Effects of aminoglycoside administration on cochlear elements in human temporal bones

Area of Science:

• Ototoxicology
• Auditory Neuroscience
• Histopathology

Background:

• Aminoglycoside antibiotics are widely used but known for ototoxicity in animal models.
• Human studies on the specific cochlear effects of aminoglycosides are limited.
• Understanding these effects is crucial for patient safety and treatment protocols.

Purpose of the Study:

• To investigate the early and late cochlear effects of aminoglycoside administration in humans.
• To examine the impact on hair cells, spiral ganglion cells, stria vascularis, and spiral ligament.
• To establish a human correlate to animal studies on aminoglycoside ototoxicity.

Main Methods:

• Temporal bones from three groups were analyzed: controls, recent aminoglycoside exposure (within 2 weeks), and prolonged exposure (2 weeks to 6 months).
• Histopathological examination, cytocochleograms, spiral ganglion cell reconstructions, and morphometric measurements of stria vascularis were performed.
• Patients receiving specific aminoglycosides (gentamicin, kanamycin, tobramycin) without other ototoxic exposures or ear diseases were included.

Main Results:

• A significant decrease in intact outer hair cells in the basal turn was observed in both recent and prolonged aminoglycoside exposure groups compared to controls.
• The mean area of the stria vascularis in the apical turn was significantly reduced in the aminoglycoside-exposed groups.
• These findings indicate structural changes in the cochlea following aminoglycoside treatment.

Conclusions:

• Aminoglycoside administration leads to a reduction in hair cells and stria vascularis area, observable even within two weeks.
• The study highlights the ototoxic potential of aminoglycosides in humans.
• Early detection and monitoring of cochlear changes are important for patients receiving these drugs.