The National Institute on Deafness and other Communication Disorders estimates that there are 32 million people in the United States with hearing loss. Hearing loss affects various segments of the population at different rates, degrees, and types of damage. No two persons have identical hearing loss, nor do they always respond similarly to the same treatment. Furthermore, there are remarkable differences in the causations of hearing loss based on age, genetics, health status, and environment.
Three out of every 1000 children born in the United States are hard of hearing or totally deaf. Nine out of ten children that are born hearing impaired are born to normal hearing parents. Premature birth, genetics, birth defects, and infection are primary causes of infantile hearing loss. As we age, one in three over the age of 60 and about a third of those over the age of 75 develop a hearing loss. Adult causations include noise exposure, drug reactions, genetic factors, heart disease, diabetes, thyroid dysfunction, and a host of other medical conditions. Of the 28 million Americans with hearing loss, two or three percent or 500,000 to 750,000 children and adults have severe to profound losses. Fortunately, for humanity, hearing loss rarely reaches total deafness and almost all patients can be helped with surgical treatment, a cochlear implant, or with hearing aids and other devices.
There are varieties of diseases and traumas that cause hearing loss. Some of these originate at the ear while others develop in the brain. Hearing loss caused by medical problems of the ear canal, eardrum, and middle ear prevents sound from being transferred to the inner ear or cochlea (coke-lee-uh) where nerve impulses are sent to the brain. Problems in the outer and middle ear are similar to having difficulty focusing with the lens of the eye and needing glasses. The pinna, ear canal, eardrum, and middle ear are actually a magnifying system to enhance hearing. Although the most common cause of decreased hearing is wax in the ear canal, the most common ear disease is the middle ear infection. Almost all hearing loss caused by diseases of the outer and middle ear including swimmers ear, chronic middle ear fluid, otosclerosis, and perforated eardrums are curable or accessible to hearing aids. The ENT physician is the best-trained professional to deal with these and all other related medical problems.
Conditions that physicians find more challenging to treat are those that can produce permanent nerve damage inside the cochlea. This is because changes that deal with the nerves of the inner ear frequently leave some permanent hearing loss. These permanent changes are primarily due to decreased blood circulation, noise exposure, individual genetic factors, and to a lesser degree, aging. Other well known causes include inner ear infections, ear trauma, syndromes, premature birth, tumors, viral and bacterial diseases, and medication or toxic substance reactions. An example of a disease that causes reduced blood circulation is microangiopathy. This process gradually restricts blood flow by building up plaque on the blood vessel walls resulting in hearing loss. A common medical disease that may produce microangiopathy is diabetes.
Noise exposure, especially combined with an aging component is another primary cause of permanent hearing loss. Industrial noise, gunfire, and motorcycles are three primary noises that are known to cause “noise induced hearing loss.” Loud music, home power tools, and recreational toys can create hearing loss and should be controlled by reducing loudness (i.e. use a factory muffler on the motorcycle) and using earplugs or muffs. Signs of over exposure are ringing in the ears and dull or muffled hearing. Although these may appear to be temporary, the damage is already done. Outside influences, such as taking aspirin at the same time as being exposed to noise, can even promote hearing loss. Multiple exposures over time cumulate into a high frequency hearing loss requiring hearing aids. Most noise-induced hearing loss does not exceed a severe degree of damage, however, when coupled with aging or other diseases the results can be significantly worse. The cure for noise induced hearing loss is ear protection when in noise and to avoid loud sound whenever possible.
Although there are reasonable treatments and solutions for many ear diseases, there are limited treatments for genetic hearing loss. One in every eight people carries a recessive gene for hearing loss. A recessive gene is one that when matched in both parents, in the absence of a dominant gene (a gene that always causes hearing loss), produces hearing loss in some of the offspring. Sometimes the loss is at birth, but in many cases genetic changes occur into adulthood. There are approximately 400 genes that may cause hearing loss. In rare cases, dominant genetic factors may produce families that have hearing loss only in one ear. For these reasons, it is not unusual to find that hearing loss from noise exposure runs in families. They carry a gene that may make them most susceptible.
One of the least recognized problems that cause hearing loss is damage to hearing nerve cells because of toxicity or allergic reaction to medication. Some powerful antibiotics taken in large quantities to combat infection can actually cause severe hearing loss. Diuretics, aspirin in large quantities, chemotherapy, and exposure to toxic waste are other examples of known substances that cause hearing loss. In fact, there are hundreds of substances that cause hearing or balance disturbance. In some cases, the hearing loss may be only temporary if the medication is discontinued. However, medication reaction in the inner ear frequently causes permanent damage. The hallmark of a reaction to a drug or toxic material is the observation of ringing or other sounds in the head or ears. This is known as tinnitus. Should tinnitus occur at the onset of any medication or exposure to chemicals, it is best to consult your physician immediately. Only the physician is qualified to determine the necessity of medication and the importance of the reaction.
In addition to problems at the ear, hearing areas deeper in the brain can also be affected resulting in very poor word understanding even with hearing aids. This is because information is not routed correctly, auditory functions no longer work, or critical cues are missing. These changes are called auditory processing disorders (APD) and occur from a variety of causes including head trauma, neurological disorders such as Parkinson’s and Alzheimer’s diseases, the aging brain, vascular abnormalities, tumors, and a host of other factors. What makes APD problems so important to identify is the need for specialized equipment and counseling. This is because; an APD hearing loss is more closely related to memory loss than it is to pure hearing loss. The functions are similar, but remarkably different. Unfortunately, some patients develop both a hearing loss and an APD and need special help with training and equipment.
In children, the earliest identification of hearing loss is the primary objective. Appropriate treatment at the correct time of development is strategic. Guidelines suggest that ideally, hearing loss should be identified by six months of age or earlier and hearing aids fitted. For those with profound loss, a cochlear implant can be scheduled by the first year of life. The purpose of each treatment is to provide access to sound and promote the development of the hearing system, speech and language, and social skills. Hearing loss prevents communication and age appropriate learning. Reducing these delays, in many cases, can be accomplished by early intervention. Fortunately, early intervention is available throughout the United States and the solutions to improve communication and foster development are available for all children.
In adults and seniors, the process of losing the ability to hear is generally very gradual taking 10-20 years before communication difficulty is realized. In fact, the changes can be so gradual that hearing loss is not identified until consistently asking people to repeat words becomes a problem. A good example of how many seniors acquire a significant hearing loss is age related hearing loss coupled with long-term noise exposure. Both cause damage directly to the high tone nerve cells within the cochlea. In both cases, high frequency speech sounds (s, sh, f, th, p, t, k, h, f, ch) are only affected, while vowel sounds and low tone consonants (b, r, w, g, n, ng, m, l, d, z) are not. Common complaints are “I can hear, but not understand”, “I have trouble hearing women and children”, and “hearing in noise is difficult.” Hearing aids are very successful in improving word clarity in most cases, because high frequencies that carry 70% of word information are, to some degree, restored. Ultimately, this translates into better word identification. In other seniors who have medical conditions that cause hearing loss, significant difficulty hearing in all tones occurs. This produces greater difficulty hearing as both word clarity and sound loudness are affected. This results in the hearing thumbprint being completely altered and normalized sound reception no longer possible without amplification.
Although the entire sense of hearing and word identification starts at the ear, it travels via a web of nerves to a variety of places in the brain. Once in the brain, sound is interpreted as speech, background noise, or sounds of interest (i.e. a moving car). The best way to remember how we hear is to think of the ear as a sophisticated and very expensive microphone that picks up sound and amplifies it selectively as commanded by the brain. The normal hearing system actually tunes sound for clarity by decreasing unwanted signals and enhancing others. This is done by the brain’s ability to control the tension of two tiny muscles attached to the middle ear bones (hammer, anvil, and stirrup), while increasing or
decreasing nerve impulses at the ear and within the brain. For these reasons, hearing loss does not only occur at the ear, but to some degree also in the brain. When the brain fails to perform its hearing duties, the results are reduced understanding in many listening situations, especially those in noise and for fast speech. Due to age, disease, and related changes, seniors have the greatest percentage of combined ear/brain problems and need special care. Therapy for these disorders include hearing aids, TV and telephone amplifiers, remote microphones, looping of rooms for t-coil reception, keeping a positive outlook, auditory therapy, and learning and using listening and communication skills.
The development of a hearing loss can be sudden or gradual and may occur in the womb or at 100 years old. Each requires proper diagnostic testing and examination to identify medical conditions requiring treatment and/or the need for amplification. The causes and solutions to hearing loss come from a wide variety options. The use of hearing aids, cochlear implants, and other devices make communication easier, reduce stress, and can be very helpful if properly fitted and used. Teaching others about hearing loss and individual communication needs is necessary if hearing loss is going to be understood and demystified. The Audiologist and Ear, Nose, and Throat physician are the only specialists licensed and university trained to provide hearing healthcare services. The ENT physician (M.D.) is the medical specialist and the Audiologist (Au.D., Ph.D.) is the scientist responsible for testing hearing and balance and providing hearing aids and rehabilitation.