How otosclerosis causes deafness

In the normal ear sound waves pass down the ear canal and cause the eardrum to vibrate.  Attached to the eardrum is a small bone called the malleus (hammer). The malleus is the first of the three tiny bones found in the middle ear which are joined together forming a chain. 


How do I know if Iíve got otosclerosis?

Otosclerosis is usually easily diagnosed by a simple inspection of the ear drum and a hearing test.  It is important that the hearing test measures both the actual hearing (air conduction) and the hearing reserve (bone conduction). If there are any concerns it is always worthwhile requesting a referral to an ENT surgeon (Ear, Nose & Throat Specialist).  Sometimes the specialist may also order a scan of the ear if the diagnosis is in doubt. You may also have other tests to measure the pressure of the eardrum and special hearing test called a speech audiogram.


Normal Ear Drum

The chain of bones conducts the vibration from the eardrum to the inner ear. The inner ear is a fluid filled structure which is coiled like a snails shell and transforms the vibrations of the sound waves into nerve impulses which are then sent to the hearing centre in the brain. The final hearing bone in the chain is the stapes (stirrup). Normally this is able to move freely but in otosclerosis this bone can become fixed so that little or no movement is possible.  This causes a block in the transmission of the sound waves and deafness results.


Frequency / Hz

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