In general terms, there are two types of hearing loss, conductive and sensorineural. A combination of both is also seen as a mixed hearing loss.
Conductive Hearing Loss
Conductive hearing loss is caused by any condition or disease that blocks or impedes the conveyance of sound through the outer or middle ear. The result is a reduction in the sound intensity (loudness) that reaches the cochlea. Generally, the cause of conductive hearing loss can be identified and treated, resulting in a complete or partial improvement in hearing. Medical treatment may include medication or surgery. Following the completion of medical treatment, hearing aids are effective in correcting the remaining hearing loss. Some examples of causes of conductive hearing loss are: impacted cerumen, atresia (closed ear canal), perforated eardrum, otitis media (fluid in the middle ear), otosclerosis and ear trauma.
Sensorineural Hearing Loss
Sensorineural hearing loss results from inner ear or auditory nerve dysfunction. Often the cause cannot be determined. It is typically irreversible and permanent. As with conductive hearing loss, this type of loss also reduces the intensity of sound, but it might also result in a lack of clarity even when sounds, particularly speech, are loud enough. The treatment for sensorineural hearing loss is amplification through hearing aids.
Some examples of causes of sensorineural hearing loss are Meniere’s disease, noise exposure, aging (presbycusis), trauma, ototoxic medication, acoustic neuroma, congenital (birth) and hereditary.
A mixed hearing loss
A mixed hearing loss is a combination of a conductive and a sensorineural hearing loss. In addition to some irreversible hearing loss caused by an inner ear or auditory nerve disorder, there is also a dysfunction of the outer or middle ear mechanism, making hearing worse than the sensorineural loss alone. The conductive component may improve with medical treatment and reversal of the associated hearing loss, but the sensorineural component will most likely be permanent. Hearing aids can be beneficial for persons with a mixed hearing loss, but caution must be exercised by the hearing care professional and patient if the conductive component is due to an active ear infection.
Hearing loss can be caused by something as simple as excessive ear wax or as complex as a congenital disorder, medical problem or disease.
The main causes of hearing loss are as follows:
- Aging (presbycusis)
- Excessive noise (i.e. construction, rock music, gun shot, etc.)
- Sudden onset
- Injury to the head or ear
- Birth defects or genetics
- Ototoxic reaction to drugs or cancer treatment (i.e. antibiotics, chemotherapy, radiation)
Age-related hearing loss (presbycusis) occurs as a natural result of the aging process. This is a progressive loss as the inner ear (cochlea) and/or other parts of the auditory system degenerate over time, with loss of hearing for the high pitch sounds affected first. The process begins after age 20, but it is not until around ages 55 to 65 that high frequencies in the speech range begin to be affected.
Noise-induced hearing loss can result from prolonged exposure to harmful levels of noise. Prolonged noise exposure damages the hair cells in the cochlea and results in permanent hearing loss. Noise-induced hearing loss usually develops gradually and painlessly. Hearing loss can also occur as a result of an acoustic trauma due to a single exposure or few exposures to very loud sound.
Sudden onset hearing loss occurs across the entire age spectrum with equal prevalence in men and women, but most patients are between 50–60 years of age. More than half also experience tinnitus, aural fullness, and/or vertigo. An estimated 4,000 people will develop sudden sensorineural hearing loss each year in the United States. There are numerous causes for this type of loss, ranging from autoimmune inner ear disease and viral infections to traumatic insult (skull fracture, puncture of the eardrum, sudden changes in air pressure). If treated expeditiously, patients can often recover or stabilize their hearing.
Infection-related hearing loss occurs when fluid from the infection builds up behind the eardrum. Sound cannot get through an ear that is filled with fluid. The scientific name for an ear infection is otitis media. Anyone can get an ear infection, but children get them more often than adults. Three out of four children will have at least one ear infection by their third birthday. An untreated ear infection may lead to permanent hearing impairment.
Hearing loss can result from physical trauma, such as injury to the head or ear. Examples include skull fractures of the temporal bone—the area of the skull just behind the ear; puncture of the eardrum by foreign objects; or sudden changes in air pressure.
Hearing loss related to birth defects or genetics—Genetic sensorineural hearing loss (SNHL) includes a broad range of disorders that affect infants, children, and adults. Affected individuals may have unilateral or bilateral hearing loss ranging from mild to profound.
Ototoxic hearing loss occurs when someone takes or is given a drug that causes hearing loss as one of its side effects. Sometimes the drug-induced hearing loss is temporary and can be reversed or stopped. Other times it is permanent. People with hearing loss need to be especially aware of the potential for ototoxic effects, as an ototoxic drug can make an existing hearing loss worse. Ototoxic drugs include some antibiotics, chemotherapy drugs and anti-inflammatory medications, including some over-the-counter drugs.
An Audiologist is a healthcare professional who specializes in identifying, diagnosing, treating and monitoring disorders of the auditory and vestibular system portions of the ear. Audiologists are trained in anatomy and physiology, hearing aids, cochlear implants, electrophysiology, acoustics, neurology, counseling and sign language. Depending on the program they pursue, Audiologists typically graduate with one of the following qualifications: Master’s degree, Doctor of Audiology (AuD), PhD, or Doctor of Science (ScD).
Audiologists perform a wide range of hearing-related services, such as:
- Diagnose, manage and/or treat hearing or balance problems
- Dispense hearing aids and recommend and map cochlear implants
- Counsel patients of all ages—from diagnosing hearing loss in infants to teaching coping and compensation skills to late-deafened adults
- Help design and implement personal and industrial hearing safety programs, newborn hearing screening programs and school hearing screening programs
- Provide custom ear plugs and other hearing protection devices to help prevent hearing loss
- Work as auditory scientists in a research capacity