Otolaryngol Clin N Am 37 (2004) 1019–1034 Silverstein MicroWick Herbert Silverstein, MD, FACS*, Jack Thompson, PhD, PA-C, Seth I. Rosenberg, MD, FACS, Neil Brown, MD, Joshua Light, MD Silverstein Institute, Ear Research Foundation, 1901 Floyd Street, Sarasota, FL 34239, USA Schuknecht in 1956 [1] was the first to perfuse the inner ear with aminoglycosides for the treatment of Meniere’s disease. The advantages of placing medications directly into the inner ear include (1) treating the diseased ear directly without affecting the entire body; (2) achieving a higher concentration of medication; and (3) avoiding systemic side effects of the drug. Perfusion of the inner ear using various medications has become a popular form of treatment for inner ear disease [2–10]. The primary route of entry of aminoglycosides into the inner ear is through the round window membrane [11]. The problem with perfusing the entire middle ear space with aminoglycosides is that it is unclear how much medication is applied directly to the round window membrane. The Silverstein MicroWick (Micromedics, Eaton, Minnesota) inner ear medica- tion delivery technique allows direct delivery of medication to the round window membrane [12,13]. After the initial injection into the middle ear by the physician, the patient self-administers the medication into the ear canal. The MicroWick absorbs the medication and transports it to the round window membrane where it perfuses directly into the inner ear fluids. This procedure allows a continuous perfusion of the inner ear fluids with medication. The method is similar to self-treatment for eye disease using medicated eye drops. A MicroWick placed through a ventilation tube into the round window niche was used in 264 patients from August 1998 through January 2003 to deliver medications to the inner ear fluids for treatment of the vertigo * Corresponding author. E-mail address:
[email protected] (H. Silverstein). 0030-6665/04/$ - see front matter � 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.otc.2004.04.002 oto.theclinics.com mailto:
[email protected] 1020 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 attacks of Meniere’s disease, sudden deafness, and occasionally autoimmune inner ear disease (AIED). The institutional review board at Sarasota Memorial Hospital approved the initial study. The surgical technique is described and treatment results are reported. Materials and methods MicroWick procedure The MicroWick is made from polyvinyl acetate and measures 1 mm in diameter by 9 mm long (Fig. 1). It is small enough to insert though a ventilation tube (Fig. 2). The Silverstein silicone ventilation tube (Micro- medics, Eaton, Minnesota) is 1.42 mm in diameter with a 3.25-mm diameter flexible flange. The MicroWick device was approved by the Food and Drug Administration in September 1999 and granted a patent in September 2000. Present indications for the direct treatment of inner ear disease include Meniere’s disease when vertigo attacks cannot be controlled by conventional medical treatment, sudden deafness, and occasionally AIED. Future indications may be viral inner ear disorders. The procedure is performed in an office minor surgery room. The details of the procedure can be found in an earlier publication [13]. The essentials of the procedure are as follows. Valium (10 mg tablet) is offered to the patient 30 minutes before the procedure. About half the patients refuse the drug. The ear is anesthetized by injecting 1 to 2 cm3 of lidocaine 2% with epinephrine 1:100,000, buffered with sodium bicarbonate (1 cm3 bicarbonate to 9 cm3 lidocaine). Once the ear is injected, a laser tympanostomy or vertical myringotomy is made over the round window niche. The round window niche is located as a dark area just posterior and inferior to the Malleus umbo. If the tympanic membrane is thickened or scarred, the round window is usually located 3.44 mm posterior and 113( from the handle of Fig. 1. Polyvinyl acetate MicroWick, which measures 1 mm in diameter by 9 mm long. 1021H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 the malleus (Fig. 3) (Silverstein H, et al. Use of the malleus handle as a landmark for localization of the round window membrane; unpublished article). The middle ear is examined with a 1.7-mm Gyrus 30( endoscope (Gyrus-ENT, Bartlett, TN) or the operating microscope to determine if there are any obstructing membranes over the round window niche. If such membranes are present, a small pick is used to remove them. A special large ventilation tube is inserted into the tympanostomy opening and should allow direct visualization of the round window niche (Fig. 4). Two hands are used to insert the tube. The tab on the tube is held with a cupped forceps, and another instrument is used to push the tube through the tympanostomy opening. The MicroWick is then inserted through the tube toward the round Fig. 2. MicroWick placed through a ventilation tube, the position after insertion through the tympanic membrane. Fig. 3. Location of the round window, usually 3.44 mm posterior and 113( from the handle of the malleus. 1022 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 window until resistance is met. Medication is injected onto the MicroWick and injected into the middle ear to deliver a high concentration at the round window and allow perfusion into the inner ear fluids (Figs. 5 and 6). Patients continue to self-administer medication, three drops in the ear three times a day while lying for 15 minutes with the treated ear facing upward. After treatment, the MicroWick and tube can be removed without the use of anesthesia. The tube and wick can be removed with little pain using a small pick or small cup forceps. The tympanostomy site is left to heal, which takes about 3 to 4 weeks. The MicroWick should be removed or replaced after 4 weeks of treatment to prevent it from becoming adherent to the mucosa of the round window niche. This adhesion makes removing the Fig. 4. Round window as seen through a ventilation tube. Fig. 5. The MicroWick in place with the distal end against the round window membrane. 1023H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 MicroWick in one piece more difficult and can result in the MicroWick breaking, leaving a portion of polyvinyl acetate in the middle ear. If resistance occurs while extracting the MicroWick, the ear is injected with buffered lidocaine with epinephrine, and a pick is used to tease the MicroWick from the mucosa. When treatment lasts longer than 4 weeks, exchanging the wick with a fresh one avoids the problem of mucosal adhesions. Treatment of Meniere’s disease In a compounding pharmacy, sterile techniques are used to prepare a dilute solution of gentamicin otic solution (10 mg/cm3) that is transferred into a sterile dropper bottle. The patient is instructed to lie in the supine position for 15 minutes with the treated ear up and to administer three drops of the medication into the ear canal three times daily. At the end of each week, a hearing test, electronystagmogram (ENG), and electrocochleogra- phy are performed to determine the response to gentamicin and to titrate the duration of treatment. Patients with poor hearing are tested every 2 weeks. Patients are also questioned regarding changes in their subjective symptoms of vertigo, aural pressure, tinnitus, and imbalance. Depending upon the objective test results and the patient’s symptoms, treatment is either continued or discontinued. The goal of this treatment is to obtain a 100% Fig. 6. Temporal bone showing the MicroWick lying in the round window niche (upper right picture). The round window niche can be seen through the ventilation tube before insertion of the MicroWick (upper left picture). 1024 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 reduced vestibular response (RVR) to both warm and ice-air caloric ENG testing without producing a hearing loss. The usual length of treatment is 2 to 3 weeks (range, 1–6 weeks). During the treatment period, if the hearing significantly decreases but vestibular function is still present, the treatment may be discontinued for 1 week. The patient is reevaluated 1 week later, and treatment can be reinstituted. If the vestibular function remains stable and does not decrease after several weeks of treatment, the treatment is discontinued. Occasionally, if there is a failure to respond to the gentamicin 10-mg/cm3 concentration, a stronger solution of gentamicin is used (ie, 20 mg/cm3). The end point is titrated using audiometric and caloric testing because the response to gentamicin is quite variable. If the patient exhibits hearing loss during gentamicin therapy, prednisone (60 mg/day for 1 to 2 weeks followed by a taper) is administered. Initial results are encouraging and have shown a significant recovery of hearing with steroid treatment (H. Silverstein, et al, unpublished data). Treatment of sudden deafness and acute cochlear Meniere’s disease A solution of dexamethasone 4 mg/cm3 is prepared at a compounding pharmacy and placed in a sterile dropper bottle. Initially 24 mg/cm3 was used as the dose but was found to be too high and resulted in permanent perforations (easily repaired in the office with fat graft myringoplasty) in 20% of patients. When instilling drops, the patient should lie in the supine position with the head turned for 15 minutes and to use three drops three times daily. In addition, antibiotic eye drops (ie, Vasocidin ophthalmic solution) are instilled in the ear once daily to prevent infection. Hearing is measured every 2 weeks to determine whether to continue or terminate the treatment. Patients who could tolerate systemic steroids were usually treated for 2 weeks with prednisone, 60 mg/day, before treatment with theMicroWick technique. If patients had diabetes, hypertension, peptic ulcers, or another contraindi- cation to systemic steroids, they were treated initially with the MicroWick and dexamethasone, 4 mg/cm3. If hearing returned completely after oral administration of prednisone, the MicroWick was not used. Statistical analysis Student’s t-test (using the built-in functions in Microsoft Excel, Microsoft Corp., Redmond, Washington) was used to compare average values. The v2 goodness-of-fit test was used to compare population distributions. Statisti- cal significance was accepted if P was less than 0.05. Published v2 critical values were used after calculating the statistic using the standard formula. Results Between August 1998 and January 2003, 264 patients have been treated using the MicroWick. The shortest follow-up was 1 year. One hundred 1025H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 eighty-three patients were treated for Meniere’s disease. The remaining 81 patients had a diagnosis of sudden deafness or autoimmune inner ear disease. Not all patients have complete follow-up data; results include only patients for whom data are available. Patient acceptance of the treatment has been excellent, and the surgical procedure is well tolerated by the patients with little discomfort. Results of treatment for Meniere’s disease Table 1 summarizes the subjective symptomatic change in the 183 patients with Meniere’s disease who treated themselves using dilute gentamicin otic solution. Follow-up is from 1 to 6 years. Vertigo symptoms were relieved in 151 patients (83%). Ten patients (5%) needed further treatment for Meniere’s disease: Five patients had re-treatment with the MicroWick and gentamicin drops; three patients had a labyrinthectomy; two patients had a combined retrosigmoid/retrolabyrinthine vestibular neurectomy; and one patient had transtympanic injections of gentamicin performed elsewhere. Pressure in the ear was improved or relieved in 82 patients (67%). Tinnitus was relieved or improved in 100 patients (57%). The average length of treatment was 3 weeks (range, 1–6 weeks). Of the 109 patients with complete ENG data, 85 (78%) experienced 100% RVR with warm air caloric testing after treatment with the Micro- Wick and dilute gentamicin. Forty-three patients (41%) achieved 100% RVR with ice-air caloric ENG (Table 2). The entire group’s average posttreatment RVR was 85% with warm air caloric testing. The average RVR of all the patients with ice-air caloric testing was 65%. Hearing results were evaluated using the 1995 American Academy of Otolaryngology–Head and Neck Surgery criteria for Meniere’s disease (ie, a 10-dB change of pure tone average [PTA] or a 15% change in discrimination). The patients were placed into two pretreatment hearing groups: (1) those with hearing better than or equal to 50 dB PTA, and (2) those with hearing worse than 50 dB PTA (Table 3). In the group with better hearing before treatment the PTA remained the same in 76 patients (51%), Table 1 Subjective response to treatment with the MicroWick and dilute gentamicin in 183 patients, 1–6 year follow-up Patient-reported Results All Patients Vertigo Pressure Tinnitus Imbalance Vestibular Rehabilitation # % # % # % # % # % None 151 83 66 36 25 14 33 24 36 27 Improved 3 2 51 28 58 32 0 0 0 0 Yes 29 16 31 17 42 23 103 76 97 72 Same 0 0 9 5 11 6 0 0 0 0 # reporting 183 183 181 136 135 1026 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 was improved in 17 patients (11%), and worsened in 56 patients (38%). The discrimination score remained the same in 70 (46%), was better in 23 (15%), and was worse in 60 (39%). The average hearing loss for all patients in the group with better hearing was 9 dB PTA and 9% in the discrimination score. For the patients with a loss of hearing, the average drop was 26 dB PTA and 24% in discrimination score. In the patients with worse hearing (>50 dB before treatment), the PTA was the same in 54 (57%), improved in 10 (11%), and worsened in 31 (33%). The discrimination score was the same in 38 (38%), improved in 19 (19%), and worsened in 43 (43%). The average loss for this group was 5 dB PTA and 10% drop in discrimination score. When averaging only the patients with a drop in hearing, the mean loss was 20 dB PTA and 26% in discrimination score. Profound hearing loss occurred in 12% pf patients (12/100). Most patients did not complain of increased hearing loss especially when the vertigo attacks were relieved. All patients electing to proceed with gentamicin treatment understood and accepted the risk of hearing loss to obtain relief from vertigo attacks. Table 4 shows results of hearing and vestibular function in those patients with a hearing loss after treatment with the MicroWick and gentamicin. In the group with poor hearing before treatment, a higher percentage of patients had a decrease in word discrimination, and more had complete vestibular ablation (RVR 100%). This finding was statistically significant Table 2 Vestibular function after treatment with the MicroWick and dilute gentamicin Reduced Vestibular Response All PTA[ 50 dB PTA � 50 dB # % # % # % # Patients 123 69 54 # Pts w 100% warm RVR 93 76 58 84 35 65 # Pts w 100% ice RVR 49 41 29 43 20 38 Average warm RVR 85 89 80 Average ice RVR 65 70 57 Abbreviations: PTA, pure tone average; RVR, reduced vestibular response. Table 3 Hearing after treatment with the MicroWick and dilute gentamicin Change In Hearing PTA Discrimination All PTA[ 50 dB PTA � 50 dB All PTA[ 50 dB PTA � 50 dB # % # % # % # % # % # % Total patients 149 95 54 153 100 54 Same 76 51 54 57 22 41 70 46 38 38 33 61 Improved 17 11 10 11 7 13 23 15 19 19 4 7 Worse 56 38 31 33 25 46 60 39 43 43 17 31 Abbreviations: PTA, pure tone average. 1027H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 (P \ 0.05), showing that gentamicin has a more ablative effect on both hearing and vestibular function in patients with poorer pretreatment hearing. Two months after completion of treatment, testing showed improved vestibular function in 21% of patients (mean 60% warm and 38% ice RVR). Hearing also improved in 30% of patients (mean, 32% improvement in discrimination score and 24 dB PTA improvement). Results of treatment for sudden deafness and autoimmune inner ear disease Of the 81 patients who were treated for sudden deafness, 35% had a positive response to the self-administered dexamethasone. The PTA was improved in 27%, was worse in 12%, and was unchanged in 61%. The speech discrimination score was improved in 35%, worse in 11%, and the same in 54% (Table 5). Patients treated early in the disease seemed to have better results, although one patient had a good response after more than 1 year. There was no statistically significant difference between patients treated less than 4 weeks after the hearing loss and those who had a delay longer than 4 weeks before treatment. Only three patients were treated for AIED, and the results were inconclusive. Complications Complications using the self-treatment technique with the MicroWick were infrequent. Originally 24 mg/cm3 was used as the treatment dose for sudden deafness. With this dose, 20% of patients had nonhealing perfo- rations that needed repair using a fat graft. It seemed that the steroid solution remained around the tube, causing devascularization of the tympanic membrane adjacent to the tube and thus preventing healing. Table 4 Hearing and vestibular function after treatment with the MicroWick and gentamicin* Initial PTA Group All PTA[ 50 dB PTA � 50 dB Hearing Change Group Better Worse Better Worse Better Worse Discrim. change (%) �4 �27 �1 �26 �3 �30 PTA change (dB) 20 �24 18 �20 19 �28 Initial avg. PTA (dB) 56 52 68 68 38 35 Final avg. PTA (dB) 45 75 56 86 24 63 Initial avg. discrim. (%) 66 66 53 47 85 87 Final avg. discrim. (%) 62 41 50 23 92 59 Initial avg. warm RVR 35% 41% 42% 41% 28% 40% Final avg. warm RVR 49% 72% 63% 86% 37% 59% Initial avg. ice RVR 26% 29% 33% 30% 13% 23% Final avg. ice RVR 49% 72% 63% 86% 37% 59% Number of patients 18 45 14 31 8 14 * Patients without significant change are excluded. Abbreviations: PTA, pure tone average; RVR, reduced vestibular response. 1028 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 When the dose was lowered to 4 mg/cm3, the incidence of permanent perforations that required repair was drastically reduced without compro- mising the results of treatment. Patients using dexamethasone were routinely treated with Vasocidin eye drops placed in the ear at night to prevent Table 5 Results of treatment of sudden deafness with the MicroWick and dexamethasone in those patients who experienced significant improvement Pre-op PTA Pre-op Discrimination Tx Delay (wks) Final PTA Final Discrimination Change PTA Change Discrimination 1 53 92 6 42 28 11 �64 2 46 84 34 68 12 �16 3 39 100 10 96 29 �4 4 110 0 1 89 0 21 0 5 63 52 0 27 56 36 4 6 58 88 6 45 100 13 12 7 115 0 90 12 25 12 8 73 40 2 60 60 13 20 9 72 28 5 72 52 0 24 10 110 48 4 110 72 0 24 11 41 64 0 40 88 1 24 12 90 0 81 24 9 24 13 82 72 1 25 96 57 24 14 58 16 8 85 44 �27 28 15 68 12 11 77 40 �9 28 16 50 32 20 53 64 �3 32 17 45 12 7 38 56 7 44 18 65 24 8 73 72 �8 48 19 60 32 59 80 1 48 20 50 40 6 40 88 10 48 21 68 24 1 51 72 17 48 22 65 40 2 41 92 24 52 23 100 0 69 52 31 52 24 88 44 0 25 96 63 52 25 58 32 2 18 96 40 64 26 84 12 1 50 80 34 68 27 75 20 2 25 88 50 68 28 57 0 4 55 76 2 76 29 68 20 26 96 42 76 30 95 0 7 110 80 �15 80 31 88 0 1 26 80 62 80 32 86 20 0 19 100 67 80 33 110 0 1 52 88 58 88 34 38 4 35 100 3 96 Min 38 0 0 18 0 �27 0 Max 115 88 20 110 100 67 96 Mean 74 25 4 54 71 20 46 Median 68 20 2 51 80 13 48 Count 31 31 25 31 31 31 31 95% CI 8 8 2 9 9 9 9 Abbreviations: CI, Confidence interval; PTA, pure tone average. 1029H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 infections. During gentamicin treatment, two patients developed acute otitis media, which responded to local antibiotic eardrops. Two patients had the MicroWick and tube spontaneously extrude from the eardrum during treatment. Two patients had severe unsteadiness after the MicroWick and gentamicin treatment that did not quickly respond to vestibular rehabilita- tion therapy. These patients had some imbalance before treatment. Discussion Intratympanic gentamicin has been used in the authors’ practice for 6 years to treat the episodic vertigo of Meniere’s disease. Its use has greatly reduced the need for vestibular neurectomy in the authors’ practice and throughout the country [16]. The results have been excellent for the most part, and patients seem to be satisfied with the treatment. The authors have tried various protocols to deliver the gentamicin to the inner ear, including transtympanic injections of buffered gentamicin (27 mg/cm3), placing buffered gentamicin (27 mg/cm3) on absorbable gelatin sponge placed in the round window niche with 5 days separation between injections, and, for the last 6 years, the self-administration technique using a MicroWick. The MicroWick technique seems to work the best, with excellent patient compliance. It also has reduced the physician’s time spent injecting the ear on multiple visits. It is interesting to compare results of this study with an earlier protocol using serial injections, 5 days apart, of gentamicin, 27 mg/cm3, onto absorbable gelatin sponge placed in the round window niche (Table 6) [4]. There is a statistical difference between the groups regarding vestibular function. One hundred percent warm caloric RVR was obtained in eight patients (36%) of the group treated 5 days apart as compared with 60 patients (78%) in the self-treated MicroWick group. The ice-air caloric ENG results were also statistically different. In the group treated 5 days apart, only two patients (9%) obtained a 100% ice-air caloric RVR, as compared with 34 patients (43%) of the self-treated group. Thus keeping dilute gentamicin against the round window membrane for weeks resulted in a more effective ablation of the vestibular system than did injecting the gentamicin every 5 days. Separating the MicroWick gentamicin groups into those with hearing better than or equal to 50 dB and those with hearing worse than 50 dB, it is apparent that more vestibular and auditory ablation occurred in the group with poorer hearing. Most patients who lost hearing did not complain of the loss, however, and many did not even realize that they had lost hearing because their hearing was so poor before the treatment. Most patients were simply happy to be free of the vertigo attacks. The symptomatic response during treatment was quite variable. In some patients there was little imbalance or disequilibrium during treatment, even 1030 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 when the caloric response was reduced to 100% loss of function. Other patients had difficulty with disequilibrium despite developing only a partial vestibular ablation. Vestibular rehabilitation exercises were given to most of the patients and helped the patients regain reasonable balance after treatment. Few patients had significant permanent disequilibrium after gentamicin ablation. In the last 10 years there has been a great increase in the number of patients treated with gentamicin inner ear perfusion and a marked reduction in vestibular neurectomies [16]. Although many patients treated with serial injections 5 days apart did not obtain a 100% RVR, the results in relieving vertigo, pressure, and tinnitus were similar in both studies. The 2-year results in relieving vertigo in patients treated with serial injections 5 days apart was 77%, compared with the 1- to 6-year results of 83% in the self-treated group. The early results in the patients treated 5 days apart have held up after 2 years. Youssef and Poe [14] found similar results. DeCicco et al [2] reported recently that they obtained excellent results giving microdoses of dilute gentamicin (10 mg/ cm3) though a microcatheter implanted in the round window niche. There was no change in hearing or reduction in vestibular response. This report indicates that the gentamicin may be relieving the symptoms of Meniere’s disease by a mechanism other than destruction of vestibular function, such as reducing the secretory function of the dark cells of the vestibular labyrinth or the secretory cells in the stria vascularis. This process may cause a reduced secretion of endolymph, thus reducing endolymphatic hydrops and the symptoms of Meniere’s disease. Hearing and vestibular function may improve after cessation of gentamicin treatment. Twenty-one percent of patients recovered some degree of vestibular function at 1 month. Likewise, decreased hearing improved in 30% of patients after termination of treatment. This finding indicates that the ototoxic and vestibulotoxic effects are reversible and may recover in some patients. In Meniere’s disease to the response of the inner ear to intratympanic gentamicin is somewhat unpredictable, as are the long-term results in relieving the attacks of Meniere’s disease. Patients should be warned that Table 6 Vestibular function comparison following treatment with the MicroWick and dilute gentamicin versus gentamicin injected onto gelfoam placed on the round window membrane Treatment # patients Bithermal 100% RVR Ice 100% RVR Bithermal Mean RVR Ice Mean RVR MicroWick and dilute gentamicin (10 mg/cm3) 80 78% 43% 88% 66% Gentamicin Injection Onto Gelfoam 22 36% 9% 62% 37% Abbreviations: RVR, reduced vestibular response. 1031H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 their symptoms may return and that they may lose some hearing. After several weeks, most patients had no problems with balance. During treatment, all patients were offered vestibular rehabilitation exercises if imbalance occurred (72% of patients). Two patients, however, had severe unsteadiness and disequilibrium after the treatment, and one did not respond to vestibular rehabilitation therapy. It is difficult to predict which patients will have difficulty with imbalance during and after the treatment. Patients who are elderly and have chronic disequilibrium before treatment should be warned of the possibility of further imbalance. The MicroWick is simple and easy to use. The advantage of using the laser to make the opening in the tympanic membrane is that it makes a bloodless opening, creating less chance of blood touching either the wick or the endoscope. Any fluid that touches the MicroWick will cause it to swell immediately and prevent its proper placement into the round window niche. If there is blood or fluid in the area that cannot be removed, the procedure can be terminated after endoscopic viewing of the middle ear and the insertion of the ventilation tube. The MicroWick can then be placed 1 week later, when the ear is dry. The advantage of looking into the round window niche with the endoscope is that obstructing membranes (present in 20% of patients) can be visualized and removed [5]. The round window niche should be completely unobstructed to accept the MicroWick and achieve the best chances for success. The MicroWick can be placed without using the laser and the endoscope if they are not available. Phenol or tetracaine-based solution can be used to anesthetize the tympanic membrane after which a vertical myringotomy 3 mm in length and 1 mm from the annulus is made over the round window area. The ventilation tube can be inserted directly over the round window niche. The placement of the incision in the tympanic membrane is critical to successful placement of the ventilation tube and MicroWick into the round window niche. The round window niche lies posterior (3.44 mm, SD � 0.68 mm) and slightly inferior to the umbo of the malleus (113(, SD � 9.8() (Silverstein H, et al. Use of the malleus handle as a landmark for localization of the round window membrane; unpublished article). Usually the round window niche can be seen through a normal tympanic membrane as a dark shadow beneath the tympanic membrane. When there is scarring of the tympanic membrane from previous infection, it can be difficult to determine the exact location of the round window beneath the tympanic membrane. Using a myringotomy incision in these cases may make it easier to locate the round window niche accurately. Pitfalls of the MicroWick techniques Occasionally an opening an opening in the tympanic membrane may be made that is not directly over the round window niche. Then, when the 1032 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 MicroWick is inserted, it may not lie directly in the round window niche. This placement does not seem critical to the results of treatment. After the medication is delivered to the middle ear, the area of the round window niche is flooded whether the wick is in the niche or not. Patients lie in the supine position for 15 minutes, allowing the medication to diffuse into the inner ear. When steroids are used to treat inner ear disease, it is important to use antibiotic eardrops daily to prevent middle ear infection. The MicroWick should be removed or replaced after 4 weeks. If left in longer, it may become adherent to the round window niche and be difficult to remove without leaving a portion of the wick in the ear. If the wick cannot be removed easily, it should be left in place, and the ear should be injected with lidocaine. A pick should be placed into the area of attachment, and the wick should be teased away form the promontory. To the authors’ knowledge, no portions of wicks have been left in the middle ear. After removal of the ventilation tube and MicroWick, persistent tympanic membrane perforation can occasionally result. These perforations can be easily repaired with fat graft myringoplasty in the office. Hearing loss can occur with gentamicin delivered through the MicroWick as with any perfusion technique. Initial results with use of oral or topical steroids to rescue and protect the hearing have been encouraging. In fact, the authors have seen complete recovery of former hearing and even improvement of hearing with these techniques (Silverstein et al, unpublished data). Light [15] recently reported that there was correlation between the degree of vestibular ablation, control of vertigo, and the risk of hearing loss. The success rates for vertigo control seem to be similar in patients with functional hearing and in patients who already had lost functional hearing before treatment. Future investigation may determine if less than 100% RVR, but greater than 75% RVR is an alternative end point with adequate vertigo control and reduced risk of hearing loss. Advantages of the MicroWick techniques Placing the MicroWick is easy to perform, safe, and inexpensive. Self- treatment of inner ear disease using otic medication is well accepted by patients. Frequent return visits to the office are unnecessary. Medication can be maintained against the round window membrane for prolonged intervals and may be more efficient than treatment with individual injections in the surgeon’s office. Most of the medication is not lost down the Eustachian tube, as may occur when the medication is injected blindly into the middle ear. Prolonged treatment using a dilute gentamicin otic solution (10 mg/cm3) has the desired ablative effect on the vestibular system, and hearing is maintained or improved in 64% of cases. The MicroWick can be safely left in place for 4 weeks. 1033H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 In the future, new drugs and medications may be developed to treat certain types of inner ear disease including sensorineural hearing loss and tinnitus. These drugs could be administered by the patient to the inner ear using a MicroWick placed in the round window niche. Summary Using the MicroWick to deliver otic medication to the inner ear fluids is a new, unique, effective, safe, efficient, and inexpensive method to treat inner ear disease. This self-treatment method using otic medication represents a major breakthrough in the treatment of inner ear disease. It allows the otologist to treat inner ear disease much as the ophthalmologist treats eye disease using eye drops. In the future, new drugs and medications will likely be developed that will relieve vertigo attacks, improve certain types of sensorineural hearing loss, and reduce tinnitus. The MicroWick will be available for patients to self-administer these medications to the inner ear through the round window membrane. References [1] Schuknecht HF. Ablation therapy for the relief of Meniere’s disease. Laryngoscope 1956; 66:859–70. [2] DeCicco MJ, Hoffer ME, Kopke RD, et al. Round-window microcatheter-administered microdose gentamicin: results from treatment of tinnitus associated with Meniere’s disease. Int Tinnitus J 1998;4:141–3. [3] Hirsh BE, Kamerer DB. Role of chemical labyrinthectomy in the treatment of Meniere’s disease. Otolaryngol Clin North Am 1997;30:1039–49. [4] Silverstein H, Arruda J, Rosenberg SI, et al. Direct round window membrane application of gentamicin in the treatment of Meniere’s disease. Otolaryngol Head Neck Surg 1999; 120:649–55. [5] Silverstein H, Rowan PT, Olds MJ, et al. Inner ear perfusion and the role of round window patency. Am J Otol 1997;18:586–9. [6] Harner SG, Kasperbauer JL, Facer GW, et al. Transtympanic gentamicin for Meniere’s syndrome. Laryngoscope 1998;108:1446–9. [7] Parnes LS, Riddell D. Irritative spontaneous nystagmus following intratympanic gentamicin for Meniere’s disease. Laryngoscope 1993;103:745–9. [8] Nedzelski JM, Bryce GE, Pfleiderer AG. Treatment of Meniere’s disease with topical gentamicin: a preliminary report. J Otolaryngol 1992;21:95–101. [9] Nedzelski JM, Schessel DA, Bryce GE, et al. Chemical labyrinthectomy: local application of gentamicin for the treatment of unilateral Meniere’s disease. Am J Otol 1992;13:18–22. [10] Sala T. Transtympanic administration of aminoglycosides in patients with Meniere’s disease. Arch Otorhinolaryngol 1988;245:293–6. [11] Smith BM, Myers MG. The penetration of gentamicin and neomycin into perilymph across the round window membrane. Otolaryngol Head Neck Surg 1979;87:888–91. [12] Silverstein H, Jackson LE, Rosenberg SI. Silverstein MicroWickTM for the treatment of the inner ear. Operative Techniques in Otolaryngology-Head and Neck Surgery 2001;12:144–7. [13] Silverstein H. The MicroWick to deliver medication to the inner ear. Ear Nose Throat J 1999;78:595–600. 1034 H. Silverstein et al / Otolaryngol Clin N Am 37 (2004) 1019–1034 [14] Youssef TF, Poe DS. Intratympanic gentamicin injection for the treatment of Meniere’s disease. Am J Otol 1998;19:435–42. [15] Light JP, Silverstein H, Jackson LE. Gentamicin perfusion vestibular response and hearing loss. Otol Neurotol 2003;24(2):294–8. [16] Silverstein H, Lewis W, Jackson L, et al. Changing trends in the surgical treatment of Meniere’s disease: results of a 10-year survey. Ear Nose Throat J 2003;82(3):185–94. Silverstein MicroWick Materials and methods MicroWick procedure Treatment of Meniere’s disease Treatment of sudden deafness and acute cochlear Meniere’s disease Statistical analysis Results Results of treatment for Meniere’s disease Results of treatment for sudden deafness and autoimmune inner ear disease Complications Discussion Pitfalls of the MicroWick techniques Advantages of the MicroWick techniques Summary References