Would you cure your hearing loss?
At the moment, that’s a hypothetical question. A cure for hearing loss does not exist. But as Dr. Tom Friedman of the National Institutes of Health told an audience at the Hearing Loss Association of America’s annual convention in June, a cure for at least one type of hearing loss may be around the corner.
Genetic, or hereditary, hearing loss is responsible for about 60 percent of hearing loss present at birth or developing in early childhood. It is also responsible for some adult-onset hearing loss, either on its own or in combination with exposure to noise or other toxins, including some medications like streptomycin or aminoglycoside antibiotics.
Hereditary hearing loss is caused by one or more mutations on a specific gene or genes. As of May 2019, scientists have identified 129 different genes causally associated with hearing loss. (“Causally” is the important word here.) Others are still being investigated. Gene sequencing can show which specific genes carry a mutation.
Hela Azaiez, PhD at the University of Iowa, who also spoke, noted that there are over 7000 possible mutations in those genes. She also said that an expert can sometimes predict which gene is responsible for the loss by the pattern on an audiogram. The more a person knows about the pattern of loss in the family, the easier it is to find the defective genes that are causing the loss, so a large family tree is helpful.
Autosomal recessive genes are the cause of hearing loss in 59 percent of cases. When the gene is recessive, the effect — in this case hearing loss — may skip generations and a pattern may not be apparent. Thirty-six percent of the genes that cause hearing loss are autosomal dominant, which means they always cause hearing loss. That leaves five percent, of which four percent are linked on the x chromosome and 1 percent in mitrochondrial DNA.
Two-thirds of those with hereditary hearing loss have no other related symptoms. But the remaining third have what is called syndromic deafness, with symptoms in addition to hearing loss. These include Usher syndrome (the disorder that Rebecca Alexander, subject of my previous post, has), Alport syndrome, and Perrault syndrome.
The next step for researchers is developing a way to correct those mutations. Several laboratories are moving ahead quickly with research.
Dr. Friedman is chief of the Laboratory of Molecular Genetics at the National Institute on Deafness and Other Communication. Dr. Hela Azaiez focuses on autosomal dominant genes at the Molecular Otolaryngology and Renal Laboratory at the University of Iowa. In the afternoon Dr. Azaiez gave a workshop with former HLAA Executive Director Brenda Battat and her family, who have hereditary hearing loss. Brenda Battat wrote about her family’s genetic search in an article for the January-February issue of Hearing Life Magazine called “Caught Up in a Whirlwind of Genetic Hearing Loss . They have been working with Dr. Azaiez.
To return to the question in my title: Would You Cure Your Hearing Loss? Many in the culturally Deaf community would answer with an emphatic No. Hearing loss/deafness/sign language are what makes them a community. As for me, with many years of hearing loss behind me, I would also probably say no, because the speech pathways in my brain are attuned to the way I hear now with a hearing aid and a cochlear implant.
But there are good reasons for determining the cause of hereditary hearing loss even if you don’t plan to treat it. Families may decide to correct the mutation in future generations. If it is too late to correct in younger family members, or if the family does not want to correct it, finding out what the mutation is and which family members have it allows them to plan ahead for future health care and other decisions.
The research symposium at Convention is always fascinating. This year’s panel included other researchers and much more information than I have room for here. Don’t miss next year’s symposium at the HLAA Convention in New Orleans.
For more about living with hearing loss, read my books, available at Amazon.com and Barnes and Noble, and maybe at your favorite bookstore or library. If it’s not there, ask for it!