Definition & Overview
Anybody of any age can experience hearing loss, including newborns. While there are a number of factors that contribute to the condition, a study performed by the American Hearing Research Foundation revealed that almost half of hearing loss cases was due to hereditary factors.
In a similar study conducted in Australia on patients with age-related hearing loss that were 50 years old and above, it was also found that a significant number had a family history of the condition and that the condition was more prevalent in women than men.
Clinical methods to diagnose hearing loss in new born infants are not effective, but by measuring an infant’s response to clicking mechanism, it is possible to identify the presence of the condition. If the infant has hearing loss right after birth, the condition is referred to as congenital. If the condition develops at a later stage, it is called an acquired hearing loss.
Undergoing a genetic testing can confirm if the condition is congenital. The two genes that are commonly tested are GJB2 and GJB6. Testing of other genes is also possible, but mostly done on a case-to-case basis.
Cause of Condition
A hearing loss associated with a family history of the condition is caused by genetic factors. In a particular type of hearing loss called congenital sensorineural deafness (CSD), studies have shown that the majority of cases are caused by alterations in the GJB2 gene on chromosome 13. CSD occurs prior to speech development. If not treated during infancy, the likelihood of an impaired speech development increases.
In CSD, the abnormality may be present in any part of the hearing pathway, to include the auditory nerves that send hearing signals to the auditory portion of the brain. An abnormality in the auditory portion of the brain rarely occurs, but when it does, it often results in complete deafness.
Many infants diagnosed with CSD also have congenital malformations of facial features or other parts of the body, including the internal organs.
In adults, hearing loss is often age-related, but as mentioned above, many cases of age-related hearing loss may also be a result of the condition being present in the family. Hearing loss that is identified in patients under 40 years old is referred to as an early-onset condition. Around 50% of very early onset conditions, or pre-lingual hearing loss, is caused by genetic factors.
Patients with a family history of hearing loss usually display symptoms other than deafness. As described above, infants diagnosed with CSD usually present other abnormalities as well. Abnormalities differ according to the type (syndrome) of hearing loss.
Those who have been diagnosed with Usher syndrome normally experience progressive blindness while those with Alport syndrome typically have kidney problems. Pendred Syndrome is usually accompanied by thyroid enlargement, and those with Stickler syndrome typically have abnormalities in their facial features, arthritis, and vision problems.
When diagnosing hearing loss caused by genetic factors, it is important to identify the root cause of the problem so the best form of treatment can be provided. To accomplish this, a series of examinations, such as a physical exam, clinical tests, a review of the family history, and genetic tests are performed. Not only will the tests help in deciding on the best course of treatment, but they will also predict the likelihood of the patient passing down the condition to future generations.
Who to See & Types of Treatment Available
A family doctor usually provides an initial diagnosis of hearing loss problems. The patient will then be referred to a specialist, or ENT physician, who will perform additional tests. If the patient fails to pass those tests, the specialist will acquire the services of an audiologist who will perform more tests that will identify the type and severity of the problem.
Due to the fact that the majority of family-history related hearing loss cases also display abnormalities in different parts of the body, it is highly likely that the patient will require the expertise of other specialists such as cardiologist, ophthalmologist, and a clinical geneticist.
Treatment will depend on the cause of the condition. In some cases, the specialist may opt to forego any form of treatment and simply observe the condition. However, if the condition worsens, the specialist will make necessary adjustments and formulate another treatment plan.
Treatment methods include the use of amplification devices, such as hearing aids. Medications may also be prescribed, but it’s important to note that these are mostly presented as supplements instead of drugs. The use of the supplements has not been proven to be effective, thus this treatment method has not been widely accepted by the medical community.
If all else fails, the doctor may opt to perform surgery. The exact surgical procedure will depend on what is causing the problem. For example, patients with conductive hearing loss will benefit from a surgical procedure called stapedectomy. This surgery involves the partial removal of the stapes and then implanting a prosthetic device. If performed using laser equipment, the procedure is more effective and has fewer side effects.
Hildebrand MS, Husein M, Smith RJH. Genetic sensorineural hearing loss. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, PA: Mosby Elsevier; 2010:chap 147.
Arts HA. Sensorineural hearing loss in adults. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, PA: Mosby Elsevier; 2010:chap 149.
Lonsbury-Martin BL, Martin GK. Noise-induced hearing loss. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, PA: Mosby Elsevier; 2010:chap 151.