Effects of Electrode Array Length on Frequency-Place Mismatch and Speech Perception with Cochlear Implants

Venail, F.; Mathiolon, C.; Champfleur, S. Menjot de; Piron, Jean Pierre; Sicard, Marielle; Villemus, Françoise; Vessigaud, Marie Aude; Sterkers-Artières, F.; Mondain, M.; Uziel, Alain

doi:10.1159/000369333

Cited by 30 publications

(31 citation statements)

References 39 publications

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“…Majority agrees that measuring the basal turn diameter which is also called as “A” value of the cochlea (Fig. 1A) from the pre-operative CT image of the cochlea, is relevant in estimating the full length of the cochlear duct length 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21. Escude et al 4 and Erixon et al 5 have proposed mathematical equations that involve “A” value as the input in estimating the CDL (LW) position, whereas the equations proposed by Alexiades et al 8 and Koch et al 22 estimates the CDL (OC) position.…”

Section: Methodsmentioning

confidence: 89%

Cochlear duct length along the outer wall vs organ of corti: Which one is relevant for the electrode array length selection and frequency mapping using Greenwood function?

Dhanasingh

2019

World j. otorhinolaryngol.-head neck surg.

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Cochlear duct length (CDL) measurement or estimation is a hot topic for various research groups in the cochlear implant (CI) field as of today. Getting the CDL along the outer wall (LW) and organ of corti (OC) is possible but considering the clinical application especially in the selection of the electrode array length and applying Greenwood's frequency function, we need to have a clear understanding on the CDL in general and as well on the Greenwood's frequency function. It is very clear from the histology images of the cochlea with straight electrode inside, that the electrode locates itself right under the basilar membrane. Also the Greenwood's frequency function involves a variable that corresponds to the CDL at the basilar membrane/organ of corti level. This brings us to conclude that the CDL at the OC is relevant for the selection of electrode array length and in applying Greenwood's frequency function. The ratio between CDL (LW) and CDL (OC) is 0.9 which is a very important number that needs to be remembered when converting CDL (LW) to CDL (OC).

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Section: Methodsmentioning

confidence: 89%

Cochlear duct length along the outer wall vs organ of corti: Which one is relevant for the electrode array length selection and frequency mapping using Greenwood function?

Dhanasingh

2019

World j. otorhinolaryngol.-head neck surg.

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“…Additionally, postimplantation custom frequency maps can be generated, whereby frequencies are programmed specific to the anatomy of the patient and the placement of their electrode array (Fitzgerald et al, 2006;Noble et al, 2014;Ali et al, 2015). Although research on the effect of fre-quency placed mismatching and the benefit of individualized image-based frequency map fitting is in its infancy, initial results are showing clinical relevance (Di Nardo et al, 2011;Hochmair et al, 2015;Venail et al, 2015;Meng et al, 2016). Image-guided CI programming approaches require the delineation of the electrode and BM in clinical CT.…”

Section: Discussionmentioning

confidence: 99%

Effects of object‐to‐detector distance and beam energy on synchrotron radiation phase‐contrast imaging of implanted cochleae

Rohani

Iyaniwura

Zhu

et al. 2018

Journal of Microscopy

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Summary Objectives To demonstrate that synchrotron radiation phase‐contrast imaging (SR‐PCI) can be used to visualize the intrascalar structures in implanted human cochleae and to find the optimal combination of the parameters object‐to‐detector distance (ODD) and beam energy (E) for visualization. Materials and Methods Three cadaveric implanted human temporal bones underwent SR‐PCI with varying combinations of parameters ODD (3, 2 and 1 m) and E (47, 60 and 72 keV). All images were then reconstructed to a three‐dimensional (3D) stack of slices. The acquired 3D images were compared using contrast‐to‐noise ratios (CNRs) of the basilar membrane (CNRitalicBM) and the electrode array (CNRE) and the standard deviation of the beam streaks (σS). Postprocessing calculations were performed using Matlab (Version 2017b, MathWorks Inc., Natick, MA, U.S.A.) with a standard significance level p < 0.05 to determine the most optimal combination of parameters. Results SR‐PCI with computed tomography reconstruction provided good visualization of the anatomical features of the implanted cochleae, specifically the exact location of the electrode with respect to the BM. A single‐factor ANOVA revealed a significant difference of variance for both CNRE and CNRBM, but failed to show significance for σS. A two‐sample t‐test failed to show any significant difference between CNRE columns of (3 m, 72 keV) and (2 m, 60 keV). The CNRBM was significantly different only at two pairs of columns, when (1 m, 72 keV) was compared against (2 m, 72 keV) and (3 m, 72 keV). Conclusions The results of this study show that SR‐PCI is a viable method to visualize implanted human cochleae. SR‐PCI is less invasive, less labour intensive and is associated with a much lower acquisition time compared to other methods for postimplantation imaging in humans, such as histological sectioning. We found that the optimal combination of E and ODD parameters was 72 keV and 2 m, respectively. These parameters resulted in high‐contrast images of the electrode as well as all internal structures of the cochleae. Lay Description Cochlear implants (CI) are currently the preferred method of treatment for hearing loss. Cochlear implantation surgery involves placement of a metallic, wire‐shaped electrode inside the cochlea, the main organ of the human hearing system. Knowledge of the exact location of the electrode after implantation is beneficial in improving the extent of restored hearing. Common clinical imaging modalities such as computed‐tomography (CT) are not ideal for providing such information, due to lack of resolution and streaking caused by the metallic electrode. Recent studies have developed algorithms to extract the electrode location from clinical computed‐tomography images and have been validated using histology or micro computed‐tomography (micro‐CT). Synchrotron radiation phase contrast imaging (SR‐PCI) is a high‐resolution imaging technique used to visualize small structures in three dimensions. Recently, SR‐PCI has been shown to be an alternative to histolog...

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“…Similarly, averaged insertion angle for the HiFocusV Mid-Scala electrode is 422° ± 20.7° (the Advanced Bionics website), again much smaller than that required for the full coverage even if at the SG anatomical level. On the other hand, the lateral wall electrodes such as Flex SOFT or Flex 28 with the length of 28 mm and 31 mm, respectively, have typical insertion angle of at least 640° and 530°, respectively, 14 , 15 sufficient to stimulate also the low frequency neurons. Based on this comparison, it is unlikely that the perimodiolar electrode arrays could stimulate the low-frequency neural fibres as effectively as the lateral wall electrodes in a simple pitch corresponding matter.…”

Section: Discussionmentioning

confidence: 99%

Challenging aspects of contemporary cochlear implant electrode array design

Mistrík

Jolly

Sieber

et al. 2017

World j. otorhinolaryngol.-head neck surg.

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ObjectiveA design comparison of current perimodiolar and lateral wall electrode arrays of the cochlear implant (CI) is provided. The focus is on functional features such as acoustic frequency coverage and tonotopic mapping, battery consumption and dynamic range. A traumacity of their insertion is also evaluated.MethodsReview of up-to-date literature.ResultsPerimodiolar electrode arrays are positioned in the basal turn of the cochlea near the modiolus. They are designed to initiate the action potential in the proximity to the neural soma located in spiral ganglion. On the other hand, lateral wall electrode arrays can be inserted deeper inside the cochlea, as they are located along the lateral wall and such insertion trajectory is less traumatic. This class of arrays targets primarily surviving neural peripheral processes. Due to their larger insertion depth, lateral wall arrays can deliver lower acoustic frequencies in manner better corresponding to cochlear tonotopicity. In fact, spiral ganglion sections containing auditory nerve fibres tuned to low acoustic frequencies are located deeper than 1 and half turn inside the cochlea. For this reason, a significant frequency mismatch might be occurring for apical electrodes in perimodiolar arrays, detrimental to speech perception. Tonal languages such as Mandarin might be therefore better treated with lateral wall arrays. On the other hand, closer proximity to target tissue results in lower psychophysical threshold levels for perimodiolar arrays. However, the maximal comfort level is also lower, paradoxically resulting in narrower dynamic range than that of lateral wall arrays. Battery consumption is comparable for both types of arrays.ConclusionsLateral wall arrays are less likely to cause trauma to cochlear structures. As the current trend in cochlear implantation is the maximal protection of residual acoustic hearing, the lateral wall arrays seem more suitable for hearing preservation CI surgeries. Future development could focus on combining the advantages of both types: perimodiolar location in the basal turn extended to lateral wall location for higher turn locations.

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Effects of Electrode Array Length on Frequency-Place Mismatch and Speech Perception with Cochlear Implants

Cited by 30 publications

References 39 publications

Cochlear duct length along the outer wall vs organ of corti: Which one is relevant for the electrode array length selection and frequency mapping using Greenwood function?

Cochlear duct length along the outer wall vs organ of corti: Which one is relevant for the electrode array length selection and frequency mapping using Greenwood function?

Effects of object‐to‐detector distance and beam energy on synchrotron radiation phase‐contrast imaging of implanted cochleae

Challenging aspects of contemporary cochlear implant electrode array design

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