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Cranial Neuropathies I, V, and VII–XII
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
The cochlea has the shape of a tapering helix. Inside, portions of the membranous labyrinth (vestibular and basilar membranes) divide this spiraling tunnel structure into three channels called scalae. The scala vestibuli and scala tympani are filled with perilymph and are contiguous at the tip of the cochlea in a part called helicotrema, whereas the scala media (also known as cochlear duct) lies between the other two scalae, is filled with endolymph, and contains the organ of Corti.
Cochlear Implants
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Andrew Marshall, Stephen Broomfield
In early ossification, it is usually possible to drill through the immature bone and identify the cochlear duct in the more distal basal turn. If this is not the case and the cochlear duct cannot be identified, the surgeon may opt to insert the electrode into the drilled-out channel (partial insertion), or to consider a dual-array electrode, drilling a further channel anterior to the oval window to access the middle turn of the cochlea. In the significantly ossified cochlea the results can be difficult to predict.60 In completely ossified cochleas, it may be necessary to consider an auditory brainstem implant (ABI) in place of CI.
The ear, nose and sinuses
Published in Professor Sir Norman Williams, Professor P. Ronan O’Connell, Professor Andrew W. McCaskie, Bailey & Love's Short Practice of Surgery, 2018
Professor Sir Norman Williams, Professor P. Ronan O’Connell, Professor Andrew W. McCaskie
The cochlea is a coiled shell of two and three-quarter turns. Within the cochlea is a spiral structure called the cochlear duct (Figure46.3) containing endolymph that is partitioned by Reissner’s membrane from the perilymph of the scala vestibuli, which joins the round window and the basement membrane from the perilymph of the scala tympani, which joins the oval window and stapes footplate. The endolymph has a high concentration of potassium, similar to intracellular fluid, and the perilymph has a high sodium concentration and communicates with the cerebrospinal fluid (CSF). Maintenance of the ionic gradients is an active process and is essential for neuronal activity.
Experimental drugs for the prevention or treatment of sensorineural hearing loss
Published in Expert Opinion on Investigational Drugs, 2023
Judith S Kempfle, David H. Jung
Each SGN only contacts one hair cell, but multiple SGNs can be in contact with a single hair cell. This allows for frequency selectivity along the cochlear duct [15]. These primary afferent (Type I) neurons comprise roughly 95% of the cochlear SGN population. A small subgroup of neurons (Type II) are efferent neurons reaching the outer hair cells [16,17]. Several subtypes of Type I afferent neurons with different thresholds and response rates contribute to tuning at the same frequency [18]: Low threshold, high-spontaneous rate (SR) neurons; high threshold, low SR neurons; and neurons with intermediate response patterns all contribute to hearing at a given frequency. High threshold, low SR fibers may be particularly relevant for sound perception in background noise, while low threshold, high SR fibers may be important for sensitivity of sound detection [19]. All the sensory and non-sensory cells within the membranous labyrinth of the inner ear are susceptible to damage and aging to varying degrees. From a clinicopathological standpoint, loss of OHCs has been associated with decreases in threshold detection, while IHC and SGN loss has been associated with decreases in clarity of sound detection, as measured by word recognition [20].
Comparison of furosemide-loading cervical vestibular-evoked myogenic potentials with magnetic resonance imaging for the evaluation of endolymphatic hydrops
Published in Acta Oto-Laryngologica, 2020
Ko Shiraishi, Noriko Ohira, Takaaki Kobayashi, Mitsuo Sato, Yasuhiro Osaki, Katsumi Doi
The MRI data were evaluated by two specialized neurotologists, who were blinded to the clinical progress of the patients. Differences in their evaluations were resolved by discussion until a final decision was reached. The degree of EH in the vestibule and cochlea was assessed by visual comparison of the hypointense signal areas of each part (cochlea, saccule, utricle) of the endolymphatic space versus the hyperintense signal of the perilymphatic space in the axial plane according to the criteria reported by Kahn et al. [13]. The degree of cochlear hydrops was categorized as none or grade I, when the area of the endolymphatic space exceeded the area of the scala vestibule. We did not consider the cochlear duct to be pathological when its area was less than that of the scala vestibule, because 30% of healthy subjects may present with this finding. The degree of saccular hydrops was defined as none; grade I, when the saccule appeared larger or equal to the utricle, surrounded by perilymphatic space; or grade II, when the saccule touched the oval window, without surrounding perilymphatic space. The degree of utricular hydrops was defined as none; grade I, herniation of the utricle in the nonampullated part of the lateral semicircular canal; or grade II, when there was no surrounding perilymphatic space.
Hearing preservation cochlear implantation in children: The HEARRING Group consensus and practice guide
Published in Cochlear Implants International, 2018
Gunesh Rajan, Dayse Tavora-Vieira, Wolf-Dieter Baumgartner, Benoit Godey, Joachim Müller, Martin O'Driscoll, Henryk Skarzynski, Piotr Skarzynski, Shin-Ichi Usami, Oliver Adunka, Sumit Agrawal, Iain Bruce, Marc De Bodt, Marco Caversaccio, Harold Pilsbury, Javier Gavilán, Rudolf Hagen, Abdulrahman Hagr, Mohan Kameswaran, Eva Karltorp, Martin Kompis, Vlad Kuzovkov, Luis Lassaletta, Li Yongxin, Artur Lorens, Manikoth Manoj, Jane Martin, Griet Mertens, Robert Mlynski, Lorne Parnes, Sasidharan Pulibalathingal, Andreas Radeloff, Christopher H. Raine, Ranjith Rajeswaran, Joachim Schmutzhard, Georg Sprinzl, Hinrich Staecker, Kurt Stephan, Serafima Sugarova, Mario Zernotti, Patrick Zorowka, Paul Van de Heyning
It is now widely recognized that successful outcomes in HPCI are influenced by various patient, surgical, and electrode array variables. Several patient factors such age, the genetics of the hearing loss, and the cochlear duct anatomy are known to impact hearing preservation. Other patient factors such as the intrinsic inflammatory and immunologic responses to cochlear implantation also appear to alter hearing preservation outcomes (selected bibliography in Table A1). Various contributing surgical factors such as steroid use, atraumatic surgical techniques at the round window/cochleostomy site and electrode array insertion have been investigated and found to affect hearing preservation (Kiefer et al., 2004; Rajan et al., 2013; Havenith et al., 2013; Rajan et al., 2012; Wanna et al., 2015; VanSkarzysnki et al., 2007; Sun et al., 2015; Van de Water et al., 2010; Table A1). Similarly, electrode array properties such as stiffness, surface architecture and coating have been shown to affect atraumaticity (Todt et al., 2016; Wanna et al., 2015; Nordfalk et al.; 2016; Wanna et al., 2014; Causon et al., 2015; Table A1).