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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.
Paediatric Implantation Otology
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
James Ramsden, Payal Mukherjee
The ideal position of the electrode is within the scala tympani where it sits close to the neural elements. Disruption of the basilar membrane by traumatic insertion or displacement into the scala vestibuli causes complete loss of residual hearing and may lead to worse outcomes.4 Electrodes can be modiolar hugging (e.g. Cochlear Contour), Midscala (e.g. Advanced Bionics Midscala electrode) or lateral wall (e.g. MED-EL FLEX electrode).
Restoration: Nanotechnology in Tissue Replacement and Prosthetics
Published in Harry F. Tibbals, Medical Nanotechnology and Nanomedicine, 2017
The chambers on either side of the cochlear duct are filled with an electrolyte solution that conducts sound from the oval window, to which the stapes is attached, into the scala vestibuli. When pressure waves travel through the upper side of the cochlear duct to the apex of the spiral, and down the lower side, the duct is compressed by the fluid, causing movements of the cell hairs. The shearing movement of the hair cells opens potassium ion channels in hair cell membranes, depolarizing the cells and initiating an electrical signal.
Electrode array positioning after cochlear reimplantation from single manufacturer
Published in Cochlear Implants International, 2023
Miriam R. Smetak, Shanik J. Fernando, Matthew R. O'Malley, Marc L. Bennett, David S. Haynes, Christopher T. Wootten, Frank W. Virgin, Robert T. Dwyer, Benoit M. Dawant, Jack H. Noble, Robert F. Labadie
The scalar location has a significant impact on audiometric outcomes. Translocation through the basilar membrane from the scala tympani (ST) into the scala vestibuli (SV) increases intracochlear trauma and negatively impacts hearing outcomes, even in the case of full SV insertion (Chakravorti et al., 2019; O'Connell, Cakir, et al., 2016). Mechanical damage from complete or partial SV insertion leads to loss of ganglion cells and residual hearing is less likely to be preserved (O'Connell, Cakir, et al., 2016). Additionally, distribution of electrical current pathways may be altered, leading to cross-turn stimulation (stimulation of ganglion cells of the next, more apical cochlear turn), causing pitch confusion and decreasing speech perception (Finley et al., 2008; O'Connell, Cakir, et al., 2016).
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
The cochlea, a portion of the inner ear, is a snail-shaped, fluid-filled compartment within the petrous portion of the temporal bone. It is divided into three chambers, two of which, the scala tympani, and scala vestibuli, are filled with perilymph (resembling cerebrospinal fluid and low in potassium chloride and high in sodium chloride), and the scala media, which contains endolymph (high in potassium chloride and low in sodium chloride). The scala media also harbors the cochlear duct, which is home to the organ of Corti with the sensory cells (hair cells) of the cochlea (Figure 1). Its unique structure allows frequency tuning along the cochlear axis – high frequencies are perceived at the base, while low frequencies are detected at the apex [10]. Along the organ of Corti, one row of inner hair cells and three rows of outer hair cells are flanked by nonsensory supporting cells and connect to the peripheral neurites of spiral ganglion neurons (SGNs). The cell bodies of the SGNs are located in Rosenthal’s canal, and their central axons project along the modiolus to the brainstem (Figure 1). Approximately 25 000 to 33 000 SGNs are found in the modiolus and connect with 3 500 inner and 12 000 outer hair cells [11].
Cochlear implantation through intracochlear fibrosis: A comparison of surgical techniques
Published in Cochlear Implants International, 2023
Anne K. Maxwell, Jacob B. Kahane, Rahul Mehta, Moises A. Arriaga
Cochlear ossification in labyrinthitis ossificans is known to occur most commonly in the basal turn of the scala tympani, typically sparing the scala vestibuli.2 Fibrosis was encountered in a similar distribution, with fibrosis of basal turn most frequently noted. Three of our patients had fibrosis limited to the proximal basal turn allowing complete removal with microdissection, permitting subsequent insertion of a non-styleted lateral wall electrode into a patent scala tympani. Those with more extensive fibrosis required dilation with a depth gauge and/or angiocatheter prior to electrode implantation. It may be possible to insert a styleted electrode through dense fibrosis without initial dilation and remove the stylet after full insertion. However, we chose instead to dilate first in order to limit mechanical forces that could potentially bend or otherwise damage the delicate electrode wires.