Concentration Gradient Along the Scala Tympani After Local Application of Gentamicin to the Round Window Membrane

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.

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

The Journal of Laryngology & Otology ◽

10.1017/s002221511400156x ◽

2014 ◽

Vol 128 (8) ◽

pp. 702-708 ◽

Cited By ~ 5

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.

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

Otology & Neurotology ◽

10.1097/mao.0b013e318161aaae ◽

2008 ◽

Vol 29 (3) ◽

pp. 401-406 ◽

Cited By ~ 119

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

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Distribution of PLGA nanoparticles in chinchilla cochleae

Otolaryngology ◽

10.1016/j.otohns.2007.04.013 ◽

2007 ◽

Vol 137 (4) ◽

pp. 619-623 ◽

Cited By ~ 52

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.

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

Audiology and Neurotology ◽

10.1159/000471840 ◽

2017 ◽

Vol 22 (1) ◽

pp. 50-55 ◽

Cited By ~ 4

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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Effect of Increased Perilymphatic Pressure on Endocochlear Potential

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348948109000314 ◽

1981 ◽

Vol 90 (3) ◽

pp. 264-266 ◽

Cited By ~ 16

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.

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Effect of Experimentally Induced Otitis Media on Cochlear Implants

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348948709600207 ◽

1987 ◽

Vol 96 (2) ◽

pp. 174-177 ◽

Cited By ~ 20

Author(s):

Burkhard K-H. Franz ◽

Graeme M. Clark ◽

David M. Bloom

Keyword(s):

Horseradish Peroxidase ◽

Cochlear Implants ◽

Round Window ◽

Round Window Membrane ◽

Group A Streptococci ◽

Scala Tympani ◽

Tracer Studies ◽

Entry Points ◽

Group A ◽

Round Window Niche

Cat cochleas implanted with scala tympani prostheses were investigated histologically after inoculating the bullae with a suspension of group a streptococci. The prosthesis was passed through the round window membrane in one ear. In the other the prosthesis bypassed the round window via an opening anteroinferior to the round window niche. Before death, horseradish peroxidase was administered as a tracer for possible pathways of infection. Results showed that group a streptococci were pathogenic to the cat and caused inflammation in the bulla. The unimplanted round window membrane and the seals around the electrode entry points prevented infection from entering the cochlea. The seals around electrodes inserted either through the round window membrane or an opening drilled anteroinferior to the niche were equally effective. The horseradish peroxidase tracer studies showed, however, that a gap existed between the electrode and membranous seal, and this could be a potentially vulnerable site under certain conditions. Drilling an anteroinferior opening into the cochlea resulted in bony sequestra entering the cochlea. This can be avoided by blue-lining the opening and removing bone with picks before making an opening through the endosteum.

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Dimensions of and Vibrations in the round Window Membrane in Cats

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348948909800608 ◽

1989 ◽

Vol 98 (6) ◽

pp. 438-442

Author(s):

Takashi Fukaya ◽

Yasuya Nomura

Keyword(s):

Round Window ◽

Low Frequency ◽

Round Window Membrane ◽

Scala Tympani ◽

Maximum Displacement ◽

Optical Displacement ◽

The Mean ◽

Vibratory Pattern ◽

Shape And Size

The shape and size of the round window membrane and its vibratory pattern were investigated in cats by use of an optical displacement meter and time-averaged holography. The round window membrane is convex toward the scala tympani and appears to be almost elliptic in shape. The major and minor axes of the membrane are 2,273 and 1,934 μm. The mean degree of convexity is 1,975 μm. Under vibration the area of maximum displacement occurs anteriorly-superiorly at low frequency. As frequency is increased, the maximum displaced area shifts posteriorly-superiorly, then breaks up into several segments.

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The Effects of Round Window Membrane Injury and the Use of a Model Electrode Application on Hearing in Rats

Ear Nose & Throat Journal ◽

10.1177/0145561321990188 ◽

2021 ◽

pp. 014556132199018

Author(s):

Murat Koc ◽

Abdullah Dalgic ◽

Mehmet Ziya Ozuer

Keyword(s):

Hearing Loss ◽

Cochlear Implant ◽

Round Window ◽

Mechanical Trauma ◽

Round Window Membrane ◽

Albino Rats ◽

Topical Steroids ◽

Distortion Product ◽

Significant Difference ◽

Group 3

Objective: To investigate the effects of the mechanical trauma to the round window, a model electrode inserted into the scala tympani on the cochlear reserve, and the efficacy of topical steroids in preventing hearing loss. Materials and Methods: 21 male Wistar Albino rats were equally categorized into three groups. In all groups an initial mechanical injury to round window was created. Only subsequent dexamethasone injection was administrated into the cochlea in the subjects of group 2 while a multichannel cochlear implant guide inserted into the cochlea prior to dexamethasone administration for group 3. Distortion product otoacoustic emissions (DPOAEs) were obtained prior to and immediately after the surgical injury, eventually on postoperative seventh day (d 7). Mean signal/noise ratios (S/Ns) obtained at 2000, 3000, and 4000 Hz were calculated. Data sets were compared with non-parametric statistical tests. Results: The early intraoperative mean S/Ns were significantly less than preoperative measurements for group 1 and 2; however, preoperative and postoperative d 7 average S/Ns did not differ. There was statistically significant difference between preoperative, intraoperative and postoperative d 7 average S/Ns for group 3. Conclusion: We observed that hearing was restored approximately to the preoperative levels following early postoperative repair. However, an electrode insertion into the cochlea via round window subsequent to mechanical trauma seems to cause a progressive hearing loss. Therefore, a special care must be taken to avoid the injury to the round window membrane in the course of the placement of a cochlear implant electrode and surgery for the chronic otitis media.

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