What is Sudden Hearing Loss?

Imagine waking up to find that your hearing has disappeared overnight, or putting your phone to your ear only to find that you cannot hear in one ear. This sudden onset of hearing loss is considered a medical emergency, and you should seek medical attention immediately. It can be frightening to suddenly lose one of your vital senses. So let’s look at what causes sudden hearing loss and what treatment options are available to you?

What is sudden hearing loss?

When experts refer to sudden hearing loss, they are referring to a condition known as sudden sensorineural hearing loss (SSNHL). This is when hearing worsens over three days or less. In most cases, SSNHL affects only one ear. People with SSNHL may also hear a noise in their ears (tinnitus) and/or feel dizzy or unsteady (vertigo). SSNHL affects up to 27 people per 100,000 in the United States. Although it is not very common, SSNHL is considered a medical emergency as the hearing loss may be permanent if it is not treated early. If this happens to you or someone you know, it is very important that you seek urgent medical attention.

What is sensorineural hearing loss?

Sensorineural hearing loss is caused by damage to the organ of hearing (cochlea) or to the nerve that transmits information from the cochlea to the brain (auditory nerve). Hearing loss from aging and noise exposure are common examples of this type of hearing loss. In most cases, sensorineural hearing loss is permanent. The good news is that SSNHL is one of the few conditions where sensorineural hearing loss may sometimes recover.
Sensorineural hearing loss is different from conductive hearing loss which is caused by problems in the outer or middle part of the ear. Wax in the ear canal can become plugged or fluid can build up behind the eardrum, causing a blocked sensation or sudden hearing loss. Most times, these conditions are easily diagnosed and treated. The ability to hear usually returns to normal with treatment.

What causes SSNHL?

Although there are over a hundred known causes of SSNHL, in over 90% of cases, the cause is unknown (called idiopathic SSNHL). Some of the known causes of SSNHL include:

  • Infections such as Lyme disease, meningitis, and mumps
  • Ear diseases such as Meniere’s disease
  • Trauma to the ear such as from a concussion or a very loud noise
  • Vascular diseases such as a stroke
  • Tumors such as an acoustic neuroma (growth on the auditory nerve)
  • Autoimmune diseases such as lupus
  • Neurological diseases such as migraines or multiple sclerosis
  • Medications that are toxic to the ear such as chemotherapy drugs.

Experts aren’t exactly sure what causes idiopathic SSNHL. They suspect that it may be caused by a lack of blood supply to the cochlea, tearing of the very delicate cochlea membrane (casing) from trauma, or inflammation of the cochlea from viral infections. It can be very upsetting and frustrating for people with SSNHL when doctors are not able to find a cause for their hearing loss.

How is SSNHL diagnosed?

A physician will take a detailed medical history and conduct a physical examination. When someone experiences sudden hearing loss, they will first need to work out if the hearing loss is conductive or sensorineural. Usually, they can easily diagnose outer or middle ear problems by examining the ear and using tuning fork tests. A tuning fork is a metal fork that makes a sound when it vibrates.

If the hearing loss can’t be explained following an exam, a hearing test should be done as soon as possible to confirm a sensorineural hearing loss. A hearing test involves responding when one hears a series of tones ranging from bass to treble, even if they are very faint.

Physicians also need to identify any known causes of SSNHL. They may recommend further tests, such as magnetic resonance imaging (MRI), to rule out retrocochlear hearing loss which occurs due to problems along the auditory nerve, brainstem, or brain.

How is SSNHL treated?

For people with idiopathic SSNHL, experts have found that hearing may improve by itself without any treatment in 32% to 65% of cases. If treatment is recommended, it should begin as soon as possible, ideally within two weeks of symptoms starting. The earlier treatment begins, the better the chances that the hearing will recover. The most common treatment is corticosteroids. Physicians may prescribe corticosteroids taken in tablet form or injected through the eardrum. A combination of corticosteroids and hyperbaric oxygen therapy are also used. Another hearing test should be done when treatment is completed and within another six months, in order to assess how successful the treatment has been.

Will SSNHL recover?

In most cases, illnesses that are known to cause SSNHL also cause permanent damage to the inner ear and result in permanent hearing loss. Sometimes early treatment can prevent further damage and hearing loss. Although hearing will recover in about half of people with idiopathic SSNHL, there is no way of knowing who will be affected or not. One factor that affects recovery is the duration of hearing loss. If a person receives treatment within two weeks of symptoms starting, there is a good chance that hearing will recover. Hearing may improve for up to six weeks or more after treatment is completed. If the hearing loss does not recover within three months of symptoms starting, with or without treatment, hearing is not likely to improve. Another factor that affects recovery is the severity of SSNHL. If the hearing loss is mild to severe, there is an estimated 80% chance of recovery with treatment. If the hearing loss is severe to profound (complete hearing loss), hearing is not likely to improve. People who have SSNHL with vertigo and people older than 65 years have a lower chance of recovery.

What happens if SSNHL doesn’t recover?

Sudden, permanent hearing loss and/or tinnitus can be very difficult to live with. If a hearing loss does not recover, physicians may recommend the care of a hearing healthcare provider. For people with mild to severe hearing loss, a hearing health care provider may recommend a hearing aid for the affected ear. For people with severe or profound hearing loss in one ear, CROS (contralateral routing of signal) or biCROS (bilateral contralateral routing of signal) hearing aids may be a good option. This device picks up sound on the side of the affected ear and transmits it wirelessly to a hearing aid on the better ear. Surgically implanted devices such as BAHAs (bone-anchored hearing aids) or cochlear implants are other options. Hearing health care providers are also trained to help people with tinnitus.

The sudden onset of hearing loss can be both scary and frustrating when the cause cannot be identified, however, if caught early, treatment may be effective for most people. The sooner you see a healthcare provider, the better your chances of recovery and a better quality of life.

Written byTarryn Sparg

Masters in Audiology

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