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Hypothesis: While the traditional treatment for idiopathic, sudden, sensorineural hearing loss (SNHL) is oral steroid therapy (and some argue that no other treatment is needed), intratympanic (IT) steroid therapy also has a role in treating this condition.
A MEDLINE literature search was performed for the years 1980 to 2004. The search strategy included the terms idiopathic hearing loss, sudden hearing loss, sudden sensorineural hearing loss, and steroids. Appropriate articles were selected and reviewed. Only articles published in English were included. Those articles addressing primarily idiopathic sudden SNHL and oral or IT steroid therapy as the preferred means of treatment were included in this analysis.
Sam J. Marzo, MD
Sudden SNHL is relatively common, affecting 5 to 20 individuals per 100 000. It is defined as a sudden hearing loss in 3 contiguous frequencies greater than 30 dB occurring within a 3-day period.1,2 While some drugs (eg, aminogycosides and cisplatinum) and diseases such as neoplasms (eg, acoustic neuroma and meningioma), local and systemic inflammatory disorders (eg, autoimmune inner-ear disease and Cogan syndrome), infection (eg, viral and/or bacterial meningitis and suppurative labyrinthitis), and trauma (eg, temporal bone fracture) can be associated with sudden hearing loss,3 in most cases, the cause is never determined (and thus the term idiopathic).
There are many theories as to the cause of idiopathic sudden SNHL, including viral or bacterial inflection and/or inflammation of the cochlea, rupture of cochlear membranes, cochlear artery occlusion, and immune-mediated tissue injury to the inner ear (via a localized or systemic illness).3 Spontaneous recovery can occur in 50% to 70% of cases.2-5 The most significant prognostic finding is the degree of hearing loss at onset: the worse the hearing loss at onset, the lower the likelihood of recovery.1 While the list of medications used to treat idiopathic sudden SNHL seems to increase each year, many physicians use oral steroids, sometimes in combination with other therapies.
It is beyond the scope of this article to discuss research into the causes of idiopathic sudden SNHL or the various immune mediators postulated to have a role in the inner-ear injury associated with this disorder. There are several issues that need to be addressed when comparing studies. A major problem with reviewing this literature is that relatively few well-designed, prospective, randomized, controlled trials exist. Many studies include the use of adjuvant therapies such as volume expanders, vasodilators, diuretics, antivirals, and vitamins, in addition to steroids. There is also little consensus on the proper dose of steroids. Some studies include all cases of idiopathic sudden SNHL, which can make interpreting results difficult owing to the excellent recovery seen in patients with only mild hearing loss. Other problems include various means of reporting hearing recovery, reliably comparing hearing improvement between studies, and the fact that not all studies include speech discrimination scores in their analysis.
The present article assumes that the standard treatment for idiopathic sudden SNHL is oral steroid therapy. The optimal goal of this therapy is the return of normal hearing, and if this is not possible, then a recovery of at least serviceable hearing (defined as a pure-tone average <50 dB and a speech discrimination score of at least 50%). Furthermore, this therapy should be applied as soon as possible after diagnosis, ideally within 6 weeks. The longer the hearing loss persists, the worse the recovery.1
Intratympanic therapy can be defined as delivering a medication to the round window membrane with uptake into the inner ear. It has also been called transtympanic therapy and is based on findings from animal studies that demonstrate steroid uptake through the round window membrane into the cochlea when the drug is instilled into the middle ear.6,7 There are several means of delivering steroids to the round window membrane: single IT injection, repeated IT injections, or insertion of sustained-release vehicles through the tympanic membrane. Theoretically, single or repeated IT injections will provide a rapid increase in the level of the drug in the inner ear, and then a falloff of the level over time. Sustained-release vehicles will provide a more constant level of drug in the inner ear while the vehicle is in place.
Research in IT therapy is relatively new, but several studies have already looked at each of these methods. In 1999, Parnes et al6 used intratympanic steroid injection of either dexamethasone or methylprednisolone to treat 13 patients with sudden SNHL. No patients were treated with oral steroids. All patients presented within 6 weeks of the onset of the hearing loss, and all underwent multiple, office-based IT injections over several weeks. Six patients showed significant improvement in auditory thresholds, with 5 progressing from a severe to profound SNHL to almost normal hearing thresholds. One patient with bilateral idiopathic sudden SNHL had some improvement in word recognition, while 6 other patients had no change in hearing.
In 2001, Chandrasekhar8 treated 10 patients with IT dexamethasone. Eight patients had hearing gain with the speech reception threshold improving a mean of 9 dB, and speech discrimination scores improved a mean of 15.8%. The hearing in 3 patients stayed the same or became worse. A problem with this study is the wide variation in causes of hearing loss: 2 patients had Ménière’s disease, 2 patients had meningiomas,1 patient had a poststapedectomy sudden SNHL, 1 patient had a brainstem infarct, and 1 patient had autoimmune inner-ear disease. Also, several patients had undergone prior oral steroid therapy, and the time interval between presentation and receiving IT dexamethasone ranged from 1 day to 270 days.
Gianoli and Li9 described 23 patients treated with IT steroid therapy. All patients had sudden SHNL refractory to oral steroid therapy. The steroid was delivered via needle puncture of the tympanic membrane. Hearing improvement was documented in 10 patients (44%).
In 2004, Ho et al10 evaluated 39 patients with severe to profound idiopathic sudden SNHL in a randomized controlled study. The study was unique in that all patients had severe or profound idiopathic sudden SNHL, all were treated within 24 hours of the onset of the hearing loss, and all patients received oral steroid therapy first (except 3 patients with diabetes mellitus). Other treatment agents were used along with the steroids, including carbogen, vasodilators, and B-complex vitamins. After 10 days of standard treatment, 10 (26%) of 39 patients showed hearing improvement (defined as complete recovery or an improvement in hearing of 30 dB or more in the pure-tone average). Of the 29 patients with less than a 30-dB hearing improvement, 15 received weekly IT dexamethasone injections over 3 weeks, while 14 received continued vasodilators and vitamins. Hearing improved in 8 (53%) of 15 patients receiving IT dexamethasone, compared with 1 (7%) of 14 patients not receiving intratympanic steroids.
While these initial results with IT steroid injection are promising, other investigators have developed sustained-release vehicles. In 1999, Silverstein11 developed a proprietary device called the MicroWick (Micromedics Inc, Eagan, Minn), a small polyvinyl acetate sponge measuring 1 mm in diameter and 9 mm in length that is inserted through the tympanic membrane into the round window niche. This procedure can be done in the office setting using local anesthesia. Then, through the external auditory canal, the patient self-instills medication, which is absorbed via the MicroWick into the inner ear where it exerts its effect. Using this technique and a 24% dexamethasone solution, Jackson and Silverstein12 treated 19 patients with idiopathic sudden SNHL, and 5 patients (31%) had a positive response. The average gain in hearing was a 45-dB improvement in pure-tone average and a 39% gain in speech discrimination. A potential complication of this therapy is tympanic membrane perforation, and the authors are currently studying a decreased concentration (4%) of the dexamethasone solution (4 mg/mL of dexamethasone).
Another sustained-release vehicle is a round window microcatheter. This device is a small vinyl catheter that is inserted into the round window niche via a posterior tympanotomy under general anesthesia. The device is then connected to a microinfusion pump. In 2002, Kopke et al13 treated 6 patients with sudden SNHL with the round-window microcatheter using methylprednisolone (62.5 mg/mL). Four patients had idiopathic sudden SNHL, 1 had an poststapedectomy SNHL, and 1 had an SNHL believed secondary to gentamicin therapy. All patients’ hearing failed to improve with a 2-week course of oral steroid therapy. After implantation of the round window microcatheter, the methylprednisolone was delivered continuously over 14 days at a rate of 10 μL/h. Four patients’ hearing returned to baseline. One patient recovered hearing that could benefit with amplification, and 1 had an improved pure-tone average but not speech discrimination score. Tympanic membrane perforation occurred in several patients.
In 2002, Lefebvre and Staecker14 treated 6 patients who failed a 10-day course of traditional therapy for idiopathic sudden SNHL, including systemic steroids. All 6 patients began receiving IT methylprednisolone (62.5 mg/mL) for 8 to 10 days via a round window microcatheter. All 6 patients showed a hearing improvement ranging from 16.25 to 25.00 dB. Furthermore, all patients had dramatic improvements in speech discrimination scores. Although these studies included only small sample sizes, the initial results are very encouraging.
Many authors present cogent arguments for the use of oral steroid therapy alone to treat idiopathic sudden SNHL. In 1980, Wilson et al,15 in a prospective, double-blind, clinical trial, showed that patients with idiopathic sudden SNHL treated with 4.5 mg of dexamethasone or 16 mg of methylprednisolone had a statistically better prognosis than patients not receiving any therapy. This study described 119 patients, all presenting within 10 days of an idiopathic sudden SNHL, which the authors defined as an SNHL occurring in at least 3 contiguous frequencies in less that 3 days. Sixty-seven patients were in a double-blind clinical trial, with 33 receiving steroids and 34 receiving placebo. Fifty-two untreated patients served as the control group. None of these patients had received prior treatment, and all had normal laboratory findings, including from complete blood cell counts, erythrocyte sedimentation rate, serum clotting and lipid studies, viscosity, rapid plasma reagin, fluorescent treponemal antibody absorption test, and blood glucose levels.
Importantly, this study15 defined 3 groups of patients by audiogram type: patients with midfrequency hearing loss, those with profound hearing loss, and patients with hearing loss in between these 2. The first group of patients (midfrequency losses) was found to have an excellent recovery (defined as recovery of hearing to within 50% or more of the pre–hearing loss speech reception score, or averaged pure-tone score), regardless of treatment. The profound hearing loss group had a poor recovery (recovery with steroids, 2/11; without steroids, 2/12), regardless of treatment. In the remaining 74 patients, overall recovery was 78% in those receiving steroids and only 38% in those receiving placebo or no treatment. This difference was statistically significant.
Moskowitz et al,16 in 1984, treated idiopathic sudden SNHL with 0.75 mg of dexamethasone and achieved a statistically better recovery than was seen in untreated patients. The authors used the same criteria as Wilson et al15 in defining idiopathic sudden SNHL, and the study included 36 patients. Of the 27 patients receiving steroids, 24 (89%) recovered at least 50% of their hearing loss. Of the 9 untreated patients, only 4 (44%) recovered hearing. Only 25% of patients with profound SNHL recovered hearing.
In 1993, Veldman et al17 also showed that steroid therapy was better than no therapy at all for idiopathic sudden SNHL, using a prednisolone dose of 2 mg/kg. In a 10-year retrospective study of 318 patients with sudden SNHL, Chen et al18 stratified patients according to the severity of their hearing loss and compared patients treated with an average initial dose of 60 mg of prednisone with patients undergoing no treatment. They found a statistically significant improvement in pure-tone average and word-recognition scores in the patients with severe to profound idiopathic sudden SNHL treated with oral steroid therapy vs those untreated.
Idiopathic sudden SNHL remains a challenging problem. Little is known about the cause, and numerous anecdotal treatment regimens exist. I believe that there is good clinical data demonstrating a role for oral steroid therapy in idiopathic sudden SNHL. However, IT steroid therapy should be considered a second-line therapy for cases in which oral steroids are contraindicated or in which the hearing loss fails to improve despite treatment. I believe that if IT steroid therapy is to be administered, it should be provided to the patient ideally within 6 weeks of onset of the hearing loss and reserved for patients with severe to profound SNHL or with unserviceable hearing (defined as a pure-tone average >50 dB and speech discrimination score worse than 50%). It is not yet clear if single injections, multiple injections, or sustained-release vehicles provide the best hearing recovery. Clearly, more clinical and basic science research is required to help solve these issues.
Correspondence: Sam J. Marzo, MD, 2160 S First Ave, Maywood, IL 60153 (email@example.com).
Marzo SJ. Intratympanic Steroid Perfusion for Sudden Sensorineural Hearing Loss. Arch Otolaryngol Head Neck Surg. 2005;131(8):730–732. doi:10.1001/archotol.131.8.730
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