Cerebral Palsy, or CP, is among the most common of all chronic motor disorders in children. It affects nerves, the brain, and muscles and can have a variety of effects on how a child moves or functions. Most children with CP experience spastic and rigid muscles that affect movement, but many also experience other complications, including intellectual impairment, speech disorders, and vision problems.
Another one of these potential complications is hearing loss. Exactly what causes hearing loss in an infant or child with CP is not always understood, but there are many potential causes. Impaired hearing can impact a child negatively and cause delays and impairments in language, speech, social, and cognitive development. Early screening for hearing loss in children with CP is important. It allows doctors and other caregivers to treat the impairment and begin interventions that will help improve any developmental delays triggered by hearing loss.
Prevalence and Causes of CP and Hearing Loss
Several studies have investigated just how common hearing loss is in people with CP. The results have varied a little bit by study, but generally show that the prevalence of this complication is significant. One study found that about seven percent of people with CP experienced moderate to profound hearing loss, while three to four percent experienced profound to severe hearing loss. Another study looked at 685 children in Australia diagnosed with CP and found that 13 percent had hearing loss of any type.
What causes hearing loss depends on the type, but there are various factors that may contribute to this impairment. For any one particular child it is probably not possible to pinpoint an exact cause. It may be genetic factors, or there may be other risk factors at play. Non-genetic risk factors for CP and hearing loss overlap: infections, oxygen restriction to the brain during development, and low birth weight.
Signs of Hearing Loss
Early screening for hearing loss is crucial to getting a child the right treatments. For parents of children with CP it is important to know and look for the signs that a child is not hearing fully. This can be tricky in infants and toddlers who cannot easily communicate that they cannot hear.
Some telltale signs in infants include not startling at loud noises, not waking up at loud noises, or not being calmed by a voice that should be familiar. Babies may also show signs of hearing loss by not reacting to being spoken too or failing to turn toward familiar sounds.
Toddlers and younger children may begin to show even more signs that hearing is impaired. These include not responding to simple requests, not talking as much as is appropriate for a given age or not repeating sounds and words, or not showing signs of listening to stories or songs. An older toddler or young child may turn of the volume on devices, not respond correctly to questions, say “what?” or “huh?” often, and continue to show delays in speech and language development.
Types of Hearing Loss
There are two main types of hearing loss that children with CP may experience: conductive hearing loss and sensorineural hearing loss. Conductive hearing loss means that sounds are not being transmitted between the outer and middle ears. The sound never makes it to the inner ear where the cochlea and nerve cells pick it up and send signals to the brain. This type of hearing loss is often caused by an otitis media, inflammation in the middle ear that leads to the buildup of fluid.
Conductive hearing loss is a physical type of hearing loss, whereas sensorineural hearing loss is related to nerves in the inner ear. Damage to the nerve receptors in the inner ear blocks transmission of sound to the brain. This can be caused by genetic factors or other risk factors that occur during fetal development, childbirth, or infancy. Some children with CP will experience both types of hearing loss.
Treatment of Conductive Hearing Loss
Treatment for conductive hearing loss is more straightforward and usually more successful than treatment for sensorineural hearing loss. Treating the underlying infection and inflammation can reverse hearing loss and hearing aids can also help, especially for those children for whom surgery is not an option. For more severe or recurring conductive hear loss, surgery can often completely and permanently restore hearing.
Treatment of Sensorineural Hearing Loss
Treating sensorineural hearing loss is trickier because it involves damaged nerves in the inner ear rather than physical damage to the middle ear as in conductive hearing loss. This type of damage is permanent and cannot be reversed. Hearing can be improved with hearing aids, though. These devices amplify sounds so that those nerve receptors that are not damaged receive more sound.
Although the damage is permanent, that damage can be bypassed to restore hearing with a cochlear implant. This device has two parts: one is inserted in the ear, under the skin, and the other is worn behind the ear. Unlike a hearing aid, a cochlear implant does not simply amplify sound; it actually bypasses damaged inner ear nerves and uses mechanical parts to collect, transmit, and convert sounds into electrical impulses that are sent to the brain as sounds. These implants may be used in children with severe or total hearing loss.
Impact of Hearing Loss on Children with CP
Hearing loss can have a profound impact on a child, especially if it is not diagnosed and treated. Not being able to hear adequately can lead to delays in all kinds of development, but especially language, speech, and social development. Being able to hear is important to learning to speak and use language. It is also important in learning how to relate socially to others. Children with hearing loss that goes untreated will struggle to communicate and are at risk of becoming socially isolated.
Both treatments for the underlying causes of hearing loss in children with CP and developmental and educational interventions can help them overcome the effects of the impairment. Recognizing and treating hearing loss early is so important, but if it is not discovered until later, interventions can help a child catch up developmentally.
Language and speech therapy, specialized language educational interventions, and behavioral and social therapies can help. Hearing loss does not have to be a permanent disability for a child with CP if treated and addressed correctly.