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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.
Stem Cells and Nanotechnology
Published in Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm, Advances in Audiology and Hearing Science, 2020
The human inner ear is divided into two main parts, the auditory system (the cochlea) and the vestibular system. The cochlea is a bony spiral canal, about 30-mm long and divided into three fluid-filled compartments, the scala tympani, the scala media, and the scala vestibuli. The round window membrane (RWM) and the blood inner ear barrier (BB) are two physical barriers that isolate the cochlea, respectively, from the middle ear and from the circulatory system. The RWM is a three-layer semipermeable membrane, composed of an outer epithelial cell layer, a middle connection layer, and an inner connection layer facing the perilymph of the scala tympani (Banerjee and Parnes, 2004). In humans, the variable thickness of RWM affects the response of patients to DD treatments. In animal models, its thickness is different among species but its composition is similar (Goycoolea and Lundman, 1997).
Auditory Brainstem Implantation
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
Shakeel R. Saeed, Harry R.F. Powell
Outcomes of ABI are far more variable than outcomes of CI. CI placement in the scala tympani naturally guides the array around the cochlear turns close to the spiral ganglion neurons with presumed tonotopic organization. Comparatively uncertain positioning in the lateral recess of the fourth ventricle adjacent to the cochlear nucleus is then reliant on patient perception and feedback of auditory tones with pitch ranking for subsequent programming of the ABI. Patient factors, either NF2/tumour-related or from concurrent medical problems, may cause disabilities that interfere with programming and auditory habilitation. Intra-operative factors from mechanical or ischaemic damage to the cochlear nucleus or brainstem are also likely to influence outcomes.21 Furthermore, habilitation and performance take longer with ABI and may not plateau for several years5 compared to several months for most CI users.
The applications of targeted delivery for gene therapies in hearing loss
Published in Journal of Drug Targeting, 2023
Melissa Jones, Bozica Kovacevic, Corina Mihaela Ionescu, Susbin Raj Wagle, Christina Quintas, Elaine Y. M. Wong, Momir Mikov, Armin Mooranian, Hani Al-Salami
The complex structure of the mammalian ear is divided into three primary sections, classified as the outer, middle, and inner ear, with all parts required to work in an organised, controlled synergistic nature for hearing to occur. Focus here will be on the inner ear, which has roles in both hearing and balance [38]. The inner ear contains the cochlea where auditory signals are transduced. Located within the cochlea are three ducts, termed the scala vestibule, scala media, and scala tympani. Within the scala media of the cochlea, the organ of Corti is positioned, with the primary function of transducing auditory signals. The organ of Corti contains both inner and outer hair cells, being mechanosensory hair cells arranged in rows, with three rows of outer hair cells and one row of inner hair cells in the luminal half of the organ. Also located within are supporting cells of a non-sensory nature, positioned throughout the basement membrane to the luminal surface in a highly organised pattern [23,39,40].
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.