Sudden sensorineural hearing loss (SSHL), or sudden deafness, is a rapid loss of hearing. SSHL can happen to a person all at once or over a period of up to 3 days. It is defined as a sudden or rapid loss of at least 30 decibels in 3 frequencies. Approximately 4,000 new cases of SSHL occur each year in the United States. It can occur at any age but most commonly affects people between the ages of 30 and 60. It occurs in both ears in 4 percent of the time.
A sudden change in hearing or the ability to understand is the usual symptom. Many people notice it when they wake up in the morning. Others first notice it when they try to use the deafened ear, such as when they make a phone call. Tinnitus is frequent and may precede the hearing loss. Ear fullness, or the ear feeling blocked, vertigo and imbalance may also occur. The presence of additional neurologic symptoms raise the possibility of a stroke.
Although there are more than 100 possible causes of sudden deafness, it is rare for a specific cause to be precisely identified. Only 10 to 15 percent of patients with SSHL are found to have a cause for their loss. A tumor of the inner ear or nerve of hearing (vestibular schwannoma) can be present in 4-10 % of patients with SSHL. Certain viruses are known to cause sudden hearing loss. The first episode of Meniere’s disease may present as a sudden hearing loss. Otosclerosis is a fairly common cause of sudden hearing loss in young women. In most patients, no cause is identified and these are labeled “idiopathic SSHL” There are many theories of why SSNHL otherwise occurs including viral infections, autoimmune, autoinflammatory, vascular and genetic. More research is required to solve this medical mystery.
The evaluation begins with a careful health history and physical examination. A complete audiometric evaluation is also performed to evaluate the type and severity of the loss. An MRI scan is universally ordered to exclude the presence of a tumor. Lab work is performed to exclude metabolic causes. Blood flow studies, balance testing and other electrophysiologic tests of the inner ear are sometimes indicated.
People who experience SSHL should see a physician immediately as early treatment increases the chances for recovery. The only effective therapy for SSHL is treatment with steroids. Oral prednisone is used to treat many different disorders and work to reduce inflammation. A high dose for 1 week followed by a taper is prescribed. Antivirals are sometimes used if viral symptoms are present with the sudden hearing loss, but their effectiveness is controversial. If the audiometric pattern is consistent with Meniere’s disease, a diuretic is prescribed.
Intratympanic steroid injections can also be considered if oral steroids are contraindicated or have not restored hearing to normal. Intratympanic injections are sometimes used in conjunction with prednisone if the hearing is very poor. This involves injecting steroid through the eardrum and into the middle ear where it is absorbed through the round window and in to the cochlea. Animal research has shown this treatment can increase the concentration of steroids into the cochlea higher than can oral steroids alone.
Recovery depends on the time delay before treatment. It should be considered a medical emergency, especially if it happens in the only or better hearing ear. Poor prognostic factors include metabolic syndrome (diabetes, hypertension, obesity) and the presence of vertigo. Less than one third of patients who seek medical help recover all their hearing back.
If hearing does not completely recover, and the ear is aidable (has good word recognition) then a hearing aid is prescribed. If the ear has such poor word recognition that a conventional hearing aid is not successfully worn (unaidable ear), then a BICROS device, a bone conduction device or a cochlear implant can be considered.
