Spiral Form of the Human Cochlea Results from Spatial Constraints

Pietsch, M; Dávila, Lukas Aguirre; Erfurt, Peter; Avci, Ersin; Lenarz, Thomas; Kral, Andrej

doi:10.1038/s41598-017-07795-4

Cited by 84 publications

(91 citation statements)

References 42 publications

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“…They argue that logarithmic models are good enough to predict the metric length of the cochlear duct, but fail to predict the details of the spiral shape. Therefore, they developed a polynomial model that requires assessment of the basic individual parameters of cochlear base width, length and their intersection by the modiolus 25 . Table 1.…”

Section: Discussionmentioning

confidence: 99%

Prediction of the Cochlear Implant Electrode Insertion Depth: Clinical Applicability of two Analytical Cochlear Models

Mertens

Rompaey

Heyning

et al. 2020

Sci Rep

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Although the spiral anatomy of the human cochlea seems evident, measuring the highly inter-variable true dimensions is still challenging. Today, only a few three-dimensional reconstruction models of the inner ear are available. Previously, spiral equations were applied to two-dimensional computed tomography (CT) images to predict the electrode insertion depth prior to cochlear implantation. The study aimed primarily to compare the clinical applicability of two analytical cochlear models using a recently introduced planning software to predict the insertion depth of the electrode array of 46 cochlear implant recipients. One was based upon the Escudé formula, which relies only on the basal turn diameter, and another based upon the Elliptic-Circular Approximation (ECA), using the diameter and width. Each case was measured twice by two ENT surgeons. Secondly, in order to measure the benefit of the new planning software over the use of the existing clinical routine method, the results were compared to the prediction based upon a two-dimensional CT image. The intra -and inter-observer agreement using the planning software was significantly better when the ECA was applied, compared to the Escudé formula (p < 0.01). As a reference, the predicted insertion depth was compared to the actual insertion depth measured on post-operative images. The mean absolute error was |2.36| (|1.11|) mm in case of the Escudé approach and |1.19| (|0.92|) mm in case of the ECA. The use of a new planning software that allows three-dimensional handling, integrating the diameter and width of the basal turn (ECA formula), resulted in the most accurate predictions of the electrode insertion depths.

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Section: Discussionmentioning

confidence: 99%

Prediction of the Cochlear Implant Electrode Insertion Depth: Clinical Applicability of two Analytical Cochlear Models

Mertens

Rompaey

Heyning

et al. 2020

Sci Rep

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“…The cochlea models were derived from parameters of the scala spine and cross-sectional areas previously used in studies, representing the whole cochlea size, producing a 50 µL model which was then scaled to create a 40 µL model 30,31 . These models reflected human total cochlear volume but did not implement a structure for the basilar membrane as there were no barriers between the scalae, allowing the electrode array to be positioned anywhere in the model.…”

Section: Electrocochleography (Ecochg) Recording and Analysis Ecochgmentioning

confidence: 99%

Four-point impedance as a biomarker for bleeding during cochlear implantation

Bester

Razmovski

Collins

et al. 2020

Sci Rep

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Cochlear implantation has successfully restored the perception of hearing for nearly 200 thousand profoundly deaf adults and children. More recently, implant candidature has expanded to include those with considerable natural hearing which, when preserved, provides an improved hearing experience in noisy environments. But more than half of these patients lose this natural hearing soon after implantation. To reduce this burden, biosensing technologies are emerging that provide feedback on the quality of surgery. Here we report clinical findings on a new intra-operative measurement of electrical impedance (4-point impedance) which, when elevated, is associated with high rates of postoperative hearing loss and vestibular dysfunction. In vivo and in vitro data presented suggest that elevated 4-point impedance is likely due to the presence of blood within the cochlea rather than its geometry. Four-point impedance is a new marker for the detection of cochlear injury causing bleeding, that may be incorporated into intraoperative monitoring protocols during CI surgery. The preservation of cochlear structure and residual functional hearing has become the standard of care for cochlear implantation (CI). Hearing preservation is important to facilitate combined electrical and acoustic stimulation of the cochlea, as this improves speech recognition in noise and music appreciation 1-4. Cochlear structural preservation will ensure that the ear is ready for future, regenerative therapies 5,6. Structural and functional preservation of the cochlea depends not only upon the electrode design, but also the surgery. Electrodes must be introduced into the cochlea without causing injury. Until recently, technologies have not existed to guide the surgeon during the implant procedure; the operation has been conducted "blind" without the provision of feedback. Over recent years, we and others have begun to monitor cochlear function during cochlear implantation 7-10 , using the CI's own electrodes to monitor the electrophysiological response of the ear to acoustic stimulation. This technique, known as electrocochleography, has provided valuable information to guide surgeons during the operation; if the electrophysiological response is preserved during surgery, residual hearing is better after implantation 7-10. This paper is motivated by a desire to increase the scope of intraoperative monitoring during CI surgery. Current methods allow real-time detection of cochlear dysfunction, but these do not assess cochlear injury directly. Here we report on a method that has this potential. We have monitored "four-point" electrical impedance (4PI) from the implant's intracochlear electrodes during CI surgery. This impedance measurement is acquired by passing current between two outer electrodes whilst the voltage (from which the impedance may be inferred) is measured between two inner electrodes (Fig. 1A). The method is believed to assess the bulk impedance between the two inner electrodes, and has been used to differentiate between tissue and fluid ...

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“…However, other taxa that spend more time in deeper waters, for example Pseudorca crassidens (false killer whale) and Tursiops truncatus, also occupy this region of morphospace, indicating that additional factors are also in play, although they may also frequent shallower waters or have coastal ecotypes (Jefferson, Webber & Pitman, 2015). Previous studies have also suggested that constraints on cochlear morphology are strong, due to several factors including frequency propagation (Manoussaki et al, 2008), spatial constraints (Pietsch et al, 2017), and its vital importance for survival in odontocetes (Ketten,1992a). As such the capacity for elaboration or innovation in cochlear shape may be limited, which could force all odontocete cochleae to fall within the same limited morphospace.…”

Section: Discussionmentioning

confidence: 99%

Peer Review #2 of "Intraspecific variation in the cochleae of harbour porpoises (Phocoena phocoena) and its implications for comparative studies across odontocetes (v0.1)"

2020

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Spiral Form of the Human Cochlea Results from Spatial Constraints

Cited by 84 publications

References 42 publications

Prediction of the Cochlear Implant Electrode Insertion Depth: Clinical Applicability of two Analytical Cochlear Models

Prediction of the Cochlear Implant Electrode Insertion Depth: Clinical Applicability of two Analytical Cochlear Models

Four-point impedance as a biomarker for bleeding during cochlear implantation

Peer Review #2 of "Intraspecific variation in the cochleae of harbour porpoises (Phocoena phocoena) and its implications for comparative studies across odontocetes (v0.1)"

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