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Aminoglycoside-induced cochlear pathology in man
Abstract:
Temporal bones from five patients with hearing loss as a result of aminoglycoside treatment were examined by the method of microdissection and surface preparations, followed by celloidin embedding and serial sectioning of the modiolus. Three patients had received the newer antibiotics, gentamicin, tobramycin, and amikacin; the other two neomycin. In the cochleas from two patients of the first group there was only a small loss of hair cells, restricted to the lower end of the basal turn. The third, who had been treated with several antibiotics over a longer period of time, showed more extensive but strikingly asymmetrical patterns of degeneration in the two ears. This patient, as well as the fourth, who had received neomycin during peritoneal lavage, had numerous patchy areas of complete disappearance of Corti's organ in the basal turn, with incipient degeneration of the distal ends of the nerve fibers in adjacent portions of the osseous spiral lamina. The fifth patient, who had become deaf after prolonged treatment with neomycin by mouth, showed a complete loss of cochlear hair cells. Nerve fibers were present only in the middle and upper turns, where supporting cells remained. Midmodiolar sections showed a proportionately much greater loss of the distal than of the proximal processes of the cells of the spiral ganglion. These findings underscore once again the special hazard for the inner ear that is associated with the clinical use of neomycin, regardless of the route of administration.
Insights
Aminoglycoside antibiotics can cause hearing loss by damaging inner ear hair cells. Neomycin, in particular, poses a significant risk to hearing, even with varied administration routes.
Area of Science:
- Ototoxicity research
- Auditory neuroscience
- Pharmacology
Background:
- Aminoglycosides are crucial antibiotics for treating severe bacterial infections.
- Hearing loss is a known, yet variable, side effect of aminoglycoside therapy.
- Understanding the precise mechanisms of aminoglycoside-induced ototoxicity is vital for patient safety.
Observation:
- Temporal bones from five patients with aminoglycoside-induced hearing loss were analyzed.
- Histological examination focused on the cochlea and spiral ganglion.
- Specific aminoglycosides studied included gentamicin, tobramycin, amikacin, and neomycin.
Findings:
- Damage patterns varied, with some patients showing minimal hair cell loss and others extensive degeneration of Corti's organ.
- Neomycin exposure, regardless of administration route, was associated with severe hair cell loss and spiral ganglion neuron damage.
- Degeneration was often concentrated in the basal turn of the cochlea, affecting nerve fibers and supporting cells.
Implications:
- Neomycin presents a substantial ototoxic risk, necessitating careful monitoring and consideration of alternative therapies.
- The findings highlight the need for individualized risk assessment in patients undergoing aminoglycoside treatment.
- Further research into protective strategies against aminoglycoside-induced hearing loss is warranted.