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Sound vibrations are collected by the outer portion of the ear and funneled down the ear canal towards the eardrum. The sounds are then transmitted through three tiny bones in the middle ear called the ossicles. These three bones are named the malleus, incus, and stapes. The stapes carries the sound vibration into the fluids of the inner ear, called the cochlea.

If the bones of the middle ear do not carry the sound to the inner ear correctly, hearing loss results. This can happen if the bones are not connected together properly (either fused together or separated apart). One cause of this problem is a disease called otosclerosis. Also, trauma or infection can lead to problems with the middle ear bones, called ossicular chain discontinuity. Some children are born with malformed middle ear bones that don’t conduct sound properly.

Otosclerosis is the abnormal growth of bone in the ear. This can fix the stapes bone in place, preventing it from transmitting sound vibrations properly. For some people with otosclerosis, the hearing loss may become severe. The cause of otosclerosis is not fully understood, although research has shown that it tends to run in families. The disorder usually affects both ears and commonly starts in adults during their 20s and 30s. The hormonal changes that occur during pregnancy often accelerate the hearing loss.

Hearing loss is the most frequent symptom. The loss may appear very gradually. Many people first notice that they cannot hear low-pitched sounds or that they can no longer hear a whisper. In addition to hearing loss, some people may experience tinnitus. Tinnitus is a sensation of ringing, roaring, buzzing, or hissing in the ears or head that accompanies many forms of hearing loss.

Management strategies include observation, hearing aids or surgery.

Keck Medicine of USC is the University of Southern California’s medical enterprise, one of only two university-owned academic medical centers in the Los Angeles area.