Remodelling of the small bones in the middle ear leading to conductive hearing loss
Usually presents before the age of 40
It is more common in women - may be precipitated by pregnancy in those who are genetically predisposed.
The development of otosclerosis is thought to result from a combination of environmental and genetic factors, although the exact mechanism is not understood. It can be inherited in an autosomal dominant pattern. However, no specific genetic mutations have been identified.
Otosclerosis may be precipiated by pregnancy in those who are genetically predisposed
Conduction throught the middle ear - M - I - S - Oval window of the chochlea. Cochlea converts these sound waves into sensory signals
In patients with otosclerosis, these tiny bones in the middle are affected by abnormal bone remodelling and formation. This mainly affects the base of the stapes, where it attaches to the oval window, causing stiffening and fixation and preventing it from transmitting sound effectively. It causes conductive hearing loss.
Typical presentation is of a 40 year old with unilateral or bilateral:
It tends to affect the hearing of lower-pitched sounds more than higher-pitched sounds. Female speech may be easier to hear than male speech (due to the generally higher pitch). This is the reverse of the pattern seen in presbycusis.
Due to conductive hearing loss with intact sensory hearing, the patient can experience their voice as being loud compared to the environment (due to bone conduction of their voice). This can lead to them talking quietly.