Congenital deafness is deafness that is present at birth. Deafness that is acquired after birth due to noise exposure, illness, or due to age is much more common than congenital deafness. Congenital deafness is present in approximately one out of every one or two thousand births. Bilateral congenital hearing loss, hearing loss affecting both ears, is more common than unilateral congenital hearing loss.

Congenital hearing loss can be caused by a genetic condition or deformity of the ear. The most common form of congenital deafness is through heredity. The parents may carry dominant or recessive genes that cause deafness. In these cases, the families may have passed deafness down through numerous generations.

Not all genetic causes of congenital deafness are inherited from the parents. Genes can mutate and cause a syndrome that was not passed down by the parents. Only twenty percent of congenital deafness is caused by syndromes. Families of children born with these syndromes may not have had any other instances of that syndrome in the family.

Many of these non-hereditary syndromes cause several birth defects including hearing loss or deafness. CHARGE syndrome is one condition that is caused by a genetic mutation. CHARGE syndrome causes many birth defects, one of which is congenital hearing loss. Mohr-Tranebjaerg syndrome, Jervell and Lange-Nielsen Syndrome, Usher syndrome and Waardenburg syndrome are other examples of syndromes that can cause congenital hearing loss.

Non-inherited causes of congenital deafness are malformations of parts of the ear. The Mondini malformation causes about twenty percent of congenital sensorineural deafness. Mondini malformation results in a misshapen cochlea.

Congenital hearing loss may not be immediately apparent in newborns. Many hospitals across the world screen newborns for hearing loss. If the infant has not had a hearing test or the test failed to detect a congenital hearing loss, a pattern of failure to respond to auditory stimuli can suggest that there might be a problem with the infant’s hearing. Infants with normal hearing have a natural startle reflex in reaction to loud noise. The absence of this reflex can mean that the infant is not hearing noise that would otherwise set off the startle reflex.