Tenotomy of the middle ear muscles causes a dramatic reduction in vertigo attacks and improves audiological function in definite Meniere s disease

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1 Acta Oto-Laryngologica, ; Early Online, 7 ORIGINAL ARTICLE Tenotomy of the middle ear muscles causes a dramatic reduction in vertigo attacks and improves audiological function in definite Meniere s disease Acta Otolaryngol Downloaded from informahealthcare.com by Medical University of Vienna on // BENJAMIN LOADER, DAVID BEICHT, JAFAR-SASAN HAMZAVI & PETER FRANZ Department of Otorhinolaryngology Head and Neck Surgery, Medical University of Vienna, Vienna General Hospital, Vienna, Austria Abstract Conclusions: Because the presented data reveal an immediate and persistent reduction of vertigo and a clear improvement in hearing function and functional scales, we conclude tenotomy to be effective in unilateral, definite Meniere s disease laying the foundation for future prospective, randomized controlled trials. Objectives: This study compares the unique longterm results of tenotomy of the stapedius and tensor tympani muscles in definite Meniere s disease refractory to medical treatment and presents a hypothesis on why tenotomy seems effective. Methods: This was an interventional cohort study. The study sample comprised patients ( males, females; average age 7 ±. years) with definite Meniere s disease (AAO-HNS criteria, 99). Patients were evaluated pre- and postoperatively using pure tone audiometry, AAO-HNS questionnaires regarding vertigo attacks, functional level scores, and tinnitus, and were followed up for 9 years. values were calculated for the patient collective as a whole and consequently divided into three equal postoperative terms of years each. Results: A statistically significant improvement of inner ear hearing levels postoperatively (p =.) and a major reduction in vertigo attacks in all groups (p <.) with complete absence of attacks in / patients was noted. Results remained constant up to 9 years postoperatively. Although tinnitus persisted, the intensity was lower overall (p =.). Keywords: Dizziness, hearing loss, tinnitus, ear surgery, AAO-HNS, aural fullness Introduction The stapedius and tensor tympani muscles and their effect on the inner ear have become a forgotten entity in the surgical therapy of Meniere s disease. Even though a multitude of noninvasive therapy strategies used in first-line treatment of Meniere s disease has been described, these middle ear muscles have not attracted great interest as a therapeutic target in Meniere s disease []. When the first-line strategy of conservative treatment is insufficient, a variety of surgical strategies such as middle ear ventilation tube placement, labyrinth anesthesia, gentamicin instillation into the affected middle ear, saccotomy or vestibular neurectomy are widely used. None of these strategies clearly and directly target the middle ear muscles as therapeutic substrate. Tenotomy of the stapedius and tensor tympani muscles, as described below, had shown promising initial results in patients with definite Meniere s disease []. The procedure was commonly used until the 9s, after which it was largely abandoned due to a high incidence of postoperative infection []. Nonetheless, tenotomy has been successfully used in patients suffering from middle ear myoclonus and its resulting tinnitus []. When combined with gentamicin instillation into the affected middle ear, tenotomy has been reported to be beneficial in cases of definite Meniere s disease. However, the authors also reported no significant difference in results Correspondence: Benjamin Loader MD, Otorhinolaryngology Department, Medical University of Vienna, Vienna General Hospital, Währinger Gürtel 8-, A-9, Vienna, Austria. Tel: Fax: +. benjamin.loader@meduniwien.ac.at (Received 7 September ; accepted November ) ISSN -89 print/issn - online Ó Informa Healthcare DOI:.9/89..8

2 Acta Otolaryngol Downloaded from informahealthcare.com by Medical University of Vienna on // B. Loader et al. between the combination of tenotomy and gentamicin, when compared to gentamicin treatment alone []. The hypothesis on the mechanism behind tenotomy s apparent therapeutic potential, as described in the discussion of our results, would explain why De Valck et al. [] showed no additional effect in therapeutic success when adding tenotomy to gentamicin therapy. It is widely accepted that gentamicin s therapeutic target is the vestibular nerve (chemical labyrinthectomy), which lies medially to the inner and middle ear structures in the vestibular tract. Tenotomy targets middle ear structures and their influence on pressure dynamics of the middle and inner ear as is explained below. Thus, when combined with gentamicin, all functional changes occurring as a result of tenotomy could not be adequately transported to the central nervous system, because the functionality of the vestibular nerve had been nullified by gentamicin therapy. Therefore it makes sense that tenotomy would have no effect when added to a gentamicin labyrinthectomy []. The goal of this study was to scrutinize the long-term effects of tenotomy on audiological function, vertigo, functional scales, and tinnitus scores according to AAO-HNS guidelines over an extended follow-up period, which to our knowledge is a novel approach []. This study also aimed to identify the middle ear muscles as clinically relevant key structures in the pathological cochlear hydrops ear and, in consequence, lay the foundation for prospective randomized trials. Material and methods A total of patients ( male, female; average age 7 ±. years) with definite Meniere s disease according to AAO-HNS guidelines (99) underwent a tenotomy of the stapedius and tensor tympani muscles under general anesthesia at the Otolaryngology Department of the Vienna General Hospital, Medical University of Vienna. ly patients received a full clinical otologic work-up, which included pure tone audiometry, tympanometry, and questionnaires as recommended by the AAO-HNS guidelines. Neurologic disorders were excluded. All patients had been treated with conservative therapy strategies with insufficient symptom control, before being included in the study. follow-up ranged from 8 months to 9 years. Surgical techniques All patients received general anesthesia. To expose the stapedius and tensor tympani tendons, an enaural tympanotomy was performed. The posterior half of the tympanic membrane s annulusfibrosus was carefully luxated to expose the stapedius tendon. The chorda tympani was elevated from its bony bed and left intact and undamaged. The chorda was followed to the maleus manubrium and an anterior tympanotomy was performed to expose the tendons of the middle ear muscles. The stapedius and tensor tympani tendons were cut with a neurectomy knife. No damage to the bony ossicular chain was caused. Reporting of results data were compared with postoperative data as a whole for the follow-up period of 8 months as suggested by the AAO-HNS criteria. The worst audiogram of the period 8 months was used for comparison. Secondly, postoperative data (pure tone average and vertigo control) were divided into three postoperative intervals (A = years, B = years, and C = 9 years) and the worst audiogram of the respective follow-up interval compared to preoperative data. All patients in group A were observed for at least 8 months. Group A included patients, group B included 7, and group C included patients. The following parameters were compared. () The pure tone average (PTA) is the arithmetic mean of pure tone thresholds at,,, and Hz in decibels (db), rounded to the nearest whole number. The worst audiogram of the relevant follow-up period was used for comparison. () The number of vertigo attacks of min or more per month. () Functional level scores were scored on a six-point scale determining how vertigo attacks influenced the patient s dailylifeasfollows:(i)activities unaffected; (ii) activities slightly affected; (iii) activities moderately affected; (iv) major adjustments of daily routine necessary; (v) onlyessentialactivities possible; (vi) completely disabled. () Tinnitus scale: patients were repeatedly asked to grade tinnitus severity on a scale of ( = barely noticeable, = intolerable). Data were analyzed with SPSS. Standard Mann- Whitney U and t tests were used for statistical analysis, depending on the data distribution. All patients gave written consent and the study was approved by the local institutional review board. Results Audiological outcome A marked improvement in postoperative bone conduction values was noted, especially in lower

3 Tenotomy and Meniere s disease Acta Otolaryngol Downloaded from informahealthcare.com by Medical University of Vienna on // Hearing level (db) frequencies (Figure ). There also was a statistically significant postoperative improvement of inner ear hearing levels (pure tone average) when comparing pre- and postoperative values of the patient collective as a whole at 8 months postoperatively (p =.) (Figure ). Hearing thresholds for groups A(n = ), B (n = 7), and C (n = ) are shown in Figure. There was no statistically significant difference between the postoperative hearing thresholds of groups A, B, and C when compared to one another. No air bone gaps could be identified pre- or postoperatively khz khz khz khz khz 8 khz Frequency (khz) Vertigo control In all, 8/ patients reported a significant reduction (p <.) in the number of vertigo attacks (Figure ); / patients reported absolute vertigo control with no postoperative attacks (Class A according to AAO- HNS guidelines). Three patients reported mild recurrence of vertigo with sporadic attacks (Class B) and one patient reported constant symptoms. When divided into groups A (n = ), B (n = 7), and C (n = ) (Figure ), two patients reported either one or two postoperative attacks per month in group A, while eight patients reported Class A vertigo control. None of the patients in group B had postoperative attacks. Additionally, of patients in group C reported a statistically significant reduction in vertigo attacks (p <.) with or attacks per month postoperatively (Class B vertigo control according to AAO- HNS guidelines), while the remaining patients of group C showed absolute vertigo control. Overall functional level scores are presented in Figure, which reveals an improvement in routine functionality (p <.). One patient still reported major postoperative influences on the daily routine by dizziness and another was still moderately affected (according to AAO-HNS criteria). A third patient was still slightly affected postoperatively. Tinnitus Figure. Bone conduction values for all patients as measured by pure tone audiometry preoperatively and 8 months postoperatively. A significant improvement of hearing was seen in the frequencies up to khz (p <.). Pure tone average (db) 8 Figure. The preoperative (white) and postoperative (gray) pure tone average (db) of the complete study population shows a significant improvement in hearing function 8 months postoperatively (p =.). A reduction in the overall tinnitus intensity was reported, as presented in Figure 7 (p =.). However, tinnitus did not disappear completely. In

4 B. Loader et al. Pure tone average (db) 8 Acta Otolaryngol Downloaded from informahealthcare.com by Medical University of Vienna on // cases tinnitus levels improved, in no significant change was observed, and in cases tinnitus worsened. Discussion Group A (- years) This study showed a profound reduction in monthly vertigo attacks and a statistically significant influence on tinnitus severity, while inner ear function and functional scale values improved postoperatively. In Group B (- years) Group C (-9 years) Figure. The pure tone average (db) was divided into three postoperative follow-up intervals, which showed constant hearing thresholds, without statistically significant differences between the postoperative groups., white; postoperative, gray. Vertigo attacks 8 all successful vertigo control cases after tenotomy, patients reported the absence of aural fullness, which might hint at the mechanism behind the success of tenotomy for vertigo control. The middle ear muscles are the therapeutic targets of tenotomy. Interestingly, no patient presenting with an air bone gap in pure tone audiometry, which usually points to middle ear pathology, could be identified in our collective. Middle ear ventilation tubes, also commonly used for surgical treatment of other middle ear pathologies, have been used for Vertigo attacks 8 Group A ( years) Group B ( years) Group C ( 9 years) Figure. Vertigo attacks per month preoperatively and 8 months postoperatively (p <.); / patients reported complete vertigo control, with no postoperative attacks. Figure. Vertigo attacks per month preoperatively and postoperatively (p <.) divided into three -year postoperative follow-up periods. Two patients experienced attacks in the first postoperative years. Two patients in group C reported attacks 9 years postoperatively, albeit at reduced frequency when compared to preoperative levels.

5 Acta Otolaryngol Downloaded from informahealthcare.com by Medical University of Vienna on // Functional level score Figure. functional level scores show a highly significant reduction in vertigo handicap (p <.). vertigo control with good results [7]. The ventilation of the middle ear enables the elevated aural pressure resulting from the cochlear hydrops to escape through the ventilation tube, in addition to the eustachian tube. Ventilation tube treatment is highly unlikely to have a permanent effect on vertigo control in Meniere s disease, seeing that the tube will at some stage be discarded into the auditory canal or become clogged, thus losing its effectiveness [7]. In contrast, tenotomy seems to have a long-lasting effect on Meniere s disease. Hearing thresholds remained improved in our whole patient collective. As seen in Figure, the postoperative pure tone average of group C is slightly worse than that of group B, without reaching statistical significance. This slow decline in inner ear hearing function might be attributed to Tinnitus level Figure 7. tinnitus intensity was reduced (p =.), without disappearing completely. In cases tinnitus levels improved, in no significant change was observed, and in cases tinnitus worsened slightly. Tenotomy and Meniere s disease presbyacutic processes or Meniere s disease progression. It is impossible to deduce whether inner ear function would have declined more rapidly, had tenotomy not been performed. This issue could be addressed in future prospective, randomized trials. Nevertheless, it is interesting to note, that up to 9 years postoperatively (group C, Figure ), inner ear performance is still markedly better after tenotomy than before the operation. To our knowledge, these results showing preservation of hearing function after surgical intervention for Meniere s disease are unique. When considering audiological and vestibular Meniere s disease progression, it is widely known that vertigo attacks in Meniere s disease may recede slowly as years pass. In contrast to published data on labyrinth anesthesia and ventilation tube treatment, which seems to be effective for years in two-thirds of all cases, our data show an immediate effect on vertigo attacks, which remained stable for long periods [8,9]. This is also true for hearing levels, as mentioned above. If the audiological preservation and elimination of attacks were not related to tenotomy itself, but were attributed to a placebo affect of an intervention regardless of the technique used, the results would not have been so uniquely constant for all parameters tested over long follow-up periods. The pathophysiology of Meniere s disease remains a controversial subject. Just as for Meniere s disease and labyrinth anesthesia themselves, the pathophysiologic process behind the apparent success of tenotomy is unclear and could be controversially discussed. It has been generally accepted that the cochlear hydrops and associated rise in pressure in the inner ear result in the prodromal sensation of aural fullness and might act as a trigger for the characteristic rotational vertigo attacks seen in patients with Meniere s disease. Interestingly, it is known that even atmospheric pressure changes have an influence on the Meniere s disease hydrops []. It is also commonly acknowledged that sudden pressure changes of the middle ear can cause inner ear damage (i.e. rupture of the round window as seen in barotrauma or soundinduced hearing loss). Patients with middle ear effusions are also discouraged from air travel, because of the audiologically relevant danger of cabin pressure changes. It has even been shown that by changing atmospheric pressure, the cochlear and middle ear dynamics are also altered, which in turn influences Meniere s disease symptoms []. Not only does the tensor tympani muscle increase tension on the tympanic membrane, but on the labyrinth as well []. Our hypothesis, although it might be seen as speculative, is based on the fact that, as a result of intracochlear dynamics, the increased cochlear pressure and greater cochlear diameter press

6 Acta Otolaryngol Downloaded from informahealthcare.com by Medical University of Vienna on // B. Loader et al. against the ossicular chain, indirectly pushing the tympanic membrane laterally. That inner ear pressure changes have an effect on ossicular chain has recently been described []. The cited animal study showed a significant reduction in ossicular chain movement at elevated endolymphatic pressure (as seen in hydrops cochlea patients). Importantly, this pressure change and change in ossicle function primarily affect lower frequencies in the exact same frequency spectrum as the primary hearing loss in Meniere s disease []. The contraction of the tensor tympani and stapedius muscles stabilizes the ossicular chain and has its tension vector in a mediocaudal plane []. When it is considered that when applying pressure on the scala vestibuli by pressing medially on the stapes, significant endolymphatic movement is caused (i.e. pressure changes), it stands to reason that the contraction of middle ear muscles has the same effect []. This would mean that the muscle tension of the middle ear muscles would increase the inner ear pressure in cochlear hydrops of Meniere s disease, by pressing the ossicular chain in the opposite direction to the bulging of the endolymphatic hydrops []. This seems plausible, considering that the rise in inner ear pressure has three main routes of escape: the vestibular aqueduct, the round window, and the oval window (upon which the stapes is mounted). In analogous fashion, if the stabilizing function of the middle ear muscles is interrupted by tenotomy, the ossicle chain can be moved laterally more freely, which results in a bulging of the tympanic membrane laterally. The ossicular chain is no longer actively pressed against the oval window and therefore the pressure on inner ear structures is not heightened even further. Thus it can be postulated that a trigger inner ear pressure value, resulting in the acute onset of rotational Meniere s disease vertigo attacks, is not as easily reached, once the tendons of the middle ear muscles have been severed. Analogous to Adunka et al. [], we opted not to include a control group because this study did not aim to prove one surgical technique superior to another, but solely to show the immediate and prolonged effects of tenotomy. We also do not deem it ethically sound to leave patients in need of invasive therapy untreated, so as to create a placebo control group. A placebo operation is not allowed by our institution. Previous placebo operations have been reported to improve vertigo symptoms, while leaving hearing levels constant [7,8]. In contrast, our study showed not only effective vertigo control, but also improved hearing function. It is our opinion that the addition of a control group would not enhance the scientific legitimacy of this study. Therefore we conclude that tenotomy of the tensor tympani and stapedius muscles of the effected ear in definite Meniere s diseaseisapromising surgical procedure with significant control of vertigo attacks and aural fullness, providing stable, longterm results. With the improvement in hearing function, reduction of subjective handicap, and the reduction of tinnitus severity, it is our sincere opinion that this study lays the foundation for future prospective randomized trials to confirm or disprove our experience. Acknowledgments The authors are indebted to Carina Kapoun for her assistance. The study was supported by the Medical University of Vienna. Declaration of interest: The authors report no conflicts of interest. 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