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. 2026 Jun 10;17:1823729. doi: 10.3389/fphar.2026.1823729

FIGURE 1.

Labeled diagram of inner ear anatomy on the left illustrates semicircular canals, cochlear duct, cochlea, and membranous versus bony labyrinth. The right panel contains a cochlear cross-section highlighting the organ of Corti, a schematic of hair cell arrangement, a color-coded graphic showing aminoglycoside damage gradient from cochlear base to apex, a bar illustrating cumulative dose-dependent damage zones from base to apex, a line graph summarizing audiometric hearing loss patterns, and a box with clinical monitoring and vulnerability notes.

Anatomy of the Inner Ear and Organ of Corti Relevant to Aminoglycoside Ototoxicity. (A) The membranous labyrinth (purple) is housed within the bony labyrinth (pale blue) and comprises the cochlea, semicircular canals, utricle, saccule, and endolymphatic sac. The cochlea transduces sound-induced vibrations into neural signals transmitted via the cochlear nerve; the semicircular canals and otolithic organs (utricle and saccule) subserve vestibular function. Both the endolymph and perilymph compartments accumulate aminoglycosides following systemic administration. (B) Cross-section through one cochlear turn showing the three fluid-filled scalae (scala vestibuli, scala media, scala tympani), Reissner’s membrane, the tectorial membrane, the basilar membrane, and the organ of Corti containing the mechanosensory hair cells. A single row of IHCs and three rows of OHCs are arranged along the full length of the basilar membrane. MET channels at the tips of the stereocilia admit K+ and Ca2+ upon deflection, depolarizing the hair cell and initiating afferent signaling. The unrolled basilar membrane schematic (center) illustrates the tonotopic arrangement of three OHC rows and one IHC row (amber, ×1) from the high-frequency cochlear base to the low-frequency apex, with audiometric frequency positions mapped to cochlear location using the Greenwood function. Colour coding of the OHC rows reflects cumulative aminoglycoside-induced hair cell loss by exposure zone: dark red (>8 kHz; basal outer hair cells, lost at low cumulative doses), orange (4–8 kHz; moderate cumulative doses), and amber (≤2 kHz; high cumulative doses, with onset of IHC involvement). The representative audiogram (lower left) illustrates the characteristic high-frequency-first pattern of aminoglycoside-induced hearing threshold elevation compared with normal hearing. OHC loss in mammals is irreversible. Aminoglycoside-induced vestibulotoxicity additionally affects hair cells of the crista ampullaris at the base of each semicircular canal. Abbreviations: IHC, inner hair cell; MET, mechanoelectrical transduction; OHC, outer hair cell; SCC, semicircular canal. Created in BioRender. Bitner-Glindzicz et al. (2009) https://BioRender.com/d58o4vz.