High-density cochlear implants with position sensing and control
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Keywords:
Modiolus (cochlea)
Basilar membrane
Parylene
Electrode array
Strain gauge
A curved electrode array and inserting tool have been developed at the University of Melbourne. This electrode array can be successfully implanted with few modifications to the surgical procedure presently in use. When implanted, the curved electrode array adopts a position closer to the modiolus than does the standard straight electrode array.
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Morphology
Electrode array
Position (finance)
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In order to investigate the characters of inner ear vessels using the microvascular corrosion casting technique and scanning electron microscope the three-dimensional spatial picture of the vessels in cochlear basilar membrane, utriculus, sacculus and three ampullae of guinea pig were observed. It was found that arteriole coils were present in the modiolus ampullae, utriculus and sacculus. The length of arterioles was therefore prolonged and could keep the blood supply in inner ear stable. The possibility of blood coagulation in these segments increased because the blood flow became slower here. Another character was that the capillary networks appeared denser in stria vascularis and central part of the crista, whereas the vessel meshes in basilar membrane of cochlea and in planum semiculatum of ampullae were looser. These findings suggested that the metabolism in stria vascularis and central part of the crista would be more prosperous than that in the basilar membrane and planum semiculatum of ampullae.
Basilar membrane
Modiolus (cochlea)
Perilymph
Crista
Endolymph
Arteriole
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To investigate the accuracy of rigid cochlear models in measuring intra-cochlear positions of cochlear implant (CI) electrodes.Ninety three adults who had undergone CI and pre- and postoperative computed tomographic (CT) imaging.Seven rigid models of cochlear anatomy were constructed using micro-CTs of cochlear specimens. Using each of the seven models, the position of each electrode in each of the 98 ears in our dataset was measured as its depth along the length of the cochlea, its distance to the basilar membrane, and its distance to the modiolus. Cochlear duct length was also measured using each model.Standard deviation (SD) across rigid cochlear models in measures of electrode depth, distance to basilar membrane, distance to modiolus, and length of the cochlear duct at two turns were 0.68, 0.11, 0.15, and 1.54 mm. Comparing the estimated position of the electrodes with respect to the basilar membrane, i.e., deciding whether an electrode was located within the scala tympani (ST) or the scala vestibuli (SV), there was not a unanimous agreement between the models for 19% of all the electrodes. With respect to the modiolus, each electrode was classified into one of the three groups depending on its modiolar distance: close, medium, and far. Rigid models did not unanimously agree on modiolar distance for approximately 50% of the electrodes tested.Inter-model variance of rigid cochlear models exists, demonstrating that measurements made using rigid cochlear models are limited in terms of accuracy because of non-rigid inter-subject variations in cochlear anatomy.
Modiolus (cochlea)
Cochlear duct
Basilar membrane
Electrode array
Cochlear Implantation
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A new electrode array embedded with nitinol shape memory alloy actuator has been designed so that it can be located beneath the basilar membrane inside the cochlear scala tympani to effectively deliver neurotrophins (growth factors) into the cochlea. The electrode array is also expected to be inserted deeper into the cochlear middle turn to stimulate further auditory neurons compared to the Nucleus standard straight array. A finite element model has been developed to design and evaluate the new electrode array. Results from the model have shown that the new electrode array can be accurately positioned close to the desired final position.
Basilar membrane
Electrode array
Modiolus (cochlea)
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A new electrode array embedded with nitinol shape memory alloy actuator has been designed so that it can be located beneath the basilar membrane inside the cochlear scala tympani to effectively deliver neurotrophins (growth factors) into the cochlea. The electrode array is also expected to be inserted deeper into the cochlear middle turn to stimulate further auditory neurons compared to the Nucleus standard straight array. A finite element model has been developed to design and evaluate the new electrode array. Results from the model have shown that the new electrode array can be accurately positioned close to the desired final position.
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Electrode array
Modiolus (cochlea)
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Hypothesis This study aims to examine the mechanism of damage to the basilar membrane caused by the proximal section of the cochlear implant electrode array. Background The electrode array has been found to severely damage the basilar membrane. Most previous studies on cochlear implant insertion damage largely focused on the injury by the front section (tip) of the electrode array to the membrane. Little attempt has been made to investigate the damage caused by the array's proximal section. Methods A computational model using the finite element method has been developed for assessing the likelihood of the damage based on two criteria: 1) frequency of contact between the proximal section of the electrode array and the upper wall of the scala tympani where the basilar membrane is located, and 2) magnitude of the associated shear stresses at the contact areas. The model has been validated and used for studying the effect of electrode array's stiffness properties on the damage. Results The proximal section of the contour array is most likely to hit the basilar membrane, compared with its previous versions (the straight array and the single wire electrode). In terms of shear stress magnitude, the proximal section of the contour array exerts higher stresses on the scala tympani's upper wall and, thus, is more likely to damage the basilar membrane, compared with that of the straight array. Conclusion Results from this study are useful for cochlear implant surgeons in better understanding the mechanism of damage by the electrode array's proximal section to the basilar membrane and in establishing advanced insertion techniques for reducing the damage (in particular, the results strongly support the "advance off-stylet" technique). The outcomes of the study also are beneficial for cochlear implant designers in selecting appropriate stiffness profiles for future electrode arrays, which are expected to cause minimal damage to the basilar membrane (a new design of the contour array with stiffness increasing from the front to the proximal section is highly recommended).
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Basilar membrane
Electrode array
Modiolus (cochlea)
Round window
Stylet
Cochlear duct
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The scalar position of the electrode array is assumed to be associated with auditory performance after cochlear implantation. We propose a new method that can be routinely applied in clinical practice to assess the position of an electrode array. Ten basilar membrane templates were generated using micro-computed tomography (micro-CT), based on the dimensions of 100 cochleae. Five surgeons were blinded to determine the position of the electrode array in 30 cadaveric cochleae. The procedure consisted of selecting the appropriate template based on cochlear dimensions, merging the electrode array reconstruction with the template using four landmarks, determining the position of the array according to the template position, and comparing the results obtained to histology data. The time taken to analyze each implanted cochlea was approximately 12 min. We found that, according to histology, surgeons were in almost perfect agreement when determining an electrode translocated to the scala vestibuli with the perimodiolar MidScala array (Fleiss' kappa (κ) = 0.82), and in moderate agreement when using the lateral wall EVO array (κ = 0.42). Our data indicate that an adapted basilar membrane template can be used as a rapid and reproducible method to assess the position of the electrode array after cochlear implantation.
Basilar membrane
Electrode array
Cadaveric spasm
Cochlear Implantation
Cochlear duct
Position (finance)
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To evaluate histologically the risk of trauma to intracochlear structures after sequential insertion of an intracochlear catheter and an electrode array.A previous computed tomographic scan-based study demonstrated that introduction of a flexible disposable intracochlear catheter for drug delivery to a distance of up to 15 mm was feasible and showed no radiologic evidence of basilar membrane trauma.Fifteen fresh human temporal bones were prepared for cochlear implantation. We sequentially performed the introduction of the catheter, the injection of 15 µl of an iodine solution into the scala tympani via the catheter, and the removal of the catheter in 14 temporal bones, and finally, 2 types of electrode array (Flex EAS and Flex Soft) from MED-EL, were inserted into 10 temporal bones. The bones were fixed and embedded in methylmethacrylate to cut the undecalcified temporal bones parallel to the modiolus axis with the electrode array in place, and each histologic section was photographed to document the location and extent of trauma in the cochlea.No specific damage (Grade 0 trauma) to cochlear structures occurred in 12 temporal bones, and elevation of basilar membrane (Grade 1 trauma) occurred in 2 cases. The electrode array was positioned in the scala tympani under the basilar membrane in all temporal bones, with one exception, in which the Flex Soft electrode array deviated behind the spiral ligament and into the scala vestibuli apically (Grade 3 trauma).The infusion of an iodine solution within an intracochlear catheter and the subsequent insertion of an electrode array was shown to be feasible and often atraumatic.
Basilar membrane
Electrode array
Modiolus (cochlea)
Round window
Cochlear Implantation
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