Last modified 10/2012
Soha N. Ghossaini, MD, is assistant professor in the Department of Otolaryngology Head and Neck Surgery at Columbia University College of Physicians and Surgeons, New York Presbyterian Hospital, Columbia Center.
- What is Sudden Hearing Loss?
- What Causes Sudden Hearing Loss?
- How is Sudden Hearing Loss Diagnosed?
- How is Sudden Hearing Loss Treated?
- Rehabilitation of patients with persistent hearing loss
- Research Studies in Sudden Hearing Loss
What is Sudden Hearing Loss?
Sudden hearing loss (SHL) is defined as greater than 30 dB hearing reduction, over at least three contiguous frequencies, occurring over a period of 72 hours or less. Some patients describe that the hearing loss was noticed instantaneously in the morning and others report that it rapidly developed over a period of hours or days. The severity of the hearing loss however varies from one patient to another and only one ear is usually affected. Sudden hearing loss frequently involves both ears (Schreiber et al 2010). Tinnitus is usually reported in patients with SHL loss and vestibular symptomsare present in roughly 40% of cases (Mattox & Simmons 1977). The incidence of SHL has been reported to be 5-30 per 100,000 person per year (Nosrati-Zarenoe et al 2007, Wu et al 2006)and accounts for 1% of all sensorineural hearing loss cases (Hughes et al 1996). Males are equally affected as females. The average age at onset is reported to be 46 to 49 years with increasing incidence with age (Byl 1984).
What Causes Sudden Hearing Loss?
There are many causes for sudden hearing loss which include infectious, circulatory, inner ear problems like meniere’s disease, neoplastic, traumatic, metabolic, neurologic, immunologic, toxic, cochlear, idiopathic (unknown cause) and other causes. Unfortunately, even after a thorough search for a possible pathology, the cause of sudden hearing loss remains unknown in most patients (Hughes et al 1996).
How is Sudden Hearing Loss Diagnosed?
Evaluation usually begins with a careful history and physical examination looking for potential infectious causes such as otitis media, systemic diseases and exposure to known ototoxic medications. In essence, SHL is diagnosed by documenting a recent decline in hearing. This generally requires an audiogram. Blood studies are usually performed in an attempt to rule potentially systemic causes of SHL including syphilis, Lyme disease, metabolic, autoimmune, and circulatory disorders. Magnetic resonance imaging (MRI) of the brain is recommended to rule out an acoustic neuroma which is reported to be existent up to 15% of patients with sudden hearing loss (Aarnisalo et al 2004).
How is Sudden Hearing Loss Treated?
Due to the lack of a definite cause of sudden hearing loss, its treatment has been controversial. Over the years, this has included systemic steroids, antiviral medications, vasodilators, carbogen therapy either (alone or in combination) or no treatment at all.
The no treatment option was based on the high reported rate of spontaneous recovery up to two third of cases (Cekin et al 2009).
Oral corticosteroid therapy is among the few treatment modalities that that have gained acceptance and proved to be effective in selected studies and most importantly when compared to placebo in 2 randomized controlled trials (Moskowitz et al 1984, Wilson et al 1980). On a different level, and in a retrospective study by Chen et al. in 2003, oral steroids were proved to be effective in the treatment of SHL. The literature is inconsistent however regarding the dose and the duration of treatment of oral steroids used in the treatment of SHL within the same study or across different studies.
A recent study (Battaglia et al 2008) indicated that a combination of high-dose prednisone taper (HDPT) in addition to intratympanic dexamethasone (IT-Dex) therapy may improve hearing recovery. Another recent study showed a non-statistical difference in hearing recovery for oral vs. intratympanic steroid treatment (Rauch et al 2011).
The effectiveness of hyperbaric oxygen treatment in SHL either as a primary, adjunct or as a secondary therapy in SHL treatment failures has not been conclusively established in the literature. Although some studies have shown improvement in hearing after hyperbaric oxygen treatment (Fattori et al 2001, Narozny et al 2004) the lack of randomized control trials makes it difficult to draw any conclusion (Horn et al 2005),
Antivirals seem reasonable, given the frequency that herpes family viruses have been associated with SHL. In an animal study, combination treatment with an antiviral (acylovir) and steroids reduced damage in animals whose ears were inoculated with herpes simplex virus type 1 (HSV-1), compared to treatment with either acyclovir or prednisolone alone (Stokroos et al 1999). Unfortunately, in humans, antiviral (like acyclovir or valacyclovir) treatment when studied in randomized controlled studies did not add any benefit to steroid treatment alone (Tucci et al 2002, Uri et al 2003, Westerlaken et al 2007). In addition these medications will unlikely be of help when the cause is a virus that is not in the herpes family, and one rarely knows at the time of the hearing loss which if any virus is responsible. In a survey of 104 ENT physicians, %50 reported using antiherpetic therapy despite lack of efficacious evidence (Conlin & Parnes 2007, Shemirani et al 2009).
Several vasodilators have been tried with mixed results (Fetterman et al 1996, Kronenberg et al 1992, Wang et al 2012). To date the effectiveness of vasodilators on SHL is not well established in the literature.
A recent meta-analysis concerning SHL and vasodiolators is available: Wang and associates (2010).
Rehabilitation of patients with persistent hearing loss:
Sudden hearing loss could result in variable degrees of hearing handicap. Patients most commonly report difficulty of hearing people sitting on their deaf side and difficulty hearing in background noise. The rehabilitation of patients after SHL depends on the degree of the resultant hearing loss and ranges from no intervention to the use of hearing aids and other assistive listening devices. In patients with resultant severe to profound sensorineural hearing loss however, regular and other powerful hearing aids might not be an option. In the past, rehabilitation of such a group of patients was limited to the use of contralateral routing of signal (CROS) hearing aid with reported mixed satisfaction, and most patients were left unaided. Currently the bone anchored cochlear stimulator (BAHA system) offers an alternative to the CROS system and was found to be effective in patients with unilateral severe to profound sensorineural hearing loss and to provide a greater perceived benefit when compared to the CROS hearing aid (Wazen et al 2003).
Research Studies in Sudden Hearing Loss
Intratympanic steroid therapy is being currently used in patients where systemic steroids are contraindicated or in patients who fail to respond to oral steroids steroids with mixed results (Herr & Marzo 2005, Slattery et al 2005). In this procedure, steroids are perfused or injected into the middle ear and absorbed into the inner ear via the round window membrane. Theoretically, when used intratympanically, the concentration of the drug at its site of action (inner ear) will be higher and its side effects will be minimized.
Incomplete response to oral steroids is not well understood and is speculative. One of many possible reasons is inability to reach adequate levels of steroids in the inner ear with conventional oral steroid treatment. Animal studies have shown a higher perilymph (inner ear fluid) concentration of steroids when installed in the middle ear as compared to their systemic use (Parnes et al 1999). However, a recent study showed only mild improvements for a group of patients treated via steroid perfusion who had initially failed to recover with systemic treatment (Haynes et al 2007).
Clinically, the success rate of Intratympanic steroid therapy in patients with SHL is variable in the literature and the available studies are limited to retrospective and non-controlled prospective ones. In those studies steroids were used in various concentrations, regimens and delivery methods and their effectiveness have not been established due to the lack of randomized controlled trials. There have been some studies in the literature that discussed the effectiveness of Intratympanic steroid therapy as a salvage mode of therapy in patients who failed to respond to oral steroids (Herr & Marzo 2005, Slattery et al 2005).
Randomized controlled trials are needed to better establish the effectiveness of Intratympanic steroid therapy in the treatment of patients with SHL. Currently a randomized controlled trial is being initiated by the author at the New York Presbyterian Hospital of Columbia and Cornell New York NY in order to evaluate the effectiveness of Intratympanic steroid therapy in patients with SHL and to compare it to the more standard method of treatment, oral steroids.
In conclusion, very few placebo controlled studies have been performed of treatment of SHL. For this reason, there is presently a limited ability to determine what the optimal treatment of SHL is. At the American Hearing Research Foundation (AHRF), we are interested in funding good research on this condition. We have funded basic research on similar conditions in the past. Learn more about donating to American Hearing Research Foundation (AHRF).
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