Types of hearing impairment

Deafness is a term used around the globe, and its definition often gets convoluted with a variety of meanings. In simple terms, ‘Deafness’ refers to a complete loss of hearing ability in one or two ears, typically at a decibel level of more than 80 hertz. ‘Hearing Impairment’ refers to both complete and partial loss of the ability to hear. It is important to remember that there are degrees of hearing impairment, and no two people may present the same level of hearing loss;. Degrees include mild, mild/moderate, moderate, moderate/severe and severe/profound, and profound.

There are two types of hearing impairment: Conductive and Sensorineural. A conductive hearing impairment is a problem in the outer or middle ear. Depending on the condition, there may be medical or surgical treatments. A common example is chronic middle ear infection, and medications when taken properly can alleviate the hearing problem. Sensorineural hearing impairment is a problem with the inner ear (cochlea), or occasionally with the hearing nerve. It is usually permanent and requires habilitation, such as the use of a hearing aid or cochlear implant.

Mixed 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 inner ear (cochlea) or auditory nerve. When this occurs, the hearing loss is referred to as a mixed hearing loss.

Degree of Hearing Loss
Degree of hearing loss refers to the severity of the loss. There are five broad categories that are typically used. The numbers are representative of the patient’s thresholds, or the softest intensity that sound is perceived:

Normal range or no impairment = 0 dB to 20 dB
Mild loss = 20 dB to 40 dB
Moderate loss = 40 dB to 60 dB
Severe loss = 60 dB to 80 dB
Profound loss = 80 dB or more

Other descriptors associated with hearing loss are:

• Bilateral versus unilateral. Bilateral hearing loss means both ears are affected. Unilateral hearing loss means only one ear is affected.
• Symmetrical versus asymmetrical. Symmetrical hearing loss means that the degree and configuration of hearing loss are the same in each ear. An asymmetrical hearing loss is one in which the degree and/or configuration of the loss is different for each ear.
• Progressive versus sudden hearing loss. Progressive hearing loss is a hearing loss that becomes increasingly worse over time. A sudden hearing loss is one that has an acute or rapid onset and therefore occurs quickly, requiring immediate medical attention to determine its cause and treatment.
• Fluctuating versus stable hearing loss. Some hearing losses change -- sometimes getting better, sometimes getting worse. Fluctuating hearing loss is typically a symptom of conductive hearing loss caused by ear infection and middle ear fluid, but also presents in other conditions such as Meniere’s disease.