Hearing connects us to the world around us. A quote from Helen Keller is “Blindness separates us from things but deafness separates us from people”. Bill Bryson in his book The Body, has a section on hearing. He says that “hearing is another seriously underrated miracle”. He describes that there are three tiny bones, some wisps of muscle and ligaments, a delicate membrane and some nerve cells that fit together to capture almost perfectly the “intimate whispers, the lushness of symphonies, and the soothing pattern of rain on leaves.
The ear consist of three parts. The floppy outside (pinna) that captures passing sound like a funnel. Not only does it capture those sound but helps us locate where the sounds come from and whether they are important. At the end of the ear canal is a tight membrane (ear drum) which begins the middle ear. When sound waves shake this membrane it vibrate three of the tiniest bones in the body (malleus, incus and stapes). A pressure wave that moves the ear drum by less than the width of an atom will activate these bones and send the sound to the brain through the cochlea.
The cochlea is a fluid filled structure that is shaped like a snail and is filled with 2,700 delicate hair-like filaments which “wave like ocean grasses as sound waves pass over them”. These little filaments (stereocilia) tend to wear out with age and can be damaged by really loud noises. Once a filament is damaged it is lost forever. Really loud noise causes an acoustic reflex in which a muscle jerks the little bone (stapes) away from the cochlea. Unfortunately, this takes about a third of a second and a lot of damage can be done.
Almost 100% of newborns are screened for hearing at birth. Hearing loss is hereditary in most childhood cases (about 80%). It is a significant factor in adult-onset hearing loss. There have been over 400 genes identified as contributing to hearing loss and the exciting news is that there are now treatments with gene therapy available for some of the genetic conditions that can restore hearing to children and adults.
Acquired hearing loss can be from infections and injuries such as loud noises, concerts, ear buds and any exposure to prolonged and repetitive loud noises. This is true for all ages
The brain of infants and children is rapidly developing pathways to interpret sounds and language. The earlier a child is identified with hearing loss, the sooner the affected child can receive educational services and hearing augmentation when indicated. Now genetic testing can be done and there may be the possibility of gene therapy to repair or replace defective genes.
by Sally Robinson, MD Clinical Professor
Keeping Kids Healthy
Published February 2025