Yes, a person can be born deaf, a condition medically termed congenital hearing loss. This term defines any reduction in hearing ability that is present at the time of birth, affecting approximately one to three out of every 1,000 children born in the United States. This hearing loss results from various factors that disrupt the normal development or function of the ear’s auditory system while the fetus is in the womb. Early identification of congenital hearing loss is paramount because timely intervention significantly influences a child’s speech and language development.
Defining Congenital Hearing Loss
Congenital hearing loss is characterized by its onset during the prenatal period or at birth. This distinguishes it from acquired hearing loss, which develops later in life after a person was born with typical hearing. Acquired hearing loss can result from factors like chronic ear infections, certain illnesses such as meningitis, or exposure to loud noise. Congenital loss may involve hereditary factors passed down through genes or non-hereditary factors that affect the fetus during gestation.
Primary Causes of Being Born Deaf
The origins of congenital deafness are divided into two main groups: genetic (hereditary) and non-genetic (environmental) factors. Genetic factors are responsible for about 50 to 60% of all congenital hearing loss cases in children.
Genetic hearing loss is further categorized as syndromic, where the hearing loss is one symptom among a collection of other medical or physical signs, or non-syndromic, where hearing loss is the only condition present. Non-syndromic forms make up the majority of inherited hearing loss, accounting for approximately 70% of genetic cases. A mutation in the GJB2 gene is the most frequent cause of autosomal recessive non-syndromic hearing loss in many populations.
Non-genetic factors involve conditions that affect the developing fetus or newborn during or immediately after birth. Prenatal infections, often grouped under the TORCH complex, are significant contributors. Cytomegalovirus (CMV) is considered a leading non-genetic cause of congenital sensorineural hearing loss. Other infections like Rubella, Toxoplasmosis, and Herpes Simplex Virus have also been implicated in causing damage to the auditory system during fetal development. Complications during the birth process can also lead to congenital hearing loss, including lack of oxygen (birth asphyxia), low birth weight, and severe jaundice (hyperbilirubinemia).
Classification by Type and Severity
Once identified, congenital hearing loss is medically classified based on the part of the ear affected and the measurable degree of the loss. The three main types are sensorineural, conductive, and mixed hearing loss.
Types of Hearing Loss
Sensorineural hearing loss (SNHL) involves damage to the inner ear, specifically the cochlea or the auditory nerve, and is often permanent. Conductive hearing loss occurs when sound is blocked from reaching the inner ear, typically due to issues in the outer or middle ear, such as fluid buildup or malformation. Mixed hearing loss is a combination of both conductive and sensorineural components.
Severity
Hearing loss is also classified by its severity, which is measured in decibels (dB) of hearing level (HL). The severity ranges from minimal/slight to profound. A mild hearing loss is typically defined as a loss between 26 and 40 dB HL, where soft sounds are difficult to hear. A profound hearing loss, defined as a loss of 91 dB HL or greater, means a person will hear only very loud sounds.
Early Detection and Newborn Screening
Early detection is accomplished through universal newborn hearing screening (UNHS) programs, which are standard procedure in the United States and many other countries. Screening is typically performed before the newborn leaves the hospital. This process is painless and does not require the baby to provide a behavioral response.
The two primary methods used for screening are Otoacoustic Emissions (OAE) and Auditory Brainstem Response (ABR) testing. The OAE test uses a small probe placed in the ear canal to play a sound and measure the “echo” that a healthy cochlea produces in response. If the cochlea is functioning normally, a measurable response is recorded.
The ABR test measures the brain’s electrical activity in response to sounds using electrodes placed on the baby’s head. This test assesses how well sound travels from the inner ear along the auditory nerve to the brainstem. If a baby does not pass the initial screening, a follow-up screening or more complete diagnostic testing with an audiologist is scheduled to confirm the presence and extent of any hearing loss.