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At least 1,171 records · Page 65Linked to original sources
PubMed1999

Cochlear hook anatomy: evaluation of the spatial relationship of the basal cochlear duct to middle ear landmarks.

The cochlear hook is an important anatomical area for the otologist performing cochlear implants and other otological procedures, who requires knowledge of the basal cochlea. A total of 15 human temporal bones were dissected and the spatial relationship of the hook segment of the cochlear duct to the stapes, round window, cochleariform process and ductus reuniens were evaluated. Inter-individual variability was noted for widths of scala tympani (average width 1.36 +/- 0.25 mm) and scala vestibuli (average width 1.18 +/- 0.18 mm) in the region of typical cochlear implant placement, with the scala vestibuli occasionally being wider than the scala tympani. The cochlear duct was in closest proximity to the stapes at the midportion of the footplate, with an average distance of 1.23 mm at this narrowest width. A fibrous anchor, not previously described in otology literature, was identified securing the most basal end of the cochlear duct. Knowing the spatial relationship of the cochlear duct to the middle and inner ear structures could prevent damage to the basilar membrane in procedures around or involving the basal cochlear, such as cochlear implantation, stapedotomy, or implantable hearing devices.

Cochlear Duct↗
PubMed1997

Effects of experimental cochlear thrombosis on oxygenation and auditory function of the inner ear.

To elucidate the etiology and pathogenesis of sudden hearing loss, the effect of experimental cochlear thrombosis on oxygenation and the auditory function of the inner ear was investigated in anesthetized guinea pigs. Impairment of cochlear blood flow (CBF) was induced by ferromagnetic obstruction of cochlear blood vessels at lowered body temperature. Perilymphatic oxygen partial pressure (PO2) in the basal scala tympani (about 200 microm below the round window membrane) was measured polarographically using micro-coaxial needle electrodes. Auditory function was examined by recording cochlear microphonic (CM) frequency responses, compound action potentials (CAP) and auditory evoked brainstem responses (ABR). Findings demonstrated a considerable decrease in the mean perilymphatic PO2 of 40%, 2 h after the start of the experiment. Mean CM and N1 CAP amplitudes were reduced by about 25% each and ABR by 18%. No significant changes were observed in the latencies of either CAP or ABR. Mean basal CBF was found to decrease by 35%, as measured by laser Doppler flowmetry in a parallel study. The present findings demonstrate that vascular impairment in the inner ear results in a considerable drop in intracochlear oxygenation, causing a significant loss in the auditory response.

Action Potentials↗
PubMed1992

[Sudden deafness--diagnosis and therapy].

Sudden deafness is defined as acute inner ear hearing loss, in the rule one-sided, of unknown etiology. The tentative diagnosis can be made easily by otoscopy and simple audiological forke tests. To exclude symptomatic acute hearing losses during the first treatment period, f.e. acoustic neurinoma, rupture of the round window membrane, multiple sclerosis, infectious diseases like Borreliosis or Lues, but also psychogenic hearing disorders we recommend an immediate hospitalization. Neurological and internal check up should look for inflammatory or degenerative diseases of the vascular or nervous system and also for metabolic risk factors like diabetes mellitus, hyperlipidemia, gout or blood hyperviscosity. Today there are some reasons to assume, that disturbances of the microcirculation of the cochlea end vessels may a possible prominent etiological factor in sudden deafness. Therefore the aim of therapy today is to improve the microcirculation and the oxygenation of the sensory cells of the inner ear.

Cochlea↗
PubMed1991

Ablation of otolithic organs with argon laser.

Utricular maculae of guinea pigs were irradiated by argon laser through the oval window without touching the perilymph. The stapes was replaced in the oval window after irradiation. The inner ear was studied morphologically and physiologically. Argon laser beam caused detachment of the sensory epithelium from the basement membrane of the utricular macula. The lesion was round and localized at the site of irradiation. The epithelium changed to a layer of cuboidal cells after 2 to 3 weeks at the irradiated spot. Degeneration of the epithelium gradually spread to the periphery, and total loss of sensory epithelium was observed 10 weeks after irradiation. Hearing was preserved, and caloric test showed normal response.

Acoustic Maculae↗
PubMed1996

A simple technique for introducing anterograde and retrograde tracers into the vestibular and cochlear sensory organs.

The standard method for labeling the afferent and efferent innervation of the cochlear and vestibular sensory organs is by microinjection of tracer substances into the labyrinth. Injection of small amounts of tracer often result in incomplete and inconsistent labeling, but large injections can cause spurious labeling of brainstem structures due to diffusion from perilymph to cerebrospinal fluid. Effective labeling with minimal artifact can, however, be achieved by a relatively simple method involving placement of a tracer-saturated pledglet of gelatin sponge in the round window after rupture of its membrane. The gelatin sponge simultaneously acts as a continuous-release vehicle for the tracer and prevents reflux of perilymph and tracer into the middle ear cavity. Use of this technique produces labeling with a degree of intensity and anatomic detail that rivals that seen with more complicated methods of tracer placement.

Animals↗
PubMed2004

[Cochlear implant in patients with congenital malformation of inner ear].

OBJECTIVE: To study surgical difficulty and key of the cochlear implant in patients with congenital malformation of inner ear. METHODS: The cochlear implantations were performed in our department from Jan. 2001 to Apr. 2003 for 18 patients with the malformation of inner ear. RESULTS: In this series, there were 11 cases of large vestibular aqueduct syndrome (LVAS), 3 cases of Waardenberg syndrome, 3 cases of Mondini malformation, and 1 case of Usher syndrome. All 18 patients accepted the Nucleus 24-channel cochlear implantations, including Nucleus straight electrode in 13 cases but Contour implantation in 5 cases of LVAS. During operations, leakage of perilymph but not cerebrospinal fluid (CSF) from the open of scala tympani occurred in 11 cases of LVAS, however, the electrode was inserted successfully. The abnormalities of round window occurred in one of 3 cases of Waardenberg syndrome and 3 cases of Mondini malformation, respectively. CONCLUSION: The cochlear implant could be conducted successfully for the LVAS, and the postoperative effect was same as the ones for the deafness persons with normal development of inner ear. However, for the patients with Mondini syndrome and common cavity, it is important to accurately assess the extent of abnormalities in the inner ear and accompanied malformation before operation, and to evaluate the full extent of difficulties of the operation in order to minimize the risk of CSF leakage and meningitis.

Adolescent↗
PubMed1999

The anatomy of the killer whale middle ear (Orcinus orca).

The paper first reviews our present understanding of the functional morphology of the odontocete (toothed whale) ear. The tympano-periotic complex forming the ear region consists of a ventral bowl-shaped tympanic bone in direct contact with the surrounding soft tissues and the incident sound, and a dorsal periotic bone containing the inner ear. Apparently sound brings the tympanic bone, and especially its thin tympanic plate, into vibration. The ossicles in the air-filled middle ear cavity form a bridge from the tympanic plate to the periotic bone connecting the vibrating plate to the oval window and the inner ear. Our computer tomography (CT) sections and camera lucida drawings reveal two hitherto unknown features of the odontocete ear, both of them of potential relevance to sound reception and impedance matching. (1) It is well known that, in addition to the ossicular chain, two other bone structures connect the tympanic to the periotic bone. We show that the most delicate parts of these extra-ossicular connections consist of thin and folded bony sheets which apparently allow compliance in the tympano-periotic bone contacts and enable plate vibration in relation to the periotic bone. (2) The round head of the malleus, in combination with a fitting round depression on the periotic side, seems to form a joint. We propose that this (hypothetical) joint, together with the adjacent structures, forms a lever producing an amplification of the vibration velocity at the level of the oval window.

Animals↗
PubMed1984

[Qualitative detection of immunoglobulins in the human endolymphatic sac].

Healthy human temporal bones and samples of the endolymphatic sac taken during surgery or from fresh cadavers were studied with regard to the presence of immunoglobulins. For demonstration of IgG, IgM, IgA and SIgA immunofluorescent methods and the immunoperoxidase-antiperoxidase method were used. Immunoglobulins are exclusively present within the endolymphatic sac whereas other structures of the healthy human inner ear do not show any positive reaction to the methods used for the demonstration of immunoglobulins.SIgA is clearly shown in epithelial cells of the rugosal part, whereas IgG predominantly is located in the flat endothelium--like cells of the extratemporal part. IgA and IgG further are detected within glycoproteins of the sac lumen and in plasma cells beneath the epithelium. Finally all subepithelial lymphatic spaces contain rich amounts of IgG. In one single temporal bone with tympanogenic labyrinthitis IgG and IgM wee present not only in all three layers of the round-window-membrane but also within the perilymphatic exudate. In this case IgM was found in the perisaccular tissue. The presence of free and local bound immunoglobulins exclusively in the region of the endolymphatic sac postulates and immunologic defense mechanism of this organ for the inner ear.

Antibody Formation↗
PubMed2002

Cochlear implantation without mastoidectomy: the pericanal electrode insertion technique.

OBJECTIVE: A new minimally invasive cochlear implantation method with direct electrode insertion through the external auditory canal (EAC) is presented. MATERIAL AND METHODS: Surgery begins with a retroauricular skin incision. The bony surface of the mastoid plane behind the ear is dissected free and the skin of the EAC is elevated together with the posterior part of the tympanic membrane. Cochleostomy is performed through the EAC with a microdrill anterior to the round window. A rim is drilled into the postero-superior region of the bony EAC immediately above the incus towards the outer border of the EAC and connected to the retroauricular surface by a short tunnel. The implant device is placed in the usual retroauricular area. The electrode is inserted through the tunnel and rim into the tympanic cavity and pushed into the cochleostomy hole. The electrode is immobilized in the rim using glass ionomer cement and covered with bone dust. After placement of the ground electrode, the retroauricular incision is closed. The tympano-meatal flap is replaced and a dressing is put into the EAC. RESULTS: The new method has been applied thus far in 15 adults and pre-adolescent deaf patients (8 females, 7 males). A MED-EL Combi 40 + device was used in 14 patients and a Nucleus CI24M in 1. Pericanal electrode insertion was easy, with insertion depths into the cochlea of > or = 30 mm with the MED-EL and of 20 mm with the Nucleus device. There were no surgical complications, infections or electrode extrusions during postoperative observation periods ranging from 6 months to > 2 years. The functional results were comparable to those obtained with cochlear implantation via mastoidectomy. The pericanal electrode insertion technique has several advantages, the most important being that the danger of facial nerve damage is minimized and that the operating time is reduced by up to 50%. CONCLUSION: Cochlear implantation with pericanal electrode insertion is a simple, fast and particularly safe option which may replace the classical transmastoidal cochlear implantation method in adults and older children.

Adolescent↗
PubMed2000

Mechanics of the inner ear of the bullfrog (Rana catesbeiana): the contact membranes and the periotic canal.

The frog inner ear consists of a complex of fluid-filled membranous sacs and canals containing eight distinct clusters of sensory hair cells. In this study we attempt to delineate the potential pathways for acoustic energy flow toward two of these clusters located within the amphibian papilla and the basilar papilla. Detailed morphological measurements of the periotic canal based on internal casts of the inner ear in the bullfrog (Rana catesbeiana) revealed that it is divided into a wide, tapered section and a narrower section comprised of two branches one short and blind projecting into the endolymphatic space and another longer, terminating in the round window. Additionally, we used laser Doppler velocimetry to record the velocity responses of the contact membranes of the amphibian papilla and basilar papilla. We found that the acoustic energy flow through these two structures is frequency dependent such that the amphibian papilla contact membrane displays a peak velocity amplitude at frequencies less than 500 Hz, whereas the basilar papilla contact membrane velocity response exhibits a maximum above 1,100 Hz. Our data advocate a mechanical substrate underlying the frequency segregation in the auditory nerve fibers innervating the amphibian papilla and the basilar papilla.

Animals↗
PubMed1985

Risk of basilar membrane perforation by intracochlear electrodes.

Insertion of intracochlear electrodes may damage the basilar membrane, the stria vascularis and adjacent structures. When electrodes were placed in human temporal bone specimens, perforations were shown to be independent of the type of implant used, the depth of insertion or the use of a lubricating agent. Helical electrode reinforcements and failure to enlarge the round window frame increase the risk of damage. Perforations are invariably localized at a distance of about 7-14 mm from the round window and occur at the site where the curvature of the basal turn is greatest.

Basilar Membrane↗
PubMedDate not supplied

[Oscillations of the internal ear basilar membrane in the sonic and ultrasonic range from the data of mathematical analysis of the hydrodynamic model of the cochlea].

Results are presented of plotting a dimeric mathematical model of human internal ear cochlea with allowance for the dependence of the basilar membrane mass on the length of its region between the registered point and the labyrinth wall of the threshold window region. Investigations carried out on such a model by means of a computer permitted calculation of the location of the rounding curve maximum point of the displacement waves of the basilar membrane for the frequencies of 0.05-95 kHz included. An analysis of the rounding waves of the sonic and ultrasonic range showed that although above 20 kHz the curves maximum acquires slured contours, it is well enough pronounced up to 75 kHz. The results obtained suggest adequate effect of ultrasounds on the internal ear and analogy of mechanical reaction of human cochlea to sonic and ultrasonic stimulation.

Acoustic Stimulation↗
PubMed2005

Damage and threshold shift resulting from cochlear exposure to paraquat-generated superoxide.

Superoxide has been implicated as a contributing factor to cochlear pathology from a number of sources, including noise and ototoxic drugs. The effects of NADPH oxidase-dependent superoxide on the cochlea were investigated in the current study using paraquat (PQ). PQ is a toxic herbicide that causes tissue damage by generating superoxide through reduction of molecular oxygen in a reaction catalyzed by NADPH oxidase. The current study examined the effects of round window PQ administration on inferior colliculus (IC) evoked potential thresholds (EVP) and hair cell damage. Using implanted IC electrodes, chinchillas were tested for IC EVP thresholds before and after PQ exposure. Ears were exposed to PQ at one of four concentrations: 10, 5, 3 mM, and vehicle control. Thresholds were increased in a dose-dependent manner, and peaked between one and seven days post-exposure. Thresholds then showed a small amount of recovery before reaching PTS by Day 22. Outer and inner hair cell losses were consistent with PTS. The similarities between PQ ototoxicity and noise-induced hearing loss suggest the possibility of similar biochemical pathways involving superoxide.

Animals↗
PubMed2000

Betahistine effects on cochlear blood flow: from the laboratory to the clinic.

The development of laser Doppler flowmetry techniques has contributed greatly to the study of cochlear blood flow (CBF). In animal models, intravenous betahistine dihydrochloride clearly increased CBF in a dose-dependent manner. This effect was greater in the cochlear vasculature than in the systemic vascular bed. The effects of betahistine were blocked by the alpha 2-antagonist idazoxan, thus suggesting an interaction between histaminergic and presynaptic adrenergic receptors. This was further supported by studies investigating the effects of electrical stimulation on CBF. Local (round window membrane) application of betahistine did not affect CBF, but had a non-specific effect on cochlear electrophysiology. This indicates that the receptors for betahistine vascular effects in the inner ear are most likely located in the modiolar artery. More recently, laser Doppler flowmetry techniques have been applied to human subjects. It has been shown that intratympanic application of adrenaline affects CBF and that this blood flow is under vigorous sympathetic control. Electrical stimulation has also been used to obtain measures of dynamic responsiveness in human subjects. This results in an increase in CBF, which is dependent on the intensity of the stimulation. Preliminary evidence indicates that this procedure can provide a standardized measure of the dynamic properties of CBF and may provide a means to differentially identify patients with compromised vasculature.

Adrenergic Agonists↗
PubMed1992

Chronic perilymph fistula in the guinea pig with implications in the human.

To improve understanding of the pathophysiology of perilymph fistulas, a predictable animal model of a chronic fistula was developed. Our findings suggest that guinea pig fistulas do not remain patent for prolonged periods. By extrapolating these findings to humans, we postulate that the symptoms and signs of perilymph fistula are possibly due not to one prolonged constant fistula, but rather a series of "blowouts" from an inherent congenital or posttraumatic weak spot in either the round or oval window. We feel that a diagnosis of perilymph fistula must be considered in any patient presenting with a Meniere's-like symptom set concomitant with a congenital inner ear deformity or a history of inner ear trauma.

Acoustic Stimulation↗
PubMed1992

Inner ear morphology of experimental perilymphatic fistula.

The inner ear pathology of experimental perilymphatic fistula (EPLF) is described. EPLF was produced by injecting artificial perilymph into the subarachnoid space, or by suctioning 4 microL of perilymph through one of the round window membranes of the guinea pig. The animals were either killed immediately, or were kept alive for 3 weeks to 3 months. The conventional celloidin embedding method was employed for morphologic study. Vestibular function of the animals was tested by observing spontaneous nystagmus and positional nystagmus after the experiment. The caloric test was also performed. Various pathologic changes of the membranous labyrinth were observed. In the cochlea these included rupture or collapse of Reissner's membrane, bulging of Reissner's membrane, loss of hair cells, and compression of the organ of Corti. Pathology of the otolithic organs and semicircular canals mainly consisted of collapse of the membranous labyrinth. Clinical symptoms in patients with perilymphatic fistula (PLF) are explained, based on our experimental findings. Electronystagmography (ENG) of EPLF animals showed either no caloric response or, with a longer duration, caloric irregularity. Prolonged unsteadiness in patients may be due to "floating" labyrinth.

Animals↗
PubMed1990

[Functional study of vestibular receptors by combined electric and rotatory stimulations].

After a brief review of the anatomical and functional characteristic of the inner ear, emphasizing audio-vestibular relationships, a direct method for recording peripheral vestibular potentials, the Electrovestibulogram (EGV) is described and compared with the techniques Electronystagmographic. Stimulating electrodes were implanted in the round window and vertex of a group of guinea-pigs, with recording electrodes near the internal acoustic meatus. A permanent electric stimulation was combined with an intermittent vestibular stimulation (horizontal angular acceleration) to derive afterfact-free vestibular specific responses. The characteristics of the EVG responses were analyzed and compared with the data in the literature concerning the responses of single fibres, to validate the technique. The diagnostic value of EGV is discussed.

Animals↗
PubMed1980

Otitis media with perforation of the tympanic membrane: a longitudinal experimental study.

Despite the high incidence and prevalence of otitis media, its pathogenesis is not thoroughly understood. In an effort to provide a better understanding of this disease, experimental animal models have been developed which corroborate the changes observed in humans. In this study a new factor was added: tympanic membrane perforation 1 week after Eustachian tube obstruction. Twelve cats were divided in 4 even groups, and sacrificed at 1 and 2 weeks, 1 and 3 months after perforation, and their temporal bones were studied. Findings revealed an early massive reaction of the mucoperiosteum with granulation and polypoidal tissue formation which filled a considerable portion of the middle ear cavity. Polypoidal changes involved the stapediovestibular joint, possibly explaining the cases of stapes fixation found at tympanomastoidectomy procedures for chronic otitis media. Cholesterol granulomas with the classic characteristics as described in humans were observed in all animals at 3 month periods. These were preceded by clefts in the effusions, at 1 month, containing red blood cells. These clefts were considered as probable precursors of cholesterol granuloma formation. The association of endolymphatic hydrops, round window membrane changes, and otitis media without purulent labyrinthitis was observed; however, it was felt that the paucity of animals precluded any definite conclusions.

Animals↗