Definition of Otosclerosis:

Otosclerosis is an abnormal bone growth in the middle ear that causes hearing loss.

Causes, incidence, and risk factors:

Otosclerosis is an inherited disorder, which means it is passed down through families. In this condition, an abnormal sponge-like bone grows in the middle ear. This growth prevents the ear from vibrating in response to sound waves -- which must happen in order for you to hear. This lack of vibration leads to hearing loss that continues to get worse with time.

Otosclerosis is the most frequent cause of middle ear hearing loss in young adults. It affects about 10% of the population of the United States, and is most common seen in women ages 15 to 30. Otosclerosis usually affects both ears.

Risks include pregnancy (which may trigger onset) and a family history of hearing loss. Caucasians are more susceptible than others to otosclerosis.