The management of patients with sudden sensorineural hearing loss (SSNHL) often includes immediate medical treatment combined with diagnostic and rehabilitative audiology strategies. The partnership of otolaryngology and audiology is critical in caring for these patients. Although treatment approaches may vary and etiologies differ, one factor that remains constant among patients is the loss of hearing and its impact on communication and function.
SSNHL—also known as acute cochlear labyrinthitis and idiopathic sudden hearing loss—is defined by unexplained hearing loss of at least 30 dB at three or more contiguous frequencies, developing over fewer than three days in an otherwise healthy patient. A sudden loss of hearing will be experienced by five to 20 per 100,000 patients annually, although a significant number of cases go unreported. In most patients, the hearing loss is unilateral. A sudden loss of hearing—like a sudden loss of vision—requires urgent medical care.
Recovery occurs in 32%–65% of patients and is more likely if there is a short interval between the onset of symptoms and treatment, an absence of concurrent vertigo, a mild to moderate hearing loss, a mid-frequency/upsloping audiometric pattern, and patient age of 15–40 years old. Because the chance of recovery is greater if the hearing loss is treated early—and because a significant percentage of patients do not recover their hearing—evaluation of treatment options is critical.
Many etiologies of SSNHL have been suggested, including infectious, inflammatory, neoplastic, and metabolic abnormalities. However, viral infection is currently the most favored etiology, with herpes simplex virus (HSV) and herpes zoster (HZ) the most commonly implicated in the development of this process.
When an adult presents with SSNHL, an audiologic evaluation should be conducted using a standard assessment battery that includes pure tone and speech audiometry, self-assessment, immittance measurement, acoustic reflexes, and otoacoustic emissions (OAE). Further evaluation may include electrophysiology measures and vestibular assessment. Medical assessments such as magnetic resonance imaging (MRI) should be performed to examine the posterior cranial fossa for the presence of a tumor, such as acoustic neuroma, that may affect hearing. Other tests, such as rheumatologic markers and immunoglobulin levels, may be pursued if autoimmune or immunodeficiency processes are suspected as a potential cause of the hearing loss.
Systemic steroids are the typical treatment for patients with SSNHL. The inner ear contains glucocorticoid and mineralocorticoid receptors and steroids have been shown to decrease inflammation associated with labyrinthitis, enhance cochlear blood flow, and improve striavascularis function and morphology. A wide range of steroid types, doses, and treatment durations have been used, but the average treatment with systemic steroids includes divided doses of 60 mg oral prednisone tapered over two weeks.
The evidence to support efficacy of systemic steroids is limited. In 1980 a placebo-controlled, double-blind study supported the use of systemic steroids, demonstrating that oral steroids improved recovery rates in 78% of patients with moderate SSNHL (Wilson et al., 1980). However, a number of studies conducted after 1980 suggest that systemic steroids perform no better than a placebo (Byl, 1984; Cinamon et al., 2001; Conlin & Parnes, 2007).
Because of the potential limited efficacy of systemic steroids, other treatment approaches have been considered. Given that SSNHL may result from viral labyrinthitis, studies have paired systemic steroids with antiviral medication. Although animal studies were promising, a randomized prospective trial in humans found no significant improvement in hearing recovery rates with the addition of valacyclovir to a systemic steroid regimen (Stokroos et al., 1999; Tucci et al., 2002). Other treatments such as the use of vasodilators, plasma expanders, diuretics, anticoagulants, and vitamins have not been proven to be efficacious. Hyperbaric oxygen treatment, based on observations that oxygen tension in the perilymph of some patients with SSNHL is decreased, has also been investigated, but no clear conclusions have been drawn about its efficacy.
The use of intratympanic (IT) steroids (also known as transtympanic therapy, middle-ear perfusion, and inner-ear perfusion) for SSNHL was first described by Silverstein et al. in 1996. This approach delivers a high concentration of steroids to the cochlea through the round window membrane. IT steroids can be administered in an office-based setting using a relatively painless procedure. Additionally, unlike systemic steroids, IT steroids can be used in patients with tuberculosis, HIV, diabetes, and other forms of immunodeficiency.
Systemic side effects are uncommon, but administration of IT steroids may be associated with complications that can include tympanic membrane perforation, pain at injection site, otitis media, vertigo (though usually temporary), and hearing loss. Dosing options for IT steroids include varying the timing of treatment, dosing schedules, and methods of administration. IT steroids may be used at the same time as primary systemic therapy, instead of systemic therapy, or after primary systemic therapy has failed (so-called salvage therapy). Other methods for delivering IT steroids include a single myringotomy with injection, multipleyringotomies and injections, or drops with tube or wick placement to facilitate the passage of medication into the middle ear.
Although a number of studies have been conducted, it is unclear whether IT steroids actually improve patient outcomes. A recent randomized, placebo-controlled, double-blind prospective study (Battaglia et al., 2008) investigated the use of IT dexamethasone in combination with high-dose systemic steroid treatment. Complete recovery was defined as recovery to within 5% of the word recognition score (WRS) or within 5 dB pure tone average (PTA) of the unaffected, contralateral ear; partial recovery was defined as recovery of 15 dB PTA or a 25% improvement in WRS.
Overall, the study found that patients treated with combination therapy demonstrated partial and complete recovery significantly more often (88%) than those treated with IT steroids (59%) or systemic steroids (39%) alone. When audiometric findings indicated response to corticosteroid treatment, patient groups treated with combination therapy and IT steroids fared significantly better than groups treated with systemic steroids alone. However, there was no difference between the IT steroids and combination therapy groups, and it remains unclear whether IT steroids should be used alone or combined with systemic steroids.
In measuring the efficacy of treatment options for SSNHL, it is important to ask how success is defined. Objective audiologic measures of success, such as an improvement in hearing threshold or an increase in word recognition ability, should be correlated with success as defined by the patients themselves. The importance of this point is highlighted by a number of studies of the use of IT steroid treatment with patients with SSNHL. In one study, Haynes et al. (2007) investigated the use of IT steroids as both a primary and salvage treatment for patients with SSNHL. Although the authors reported that 40% of patients demonstrated improvement with IT steroid treatment and recovered 20 dB or 20% of WRS, dramatic recovery was uncommon. Only one of 40 patients recovered to within 10 dB of the contralateral, unaffected ear (Haynes et al., 2007). While a 20 dB improvement in hearing threshold in a severely or profoundly deaf ear may represent improvement from an audiologic standpoint, it may not represent a successful outcome from the patient's perspective.
As we treat the underlying medical causes of SSNHL, we must never lose sight of the impact hearing loss can have on communication and psycho-social functioning. For this reason, the use of a self-assessment measurement becomes a critical component of the audiologic assessment battery. The resulting hearing loss may be unilateral in many cases, but the impact of the loss should not be minimized. In one study (Chiossoine-Kerdel et al., 2000), 86% of adults with unilateral SSNHL reported the presence of hearing handicap as measured by the Hearing Handicap Inventory of Adults (Newman et al., 1990) and 57% reported tinnitus handicap as measured by the Tinnitus Handicap Scale (Newman et al., 1996). Patients who have hearing loss may lose more hearing, as shown in a retrospective study by Stahl and Cohen (2006), who reported that 20% of their subjects developed SSNHL in their only normal-hearing ear resulting in bilateral hearing loss.
Audiologic rehabilitation must be addressed at the time of identification of hearing loss whether the loss is unilateral or bilateral. Components of an audiologic rehabilitation program designed for patients experiencing SSNHL should include counseling, amplification options such as CROS hearing instruments, implantable devices (BAHA, cochlear implants), and hearing assistive technology such as FM systems and signal-alerting devices.
The counseling role of the audiologist is critical to the management of SSNHL (Schein & Miller, 2005). The audiologist must address the presence of hearing loss throughout the course of treatment and should not wait until it is determined if medical intervention has been successful or if there is complete, partial, or no hearing recovery. Patients want to address several important questions: Will my hearing return? Will I have to wear a hearing aid? Will I lose the hearing in my other ear? How long will I have this hearing loss? Audiologists cannot be expected to answer these questions immediately, but information-sharing and personal adjustment counseling will help the patient better understand what is happening and begin to deal with the changes that may need to take place.
Time for counseling should be included at each follow-up assessment during the treatment period to address communication issues, even if there is an indication that hearing will return. Including the family and significant others in this process is critical during this phase of treating SSNHL, and the patient may need to consider individual and/or group treatments such as auditory training and speechreading as intervention options. Referral to consumer support groups may assist in the patient's adjustment to hearing loss.
Our understanding of the etiology and treatment of SSNHL continues to evolve. Because multiple etiologies have been implicated in the development of SSNHL, a single therapy is unlikely to help all patients. Ideally, in the future it may be possible to identify the cause of each patient's SSNHL and tailor treatment to target a specific etiology.
Patients are best served by a team approach that combines the efforts of audiologists, otolaryngologists, and allied health professionals. Medical and audiologic rehabilitation services form critical cornerstones in treatment because both audiological and clinical measures are important for identifying patients with SSNHL and monitoring the course of treatment.