Types of Hearing Loss
Though approximately half of all congenital hearing loss is connected to, genetic factors, for some, hearing loss causes are not clearly determined. When there is a genetic factor, most deaf children are born to hearing parents because the gene responsible for hearing defects is recessive. Other than genetics, some children are born with hearing loss due to infections during pregnancy or as complications from other syndromes that include deafness such as Usher’s or Down’s . Hearing loss that is present at birth is congenital hearing loss. When loss of hearing occurs after birth, it is acquired hearing loss. Regardless of when it occurs, there are three main types of hearing loss.
Conductive Hearing Loss
When loss of hearing occurs due to damage or disease to the outer or middle ear, it is conductive hearing loss. Conductive loss involves the outer ear, the ear canal, as well as the eardrum and middle ear structures. Conductive hearing loss causes include a number of illnesses or injuries such as:
- Birth defects
- Damage to bones of the middle ear
- Fluid in the middle ear
- Repeated ear infections
- Excessive ear wax
Conductive hearing loss may be helped to some degree with use of a hearing aid. Medical treatment or surgery may sometimes correct damage to the ear and improve or restore hearing. The success of treating conductive loss with medical or surgical intervention depends on early diagnosis and treatment. Common hearing loss causes often result in temporary hearing loss that responds well to early intervention. If medical or surgical treatment is not successful, most individuals with conductive hearing loss experience very good results using a hearing aid.
Sensorineural Hearing Loss
Sensorineural hearing loss involves the inner ear nerves, also called hair cells. Sensorineural hearing loss occurs when these cells fail to develop properly. Loss of hearing may also occur with inner ear nerve damage. The clarity and loudness of sounds heard are affected and unlike conductive loss, sensorineural loss is usually permanent. However, cochlear implant is the only surgery that may restore some level of hearing in potential candidates. Children who are deaf resulting from sensorineural hearing loss need early diagnosis and intervention to develop language skills during their early years. The pitches and sounds an individual with sensorineural loss is able to distinguish vary according to the extent of nerve damage. Due to individual differences, hearing aids may help some individuals process spoken words, while individuals with profound loss may use a hearing aid to distinguish sounds such as door buzzers, or phones. Sensorineural loss has a number of causes that may before birth or later in life. Some of these known causes are:
- Perinatal infections or disease
- Lack of oxygen during the birth process
- Low birth weight below 1500 grams
- Bacterial meningitis
- Drug induced nerve damage in the inner ear
- Chronic exposure to intensive or loud noises
Mixed Hearing Loss
A deaf person may have a combination of sensorineural and conductive loss resulting in distortion in both the loudness and clarity of sounds. Mixed hearing loss varies in severity. When conductive loss is the primary cause of hearing loss, with minor nerve damage, sounds may be hard to distinguish due to softness, but lack of clarity is not an obstacle. If the majority of damage involves the nerves within the inner ear, this will result in a loss of volume and clarity. Due to various types of conductive loss, the ability to distinguish sounds may fluctuate day to day. With mixed hearing loss, when conductive loss is the greater damage, there may be daily fluctuations in what is heard. Many deaf individuals have some level of residual hearing and can benefit from intervention and training in ASL, the use of hearing aids, language therapy, lip reading, or a combination of alternate means of communication.
Sudden Hearing Loss
Sudden hearing loss should always be considered a medical emergency. Sudden hearing loss may be due to infection or obstruction in the outer ear chamber, resulting in sudden conductive loss, or a dysfunction or damage to the nerves within the inner ear, resulting in a sensorineural loss. How sudden hearing loss is treated depends on accurately identifying the loss as conductive or sensorineural. Treatment is vastly different for these two losses. Sudden conductive loss may be restored with accurate diagnosis and treatment. Sudden sensorineural loss is often permanent. Should you experience sudden loss of hearing, make an appointment immediately with an Audiologist to have your hearing tested as well as with an Otolaryngologist or ear specialist to determine the type of hearing loss and course of intervention.