Sudden hearing loss is defined as a loss of hearing that begins with no warning and for no apparent reason, developing over 24 hours or less. The hearing loss arises in the hearing organ of the inner ear (cochlea) or in the hearing nerve, not in the middle or outer ear.

Most cases of sudden hearing loss are viral, and most patients are treated with steroids. Patients with mild degrees of hearing loss usually recover.

Despite the fact that sudden hearing loss is a relatively common disease that has been the subject of considerable clinical research, sudden hearing loss continues to be vexing for doctor and patient because the cause often cannot be determined, the treatment isn’t always effective, and the prognosis is usually uncertain.

Many patients with sudden hearing loss are initially given another diagnosis, such as ear infection or wax impaction, and so the true nature of their problem may not be recognized until later, delaying appropriate treatment. Even with prompt treatment, however, patients may not improve, and hearing loss may be permanent.

Causes of Sudden Hearing Loss

In many cases, the cause of the hearing loss cannot be determined with certainty. Possible causes of sudden hearing loss include:

• Viral infection
• Stroke
• Loss of blood flow (ischemia) to the inner ear
• A ruptured membrane in the inner ear

Viruses are believed to be the most common cause of sudden hearing loss.

Secondary Causes of Hearing Loss

Sudden hearing loss can be an indication of an underlying medical condition, such as Meniere's disease (a disruption of the fluid balance in the inner ear), autoimmune inner ear disease (when the body’s immune system mistakenly attacks the tissues of your inner ear), or a tumor of the hearing nerve (acoustic neuroma). Tumors are quite rare and can be ruled out by MRI.

How is Sudden Hearing Loss Treated?

It is generally accepted that steroids (cortisone), taken orally over 1 to 2 weeks, are the single most beneficial treatment for sudden hearing loss, although they do not lead to improvement in every case. Sometimes an additional (“booster”) dose of steroids is injected directly into the ear. Injection achieves higher doses in the inner ear fluids, but it does not always lead to recovery of hearing.

Other treatments are used selectively, depending on the findings and suspected cause of the hearing loss. Anti-oxidants have been shown to promote healing of the inner ear. Antivirals have also been used, but two well-controlled studies, one in the U.S. and one in Europe, have failed to show any benefit. Stroke or ischemia can be treated with blood thinners. Inner-ear membrane rupture is treated with bedrest; in certain cases, surgical exploration of the ear may be recommended to patch the inner ear membranes (round and oval windows) with fat from the earlobe (a minor procedure with low risk but uncertain benefit). Specific causes have specific treatments: AIED is treated with steroids or immune suppressants, Meniere’s disease with diuretics and low-salt diet, acoustic neuroma with surgery or radiotherapy.

Most doctors agree that treatments are most effective when started as early as possible after the onset of the loss. Although not all patients regain hearing, options exist even for patients left with permanent hearing loss.