Types of Hearing Impairment
A conductive type of hearing impairment occurs when sound is not conducted efficiently through the ear canal, eardrum or tiny bones of the middle ear. Conductive losses reduce the loudness of sound that is heard. Frequent colds, allergies or certain childhood illnesses may cause a blockage of sound due to fluid in the middle ear and may lead to temporary hearing loss or permanent damage. Buildup of wax, inflammation or infection in the ear canal, heredity and birth defect also may cause conductive hearing loss.
A sesorineural type of hearing impairment occurs when there is damage to the inner ear or to the nerve pathways from the inner ear to the brain. Sesorineural losses usually involve both reductions in sound level and speech understanding. The aging process, heredity, birth defects, certain drugs, head injuries, tumors and exposures to loud noise can lead to this type of hearing loss.
A mixed type of hearing loss is the combination of conductive and sesorineural types. For example, a child with a hereditary sesorineural loss may still develop infections or other ear diseases.
A central type of hearing impairment occurs when auditory centers of the brain are affected by injury, disease, tumor, heredity or unknown causes. Loudness of sound is not necessarily affected, but understanding speech is.