change of the whole periotic bone. Bony fixation of the stapedial footplate occurred with the generalized inflammatory process of the otic capsule. Severe and diffuse labyrinthitis ossificans occurred in one case due to tympanogenic inflammation spreading through the round window membrane in the course of suppurative otitis media. A general immunosuppression leading to fatal termination was the apparent factor predisposing to the inner ear complication.

Adult↗
PubMedDate not supplied

The effect of ultrasonic irradiation on the structural integrity of the inner ear labyrinth.

The histological appearance of the inner ear labyrinth was examined following ultrasonic irradiation of the vestibule and the cochlea in cats and guinea pigs. Directing ultrasound through the round window towards the ampulla of the superior semicircular canal produced severe balance dysfunction together with histological damage throughout the vestibular labyrinth. Cochlear damage was restricted to a small region of the basilar membrane proximal to the round window. When ultrasonic energy was directed into the cochlea cellular disruption extended over an area of at least two cochlear turns and included changes in the stria vascularis as well as to hair cells. The outer hair cells were found to be more sensitive than the inner hair cells to the damaging effects of ultrasound.

Animals↗
PubMed2001

[Response property of tone burst transmission of partially implantable middle ear implant in vivo].

OBJECTIVE: To investigate the characteristics of tone burst transmission of the middle ear implant(MEI). METHODS: Ten adult rabbits with normal hearing were used. A silver ball electrode was placed at the round window membrane to measure cochlear microphonics (CM) when sounds were presented before and after the implantation of the MEI. The tone burst was the acoustic stimulus. RESULTS: Frequency response functions without and with the MEI in rabbit model were calculated, and their amplitude-frequency curves ranging from 0.5 to 6 kHz resembled each other in shape with gain factors about 15 dB at the frequencies above 1 kHz. CONCLUSION: The results of this study indicated that the frequency response of the device fitted the speech transmission and it had high fidelity with little noise.

Animals↗
PubMed2003

[Construction of bicistronic eukaryotic vector containing basic fibroblast growth factor and study of their functions in gene therapy for hearing impairment].

OBJECTIVE: To construct basic fibroblast growth factor(bFGR) and enhance green fluorescence protein(EGFP) fusion gene eukaryotic expression vector internal ribosome entry site (pIRES)-bFGF-GFP and to evaluate the effect of transduction bFGF gene on noise induced hearing-loss in inner ear hair cells of guinea pigs. METHODS: Human bFGF cDNA was inserted into mammalian expressed plasmid pIRES-EGFP. The recombinant expression plasmid pIRES-bFGF-EGFP was transfected into inner ear of guinea pigs, using lipofectin method. The transduced bFGF gene was mediated by SA lipidsome. IRES- bFGF-GFP was administered into the round window as rescue agent at the same time of noise exposure or as a protective agent 7 days before. RESULTS: SA liposome-mediated bFGF expressed at a high level in the cochlea of guinea pigs, and in the rescue group, a significant lower hearing thresholds was displayed. pIRES- bFGF-EGFP could protect hair cells. It demonstrated that pIRES- bFGF-GFP could protect the inner ear both structurally and functionally. bFGF/EGFP gene could be transcripted and translated into inner ear hair cells of guinea pig. bFGF/EGFP gene could express a specific protein. The recombinant bFGF/EGFP had significant protective effect as well as manifestation of autonomous fluorescence. CONCLUSION: bFGF/EGFP fusion protein not only expressed in hair cells of guinea pig but also showed significant bFGF activity and autonomous fluorescence. IRES induced exogenous gene could enter the hair cells.

Animals↗
PubMedDate not supplied

The ototoxic potential of EMLA. A new local anesthetic for the tympanic membrane.

Instillation of EMLA, a new local anesthetic, into the middle ear of the guinea pig caused severe morphological damage to the organ of Corti in the first 4 mm from the round window. Further up the cochlea, only derangements of the stereocilia were found. The extent of morphological damage was the same, whether the agent was administered once or several times. The ototoxic potential of EMLA was obvious and is probably due to direct damage in areas where present in high concentrations. Over a short distance of approximately 0.1 mm there is a transition from a total destruction of the organ of Corti to a completely normal morphology.

Anesthetics, Local↗
PubMed2005

Prevention of noise-induced hearing loss with Src-PTK inhibitors.

Studies from our lab show that noise exposure initiates cell death by multiple pathways [Nicotera, T.M., Hu, B.H., Henderson, D., 2003. The caspase pathway in noise-induced apoptosis of the chinchilla cochlea. J. Assoc. Res. Otolaryngol. 4, 466-477] therefore, protection against noise may be most effective with a multifaceted approach. The Src protein tyrosine kinase (PTK) signaling cascade may be involved in both metabolic and mechanically induced initiation of apoptosis in sensory cells of the cochlea. The current study compares three Src-PTK inhibitors, KX1-004, KX1-005 and KX1-174 as potential protective drugs for NIHL. Chinchillas were used as subjects. A 30 microl drop of one of the Src inhibitors was placed on the round window membrane of the anesthetized chinchilla; the vehicle (DMSO and buffered saline) alone was placed on the other ear. After the drug application, the middle ear was sutured and the subjects were exposed to noise. Hearing was measured before and several times after the noise exposure and treatment using evoked responses. At 20 days post-exposure, the animals were anesthetized their cochleae extracted and cochleograms were constructed. All three Src inhibitors provided protection from a 4 h, 4 kHz octave band noise at 106 dB. The most effective drug, KX1-004 was further evaluated by repeating the exposure with different doses, as well as, substituting an impulse noise exposure. For all conditions, the results suggest a role for Src-PTK activation in noise-induced hearing loss (NIHL), and that therapeutic intervention with a Src-PTK inhibitor may offer a novel approach in the treatment of NIHL.

Animals↗
PubMed1975

Tympanoplasty of the radical operated middle ear.

A type of tympanoplasty is described to restore hearig at patients who had a radical mastoidectomy. The technique of middle ear reconstruction was first studied at the testanimal. It was found that a certain resonance frequency could be of use to get an extra hearing gain. Furtheron amplitude and fase-difference between the round and oval window are explored. The results of 16 patients 5 years after operation are discussed.

Adolescent↗
PubMed2004

Clinical, experimental, and theoretical investigations of the effect of superior semicircular canal dehiscence on hearing mechanisms.

HYPOTHESIS: A superior semicircular canal dehiscence affects hearing by introducing a third window into the inner ear that 1) lowers cochlear input impedance, 2) shunts air-conducted sound away from the cochlea resulting in conductive hearing loss, and 3) improves bone-conduction thresholds by increasing the difference in impedance between the vestibule and the round window. BACKGROUND: Superior semicircular canal dehiscence has been linked to a "conductive" hearing loss characterized by a decrease in the sensitivity to air-conducted sound and hypersensitivity to bone-conducted sound. METHODS: Four investigations were performed: 1) laser-Doppler vibrometer measurements of sound-induced umbo velocity in patients with computed tomographic scan-confirmed superior semicircular canal dehiscence; 2) laser-Doppler vibrometry of sound-induced motions of the vestibular lymph (either perilymph or endolymph) exposed in a chinchilla model of superior semicircular canal dehiscence; 3) studies in chinchillas of the effect of superior semicircular canal dehiscence on the cochlea's sensitivity to bone-conducted sounds; and 4) anatomically based theoretical analyses of sound flow through the human cochlea and semicircular canals. RESULTS: The low-frequency umbo velocity in superior semicircular canal dehiscence patients without previous middle ear surgery ranged from normal through high normal. This tendency toward hypermobility suggests a decrease in cochlear impedance. Measurements of sound-induced velocity of the lymph within a superior semicircular canal dehiscence in chinchillas demonstrated sound flow through the dehiscence. Measurements of the cochlear potential demonstrated a superior semicircular canal dehiscence-induced increase in response to bone-conducted sound in eight of nine chinchillas. An anatomically based model of the human ear predicts changes in auditory sensitivity similar to audiometric changes in superior semicircular canal dehiscence. CONCLUSION: The results suggest that superior semicircular canal dehiscence can affect hearing function by introducing a third window into the inner ear.

Animals↗
PubMed1996

[Pneumococcal meningitis revealing dysplasia of the bony labyrinth in an infant].

BACKGROUND: Dysplasias of the bony labyrinth are frequently associated with cerebrospinal fluid fistula and are usually discovered because of recurrent meningitis. CASE REPORT: A 1 year-old infant was admitted for a pneumococcal meningitis which appeared 2 days after the occurrence of a clear otorrhea from the right ear. The same organism was isolated from the otorrhea fluid, which also contained cerebrospinal fluid as confirmed cytochemically. The meningitis rapidly resolved with antibiotic treatment. Auditory brain stem responses were abolished from the right ear. CT of the temporal bones showed a pseudo-Mondini type labyrinth dysplasia at the right ear and Mondini type dysplasia at the left one. A translabyrinthine cerebrospinal fluid fistula was discovered by surgical exploration of the right ear, occurring through a perforation in the stapedial foot plate. The leak was cured by packing the vestibule and obturating both oval and round windows. Three years after the operation, the child did not experience any further episode of otorrhea or meningitis. CONCLUSIONS: Features suggesting a translabyrinthine fistula, especially otorrhea and deafness, should be systematically searched in any child with bacterial meningitis. Closure of these fistulas can prevent severe infectious recurrences.

Cerebrospinal Fluid Otorrhea↗