Intracochlear Pressure Changes due to Round Window Opening: A Model Experiment

The Scientific World Journal (Impact Factor: 1.73). 05/2014; 2014(7). DOI: 10.1155/2014/341075


To preserve residual hearing in cochlea implantation, the electrode design has been refined and an atraumatic insertion of the cochlea electrode has become one aspect of cochlea implant research. The opening of the round window can be assumed to be a contributing factor in an atraumatic concept. The aim of our study was to observe intracochlear pressure changes due to different opening conditions of an artificial round window membrane. The experiments were performed in an artificial cochlea model. A round window was simulated with a polythene foil and a pressure sensor was placed in the helicotrema area to monitor intraluminal pressure changes. Openings of the artificial round window membrane were performed using different ways. Opening the artificial round window mechanically showed a biphasic behaviour of pressure change. Laser openings showed a unidirectional pressure change. The lowest pressure changes were observed when opening the artificial round window membrane using a diode laser. The highest pressure changes were seen when using a needle. The openings with the CO2 laser showed a negative intracochlear pressure and a loss of fluid. In our model experiments, we could prove that the opening of the artificial round window membrane causes various intracochlear pressure changes.

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Available from: Ingo Todt, Jul 14, 2014
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    ABSTRACT: Introduction Improvement of the surgical options in active middle ear implants and cochlear implants is widely discussed in the literature. Over the past decades the indication for active middle ear and inner ear implants have been extended. The change of the indications involved new surgical techniques. The presented studies deal with the quality control in middle ear implants and with intracochlear pressure changes due to insertions of cochlear implants which are important in preservation of residual hearing. Material and methods In 20 patients who recieved a Vibrant Soundbridge (Med-El) several parameter were evaluated in a mixed retrospective and prospective observational study. The radiological position of the floating mass transducer (FMT) at the round window (RW) was evaluated and compared with the audiological results and a specific coupplingquotient. Intracochlear pressure measurements took place in an artificial cochlear model. Intracochlear pressure changes related to RW opening with different instruments were measured as well as intracochlear pressure changes due to different insertion speeds of a CI electrode. Results The position of the FMT in the RW niche was classified radiologically. A good correlation was seen between the position of the FMT in the RW and the audiological results. RW openings with sharp tools showed high maximum pressure values, whereas RW opening with the diode laser showed rather low pressure values. Slow insertion speed (0,1mm/s) causes clearly lower intracochlear pressure values than fast insertion speed (2mm/s). Conclusion The postoperative control of the FMT in the RW niche led to a classification of the position of the FMT in proportion to the RW-Membrane. The audiological results correlate if surgical guidelines are kept in mind. Intracochlear pressure changes due to RW opening and CI insertion with different speed of insertion are enormous. To which extent the pressure changes observed in the cochlear model can be transferred to the human cochlear needs further investigation. An important part in preservation of residual hearing in CI surgery can be estimated.
    09/2015, Degree: Dr. med., Supervisor: Ingo Todt
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    • "Different factors can be assumed to contribute to hearing preserving cochlear implant surgery. Variations in opening the round window have been described and have shown a significant impact on the transmission of intracochlear fluid pressure force in a cochlear implant model [12]. Various forms of application (i.v., middle ear, topical) and different medications (triamcinolone, dexamethasone, prednisolone) are used and thought to be important factors for the preservation of residual hearing [13] [14]. "
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    ABSTRACT: Introduction. To preserve residual hearing the atraumaticity of the cochlea electrode insertion has become a focus of cochlear implant research. In addition to other factors, the speed of insertion is thought to be a contributing factor in the concept of atraumatic implantation. The aim of our study was to observe intracochlear fluid pressure changes due to different insertional speeds of an implant electrode in a cochlear model. Materials and Methods. The experiments were performed using an artificial cochlear model. A linear actuator was mounted on an Advanced Bionics IJ insertional tool. The intracochlear fluid pressure was recorded through a pressure sensor which was placed in the helicotrema area. Defined insertions were randomly performed with speeds of 0.1 mm/sec, 0.25 mm/sec, 0.5 mm/sec, 1 mm/sec, and 2 mm/sec. Results. A direct correlation between speed and pressure was observed.Mean maximum values of intracochlear fluid pressure varied between 0.41mmHg and 1.27mm Hg. Conclusion. We provide the first results of fluid pressure changes due to insertional speeds of CI electrodes in a cochlear model. A relationship between the insertional speed and intracochlear fluid pressure was observed. Further experiments are needed to apply these results to the in vivo situation.
    BioMed Research International 07/2014; 2014. DOI:10.1155/2014/507241 · 3.17 Impact Factor