Most children develop language through hearing. Unless given access to sign language, hearing is essential for learning language. In addition to language acquisition, hearing loss also can impact a child's social and emotional development including self-esteem, as well as their reading skills and ability to learn. Furthermore, hearing loss can cause safety concern due to limited access to sound. Early identification and treatment for hearing loss is needed to minimize its impact on a child's development. From this necessity, newborn hearing screening programs were developed. The purpose of this module is to introduce you to newborn hearing screening. Before jumping into newborn hearing screening, let's get a little background on hearing and hearing loss. Hearing is one of the first senses to develop in an embryo. As a matter of fact, the entire structure of the ear is fully formed by 24 weeks of pregnancy. By the time babies are born they can tell the difference between their mother's voice and the voices of strangers all based on their learning experience during pregnancy. Hearing loss is the most common disability at birth, also known as a congenital disability. In the United States, 1-3 per 1,000 infants are born with hearing loss in one or both ears annually. The prevalence increases in the newborn intensive care unit or NICU to 1-2 per 100 newborns, and additional three per 1,000 children will acquire hearing loss during childhood. So, what are some reasons babies have hearing loss? 30-50 percent of hearing losses are genetic. Of the genetic causes of hearing loss, 70 percent are non-syndromic or do not exhibit any other symptoms. Five to 10 percent of hearing loss is caused by prenatal, congenital infections such as Cytomegalovirus CMV, toxoplasmosis, herpes simplex, syphilis, and rubella. Still 20-30 percent of babies born with hearing loss have an unknown cause. Many of these unknown causes likely are caused by asymptomatic congenital CMV. Hearing losses is associated with over 400 syndromes. Here are some of the most common. Now, let's talk about some perinatal or post-natal causes of hearing loss which can account for 15-35 percent of hearing loss in infants. These are common things you can look for or ask about in infants. If a child has any of these risk factors, they may need additional follow-up after the newborn hearing screening. Before we talk about types of hearing loss, let's review the parts of the ear. There are three basic parts of the ear, the outer ear which includes the pinna and the ear canal or the opening to the ear, the middle ear includes the ear drum and the three smallest bones in your body which transmit sound to the inner ear. These bones are the malleus, the incus, and the stapes also known as the hammer, the anvil, and the stirrup. The cochlea or the hearing organ and the semicircular canals, as well as the utricle and saccule or the balance organs make up the inner ear. One sound makes its way through all three parts of the ear, the signal is sent up the auditory nerve to the brain. Now let's discuss types of hearing loss. All of these types of hearing loss are reasons that a baby may get referred to a specialist after newborn hearing screening. Conductive hearing loss means that the inner ear is functioning normally, but there is a problem with the middle or outer ear. A common cause of temporary conductive hearing loss is ear infections. A common cause of permanent conductive hearing loss is atresia or no opening of the ear canal. Sensorineural hearing loss is when there is damage to the cells that live inside the cochlea. This is the most common hearing loss that elderly people experience. It is also the most common permanent hearing loss in children. This type of hearing loss is considered to be permanent. Mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss. This type of hearing loss is typically permanent. You may also hear of auditory neuropathy spectrum disorder, ANSD, which is another type of hearing loss that could cause a baby to get referred to a specialist after newborn hearing screen. Usually in cases of ANSD, the outer, middle, and inner ear are working appropriately, but there's a problem with the way the cochlea transmits the signal to the auditory nerve, and/or the way the auditory nerve processes the signal. This diagnosis is not common and is more likely to occur in babies who have spent time in the NICU.
