Auditory Science Lab

Hearing loss

The following pictures illustrate varying types of damage to the sensory cells of the cochlea caused by noise or drug exposure which result in a loss of hearing.

Sensory surface of the normal organ of Corti. Three rows of outer haircells and one row of inner hair cells are seen.Mildly damaged outer haircell. Stereocillia are somewhat disarrayed, linkages between them are at least partially damaged impairing the function of the cell.A mildly damaged inner haircell. Stereocillia are slightly disordered and several have fused together to form a "giant" stereocilium.

Severely damaged outer haircells. To the left a missing haircell has been replaced by ingrowing supporting cells. To the right are two haircells with stereocillia which are totally fused and/or disintegrating. It is highly improbable that these cells serve any active function.

In these severely damaged outer haircells the cuticular plate, into which the stereocillia are anchored, has been ejected from the cell.

A severely damaged organ of Corti demonstrating an often seen sequence of haircell damage resulting from either noise trauma or ototoxic drugs.

First row outer haircells are most susceptible to many types of cochlea insult with second and third row outer haircells showing decreasing degrees of sensitivity.

Inner haircells frequently survive in regions of the cochlea devoid of any outer haircells. While this pattern of damage is common other patterns or a lack of pattern can often be found.

The edge of a lesion to the organ of Corti produced by severe sound trauma. To the left some structure can be identified. Inner hair cells remain, however outer hair cells have been totally destroyed and their positions occupied by ingrowing supporting cells. On the right of the micrograph only the basillar membrane can be seen, all organ of Corti structure has been destroyed.

Copying and use of these images is permitted for any non-commercial use with the understanding that, in all instances, the Auditory Science Lab at The Hospital for Sick Children will be credited.