Definition
Sudden hearing loss is a rapid, sudden hearing loss that usually occurs within a 72-hour period. Typically, sudden hearing loss occurs in only one ear. It may affect the hearing cells in the inner ear or the auditory nerve. It may also involve central damage to the auditory areas of the brain responsible for sound processing. It may affect some or all of the sounds heard by the ear, and can vary in severity from mild to severe. Unfortunately, there are often no warning signs that hearing loss is imminent.
Prevalence
According to an article by the College of Family Physicians of Canada (2014), sudden sensorineural hearing loss (affecting hearing cells) affects between 5 and 20 people per 100,000 population. It affects both men and women. The greatest number of cases occurs in people aged between 50 and 60, but can occur at any age.
Symptoms
Hearing loss is a rapid and drastic decrease in hearing of at least 30 dB in some or all of the sounds heard by the ear. It occurs over a period of up to 3 days. It usually affects only one ear. Depending on the sounds affected, it may feel like a blocked ear. In many cases, sudden hearing loss is also accompanied by tinnitus, i.e. the person will hear a continuous ringing or whistling in the affected ear. Some people will also experience rotary vertigo or dizziness, which may have occurred before or at the onset of hearing loss.
Causes
It is often difficult to find the exact cause of sudden hearing loss. It is therefore often defined as idiopathic, i.e. with no known cause, as in the case of Meniere’s disease. There are, however, several possible causes:
Vascular
The blood vessels in the inner ear are particularly small and narrow. Thrombosis may occur, i.e. the formation of a blood clot that blocks the blood vessels. Or it could be an embolism, where the blood clot originates elsewhere in the body and travels through the bloodstream to the blood vessels in the inner ear. In both cases, as blood flow to the ear area is cut off, the oxygen supply necessary for the proper functioning of the hearing cells is severely reduced, if not completely suspended. This lack of oxygen can lead to potentially permanent damage to the hearing cells, resulting in hearing loss.
Infectious
It is possible that a virus is attacking the cells of the inner ear. However, it is not always possible to identify the virus. In labyrinthitis, for example, a virus attacks the entire inner ear, causing permanent hearing loss and intense, rotary vertigo. It could also be a middle ear infection, commonly known as otitis. Fluid accumulates behind the eardrum, limiting the propagation of sound to the hearing cells. Meningitis is another possible cause. This is an inflammation of the tissues surrounding the brain, which can reach the auditory areas processing sound signals and cause hearing loss.
Traumatic
Hearing loss can also occur as a result of acute sound trauma. This refers to exposure to very high levels of sound, such as a gunshot or explosion. These sudden exposures to high sound levels will permanently damage the hearing cells. Barotrauma is also possible. A tube called the Eustachian tube links the ears to the nose. Among other things, it allows air pressure changes in the middle ear to maintain a balance between the pressure inside the ear and that outside, in order to protect the eardrum. Thus, when there is a pronounced change in external pressure, such as when scuba diving or flying at altitude, the eustachian tube may not be able to balance the air pressure behind the eardrum, causing it to rupture and leading to reduced hearing. Injuries can also occur directly in the ear, such as a blow to or near the ear, affecting the hearing cells and leading to hearing loss. Head trauma could also be the cause of sudden deafness.
Other
Tumors, benign or malignant, can also develop on the auditory nerve, reducing the passage of electrical signals to the auditory areas of the brain. Autoimmune diseases such as polyarthritis and lupus can cause hearing damage. This type of disease is characterized by a dysfunction of the immune system. The immune system will attack the body’s normal components, such as the hearing cells. One possibility is an accumulation of earwax in the ear canal. When the ear canal is blocked, sounds from the outside cannot reach the other parts of the ear properly.
Treatment
When sudden hearing loss is suspected, the first step is to consult an audiologist as soon as possible. It is suggested that you see the audiologist at least within 3 days of the onset of hearing loss symptoms. The audiologist will ask you several questions to better understand your symptoms. Next, he or she will perform a complete hearing evaluation to determine whether hearing loss is, in fact, present and what type it is. Following this, a referral to an ENT doctor, an ear specialist, will be made so that appropriate treatment can be provided.
Depending on the type of hearing loss and its cause, the referral may be more urgent, so that you can receive treatment as quickly as possible. This may involve medication such as corticosteroids. On some occasions, steroid administration directly through the eardrum is also considered by the treating ENT doctor. He or she will determine the appropriate treatment.
In the case of conductive hearing loss, as in the case of otitis, hearing loss can disappear on its own, with antibiotics in case of infection or regular nasal hygiene.
In the case of sensorineural hearing loss, i.e. damage to the hearing cells, prompt treatment by an ENT specialist is essential to ensure appropriate therapy. The faster a sudden hearing loss is treated, the greater the chance of recovering hearing. The prognosis is increasingly poor as the time of onset of hearing loss increases.
Follow-up with the audiologist will be scheduled to measure changes in your hearing. In the event of persistent partial or total hearing loss, the use of a hearing aid may be considered to reduce the hearing difficulties caused by the hearing loss. Communication strategies can also be put in place to promote speech understanding. The audiologist you meet will be able to inform you and help you in your decision-making process.
Things to remember
If your hearing diminishes drastically within a few days, consider consulting a hearing health specialist as soon as possible, so that you can receive the appropriate treatment if necessary.
Don’t hesitate to contact an audiologist if you have any questions about your hearing or that of a loved one, so that he or she can direct you to the right professionals.
