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H P Wit - One of the best experts on this subject based on the ideXlab platform.

  • the relationship of the round window membrane to the Cochlear Aqueduct shown in three dimensional imaging
    Hearing Research, 2005
    Co-Authors: Rutger Hofman, F W J Albers, J M Segenhout, H P Wit
    Abstract:

    The round window membrane and Cochlear Aqueduct complex in the guinea pig are reconstructed with 3D-imaging, using orthogonal plane fluorescence optical sectioning (OPFOS). The 3D-images show that the periotic duct and the Aqueduct are connected to a pouch-like extension of the round window. The function of this may be regulation of Aqueduct flow resistance under the influence of a pressure difference between inner ear fluid and middle ear.

  • Cochlear Aqueduct Flow Resistance Depends on Round Window Membrane Position in Guinea Pigs
    Journal of the Association for Research in Otolaryngology, 2004
    Co-Authors: Robert A Feijen, F W J Albers, J M Segenhout, H P Wit
    Abstract:

    The resistance for fluid flow of the Cochlear Aqueduct was measured in guinea pigs for different positions of the round window membrane. These different positions were obtained by applying different constant pressures to the middle ear cavity. Fluid flow through the Aqueduct was induced by small pressure steps superimposed on these constant pressures. It was found that the resistance for fluid flow through the Aqueduct depended on the round window position but not on flow direction. The results can be explained by special fibrous structures that connect the round window with the entrance of the Aqueduct. It was also found that the equilibrium inner ear pressure depends on middle ear pressure, indicating that the Aqueduct does not connect the inner ear with a cavity with constant pressure.

  • direct measurement flow resistance of Cochlear Aqueduct in guinea pigs
    Acta Oto-laryngologica, 2004
    Co-Authors: Elisabeth O Laurensthalen, H P Wit, J M Segenhout, F W J Albers
    Abstract:

    Objective The Cochlear Aqueduct connects the scala tympani to the subarachnoid space and is the main pressure equalization canal for the inner ear. Increases in inner ear volume and pressure are thought to cause clinical symptoms such as vertigo, tinnitus and fluctuating hearing loss. In this study the flow resistance of the Cochlear Aqueduct was determined and its relation with inner ear pressure was studied. Material and Methods Inner ear pressure was measured in the scala tympani through the round window using a micropipette. Through a second micropipette, artificial perilymph was infused into, or withdrawn from, the scala tympani at various constant rates. From the infusion rate and the change in perilymphatic pressure during infusion the flow resistance of the Cochlear Aqueduct was calculated. Results The flow resistance was found not to be constant but to depend on the position of the round window membrane and possibly on the magnitude and direction of fluid flow through the Aqueduct. Measured flow ...

  • Cochlear Aqueduct flow resistance is not constant during evoked inner ear pressure change in the guinea pig
    Hearing Research, 2003
    Co-Authors: H P Wit, Robert A Feijen, F W J Albers
    Abstract:

    Inner ear fluid pressure was measured during 6.25 mHz square wave middle ear pressure manipulation, with a perforated tympanic membrane. After a negative-going middle ear pressure change the calculated flow resistance of the inner ear pressure release routes (mainly the Cochlear Aqueduct) was approximately constant, with a value of 12 Pa s/nl (averaged over two ears), when values for the inner ear window compliance are taken from the literature. After a positive-going middle ear pressure change the calculated flow resistance changed with round window position and with the pressure difference across the Cochlear Aqueduct. It reached an average maximum value of 114 Pa s/nl. The change of flow resistance during inner ear pressure variation can be explained by a permeability change of the Cochlear Aqueduct, caused by a change of structures filling the Aqueduct and its entrance in scala tympani.

F W J Albers - One of the best experts on this subject based on the ideXlab platform.

  • the relationship of the round window membrane to the Cochlear Aqueduct shown in three dimensional imaging
    Hearing Research, 2005
    Co-Authors: Rutger Hofman, F W J Albers, J M Segenhout, H P Wit
    Abstract:

    The round window membrane and Cochlear Aqueduct complex in the guinea pig are reconstructed with 3D-imaging, using orthogonal plane fluorescence optical sectioning (OPFOS). The 3D-images show that the periotic duct and the Aqueduct are connected to a pouch-like extension of the round window. The function of this may be regulation of Aqueduct flow resistance under the influence of a pressure difference between inner ear fluid and middle ear.

  • Cochlear Aqueduct Flow Resistance Depends on Round Window Membrane Position in Guinea Pigs
    Journal of the Association for Research in Otolaryngology, 2004
    Co-Authors: Robert A Feijen, F W J Albers, J M Segenhout, H P Wit
    Abstract:

    The resistance for fluid flow of the Cochlear Aqueduct was measured in guinea pigs for different positions of the round window membrane. These different positions were obtained by applying different constant pressures to the middle ear cavity. Fluid flow through the Aqueduct was induced by small pressure steps superimposed on these constant pressures. It was found that the resistance for fluid flow through the Aqueduct depended on the round window position but not on flow direction. The results can be explained by special fibrous structures that connect the round window with the entrance of the Aqueduct. It was also found that the equilibrium inner ear pressure depends on middle ear pressure, indicating that the Aqueduct does not connect the inner ear with a cavity with constant pressure.

  • direct measurement flow resistance of Cochlear Aqueduct in guinea pigs
    Acta Oto-laryngologica, 2004
    Co-Authors: Elisabeth O Laurensthalen, H P Wit, J M Segenhout, F W J Albers
    Abstract:

    Objective The Cochlear Aqueduct connects the scala tympani to the subarachnoid space and is the main pressure equalization canal for the inner ear. Increases in inner ear volume and pressure are thought to cause clinical symptoms such as vertigo, tinnitus and fluctuating hearing loss. In this study the flow resistance of the Cochlear Aqueduct was determined and its relation with inner ear pressure was studied. Material and Methods Inner ear pressure was measured in the scala tympani through the round window using a micropipette. Through a second micropipette, artificial perilymph was infused into, or withdrawn from, the scala tympani at various constant rates. From the infusion rate and the change in perilymphatic pressure during infusion the flow resistance of the Cochlear Aqueduct was calculated. Results The flow resistance was found not to be constant but to depend on the position of the round window membrane and possibly on the magnitude and direction of fluid flow through the Aqueduct. Measured flow ...

  • Cochlear Aqueduct flow resistance is not constant during evoked inner ear pressure change in the guinea pig
    Hearing Research, 2003
    Co-Authors: H P Wit, Robert A Feijen, F W J Albers
    Abstract:

    Inner ear fluid pressure was measured during 6.25 mHz square wave middle ear pressure manipulation, with a perforated tympanic membrane. After a negative-going middle ear pressure change the calculated flow resistance of the inner ear pressure release routes (mainly the Cochlear Aqueduct) was approximately constant, with a value of 12 Pa s/nl (averaged over two ears), when values for the inner ear window compliance are taken from the literature. After a positive-going middle ear pressure change the calculated flow resistance changed with round window position and with the pressure difference across the Cochlear Aqueduct. It reached an average maximum value of 114 Pa s/nl. The change of flow resistance during inner ear pressure variation can be explained by a permeability change of the Cochlear Aqueduct, caused by a change of structures filling the Aqueduct and its entrance in scala tympani.

Saumil N. Merchant - One of the best experts on this subject based on the ideXlab platform.

  • anatomy of the normal human Cochlear Aqueduct with functional implications
    Hearing Research, 1997
    Co-Authors: Saumil N. Merchant, Quinton Gopen, John J Rosowski
    Abstract:

    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) μm which occurred 200–300 μm 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.

  • a human temporal bone study of acute bacterial meningogenic labyrinthitis
    American Journal of Otology, 1996
    Co-Authors: Saumil N. Merchant, Quinton Gopen
    Abstract:

    It is well established that sensorineural hearing loss (SNHL) is an important sequela of acute bacterial meningitis. Previous human temporal bone histopathologic studies have suggested that such hearing loss is due to labyrinthitis. This study involved a detailed and systematic evaluation of the auditory and vestibular end-organs in 41 human temporal bones from patients with acute bacterial meningitis, aimed at describing the spectrum of histopathologic changes within the labyrinth, ascertaining likely routes for spread of infection from the meninges to the inner ear, and comparing the data from humans with those described in a rabbit model of meningogenic labyrinthitis. Our study revealed the following : (a) Suppurative labyrinthitis occurred in 20 (49%) bones. Of these 20 bones, the cochlea was affected in all, whereas the vestibular organs were involved in 10. Eosinophilic staining of inner ear fluids without the presence of inflammatory cells (so-called serous labyrinthitis) occurred in 14 of the remaining 21 bones. This staining occurred primarily within the vestibular system. Its significance and pathogenesis remains unknown ; (b) Sensory and neural structures of the inner ear appeared intact in the majority of specimens, including bones with suppurative labyrinthitis and those with eosinophilic staining of inner ear fluids. This finding raises the possibility of preventing or reversing SNHL by therapeutic intervention. Spiral ganglion cells were severely degenerated in 12% of bones, indicating a retroCochlear site of hearing loss in addition to the cochlea. This subset of patients may perform poorly after Cochlear implantation ; (c) It has been traditionally assumed that irreversible and permanent SNHL is caused by suppurative labyrinthitis, whereas reversible SNHL is caused by serous labyrinthitis. Our findings question the validity of these assumptions ; (d) The data were consistent with the hypothesis that both the Cochlear modiolus and Cochlear Aqueduct can serve as potential pathways for spread of infection from the meninges to the inner ear ; (e) There were many similarities in the histopathology of the inner ear in humans when compared with the rabbit model of meningogenic labyrinthitis. A notable difference was that the Cochlear Aqueduct appeared to be the sole pathway for spread of infection in the rabbit, whereas in the human, both the modiolus and Aqueduct were possible pathways.

J M Segenhout - One of the best experts on this subject based on the ideXlab platform.

  • the relationship of the round window membrane to the Cochlear Aqueduct shown in three dimensional imaging
    Hearing Research, 2005
    Co-Authors: Rutger Hofman, F W J Albers, J M Segenhout, H P Wit
    Abstract:

    The round window membrane and Cochlear Aqueduct complex in the guinea pig are reconstructed with 3D-imaging, using orthogonal plane fluorescence optical sectioning (OPFOS). The 3D-images show that the periotic duct and the Aqueduct are connected to a pouch-like extension of the round window. The function of this may be regulation of Aqueduct flow resistance under the influence of a pressure difference between inner ear fluid and middle ear.

  • Cochlear Aqueduct Flow Resistance Depends on Round Window Membrane Position in Guinea Pigs
    Journal of the Association for Research in Otolaryngology, 2004
    Co-Authors: Robert A Feijen, F W J Albers, J M Segenhout, H P Wit
    Abstract:

    The resistance for fluid flow of the Cochlear Aqueduct was measured in guinea pigs for different positions of the round window membrane. These different positions were obtained by applying different constant pressures to the middle ear cavity. Fluid flow through the Aqueduct was induced by small pressure steps superimposed on these constant pressures. It was found that the resistance for fluid flow through the Aqueduct depended on the round window position but not on flow direction. The results can be explained by special fibrous structures that connect the round window with the entrance of the Aqueduct. It was also found that the equilibrium inner ear pressure depends on middle ear pressure, indicating that the Aqueduct does not connect the inner ear with a cavity with constant pressure.

  • direct measurement flow resistance of Cochlear Aqueduct in guinea pigs
    Acta Oto-laryngologica, 2004
    Co-Authors: Elisabeth O Laurensthalen, H P Wit, J M Segenhout, F W J Albers
    Abstract:

    Objective The Cochlear Aqueduct connects the scala tympani to the subarachnoid space and is the main pressure equalization canal for the inner ear. Increases in inner ear volume and pressure are thought to cause clinical symptoms such as vertigo, tinnitus and fluctuating hearing loss. In this study the flow resistance of the Cochlear Aqueduct was determined and its relation with inner ear pressure was studied. Material and Methods Inner ear pressure was measured in the scala tympani through the round window using a micropipette. Through a second micropipette, artificial perilymph was infused into, or withdrawn from, the scala tympani at various constant rates. From the infusion rate and the change in perilymphatic pressure during infusion the flow resistance of the Cochlear Aqueduct was calculated. Results The flow resistance was found not to be constant but to depend on the position of the round window membrane and possibly on the magnitude and direction of fluid flow through the Aqueduct. Measured flow ...

Sally L Gewalt - One of the best experts on this subject based on the ideXlab platform.

  • quantitative anatomy of the round window and Cochlear Aqueduct in guinea pigs
    Hearing Research, 2001
    Co-Authors: Adam F Ghiz, Alec N Salt, John E Demott, M M Henson, William O Henson, Sally L Gewalt
    Abstract:

    In order to analyze the entry of solutes through the round window membrane, a quantitative description of round window anatomy in relationship to scala tympani is required. High-resolution magnetic resonance microscopy was used to visualize the fluid spaces and tissues of the inner ear in three dimensions in isolated, fixed specimens from guinea pigs. Each specimen was represented as consecutive serial slices, with a voxel size of approximately 25 Wm 3 . The round window membrane, and its relationship to the terminal portion of scala tympani in the basal turn, was quantified in six specimens. In each image slice, the round window membrane and scala tympani were identified and segmented. The total surface area of the round window membrane averaged 1.18 mm 2 (S.D. 0.08, n = 6). The length and variation of cross-sectional area as a function of distance for the Cochlear Aqueduct was determined in five specimens. The Cochlear Aqueduct was shown to enter scala tympani at the medial limit of the round window membrane, which corresponded to a distance of approximately 1 mm from the end of the scala when measured along its mid-point. These data are of value in simulating drug and other solute movements in the Cochlear fluids and have been incorporated into a public-domain simulation program available at http://oto.wustl.edu/cochlea/. fl 2001 Elsevier Science B.V. All rights reserved.