The ABR can also see if a sensorineural hearing problem lies in the cochlea, the auditory nerve, or in the part of the brain that first receives the sound information. Vestibular testing can tell if the vestibular system in the inner ear which contributes to the sense of balance has been affected as well. In some genetic forms of hearing loss, the vestibular system may not have developed, and meningitis can also damage the vestibular system. Blood and urine tests that look at kidney function are also important because of the genetic conditions that involve both the ears and kidneys. A blood test for thyroid function may be done to screen for Pendred syndrome, which includes goiter.
Chromosomes are the tiny pieces of DNA in each cell of the body that carry the genes.
The chromosomes can be examined under the microscope to see if a chromosome or part of a chromosome is missing or duplicated. However, in order for an abnormality to be seen under the microscope, it must be fairly large and involve many genes. At this time, geneticists cannot see individual genes, such as the gene for Waardenburg syndrome, so this test cannot be used to diagnose a hearing loss caused by a single gene. If the hearing loss is genetic, the way it is inherited will be discussed. If a syndrome is identified, the geneticist describes the medical or physical features, and if there are any, concerns for future medical problems and how they can be managed.