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Background
Meniere's disease (MD) is a pathological condition of the inner ear characterized by vertigo, tinnitus and a progressive loss of hearing. Delayed MD can develop in an ear that was damaged years earlier, usually by viral or bacterial infection. The majority of patients with MD also experience a sense of fullness and pressure in the area of the affected ear. This disorder affects male and female equally; it may occur in children, but has a peak onset between 20 and 50 years of age. The incidence of disease affecting both ears increases to over 40 % with long-term follow-up. Moreover, it has been reported that a high percentage of patients (57 %) had complete resolution of symptoms in 2 years.
The key pathological finding for patients with MD is an increase in the volume of endolymph, in conjunction with distention of the whole endolymphatic system (known as endolymphatic hydrops). However, the exact cause of MD is still unclear, and no treatment has prospectively modified the clinical course of the condition and thereby prevented the progressive hearing loss. Conservative management of patients with MD may include dietary salt restriction (1 to 2 g sodium daily) with or without diuretic (e.g., hydrochlorothiazide, dyazide, furosemide, amiloride, acetazolamide, and methazolamide), avoidance of caffeine, alcohol and nicotine. For acute attacks, vestibular suppressants (e.g., benzodiazepines and diazepam) or anti-emetics (e.g., anti-cholinergics such as glycopyrrolate, anti-dopaminergics such as droperidol, prochlorperazine, and anti-histamines such as dimenhydrinate, diphenhydramine, meclizine, and promethazine) have been used. Medical ablation of the inner ear with systemic administration of ototoxic aminoglycosides, such as streptomycin and gentamicin, has been useful in advanced bilateral MD when poor but aidable hearing precludes surgical intervention. Moreover, the indications for this approach are limited, especially with the advent of intra-tympanic placement of gentamicin.
For MD patients whose vertiginous symptoms are disabling and refractory to dietary and medical treatments, surgery may be the last resort in achieving relief. In general, surgical procedures for MD can be categorized as non-destructive or destructive regarding to hearing. The former includes endolymphatic sac surgery and vestibular nerve section (vestibular neurectomy), while the latter includes labyrinthectomy (extirpation of the labyrinth) and cochleosacculotomy.
Endolymphatic sac surgery is the most frequently employed conservative surgical approach for patients with MD when hearing is still serviceable. It has been reported to achieve complete or substantial control of vertigo in 81 % of patients, with significant improvement in hearing in about 20 % of patients. Although it has shown to be less likely to completely eliminate vertigo than vestibular nerve section, endolymphatic sac surgery has been reported to be a low morbidity procedure. Endolymphatic sac decompression and sacculotomy are two common types of endolymphatic sac surgery. In the former procedure, some of the bone surrounding the inner ear is removed. In some cases, endolymphatic sac decompression is coupled with the placement of an endolymphatic shunt. Sacculotomy entails the implantation of a permanent device that allows endolymph to drain out of the inner ear whenever pressure builds up.
Brinson et al (2007) compared the effectiveness of endolymphatic mastoid shunt (EMS, n = 88) versus endolymphatic sac decompression (ESD, n = 108) without sac incision for the treatment of MD. The American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines for the diagnosis and evaluation of therapy in MD were used to retrospectively identify suitable candidates for the study. All patients who failed medical management and underwent either EMS or ESD were selected for review using the AAO-HNS guidelines. The study was carried out at a tertiary care neurotology private practice. EMS and ESD were equally effective in reducing the incidence and severity of vertigo attacks with significant improvement in 67 % and 66 % of patients, respectively. The authors concluded that both EMS and ESD are effective, non-destructive alternatives for patients who have failed medical management of MD with similar long-term hearing outcomes.
Available medical literature suggests that vestibular nerve section can be performed by exposing the middle fossa or the posterior fossa. The posterior fossa vestibular neurectomy can be further divided into the retrolabyrinthine approach, the retrosigmoid-internal auditory canal approach, and the combined retrolabyrinthine-retrosigmoid approach. Vestibular nerve section has been shown to be generally very effective in the control of vertigo. According to available literature, vestibular nerve section is contraindicated in persons with vertigo arising from the only hearing ear (i.e., the other ear is deaf); central nervous system disease; persons in poor medical condition; persons with ataxia; and in most cases of bilateral MD.
Labyrinthectomy is indicated for patients with symptoms who have poor or non-serviceable hearing. There are several approaches to the labyrinth -- transcanal labyrinthectomy with section of the posterior ampullary nerve, transmastoid labyrinthectomy, and transmeatal cochloevestibular neurectomy. For the older patients (greater than 60 years of age), available medical literature suggests that a transmastoid labyrinthectomy may be preferable to a transcanal labyrinthectomy because the incidence of permanent post-surgical imbalance is less with the former approach. Labyrinthectomy has been reported to produce similar or better results than vestibular neurectomy. Cochleosacculotomy creates a permanent fistula in the cochlear duct by passing a small pick through the round window. It is mainly used for elderly patients with poor hearing who are unable to tolerate a prolonged operation.
Lacombe (2009) stated that spontaneous recovery or central compensation makes surgical procedures rare in patients with vertigo. The main target in treating MD is to promote vestibular compensation, which is possible only with a non-progressive and stable deficit leading to readjustment of vestibular reflexes. Surgical procedures can be classified as non-destructive (endolymphatic sac decompression, vestibular nerve decompression, patching of perilymphatic fistulas), selectively destructive (middle fossa or retrosigmoid vestibular neurotomy, lateral semi-circular canal plugging) and destructive (labyrinthectomy). Surgical indications essentially concern incapacitating vertigo and depend mainly on hearing status. In MD, vestibular neurotomy can be regarded as the gold standard considering its good results on vertiginous episodes; however, scoring with functional and quality-of-life scales bring out residual deficiency in some cases.
In a prospective, follow-up study, Charpiot and colleagues (2010) assessed the safety and effectiveness lateral semi-circular canal plugging to control vertigo in severe MD. A total of 28 MD patients with refractory vertigo and severe disability (functional scale 5 or 6) were included in this study. Lateral semi-circular canal plugging was performed in the pathological ear for each patient. The evaluation of therapy followed the guidelines for diagnosis and evaluation of therapy in MD. Hearing, frequency of vertigo, and functional disability were assessed in the early follow-up (6 months) for all the patients and in the late follow-up (2 years) for 16 patients. In addition, canal paresis was evaluated by the caloric test. No vital complication occurred. The hearing was preserved in 82 % of cases. Lateral semi-circular canal plugging induced in all cases canal paresis that was persistent after 2 years. After 2 years (n = 16), the control of vertigo was complete or substantial in 75 % of cases (restoration of a normal life = 62.5 %; no functional restriction =12.5 %). The authors concluded that lateral semi-circular canal plugging is a safe procedure that induces canal paresis and allows a good control of vertigo. In view of these results, lateral semi-circular canal plugging should be a therapeutic option for controlling rotatory vertigo in severe MD.
In a review on bilateral MD, Nabi and Parnes (2009) stated that for bilateral MD, ablative treatments are relatively contraindicated due to the risks of bilateral vestibular and cochlear hypofunction.
In a Cochrane review, Pullens et al (2011) evaluated the effectiveness of intra-tympanic gentamicin in the treatment of vertigo in MD. These investigators searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; BIOSIS Previews; Cambridge Scientific Abstracts; ISRCTN and additional sources for published and unpublished trials. The date of the most recent search was June 30, 2010. All randomized or quasi-randomized controlled trials of intra-tympanic gentamicin versus placebo, or versus another treatment for MD were selected for analysis. Two review authors independently assessed trial quality and extracted data. They contacted study authors for further information. These investigators identified 2 trials, involving 50 participants, which fulfilled the inclusion criteria. Both of these trials are prospective, double-blind, placebo-controlled randomized clinical trials on the effect of intra-tympanic gentamicin on vertigo complaints. Both of these trials found a significant reduction in vertigo complaints in the gentamicin group when compared to the placebo group. Due to clinical heterogeneity these researchers could not perform a meta-analysis. The authors concluded that based on the results of the 2 included studies, intra-tympanic gentamicin seems to be an effective treatment for vertigo complaints in MD, but carries a risk of hearing loss.
Gawecki et al (2012) estimated the results of treatment of MD with intra-tympanic injections of gentamicin. A total of 37 patients with defined, pharmacological treatment resistant MD were injected intra-tympanic with 0.3 ml (12 mg) of gentamicin once or few times with 7 days or longer breaks and a number of injections depended on the reaction of the inner ear. These investigators estimated the patients' subjective feelings and results of equilibrium and hearing organ examination in early (3 months) and late (2 years) period after treatment. Complete control of vertigo (class A) was achieved in 84.6 %, and complete and essential control (class A and B) in 96.1 %. Hearing deterioration usually mild or moderate was observed directly after treatment in 16.2 % and after 2 years in 23 % patients. The results of pure tone audiometry showed deterioration of hearing in 16.2 % (early) and 26.9 % (late). In 1 patient hearing deterioration was essential. The authors concluded that intra-tympanic injections of gentamicin are effective and not troublesome method of treatment of pharmacological treatment resistant MD. In most of patients hearing can be preserved, but they should be always informed about possible risk of hearing deterioration. The number of injections and breaks between them depends on the effect of therapy and of expectations of patients.
An UpToDate review on “Meniere disease” (Dinces and Rauch, 2013) states that “Destructive procedures for the treatment of Meniere disease include intratympanic gentamicin injection, surgical labyrinthectomy, and vestibular nerve section. In general, destructive techniques are better suited to patients who have failed medical therapy and who have unilateral disease”.
The National Coverage Determination (NCD) for “Cochleostomy with Neurovascular Transplant for Meniere's Disease” stated that “While there are 2 recognized surgical procedures used in treating MD (decompression of the endolymphatic hydrops and labyrinthectomy), there is no scientific evidence supporting the safety and effectiveness of cochleostomy with neurovascular transplant in treatment of Meniere's syndrome. Accordingly, Medicare does not cover cochleostomy with neurovascular transplant for treatment of MD”.
In an interventional cohort study, Loader et al (2012) compared the unique long-term results of tenotomy of the stapedius and tensor tympani muscles in definite MD refractory to medical treatment and presented a hypothesis on why tenotomy seems effective. The study sample comprised 30 patients (15 males, 15 females; average age of 57 +/- 13.1 years) with definite MD (AAO-HNS criteria, 1995). Patients were evaluated pre- and post-operatively using pure tone audiometry, AAO-HNS questionnaires regarding vertigo attacks, functional level scores, and tinnitus, and were followed-up for 2 to 9 years. Post-operative values were calculated for the patient collective as a whole and consequently divided into 3 equal post-operative terms of 3 years each. A statistically significant improvement of inner ear hearing levels post-operatively (p = 0.041) and a major reduction in vertigo attacks in all groups (p < 0.001) with complete absence of attacks in 26/30 patients was noted. Results remained constant up to 9 years post-operatively. Although tinnitus persisted, the intensity was lower overall (p = 0.013). Based on the immediate and persistent reduction of vertigo and a clear improvement in hearing function and functional scales, the authors concluded that tenotomy is effective in unilateral, definite MD. They stated that the findings of this study laid the foundation for future prospective, randomized controlled trials.
Furthermore, UpToDate reviews on “Meniere disease” (Dinces and Rauch, 2013) and “Treatment of vertigo” (Furman and Barton, 2013) do not mention the use of cochleostomy and tenotomty as therapeutic options.
Appendix
Selection criteria for surgery for Meniere's disease:
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Member has disabling vertigo; and
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Member has exhibited symptoms (hearing loss, tinnitus, vertigo) for at least 2 years; and
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Member has failed conservative management, including dietary restrictions (avoidance of caffeine, alcohol and nicotine; low sodium), and medical therapy (anti-emetic, diuretic, and vestibular suppressants); and
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Member has unilateral Meniere's disease and hearing loss is severe to profound in the involved ear (for labyrinthectomy only).
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