Congenital hearing loss can be a result of maternal factors (rubella, cytomegalovirus, or herpes simplex virus, syphilis, diabetes), infections, toxicity (pharmaceutical drugs, alcohol, other drugs), asphyxia, trauma, low birth weight, prematurity, jaundice, and complications associated with the Rh factor in the blood.
[10] Acquired hearing loss can be the result of toxicity (drugs given as treatment when in the neonatal intensive care unit) and infections such as meningitis.
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.
[11] Children who are prelingually deaf and cannot hear noise beneath 60 decibels—about the intensity level of a vacuum cleaner[12]—do not develop oral language comparable to their peers.
Children born with profound hearing impairment, 90 decibels and above (about the level of a food blender),[12] are classified as functionally deaf.
Such children display speech comprehension difficulties, even when other modes of language (such as writing and signing) are up to their age level standard.
[14] Spoken language is based on combining speech sounds to form words which are then organized by grammatical rules in order to convey a message.
After a year and a half of experience, researchers found the deaf culture[vague] was able to identify words and comprehend the movements of others' lips.
[19] In addition, individual capacities, as well as the neural supply to the cochlea, play a role in the process of learning with cochlear implantation.
[19] Studies continue to show that children with prelingual deafness are able to interact in society comfortably when implantation occurs before the age of five.
[17] Deaf children who have not been exposed to sign language create their own gesture communication known as homesign for the purpose of expressing what they are feeling.
Homesign is viewed as a biological component of language because it originates directly from the deaf child and because it is a global occurrence, transcending culture.
[21] Learning three-dimensional grammar, such as in ASL, boosts the child's visual and spatial abilities to higher than average levels.
Deaf children vary widely in their developmental experience with sign language, which affects development of short-term memory processes.
Congenitally deaf adults who used sign language showed ERPs that were 5-6 times larger than those of hearing adults over the Left and Right occipital regions and ERPs 2-3 times larger than hearing participants over the left temporal and parietal regions (which are responsible for linguistic processing).
The movement processed on the left side (language) implies that the right visual field is stronger in deaf and hearing ASL due to the hemispheric association being contralateral.
[24] Deaf children from a lower socioeconomic status are at a high risk for not being exposed to accessible language at the right time in early childhood.
This is because in most countries poverty translates into a lack of access to the educational and clinical services that expose deaf children to language at the appropriate age.