Hereditary deafness is a condition that is passed to children from one or both parents through genetic makeup. The end result is hearing loss, which may or may not be present from birth. For some children, it simply means that they are predisposed to suffering from hearing loss later in life. Others may demonstrate signs of not only hearing loss but other related conditions such as blindness or impaired speech.
The genetic information can be carried on dominant or recessive genes. In cases where it is carried on a dominant gene, it is only required that one parent have the gene in order for it to affect the child. For recessive genes, the child must get the gene from both parents in order for it to manifest itself. One of the most common types of recessive hereditary deafness is Usher syndrome, in which the individual demonstrates not only hearing loss but also varying levels of blindness.
Symptoms of hereditary deafness can manifest themselves in a number of ways. Those afflicted with syndromic hearing loss may display impairments of facilities associated with hearing, such as difficulties with speech or balance. With nonsyndromic hearing loss, the only thing affected is hearing. Onset varies based on the individual, and can be noticeable before or after the ability to speak develops. There is also no set severity of hearing loss, as some individuals can suffer only mild hearing loss while others can have profound or severe loss.
Hereditary deafness can affect different areas of the body. Conducive hearing loss occurs when there is an inherited abnormality in the formations and structures of the middle or external ear, while sensorineural hearing loss occurs because of abnormalities in the inner ear. There are other structures that are associated with a person's ability to hear, including the cranial nerve, the cerebral cortex, and the brain stem. The name given for inherited malfunctions of these other structures is central auditory dysfunction.
There are more than 400 different inherited conditions that include hearing loss as a component of their condition. Waardenburg syndrome is characterized by different levels of hearing loss accompanied by abnormal pigments in the skin, eyes, and hair. Osteoarthritis is associated with hearing loss in Stickler syndrome, and Branchiootorenal syndrome occurs in individuals that display hearing loss alongside abnormalities of the external ear.
Genetic testing can establish whether or not individuals carry the gene for hereditary deafness. When a child displays hearing loss, it is not always because of a hereditary condition. It can be caused by environmental factors, prenatal infections, or even bacterial infections. Causes of hearing loss can be determined by parents who intend to have more children.