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Sudden Hearing Loss

Sudden Sensorineural Hearing Loss (SSNHL)

The onset of sudden hearing loss can be the cause of significant stress and worry in the affected individual. Sudden hearing can be the result of numerous different causes. In general, there are two types of hearing loss. One is conductive hearing loss, in which there is a problem getting sound from the environment to the inner ear. In conductive hearing loss, there is typically a problem with the external ear canal, eardrum, or middle ear. In the second general category of hearing loss, sensorineural hearing loss, the ear canal, eardrum, and middle ear space are normal. The problem is located in a site out of view of the physical exam, namely the inner ear or nerve to the inner ear. Patients with sudden sensorineural hearing loss (SSNHL) most commonly present to their physician with a rapid onset of hearing loss, but a normal physical exam of the ear.

How common is SSNHL?

SSNHL is not a common problem, in a population of 100,000 people, between 5-27 people will develop this type of hearing loss each year [1, 2]. In the United States, there are reports of up to 66,000 new cases diagnosed each year [2].

How is SSNHL defined?

SSNHL is most commonly defined as a sensorineural hearing loss of at least 30 dB at three frequencies developing over a time period less than a 3 days [3, 4]. Typically, only one ear is affected, however, in less than 2% of cases, the loss involves both ears [5]. Most studies quote a rate of spontaneous improvement (improvement in hearing without any treatment) of about 30-60% of patients [6, 7]. If spontaneous recovery does occur, it most commonly occurs within the two weeks after onset [6].

What Causes SSNHL?

Numerous causes of SSNHL are known, but a certain cause for SSNHL is not identified in 90% of cases [8]. In those cases of unknown cause, most are generally thought to be of a virally-mediated process [9, 10]. In the physician’s office in the setting of a new onset SSNHL, there is no current way to determine with certainty if a virus is the cause, or if so, which virus is at fault. Direct sampling of fluid from the inner ear or tissue from the hearing nerve to sample for viruses is not possible without the likely result of irreversible hearing loss. Other potential causes include insufficient blood supply to the ear or the body’s own immune system attacking the ear.

What other symptoms accompany SSNHL?

Numerous symptoms can accompany SSNHL. One of the most common symptoms that occurs is a sensation of fullness or pressure in the ear. This frequently leads patients or primary care doctors to treat patients as if the problem is caused by fluid in the middle ear space. Treatment and the correct diagnosis can be delayed by treatment with unhelpful medications such as antibiotics, decongestants, and nasal sprays. Vertigo is a commonly associated symptom and is seen in roughly 30% of patients with SSNHL [11].

What Testing is needed for SSNHL

After the onset of SSNHL, testing is very important and requires an audiogram (hearing test). This involves testing the ability to hear tones and to understand speech. It is one thing to be able to hear tones, but far more important is the ability to hear and understand speech. A tympanogram is performed to assess the mobility of the eardrum to ensure it is appropriately mobile. Hearing loss is best described in terms of a descriptive term such as mild, moderate, moderately-severe, severe and profound. People are frequently told a percentage of hearing they have lost, which is a complicated calculation that is rarely performed.

Another important diagnostic test is an MRI scan. This is important because roughly 3% or more of SSNHL cases are caused by a benign tumor of the hearing and balance nerve called a vestibular schwannoma [12-14]. Classically, an MRI was performed with gadolinium contrast, but studies have shown a protocol that does not require contrast (FIESTA, CISS) is as sensitive in identifying tumors if they are present [15]. An imaging center must have some expertise to be able to appropriately perform this study with sufficiently high quality, therefore contrast may be required at some centers. With an open MRI, contrast will also be required. If an MRI cannot be performed (as in the case of a pacemaker), other studies can be used to lessen the suspicion of a vestibular schwannoma, such as auditory brainstem response testing [16].

In general, laboratory testing is not needed or helpful in the treatment of SSNHL. The American Academy of Otolaryngology – Head and Neck Surgery recommends against routine blood testing after the onset of SSNHL [3].

What is the appropriate treatment for SSNHL?

Once the diagnosis of SSNHL is confirmed, a discussion of available treatment options must be carried out with a physician knowledgeable in the disorder. A great number of treatments have been described over time, but most have been found to be unhelpful. Treatments found to be unhelpful include: antiviral medications [17], volume expanding agents (dextran) [18], and vasodilators [19].

One possible treatment is no treatment at all, or a period of observation. As described previously, some patient will improve without any medical intervention. There are some features of the hearing loss that may indicate a favorable result with simple observation. These include a low frequency hearing loss and a mild hearing loss. Most hearing improvement noted with observation is seen within the first two weeks after onset [6].

Oral “Systemic” Steroids

Although controversial, the most commonly prescribed treatment for SSNHL is the use of oral steroids. A randomized, placebo-controlled trial in 1980 demonstrated two-third of patients treated with steroids showed improvement while only one-third of patients treated with placebo had improvement of their hearing[20]. Other studies have shown no effect with steroid use [21, 22]. Prednisone is typically used at doses ranging from 60-80 mg daily for 7-14 days, then a tapering of the dosage over the following days. The optimal dosage of steroid and the time needed for treatment in not defined by any medical study. The amount of steroid used in a pre-packaged “dosepack” is generally considered to be an inadequate dosage and duration of steroid.

Steroids are clearly not effective in all patients, as not all patients have improvement with their use. However, some patients are clearly responsive to steroids which is demonstrated in trials of patients receiving steroids injected into the middle ear space (discussed below).

Steroids are associated with side-effects that can include: elevation in blood glucose, increased pressure within the eye, hip joint problems with possible need for joint replacement surgery, inability to sleep, weight gain, fluid retention, bone weakening, psychiatric disturbances, among others.

In an ideal situations, steroids would only be prescribed to patients that will benefit from their use, and avoided in those who will improve with no treatment. However, we do not currently have a laboratory test that will demonstrate who will or will not respond to steroids. While treating some patients that will derive benefit, some patients are exposed to the side effects of steroids without hearing benefit. In our opinion, since major long-term complications of steroids are rare, we feel the benefit of treatment with oral steroids outweighs the risk.

Transtympanic/Intratympanic Steroids

Steroids can be delivered to the inner ear by injection of medication through the eardrum into the middle ear. The steroid then passes through a membrane called the round window and into the inner ear. Delivery of steroid by this injection achieves much higher concentrations of steroid within the inner ear than that seen with oral steroid administration [23, 24]. In animals, the medicine within the inner ear lasts for less than 24 hours [23]. For this reason, to maintain a prolonged, adequate dosage of steroid within the inner ear, multiple injections are performed.

The steroid injection procedure is well-tolerated and performed in the office. The eardrum is visualized under a microscope, and a small needle is used to inject the medicine into the middle ear. The patient lies in the exam chair with her head turned for 30 minutes to allow the medicine to diffuse into the inner ear. The patient does her best not to swallow or speak during this period to minimize opening of the eustachian tube. Eventually, the fluid will exit the middle ear via the eustachian tube and run into the back of the nose. A small amount of steroid is absorbed into the bloodstream, but at much lower concentrations than that seen with oral use. There is a tiny chance that a persistent hole in the eardrum may form.

Transtympanic steroids have been shown to be equally effective to oral steroids [25]. In addition, transtympanic steroids have been shown, in a majority of studies, to be effective in treating patients who have failed to improve with observation, oral steroids alone, or other treatments[26-29]. This “salvage” treatment with transtympanic steroids has been shown to be effective even 3 months after the onset of hearing loss [26].

Combination Oral and Transtympanic Steroids

Combination therapy with oral and transtympanic steroids have been shown to be superior to one form of steroid alone [30]. This combination treatment is our preferred treatment at the Tampa Bay Hearing and Balance Center.

Rationale for the Treatment Algorithm at the Tampa Bay Hearing and Balance Center

For most patients, we recommend an initial treatment with a combination of oral and transtympanic steroids for SSNHL. The transtympanic steroids result in a high dose of steroid within the inner ear, and we know a higher dosage of steroid leads to better results [31]. Because steroid within the inner ear persists for less than 24 hours, we recommend daily injections. We typically recommend a minimum of three injections, but do not have a set maximum of injections, instead we treat until the hearing improvement stabilizes. We do not place a tube or wick as the rates of persistent eardrum perforation has been reported to be as high as 29% [32].

We utilize oral steroids due to the fact that transtympanic steroids alone will not reach the hearing (cochlear) nerve. Oral steroids will deliver steroid to the hearing nerve, which may be a site of dysfunction.

By way of this combination, the fluid of the inner ear and the hearing nerve can be treated with steroids to maximize treatment success.

Each patient much be treated on an individual basis and only with a thorough examination and history can a treatment regimen be recommended.

 

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