Definitions of sudden sensorineural hearing loss (SSHL) vary widely, depending on severity, time course, audiometric criteria, and frequency spectrum of the loss. A commonly used criterion to qualify for this diagnosis is a sensorineural hearing loss of greater than 30 dB over three contiguous pure-tone frequencies occurring within a three-day period. Fortunately, the vast majority of cases of sudden hearing loss are unilateral, and the prognosis for some recovery of hearing is good.
Only about 10 to 15 percent of people with SSHL will ever know what actually caused their loss. That may be because there are many possible etiologies, including:
- Labyrinthine viral infection
- Labyrinthine vascular compromise
- Intracochlear membrane ruptures
- Immune-mediated inner-ear disease
- Infectious diseases such as Lyme disease
Sudden sensorineural hearing loss most often occurs a week or so after a person has experienced a viral or bacterial infection, such as a head cold or the flu. When they see their family physician, it is often mistakenly confused with a common middle-ear infection and treated thusly. However, if the hearing loss is one sided and/or accompanied by tinnitus or vertigo, you should see an audiologist or otologist immediately. Although spontaneous recovery does occur, SSHL is a medical emergency and requires immediate medical evaluation.
Estimates of the annual incidence of sudden sensorineural hearing loss range from five to 20 cases per 100,000 people. Many cases likely go unreported, and so the incidence may be higher. Early treatment for SSHL can save your hearing, so it’s important to see a hearing healthcare professional for immediate evaluation. Evaluation should include a careful history and physical examination, including diagnostic audiometric testing.
Due to the elusive causes of SSHL, treatment options have been somewhat controversial. No single treatment has been shown to be unequivocally effective in treating patients with SSHL. However, the anti-inflammatory properties of corticosteroids make them a common treatment option. Most people do recover at least some of the hearing lost, but about 15 percent have symptoms that continue to worsen. For those patients with resultant permanent hearing loss, hearing technologies such as hearing aids and implantable devices can often help.