Sensorineural Hearing Loss
Sensorineural hearing loss occurs from lack of development or damage to either the nerve of hearing or the special sensory cells for hearing in the inner ear, known as hair cells.
Congenital Sensorineural Hearing Loss
The vast majority of permanent hearing loss that is present at birth is sensorineural. Approximately half of sensorineural hearing loss in children occurs on a genetic basis. Most children with genetic sensorineural hearing loss have two parents with normal hearing, as most genes for sensorineural hearing loss are recessive. However, if each hearing parent has one gene for hearing loss as well as a gene for normal hearing, their child may acquire two genes for hearing loss (one from each parent). Fortunately, most children with sensorineural hearing loss that has occurred on a genetic basis are otherwise healthy. These children have nonsyndromic sensorineural hearing loss.
A smaller number of children have a syndrome in which the hearing loss is present in association with another medical problem. Syndromes associated with sensorineural hearing loss that occur on a genetic basis include:
- Jervell and Lange-Nielsen
Sensorineural hearing loss can also be present at birth because the mother suffered certain types of infections during pregnancy, such as toxoplasmosis, rubella, cytomegalovirus or syphilis. It is estimated that 50% of sensorineural hearing loss present at birth does not occur on a genetic basis. No identifiable cause can be found in more than half of these non-genetic cases.
Acquired Sensorineural Hearing Loss
Children may be born with normal hearing, but develop sensorineural hearing loss after birth as a result of significant, often life-threatening illness. Children with respiratory problems after birth that require life-saving measures, such as several weeks of a mechanical ventilator, oscillating ventilator or extracorporeal oxygenation (ECMO), have been found to have an increased likelihood of developing hearing loss.
Children born with congenital diaphragmatic hernia (a life-threatening condition in which the child's intestines are inside the chest cavity, compressing the lung) are at high risk for development of sensorineural hearing loss. Other risk factors include high bilirubin levels, exposure to certain medications and poor apgar scores at birth. These risk factors are not necessarily the cause of the hearing loss, but do occur in very sick newborns at risk to suffer damage to their inner ear or hearing for reasons not well understood.
We have found it helpful to monitor the hearing of children who have risk factors at birth, even if they pass a newborn hearing test. We recommend repeated testing every 6 to 12 months for several years in order to look for the onset of a delayed sensorineural hearing loss.
Sensorineural hearing loss can also occur as a result of:
- Bacterial meningitis, causing partial or complete hearing loss
- Trauma causing a fracture or severe concussion of the part of the skull that protects the ear
- Exposure to very loud noises, especially over a long period of time
- Certain medications that are known to have the potential to cause hearing loss (but may be required to treat infection or cancer)
Children with sensorineural hearing loss in both ears need to be identified and fit with hearing aids as soon as possible. It is important that the degree of hearing loss in each ear be diagnosed as accurately as possible. In infants and young children, this requires a series of specialized hearing tests .
Once information is obtained about the child's degree of hearing loss, they should be fit with appropriate hearing aids. Children with bilateral sensorineural hearing loss often benefit from therapy focused on assisting them to develop listening and spoken language abilities. Intensive therapy that focuses on development of listening skills and hearing skills (auditory skill development) is critical for children who have a greater degree of hearing loss. Children with bilateral sensorineural hearing loss in the severe-to-profound range are potential candidates for cochlear implantation, the only medical treatment available for childhood deafness.