Sudden hearing loss is moderate to severe hearing loss that develops over about 72 hours or is noticed on awakening.
Such hearing loss typically affects only one ear (unless the cause is a medication). Depending on the cause of sudden hearing loss, people may have other symptoms such as ringing in the ears (tinnitus), dizziness, or a false sensation of spinning or moving (vertigo). About 1 in 5,000 to 1 in 10,000 people each year develop sudden hearing loss. For hearing loss that develops gradually, see Hearing Loss.
Causes of Sudden Hearing Loss
Causes of sudden hearing loss fall into 3 general categories:
An unknown cause
An obvious explanatory event (such as a brain infection or head injury)
An underlying disorder
Unknown cause
In most people, no cause can be found for their sudden hearing loss. However, doctors have several theories. Possible causes include viral infections (particularly infections with herpes simplex virus), an attack on the inner ear or its nerves by the body's immune system (autoimmune reaction), and blockage of the small blood vessels of the inner ear or the blood vessels of its nerves. Perhaps different causes affect different people.
Obvious event
In many other people, a cause for the sudden hearing loss is obvious. Such causes include
Medications that damage the inner ear (ototoxic medications)
Infections
Head injury (such as a fracture of the temporal bone in the skull or sometimes a severe concussion without a fracture) can damage the inner ear and cause sudden hearing loss.
Severe pressure changes (such as those that can occur with diving or less often by bearing down during weightlifting) can cause a hole (fistula) to form between the middle and inner ear. Sometimes, such a fistula is present from birth and can spontaneously cause sudden hearing loss or make the person more susceptible to hearing loss after a head injury or pressure changes.
Ototoxic medications are medications that have damaging side effects to the ears. Some medications can rapidly cause hearing loss, sometimes within a day (especially if the dose given is too high). A few people have a rare genetic disorder that makes them more susceptible to hearing loss caused by the class of antibiotics called aminoglycosides. All people taking such antibiotics should have blood tests while taking the medication to screen for toxic levels that can cause hearing loss.
A number of infections cause sudden hearing loss during or immediately after acute illness. These infections include bacterial meningitis, Lyme disease, and many viral infections. The most common viral causes in the developed world are mumps and herpes simplex brain infection. Measles is a very rare cause because most people are immunized against the infection.
Underlying disorders
Sudden hearing loss rarely can be the first symptom of some disorders that usually have other initial symptoms. Such disorders include a tumor of the auditory nerve called vestibular schwannoma, multiple sclerosis, Meniere disease, or a small stroke due to a blockage of a branch of the artery that goes to the balance center of the brain (the cerebellum). Sometimes a syphilis infection reactivates in people who have HIV infection. This reactivation can cause sudden hearing loss.
Rarer disorders include Cogan syndrome, in which an autoimmune reaction attacks the inner ear (and also the surface of the eye); other disorders also involving blood vessel inflammation (vasculitis); and blood disorders such as macroglobulinemia, sickle cell disease, and some forms of leukemia.
Evaluation of Sudden Hearing Loss
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
Warning signs
Sudden hearing loss is itself a warning sign.
When to see a doctor
Anyone with sudden hearing loss should see a doctor right away because some causes must be treated quickly. If symptoms of dysfunction of the nervous system other than hearing loss are present, hearing loss may be a symptom of nerve or brain dysfunction.
What the doctor does
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination may suggest a cause of the sudden hearing loss and the tests that may need to be done.
Doctors note whether hearing loss affects one or both ears and whether a specific event such as head injury, diving injury, or infectious illness occurred. They ask about accompanying symptoms that involve the ear (such as ringing in the ears or ear discharge), balance center (such as disorientation in the dark or vertigo), and other parts of the brain and nervous system (such as headache, weakness, or an abnormal sense of taste). They try to identify whether people are currently taking (or recently took) any ototoxic medications.
The physical examination focuses on the ears and hearing and on examination of the nervous system.
Some Causes and Features of Sudden Hearing Loss
Cause | Common Features* | Diagnostic Approach† |
|---|---|---|
Unknown | ||
— | Deafness in only one ear No other symptoms | MRI using a contrast agent (gadolinium) |
Obvious causes | ||
Acute infection (such as bacterial meningitis, Lyme disease, mumps, or herpes simplex) | Deafness in one or both ears In people with a serious, acute illness Often headache and confusion With Lyme disease, deafness preceded by a typical rash and flu-like symptoms With mumps, pain in cheeks with swallowing | If not already done, blood tests and a spinal tap (lumbar puncture) |
Deafness usually in only one ear Sometimes fluid (bloody, blood-tinged, or clear) coming from the affected ear | CT and/or MRI | |
Pressure changes (as may occur during diving) | Deafness in one or both ears Sudden onset during causative activity (for example, scuba diving, rapid descent in airplane) or after a blow to the ear Sometimes accompanied by pain, an explosive sound, dizziness, or ringing in the ear | Tympanometry (placement of a device in the ear to measure how well sound passes through the ear) Balance testing with electronystagmography (a test to record involuntary movements of the eye caused by a condition known as nystagmus) CT or MRI |
Medications that can damage the ear (ototoxic medications), including | Deafness in both ears Sometimes dizziness and loss of balance In people who recently started taking or have recently taken an ototoxic medication | A doctor's examination Sometimes blood medication levels |
Underlying disorders‡ | ||
Vestibular schwannoma, a tumor of the auditory nerve | Deafness in only one ear Often dizziness or a false sensation of spinning or moving (vertigo) and loss of balance Sometimes drooping facial muscles and/or numbness of the face and taste abnormalities | MRI using a contrast agent (gadolinium) |
Autoimmune inner ear disease | Hearing loss in both ears that can come and go and may worsen over time | Blood tests |
Systemic rheumatic disorders and other autoimmune disorders, such as some blood disorders, disorders that cause vasculitis, and Cogan syndrome | Deafness in one or both ears Sometimes joint pains or a rash | Blood tests |
Meniere syndrome (including Meniere disease) | Deafness in only one ear in most affected people Sometimes dizziness and/or ringing in the ear | MRI using a contrast agent (gadolinium) |
Deafness in only one ear Sometimes weakness or numbness that comes and goes and occurs in different parts of the body | MRI using a contrast agent (gadolinium) Sometimes a spinal tap | |
Stroke (affecting the cerebellum) | Deafness in only one ear Sometimes difficulty with balance or coordination | MRI using a contrast agent (gadolinium) |
Reactivation of syphilis in people with HIV infection | Deafness in one or both ears Sometimes risk factors for sexually transmitted infections (such as unprotected sex, multiple partners) | Blood tests Sometimes, spinal tap (lumbar puncture) |
* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present. Features overlap between causes. | ||
† Although a doctor's examination with an audiogram should always be done, it is only mentioned in this column if the diagnosis can sometimes be made only by the doctor's examination with an audiogram, without any additional testing. In other words, additional tests may not be needed. | ||
‡ Rarely, sudden hearing loss is the first symptom of a disorder that usually has other symptoms first. Symptoms typical of these disorders may not be present at all. However, some people disregard mild symptoms that may be discovered by the doctor through careful questioning and examination. | ||
CT = computed tomography; MRI = magnetic resonance imaging. | ||
Testing
Typically, people should have an audiogram (a hearing test). Unless doctors think the problem is clearly an acute infection or medication toxicity, they usually also do gadolinium-enhanced magnetic resonance imaging (MRI) or computed tomography (CT), particularly when the hearing loss is greater in one ear. Other tests are done based on the likely cause. For example, people who had a head injury should have MRI. People at risk of sexually transmitted infections should have blood tests for HIV infection and syphilis.
Treatment of Sudden Hearing Loss
When the cause is unknown, about half of people regain normal hearing and hearing is partially recovered in others. Improvement, if it can be achieved, usually occurs within 10 to 14 days. Recovery from an ototoxic medication
Key Points
Why sudden hearing loss occurs is usually unknown.
A few people have an obvious cause (such as severe head injury or infection or use of medications that can damage hearing).
In a very few people, sudden hearing loss is the first sign of an underlying disorder.
Doctors do audiometry, CT and/or MRI, and other tests for suspected causes.
Treatment is focused on known causes of the sudden hearing loss.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institute on Deafness and Other Communication Disorders: Information regarding hearing loss and other communication disorders, spanning functions of hearing, balance, taste, smell, voice, speech, and language
