There are two traditional types of hearing loss: conductive and sensorineural. The classification of each relates to the specific physiological cause. Some cases of hearing loss can involve a combination of the two – what hearing healthcare providers call mixed hearing loss. Recently, a third category called “Hidden Hearing Loss” has been described in peer reviewed research. *
Conductive Hearing Loss
When a person has a condition or disease that prevents the transmission of sound through the middle ear cavity to the inner ear, this is what is known as conductive hearing loss. Often the result of blockage in the ear canal, conductive hearing loss means that the conduction of sound intensity (loudness) to the inner ear is obstructed. A person with this type of hearing loss must strain to hear adequately. This type of hearing loss is usually overcome by adjusting the volume of the stimuli.
“Generally, the cause of conductive hearing loss can be identified and treated, resulting in a complete or partial improvement in hearing,” says the Better Hearing Institute (BHI) in Washington, DC. “Following the completion of medical treatment for the cause of the conductive hearing loss, hearing aids are effective in correcting any remaining hearing loss.”
Indicators of conductive hearing loss include better hearing by bone conduction than by air conduction, the ability to recognize words when heard at a comfortable volume, and evidence of middle ear dysfunction.
Sensorineural Hearing Loss
Sensorineural hearing loss is the result of dysfunction in the inner ear (sensory) or with the auditory nerve (neural). “The sensory component may be from damage to the organ of Corti or an inability of the hair cells to stimulate the nerves of hearing or a metabolic problem in the fluids of the inner ear,” says BHI. “The neural component can be the result of severe damage to the organ of Corti that causes the nerves of hearing to degenerate, or it can be an inability of the hearing nerves themselves to convey neurochemical information through the central auditory pathways.” The cause of this type of hearing loss can be difficult to diagnose, and it is often medically untreatable. Characteristics of sensorineural hearing loss include a reduction in sound intensity as well as sound distortion, much of which can be mitigated with the use of a hearing aid.
Hidden Hearing Loss
Hidden Hearing Loss is related to is related to neural hearing loss except that hearing levels are typically within the normal range. Despite an essentially normal hearing test with pure tone signals and normal speech testing in quiet, individuals with Hidden Hearing loss have notable difficulty understanding speech in noise. New research is emerging, and the causes and specific treatments are under investigation. Hearing specialists have been treating this condition with products and accessories such as remote microphones that help to reduce the effects of competing noise.
Mixed Hearing Loss
“A mixed hearing loss can be thought of as a sensorineural hearing loss with a conductive component overlaying all or part of the audiometric range tested,” says BHI.
In these cases, some aspects of the condition may respond to medical treatment, while the sensorineural factors may not. In any case, a hearing aid is generally helpful.
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*Liberman MC, Epstein MJ, Cleveland SS, Wang H, Maison SF (2016) Toward a Differential Diagnosis of Hidden Hearing Loss in Humans. PLoS ONE 11(9): e0162726. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0162726