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

The cause of otosclerosis is unknown, but there appears to be a hereditary component, meaning it can be 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 U.S. population. It is a disorder that gets worse slowly, usually beginning in early to mid- adulthood. It is more common in women than in men. Otosclerosis usually affects both ears.

Otosclerosis can lead to not only conductive hearing loss, but to nerve loss as well.

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