Sudden Sensorineural Hearing Loss (SSNHL)

What sudden hearing loss feels like

• one ear suddenly sounds muffled or dull, often noticed on waking
• difficulty hearing on the phone with that ear
• sounds seem distorted or tinny
• ringing, buzzing or hissing in the affected ear (tinnitus)
• a full or blocked feeling, as if the ear needs to "pop"
• dizziness or a spinning sensation (vertigo) in some people

Because a blocked ear from wax, a cold or fluid feels similar, many people delay seeking care. A doctor can quickly tell the difference.

How it is defined

Doctors define SSNHL as a sensorineural hearing loss of at least 30 decibels across three consecutive frequencies, developing within 72 hours. Sensorineural means the problem lies in the inner ear (cochlea) or the hearing nerve, rather than the outer or middle ear (conductive hearing loss).

Causes

In about 9 out of 10 cases, no specific cause is found (idiopathic). Suspected mechanisms include:

• viral infection of the inner ear
• reduced blood flow to the inner ear
• immune-related inflammation (autoimmune inner ear disease)

Identifiable causes include:

• acoustic neuroma (vestibular schwannoma), a benign tumor on the hearing nerve, found in a small percentage of people with SSNHL
• Meniere's disease, with episodes of vertigo, fluctuating hearing and ear fullness
• head trauma or a ruptured inner ear membrane from pressure changes
• stroke affecting the blood supply to the inner ear or brainstem
• medicines that harm the ear (ototoxic), such as some antibiotics and chemotherapy
• infections such as Lyme disease, syphilis, mumps and meningitis
• multiple sclerosis and other neurological diseases

Diagnosis

First assessment

A doctor looks in the ear to rule out wax, infection or fluid, and may use a tuning fork test:

• Weber test: in sensorineural loss, the sound is heard louder in the good ear
• in conductive loss (such as wax), it is heard louder in the blocked ear

Hearing test

An audiogram measures hearing at different frequencies and confirms sensorineural loss. It should be done promptly.

Further tests

• MRI of the brain and inner ear canals with contrast to rule out acoustic neuroma and other causes
• blood tests are not routinely needed but may be done if a specific cause, such as Lyme disease or autoimmune disease, is suspected

Treatment

Steroids

Corticosteroids are the main treatment and work best when started as soon as possible, ideally within 2 weeks of onset:

• oral steroids (such as prednisone) for 1 to 2 weeks, if safe for you
• intratympanic steroid injections: a doctor injects steroid through the eardrum into the middle ear. Used when oral steroids are not suitable, or as "salvage" therapy if hearing has not recovered after oral treatment

People with diabetes need blood sugar monitoring during steroid treatment.

Hyperbaric oxygen therapy

Breathing pure oxygen in a pressurized chamber may be offered alongside steroids, ideally within 2 weeks of onset, or as salvage therapy within a month.

Treating specific causes

If a cause is found, such as acoustic neuroma, infection or Meniere's disease, it is treated directly.

Hearing rehabilitation

If hearing does not recover:

• hearing aids
• CROS hearing aids that route sound from the deaf side to the good ear
• bone-anchored hearing devices
• cochlear implants for single-sided deafness in selected people
• tinnitus management and counseling

Outlook

Many people recover some hearing, and some recover fully. A substantial proportion improve even without treatment, usually within the first 2 weeks. Recovery is more likely with:

• mild to moderate loss
• no vertigo
• younger age
• early treatment

Hearing that has not recovered after about 3 months is less likely to improve further.

Frequently asked questions

Is sudden hearing loss an emergency?

Yes. Sudden sensorineural hearing loss should be assessed within days, because steroid treatment works best when started early. If hearing loss comes with face drooping, weakness or slurred speech, call 911 as it may be a stroke.

What causes sudden hearing loss in one ear?

Most cases have no identifiable cause and may be due to viral infection, reduced blood flow or inflammation in the inner ear. Known causes include acoustic neuroma, Meniere's disease, head injury, stroke, certain medicines and infections.

Can sudden hearing loss come back on its own?

Yes, in some people. A significant proportion recover some hearing without treatment, usually in the first two weeks. But early steroid treatment improves the chances, so do not wait to see if it gets better.

How do I know if my ear is blocked or I have sudden hearing loss?

You cannot reliably tell on your own. Earwax, colds and fluid can feel similar. A doctor can examine the ear, use a tuning fork test and arrange a hearing test to tell the difference quickly.