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Sensorineural Hearing Loss
Published in R James A England, Eamon Shamil, Rajeev Mathew, Manohar Bance, Pavol Surda, Jemy Jose, Omar Hilmi, Adam J Donne, Scott-Brown's Essential Otorhinolaryngology, 2022
Linnea Cheung, David M. Baguley, Andrew McCombe
Table 14.2 summarises known ototoxic agents and their mechanisms of action. These agents enter the inner ear through various mechanisms where they can cause damage. Entry is predominantly via the blood supply into the perilymph, although the precise mechanism of diffusion across this blood-perilymph barrier is unknown. Endolymph can be accessed via perilymph through selectively permeable membranes and tight junctions between adjacent cells. Diffusion can also occur via the round and oval windows from the middle ear. Any hearing deficit caused by hair cell loss is usually permanent as the organ of Corti cannot spontaneously regenerate hair cells
Noise, hearing and vibration
Published in Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol, Handbook of Aviation and Space Medicine, 2019
Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol
Inner ear: Cochlea Fluid-filled tube divided into three cavities (scala media, scala tympani and scala vestibuli).Basilar membrane forms a partition between the scala media and scala tympani, contains the Organ of Corti.Organ of Corti contains approximately 20,000 hair cells; hair-like projections (stereocilia) attached.Hair cells respond based on sound frequency; create signals that become nerve impulses.Vestibular system: Utricle, saccule, three semicircular canals.Semicircular canals respond to angular acceleration; utricle and saccule respond to linear acceleration (control posture and balance).
Special Senses
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Kenneth A. Schafer, Oliver C. Turner, Richard A. Altschuler
Hair cells, particularly the outer hair cells, are commonly lost as a consequence of a variety of stresses to the cochlea, including ototoxic drugs, noise overstimulation, diseases, genetic disorders, and aging, and in mammals, the loss is permanent. A scattered loss of outer hair cells can be expected in the organ of Corti of control laboratory animals and in humans with normal hearing. This loss is most often in the basal half of the cochlea, and in the first row of outer hair cells. The most apical cochlea also commonly has confined regions where outer hair cells are absent; however, this is a consequence of disorganization of the outer hair cells in this most apical region rather than being initially present and then lost. Recently loss of outer hair cells in the apical region of the cochlea has been appearing in several commercial guinea pigs strains. This is a region that cannot be screened by ABR to eliminate these animals from study before inclusion, because of the very low frequency stimulation needed to elicit response in this region. Because this apical loss is most often bilateral, one ear can be used as untreated control if the test article is applied unilaterally, but this cannot be done if there is systemic or bilateral application.
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].
Is tinnitus an early voice of masked hypertension? High masked hypertension rate in patients with tinnitus
Published in Clinical and Experimental Hypertension, 2019
Taylan Gun, Selçuk Özkan, Bunyamin Yavuz
Tinnitus, which affects 17% of the general population and is seen in 33% of the elderly population, constitutes the primary symptom for 60% of patients presenting to the audiology department (1,2). Tinnitus is defined as the perception of sound without an external stimulus (3). It is known that tinnitus the pathophysiology of which is not fully understood and the assessment of which is, for this reason, difficult may accompany almost all disorders occurring in the hearing system (4). The hearing system has a complex structure consisting of the organ of Corti, afferent and efferent conduction pathways, cortical hearing center and connections providing integration of these. Pathologies developing in any part of these connections lead to increased perception of sound with unknown mechanisms (5).
The involvement of liquid crystals in multichannel implanted neurostimulators, hearing and ENT infections, and cancer
Published in Acta Oto-Laryngologica, 2019
Chouard Claude-Henri, Christiane Binot, Jean-François Sadoc
Since Bekezy’s work on the traveling wave, it has been known that acoustic signals from the external environment induce, via the ossicles and the stapes, in particular, a perilabyrinthine fluid wave running the length of the spiraling hairpin groove in which they lie. Acoustic information is transmitted to the outer and inner hair cells and auditory neurons comprising the organ of Corti, which is separated from these fluids by only a fine osteomembranous septum closing the bony groove in which the vibration is propagated. From the stapes to the tip of the cochlea, the successive shapes of the groove act as a frequency analyzer with a range meeting any acoustic input, transforming the long ribbon which is the organ of Corti, from the apex to the base of the cochlea, into a cochlear ‘keyboard,’ from low to high frequencies. The shape of this wave, however, would be too weak, fuzzy and nonselective if the information it carries were not refined and boosted by the three rows of outer hair cells (OHC) before passing to the inner hair cells (IHC); these are fewer in number, in a single row, and are almost alone in synapsing with the afferent auditory neurons that transmit the information up to the auditory cortical centers.