The causes of hearing loss are varied and their impact on hearing is variable. Sometimes the cause or etiology is readily apparent, such as a wax build-up in the external ear canal or an ear infection. At other times, the cause of the hearing loss is presumed or indefinite given current levels of technology and the information they provide, such as in cases of sudden onset or non-syndromic sensorineural hearing loss.
The most common causes of hearing loss are as follows:
- Excessive noise (i.e. construction, rock music, gun shot, etc)
- Aging (presbycusis)
- Infections (otitis media)
- Injury to the head or ear
- Birth defects or genetics
- Ototoxic reaction to drugs or cancer treatment (i.e. antibiotics, chemotherapy, radiation)
- Other diseases/disorders such as: Diabetes, Cardiovascular, Thyroid, Kidney,Glaucoma,Sickle-cell, & Hormone Replacement Therapy
Exposure to Loud Levels of Noise: from occupational work, military duties, recreational sources such as hunting, racing, loud music/musicians, and so on. It doesn’t matter if it was “years ago,” once the damage occurs to the inner ear, it is damaged forever.
Ototoxic Drug Therapies and/or Cancer Treatment: Many drugs used in cancer treatments are toxic to the inner ear and can cause hearing loss during or even 6 months following treatments. The hearing loss may continue to progress over the years. Other drugs used in certain combination with loop diuretics also put the inner ear at risk for damage. Aminoglycoside antibiotics are well known for causing hearing loss in children and adults. Other medications such as heart and blood pressure medications, anesthetics, glucocorticosteroids, and others all have the potential to damage the inner ear. Ototoxic Monitoring during drug therapies/cancer treatment can detect small changes in the auditory system so drug adjustments can possibly be made or rehabilitation measures can be started.
Genetics: If other family members have hearing loss you may have a genetic predisposition for your hearing loss.
Presbycusis: This is one form of hearing loss no one can avoid because it is age related hearing loss. The inner ear reacts like other body systems and deteriorates over time. Many other factors will affect age of onset and severity of hearing loss.
Diabetes: Usually results in hearing loss due to changes in the auditory nerve endings.
Cardiovascular Disease: Untreated high blood pressure, very high cholesterol and triglyceride levels in the blood, poor overall cardiovascular health (blockages), hypercoagulability, or polycythemia can cause insufficient blood flow to the inner ear causing damage and resulting in hearing loss.
Thyroid Disorders, Kidney Disease, Glaucoma, and Sickle Cell Disease are also associated with high incidences do hearing loss.
- congenital malformation where pinna and ear canal fail to form
- blockage in ear canal – foreign body, accumulated cerumen (ear wax), bony growths
- infection of skin lining ear canal- swimmers ear
- perforation in tympanic membrane (ear drum) from trauma or disease
- otitis media (ear infection)
- broken ossicular chain due to head trauma or trauma to the ear
- calcification around the stapes- otosclerosis
- eustachian tube dysfunction
- tympanosclerosis- scarring of the eardrum
- neonatal risk indicators
- genetic disorders causing non-syndromic sensorineural hearing loss
- presbycusis – hearing loss from aging
- ototoxic drugs such as some antibiotics
- cancer treatments – chemotherapy and radiation therapy
- head trauma – fractured temporal bone
- excessive noise expose
- diseases of the vascular system such as sickle cell anemia
- kidney disease
- Meniere’s syndrome
- congenital infections such as toxoplasmosis, rubella, CMV, herpes, other bacterial infections like syphilis
A comprehensive audiologic evaluation must be completed in order to determine the type and severity of hearing loss and to make appropriate recommendations for each patient. Pure tone and speech audiometry as well as the immittance test battery and otoacoustic emissions must be completed, in addition to any additional assessments necessary for an exhaustive profile of the hearing system. A balance test called electronystagmography (ENG) might also be needed if dizziness or imbalance is also a complaint. In certain situations an Auditory Brainstem Response (ABR) test or imaging studies such as an MRI, may be recommended to assess integrity of the auditory neural pathways. Some patients who are bothered by tinnitus only might have a complete tinnitus evaluation. Questionaires on hearing and communication abilities should be administered to determine rehabilitation needs and goals. Central Auditory Function tests may also be used to determine speech ability in noise and auditory processing strengths and weaknesses. Finally, the audiologic data provide the clinical foundation for recommendations regarding hearing aids and other assistive devices.
In general terms, there are 2 types of hearing loss, conductive and sensorineural. A combination of both is also referred to as a mixed hearing loss. An in depth discussion of each type is below.
CONDUCTIVE HEARING LOSS
Conductive hearing loss is caused by any condition or disease that impedes the conveyance of sound in its mechanical form through the middle ear cavity to the inner ear. A conductive hearing loss can be the result of a blockage in the external ear canal or can be caused by any disorder that unfavorably effects the middle ear’s ability to transmit the mechanical energy to the stapes footplate. This results in the reduction of one of the physical attributes of sound called intensity (loudness), so the energy reaching the inner ear is lower or less intense than that in the original stimulus. Therefore, more energy is needed for the individual with a conductive hearing loss to hear sound, but once it’s loud enough and the mechanical impediment is overcome, that ear works in a normal way. Generally, the cause of conductive hearing loss can be identified and treated resulting in a complete or partial improvement in hearing. Following the completion of medical treatment for cause of the conductive hearing loss, hearing aids are effective in correcting the remaining hearing loss.
The audiometric profile that indicates a conductive hearing loss is the presence of air-bone gaps (better hearing by bone conduction than by air conduction), excellent word recognition at a comfortable listening level, and evidence of a middle ear dysfunction on immittance. Dr. Vowell refers to your primary care physician or several excellent local otolaryngologists when medical and/or surgical treatment is warranted.
SENSORINEURAL HEARING LOSS
The second type of hearing loss is called sensorineural hearing loss. This word can be divided into its two components – sensory and neural – to allow us more clarity in specifying the type of hearing loss. The comprehensive audiometric assessment and supplemental tests can yield the information needed to differentiate between a sensory and a neural hearing loss, although they can co-exist in the same ear. Neural hearing loss is another name for retrocochlear hearing loss.
Sensorineural hearing loss results from inner ear or auditory nerve dysfunction. The sensory component may be from damage to the organ of Corti or an inability of the hair cells to stimulate the nerves of hearing or a metabolic problem in the fluids of the inner ear. The neural or retrocochlear component can be the result of severe damage to the organ of Corti that causes the nerves of hearing to degenerate or it can be an inability of the hearing nerves themselves to convey neurochemical information through the central auditory pathways.
The reason for sensorineural hearing loss sometimes cannot be determined, it does not typically respond favorably to medical treatment, and it is typically described as an irreversible, permanent condition. Like conductive hearing loss, sensorineural hearing loss reduces the intensity of sound, but it might also introduce an element of distortion into what is heard resulting in sounds being unclear even when they are loud enough. Once any medically treatable conditions have been ruled out, the treatment for sensorineural hearing loss is amplification through hearing aids.
MIXED HEARING LOSS
A mixed hearing loss can be thought of as a sensorineural hearing loss with a conductive component overlaying all or part of the audiometric range tested. So, in addition to some irreversible hearing loss caused by an inner ear or auditory nerve disorder, there is also a dysfunction of the middle ear mechanism that makes the hearing worse than the sensorineural loss alone. The conductive component may be amenable to medical treatment and reversal of the associated hearing loss, but the sensorineural component is genrally permanent.
90% of hearing loss is not medically or surgically treatable!
Audiologists: America’s Most Qualified Hearing Care Providers
An audiologist has a graduate degree and has completed a clinical internship, has passes a comprehensive national standardized examination and has professional credentials. Most states also have licensure for audiologists. These credentials will help you identify the most qualified person to provide your hearing care services.