Effect of Increased Perilymphatic Pressure on Endocochlear Potential

1981 ◽  
Vol 90 (3) ◽  
pp. 264-266 ◽  
Author(s):  
Tsutomu Nakashima ◽  
Akikazu Ito
Keyword(s):  
Blood Flow ◽  
Stria Vascularis ◽  
Round Window ◽  
Fluid Pressure ◽  
Endocochlear Potential ◽  
Round Window Membrane ◽  
Scala Tympani ◽  
Cochlear Blood Flow ◽  
India Ink ◽  
High Level

A study was done to determine how increased fluid pressure in the inner ear influences cochlear blood flow. Hydrostatic pressure was applied to the scala vestibuli or scala tympani in guinea pigs. Endocochlear potential, which is sensitive to the lack of oxygen, was measured through the round window membrane or through the stria vascularis. Cochlear blood flow was confirmed by intravenous injection of India ink. When the perilymphatic pressure was raised to a relatively high level, endocochlear potential decreased, in a similar way as in response to anoxia, because of the cessation of the cochlear blood flow. This change was completely reversible upon applications of pressure for brief periods of time. We consider that the cochlear blood flow ceases when the fluid pressure reaches the level of intracochlear arterial pressure.

scholarly journals Effects of Round Window Membrane Rupture on Cochlear Blood Flow and Endocochlear Potential

2003 ◽  
Vol 106 (7) ◽  
pp. 723-729 ◽  
Author(s):  
Xiuli Liu ◽  
Michihiko Sone ◽  
Mitsuo Tominaga ◽  
Hideo Hayashi ◽  
Hiroshi Yamamoto ◽  
...  
Keyword(s):  
Blood Flow ◽  
Round Window ◽  
Endocochlear Potential ◽  
Round Window Membrane ◽  
Cochlear Blood Flow ◽  
Membrane Rupture

Effects of Round Window Membrane Rupture on Cochlear Blood Flow and Inner Ear Pressures

1988 ◽  
Vol 105 (sup457) ◽  
pp. 129-132 ◽  
Author(s):  
Tsutomu Nakashima ◽  
Yusuke Watanabe ◽  
Masahide Kaida ◽  
Noriyuki Yanagita
Keyword(s):  
Blood Flow ◽  
Inner Ear ◽  
Round Window ◽  
Round Window Membrane ◽  
Cochlear Blood Flow ◽  
Membrane Rupture

scholarly journals Surgical anatomy of the round window with special reference to cochlear implantation

1987 ◽  
Vol 101 (2) ◽  
pp. 97-102 ◽  
Author(s):  
Burkhard K. H. Franz ◽  
Graeme M. Clark ◽  
David M. Bloom
Keyword(s):  
Cochlear Implant ◽  
Special Reference ◽  
Cochlear Implantation ◽  
Round Window ◽  
Surgical Anatomy ◽  
Round Window Membrane ◽  
Scala Tympani ◽  
Good View ◽  
Posterior Tympanotomy ◽  
Round Window Niche

AbstractWhen the multi-channel cochlear implant electrode is inserted into the scala tympani through the round window the operation is best performed via a posterior tympanotomy. The view of the round window membrane, however, is incomplete because of its orientation and the fact that it has a conical shape. Nevertheless, a good view along the basal turn is obtained after the antero-inferior overhang of the round window niche and the crista fenestrae have been removed. It might be damaging to drill away the postero-superior overhang as the osseous spiral lamina lies extremely close to the round window membrane.

Histopathological and audiological effects of mechanical trauma associated with the placement of an intracochlear electrode, and the benefit of corticosteroid infusion: prospective animal study

2014 ◽  
Vol 128 (8) ◽  
pp. 702-708 ◽  
Author(s):  
G Malkoc ◽  
A Dalgic ◽  
M Koc ◽  
T Kandogan ◽  
S Korkmaz ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Topical Corticosteroid ◽  
Animal Study ◽  
Hair Cells ◽  
Normal Saline ◽  
Round Window ◽  
Osmotic Pump ◽  
Mechanical Trauma ◽  
Round Window Membrane ◽  
Scala Tympani

AbstractObjective:This study aimed to present the histopathological and audiological effects of mechanical trauma associated with the placement of a model electrode in the scala tympani in rats, and the effects of continuous topical corticosteroid application.Method:The study comprised three groups of rats. The round window membrane was perforated in all three groups and a model electrode was inserted in the round window. Group one received no further treatments. Groups two and three also had an intrathecal microcatheter compatible with a mini-osmotic pump inserted; in group two this was used to release normal saline and in group three the pump released 400 µg/ml dexamethasone.Results:Dexamethasone infusion given after implantation of the intracochlear model electrode was more effective for preventing hearing loss than the administration of just one dose of dexamethasone.Conclusion:The findings suggest that continuous dexamethasone infusion is beneficial for preventing the loss of hair cells and neurons associated with early and late periods of intracochlear electrode trauma.

scholarly journals Dexamethasone Concentration Gradients Along Scala Tympani After Application to the Round Window Membrane

2008 ◽  
Vol 29 (3) ◽  
pp. 401-406 ◽  
Author(s):  
Stefan K. Plontke ◽  
Thorsten Biegner ◽  
Bernd Kammerer ◽  
Ursular Delabar ◽  
Alec N. Salt
Keyword(s):  
Round Window ◽  
Round Window Membrane ◽  
Scala Tympani ◽  
Concentration Gradients

Distribution of PLGA nanoparticles in chinchilla cochleae

2007 ◽  
Vol 137 (4) ◽  
pp. 619-623 ◽  
Author(s):  
Xianxi Ge ◽  
Ronald L. Jackson ◽  
Jianzhong Liu ◽  
Elizabeth A. Harper ◽  
Michael E. Hoffer ◽  
...  
Keyword(s):  
Inner Ear ◽  
Round Window ◽  
Organ Of Corti ◽  
Plga Nanoparticles ◽  
Round Window Membrane ◽  
Scala Tympani ◽  
Magnetic Forces ◽  
Magnetic Exposure ◽  
Transmission Electron ◽  
Electron Energy Loss

Objectives To study the distribution of polylactic/glycolic acid–encapsulated iron oxide nanoparticles (PLGA-NPs) in chinchilla cochleae after application on the round window membrane (RWM). Study Design and Setting Six chinchillas (12 ears) were equally divided into controls (no treatments) and experimen-tals (PLGA-NP with or without magnetic exposure). After 40 minutes of PLGA-NP placement on the RWM, perilymph was withdrawn from the scala tympani. The RWM and cochleae were fixed with 2.5% glutaraldehyde and processed for transmission electron microscopy. Results Nanoparticles were found in cochleae with or without exposure to magnet forces appearing in the RWM, perilymph, endolymph, and multiple locations in the organ of Corti. Electron energy loss spectroscopy confirmed iron elements in nanoparticles. Conclusion The nanoparticles were distributed throughout the inner ear after application on the chinchilla RWM, with and without magnetic forces. Significance PLGA-NP applied to the RWM may have potential for sustained therapy to the inner ear.

The Effect of Pentoxifylline on Cochlear Blood Flow

1992 ◽  
Vol 106 (1) ◽  
pp. 87-91 ◽  
Author(s):  
Michael J. LaRouere ◽  
Jonathan S. Sillman ◽  
Mary T. Tsai ◽  
Alfred L. Nuttall
Keyword(s):  
Blood Flow ◽  
Mechanism Of Action ◽  
Round Window ◽  
Phosphodiesterase Inhibitor ◽  
Dependent Manner ◽  
Cochlear Blood Flow ◽  
Ischemic Tissue ◽  
Normovolemic Hemodilution ◽  
Rheologic Properties ◽  
Dose Dependent

Pentoxifylline, a phosphodiesterase inhibitor and hemorrheologic agent has been found to increase oxygen delivery to ischemic tissue. Intravenous pentoxifylline was administered to normal guinea pigs in order to assess the effect of pentoxifylline on cochlear blood flow and to elucidate its mechanism of action. Intravenous pentoxifylline was found to acutely increase cochlear blood flow in a dose-dependent manner. In normal animals, the effect appeared strongly related to the rheologic properties of this agent rather than a vasodilative action. Normovolemic hemodilution with 75% dextran resulted in no Increase in cochlear blood flow during Infusion of pentoxifylline, whereas the application of nitroprusside over the round window failed to abolish the effect of pentoxifylline.

The Crista Fenestra and Its Impact on the Surgical Approach to the Scala Tympani during Cochlear Implantation

2017 ◽  
Vol 22 (1) ◽  
pp. 50-55 ◽  
Author(s):  
Roberto D. Angeli ◽  
Joel Lavinsky ◽  
Enio T. Setogutti ◽  
Luiz Lavinsky
Keyword(s):  
High Resolution ◽  
Cochlear Implantation ◽  
Round Window ◽  
Ct Scanning ◽  
Round Window Membrane ◽  
Scala Tympani ◽  
High Resolution Computed Tomography ◽  
High Resolution Ct ◽  
Round Window Niche ◽  
Temporal Bones

Objective: The aim of this work was to describe the dimensions of the crista fenestra and determine its presence by means of high-resolution computed tomography (CT) for the purpose of cochlear implantation via the round window approach. Methods: A series of 10 adult human temporal bones underwent high-resolution CT scanning and were further dissected for microscopic study of the round window niche. Results: In all of the specimens, the round window membrane was fully visualized after the complete removal of bony overhangs. The crista fenestra was identified as a sharp bony crest located in the anterior and inferior borders of the niche; its area ranged from 0.28 to 0.80 mm2 (mean 0.51 ± 0.18). The proportion of the area occupied by the crista fenestra in the whole circumference of the round window ranged from 23 to 50% (mean 36%). We found a moderate positive correlation between the area of the niche and the dimensions of the crista fenestra (Spearman rho: 0.491). In every case, high-resolution CT scanning was unable to determine the presence of the crista fenestra. Conclusion: The crista fenestra occupies a variable but expressive area within the bony round window niche. Narrower round window niches tended to house smaller crests. The presence of the crista fenestra is an important obstacle to adequate access to the scala tympani. Nevertheless, a high-resolution CT scan provides no additional preoperative information with regard to its presence for the purpose of surgical access to the scala tympani via the round window niche.

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