Types of Hearing Loss - Conductive, Sensorineural, & Processing Disorders

Hearing loss can be categorized by where or what part of the auditory system is damaged. There are three basis types of hearing loss, conductive hearing loss, sensorineural hearing loss and central auditory processing disorders.

Conductive Hearing Loss

Conductive hearing loss occurs when sound is not conducted efficiently through the outer and middle ears, including the ear canal, eardrum, and the tiny bones, or ossicles, of the middle ear. Conductive hearing loss usually involves a reduction in sound level, or the ability to hear faint sounds. This type of hearing loss can often be corrected through medicine or surgery.

Absence or malformation of the pinna, ear canal, or ossicles can cause a conductive hearing loss. Presence of a foreign body; impacted ear wax (cerumen); fluid in the ear associated with colds, allergies, ear infections (otitis media); or a poorly functioning eustachian tube are all examples of conditions that may cause a conductive hearing loss.

Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss. In other words, there may be damage in the outer or middle ear and in the cochlea or auditory nerve. When this occurs, the hearing loss is referred to as a mixed hearing loss.

Sensorineural Hearing Loss

Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or to the nerve pathways from the inner ear (retrocochlear pathway of the acoustic nerve) to the brain.

Sensorineural hearing loss not only involves a reduction in sound level, or ability to hear faint sounds, but also affects speech understanding or ability to hear clearly.

Sensorineural hearing loss can be caused by diseases, birth injury, drugs that are toxic to the auditory system, and genetic syndromes. Sensorineural hearing loss may also occur as a result of noise exposure, viruses, head trauma, aging, and tumors. Sensorineural hearing loss affects some 17 million Americans.

Sensorineural hearing loss cannot be corrected medically or surgically. It is a permanent loss.

Sometimes a sensorineural hearing loss occurs in combination with a conductive hearing loss. In other words there may be damage in the outer or middle ear and the cochlea or auditory nerve. When this occurs, the hearing loss is referred to as a mixed hearing loss.

Central Auditory Processing Disorders

A central auditory processing disorder (CAPD) occurs when auditory centers of the brain are affected by injury, disease, tumor, heredity or unknown causes. CAPD does not necessarily involve (although it may) hearing loss. Central auditory processing involves sound localization and lateralization, auditory discrimination, auditory pattern recognition, the temporal aspects of sounds, and the ability to deal with degraded and competing acoustic signals. Therefore, a deficiency in one or more of the above listed behaviors may constitute a central auditory processing disorder. CAPD is often associated with Attention Deficit disorder (ADD) or Attention Deficit Hyperactivity Disorder (ADHD) .