Pathology of hair cells and neurones
Overview / Aminoglycosides / Noise Trauma / Excitotoxicity / Presbycusis / Tinnitus
Pictures : M. Lenoir

Aminoglycoside ototoxicity

Antibiotics from the aminoglycoside family have been known for years to cause severe damage to the organ of Corti, especially to hair cells in a dose-dependent manner. Firstly OHCs in the first row of the basal turn of the cochlea are affected, then progressively the other rows of OHCs and then the IHCs: the damage progresses towards the apex of the cochlea. The following set of scanning electron microscopy (SEM) pictures from the surface of the organ of Corti summarises an aminoglycoside antibiotic poisoning of the rat cochlea.

M. Lenoir
SEM picture of the rat organ of Corti. Normal organisation, with 1 row of IHCs (top) and 3 rows of OHCs (bottom).

scale bar: 12 µm
Progressive damage of hair cells

M. Lenoir
The loss of hair cells begins with OHCs from the first row in the basal turn.

In humans, such a cochlea would show a mild hearing loss with speech discrimination problems.

scale bar: 16 µm

M. Lenoir
At higher dosage, the aminoglycoside kills almost all OHCs, thus destroying their function (active mechanism).
In humans, such an organ of Corti would show a 60 dB threshold shift and no fine tuning. A hearing aid would easily restore the gain (loudness), but not the frequency selectivity (discrimination).

scale bar: 16 µm

M. Lenoir

At even higher doses, all hair cells are missing (red arrow points to two giant stereocilia on a damaged IHC).

This organ of Corti would no longer respond to any sound stimulation.

scale bar: 10 µm


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