Prelingual deafness

A prelingual deaf individual is someone who was born with a hearing loss, or whose hearing loss occurred before they began to speak. Infants usually start saying their first words around one year. Therefore a prelingually deaf typically was either born deaf or lost their hearing before age one (the age when most hearing loss in children occurs). Congenital (present at birth) hearing loss is also considered prelingually, since a newborn infant has not acquired speech and language.

Each year in the United States, approximately 12,000 babies are born with a hearing loss. Profound hearing loss occurs somewhere between 4-11 children per every 10,000 children.

Prelingual hearing loss can be either acquired, meaning it occurred after birth due to illness or injury, or it can be congenital, meaning it was present at birth. Congenital hearing loss can be caused by genetic or nongenetic factors. The nongenetic factors account for about one fourth of the congenital hearing losses in infants. These factors could include: Maternal infections, such as rubella, cytomegalovirus, or herpes simplex virus, lack of oxygen, maternal diabetes, toxemia during pregnancy, low birth weight, prematurity, birth injuries, toxins including drugs and alcohol consumed by the mother during pregnancy, and complications associated with the Rh factor in the blood/jaundice. Genetic factors account for over half of the infants with congenital hearing loss. Most of these are caused by an autosomal recessive hearing loss or an autosomal dominant hearing loss. Autosomal recessive hearing loss is when both parents carry the recessive gene, and pass it on to their child. The autosomal dominant hearing loss is when an abnormal gene from one parent is able to cause hearing loss even though the matching gene from the other parent is normal.

Hearing aids and cochlear implants may make the child able to hear sounds in their hearing range—but they don't restore normal hearing. Cochlear implants can stimulate the auditory nerve directly to restore some hearing, but the sound quality isn't that of a normal hearing ear, suggesting that deafness cannot be fully overcome by medical devices. Some say that the benefits and safety of cochlear implants continues to grow, especially when children with implants receive a lot of oral educational support. It is a goal for some audiologists to test and fit a deaf child with a cochlear implant by six months of age, so that they don't get behind in learning language. In fact, there are expectations that if children get fit for implants early enough, they can acquire verbal language skills to the same level as their peers with normal hearing.

Children who are prelingually deaf and cannot hear noise beneath 60 decibels—about the intensity level of a vacuum cleaner—don't develop oral language comparable to their peers. Children born with profound hearing impairment, 90 decibels and above (about the level of a food blender), are classified as functionally deaf. These children do not develop speech and language skills without help from a speech pathologist. Such children acquire language comprehension difficulties, even when other modes of language (such as writing and signing) are up to their age level standard. Generally, prelingual deaf individuals have reading levels that do not exceed the level of a fourth grader's. Children who lose their hearing after they have acquired some amount of language, even if it is just for a short while, demonstrate a much higher level of linguistic achievement than those who have not had any language exposure.

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