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Controversies in the Management of Meniere's Disease

As Published In “Controversies in Otolaryngology”

Mitchell K. Schwaber, M.D.
Nashville Ear, Nose and Throat Clinic

• Diagnosis of Meniere's Disease
• Staging of Definite and Certain Meniere's
• References

Perhaps the most controversial subject in Neurotology concerns the diagnosis and management of patients with Meniere's disease. Not only is there uncertainty regarding the etiology and pathophysiology, but also the role of medical management, particularly in light of the fact that the exact cause is not known, the illness has frequent periods of remission, and only anecdotal reports of efficacy exist for most treatments. Furthermore there is a perception that many of the surgical procedures used to control the disorder may merely be inducing a remission phase or may have no effect at all. Needless to say much of conventional wisdom regarding Meniere's disease merely reflects the opinion of experienced clinicians, rather than scientific fact.

With such a controversial subject, it is easy to extrapolate that certain findings, symptoms, or responses to treatment are indicative of the nature of the problem. The reader should be reminded that neither an apparent response to therapy nor post-mortem histopathological findings represent scientific evidence of the exact pathophysiology of a condition. Plainly stated, Meniere's disease is a chronic condition characterized by a progressive dysfunction of the inner ear and/or the cochleovestibular nerve. Beyond this basic description, the exact etiology of the problem has still not been clearly elucidated at this writing.

As a consequence, to successfully "manage" Meniere's syndrome patients, the physician must assume their care for many years, albeit, the need for services may vary considerably. This is particularly true in light of the long periods of remission as well as the cyclic nature of this condition in some patients. Therefore, if the physician chooses to manage these patients, he should do so from the mindset of a long-term chronic disorder, much like adult-onset Diabetes Mellitus, chronic pain, or hypertension. While treatment may modify the clinical course of Meniere's disease patients somewhat, cures are indeed rare. Patients must be followed and therapy adjusted as clinical circumstances warrant. Also measuring the effects of therapy can be extremely difficult, and the physician should never assume that the recommended intervention or treatment has actually stopped the progression of this disorder. Rather, the condition may have entered a remission phase.

Having stated that the exact etiology is not known, what is known of Meniere's disease at this time? Meniere's disease is a clinical disorder associated with the histopathological finding of endolymphatic hydrops. Most of the hydropic distention found in post-mortem specimens is seen in the cochlea and the saccule, although occasionally the utricle and the ampullae are involved. Other histopathological features include ruptures or fistulae, collapse of membranes, and vestibular fibrosis. Minimal histopathological changes are seen in the sensory epithelia , although the loss of ganglion and neuronal cells, inner and outer hair cells, and strial vascularity have been reported. Recognized causes of Meniere's syndrome include idiopathic, posttraumatic, post-infectious i.e. delayed-onset following a viral illness, late- stage syphilitic, and Cogan's syndrome or one of its variants.

One theory of Meniere's disease is that increased endolymphatic pressure causes the symptoms as well as the histopathological features. According to this theory, pressure buildup leads to membrane ruptures, so that potassium-rich endolymph gains access to the sensory and neural structures, causing sudden or fluctuant hearing loss and episodic vertigo. According to this theory, pressure buildup develops as a result of altered resorption of fluid by the endolymphatic sac. Abnormalities that lead to this altered resorption include perisaccular and vestibular epithelial fibrosis, altered glycoprotein metabolism, viral infection of the inner ear, and autoimmune mediated dysfunction of the sac. Furthermore, bony narrowing of the endolymphatic duct might also contribute to the obstruction and dysfunction of the sac.

A number of studies from the Massachusetts Eye and Ear Infirmary refute the pressure theory and suggest that endolymphatic hydrops is an epiphenomenon. These studies propose that Meniere's disease develops as a result of a problem with altered biochemical gradients within the endolymphatic space. Findings that support this theory include a number of biochemical alterations found in hydropic inner ears. These alterations include a decrease in endocochlear potential, an increase in intracochlear calcium, alterations in potassium permeability, inhibition of electrogenic transport processes, and increased endolymph fluid protein content.

It seems likely that Meniere's disease can be caused by a number of factors, each resulting in an alteration that leads to similar clinical features. It also seems likely that, at some point, idiopathic endolymphatic hydrops will no longer be an appropriate description of this syndrome. Rather, the specific biochemical or cellular abnormality will be identified and treated by the clinician.

In the era of managed care with declining health care revenues, most clinicians are uncertain as to which studies are needed to properly evaluate patients with suspected Meniere's disease. The history can be helpful, specifically with regard to fluctuating hearing loss, ear pressure, hearing distortion or hypersensitivity, and severe episodic vertigo accompanied by increased tinnitus or hearing loss. Physical findings that should be elicited include spontaneous or gaze-evoked nystagmus (usually away from the affected ear), fistula test, Dix-Hallpike maneuver, Romberg and gait tests. The otological exam, while usually unremarkable, occasionally reveals other causes such as cholesteatoma or middle ear tumor. A comprehensive audiogram is also essential, with particular attention to the presence of a low-frequency sensorineural hearing loss. Unexpectedly low speech discrimination scores or abnormal acoustic reflexes may be helpful in determining the need for additional testing.

Additional audio-vestibular testing, including otoacoustic emissions, electrocochleography, and electronystagmography, should be obtained if there is a need for further supporting data for the diagnosis of Meniere's disease. An elevated summating potential may also raise the clinician's suspicion of bilateral dysfunction, but medical judgements based on this study should be made conservatively. Auditory brainstem response testing can be used to screen for retrocochlear disorders masking as Meniere's syndrome, although an imaging study such as an MRI scan is much more definitive, and should be obtained prior to any surgical procedure. Other studies indicated in the evaluation of Meniere's syndrome patients include syphilis screening tests, rheumatoid factor, sedimentation rate, anti-nuclear antibody titers, blood glucose levels, cholesterol and triglyceride levels. In cases of bilateral Meniere's syndrome, in cases with rapidly progressive hearing loss, or in cases of suspected Cogan's syndrome, specific studies for auto-immune inner ear antibodies (heat shock protein) should be obtained.

The diagnosis of Meniere's disease has been formalized by the American Academy of Otolaryngology-Head and Neck Surgery, and is detailed in Table 1. A single episode of severe vertigo with hearing loss is classified as probable Meniere's disease, while multiple episodes of vertigo associated with hearing loss represents definite Meniere's disease. Staging the disease currently depends on the severity of the hearing loss, as noted in Table 2. This staging system is in contrast to prior staging systems that depended on the frequency of the vertigo episodes. Stages 1 and 2 are considered to be representative of early, reversible disease, i.e. prone to remission. Stages 1 and 2 cases are more likely to be amenable to remission type therapies including endolymphatic sac surgery or steroid perfusion. Stage 3 is considered fixed or not reversible, and these patients might be considered for deafferentation procedures including aminoglycoside perfusion of the round window or retrosigmoid vestibular nerve section. Stage 4 cases are usually considered candidates for destructive procedures such as transmastoid labyrinthectomy or triple canal ablation with laser.

The medical management of Meniere's disease is directed at either decreasing the fluid volume of the endolymph, increasing the circulation of the inner ear, or altering the immune reactivity or blockage of the endolymphatic duct. None of these proposed regimens has ever been shown to be effective in a double-blind controlled study. Despite that fact, most clinicians utilize one or more of these strategies in an effort to alter the natural history of the disorder. The most common management strategy is the use of a low-sodium diet and diuretic to decrease endolymph volume. It is entirely possible that if this treatment works, it is through an unrecognized indirect mechanism, such as altering the ionic balance in some way. Recent reports indicate that the epithelial cells of the endolymphatic sac have a large number of receptors that specifically bind with AVP or anti-diuretic hormone vasopressin. One can only speculate at present if this explains the action of diuretics and low salt diet on this condition. However, if this is the case, dehydration and hypovolemia should be avoided as these would tend to raise AVP levels. Simply stated, to keep AVP levels low the most effective route would be a mild diuretic, a modest 2000 to 2500 milligrams salt diet, and plenty of water.

Vasodilator therapy is based on the belief that Meniere's disease is related to decreased inner ear blood flow. In this treatment strategy, the patient is instructed to avoid caffeine and nicotine completely. A vasodilator drug such as niacin, B-histamine, or papaverine is prescribed to improve blood flow. The patient is asked to avoid stress, and to begin an exercise program for conditioning and stress reduction. While the efficacy of this regimen can be questioned, it is extremely beneficial to the patient both physically and psychologically, and it has few side effects.

A third medical regimen is to alter the immune response with either steroids, methotrexate, cytoxan, or allergic desensitization. Steroids are usually recommended first for patients with severe vertigo unresponsive to low salt diet, diuretics, and vestibular suppressants, and for patients with a sudden decline in hearing. Patients with bilateral Meniere's disease or with suspected autoimmune inner ear syndrome may also be candidates for steroid therapy. If the patient is initially responsive to steroids, other immunosuppressive therapies can be tried, usually with success. If the symptoms can be stabilized for one year, the immunosuppressive drug can be tapered and discontinued.

If a patient continues to have episodic vertigo in spite of an adequate trial of medical therapy, surgical management should be considered. Episodic vertigo occurring once a month or more often is considered life altering, and these patients are usually prepared to have a procedure if the clinician recommends it. The type of procedure recommended depends on the duration and stage of the Meniere's disease and the desires of the patient.

In explaining the available surgical options to the patient, it is helpful to divide the procedures into three types- remission procedures, deafferentation procedures, and destructive procedures.

Remission procedures include steroid perfusion of the round window and endolymphatic sac surgery. The term remission is used to indicate that these procedures attempt to restore function to the inner ear rather than destroy or decrease function. Also, this term clearly explains that the remission may be short lived, and that symptoms may then reoccur. Patients are much more understanding of this concept, rather than predicting the duration of relief. Remission procedures are recommended for Stage 1 or 2 disease, particularly with a history of long remissions in the past. These procedures are particularly appropriate in patients with relatively short histories of the illness, that is, less than two to three years.

Few procedures in otologic surgery have been as controversial as endolymphatic sac surgery, and opinions vary from those who conclude the procedure is effective in over 80% of cases to those who believe it is nothing more than a placebo procedure. Endolymphatic sac surgery offers the possibility of vertigo control with little risk of morbidity, and theoretically surgery improves the function of the sac or opens a blocked endolymphatic duct. Alternatively, endolymphatic sac surgery might cause a temporary subclinical labyrinthitis that perhaps alters the natural history of the Meniere's disease.

Steroid perfusion, like endolymphatic sac surgery, is also a controversial procedure. This procedure can be performed alone in the office or in conjunction with endolymphatic sac surgery. Theoretically the drug penetrates the round window membrane, and then through an unknown mechanism, leads to improvement in the function of the labyrinth. This improvement is reflected by a period of remission with improved hearing and relief from vertigo, which often lasts for months. Like endolymphatic sac surgery, this transient improvement may be a placebo effect, or quite possibly a result of the induction of a mild labyrinthitis.

Deafferentation procedures are those that remove the vestibular nerve function without necessarily destroying the end-organ or decreasing the cochlear function. These include retrosigmoid vestibular nerve section and gentamicin perfusion of the round window. While either procedure might be appropriate for Stage 1 or 2 disease with hearing fluctuation, they are more often applied in Stage 3 disease. Each has advantages and disadvantages. Gentamicin perfusion can be performed in the office under local anesthesia and it effectively decreases vestibular function in the treated ear in approximately 80 to 85% of patients. In these cases, patients either have no vertigo episodes or very mild ones. This treatment is associated with hearing loss and persistent unsteadiness in 10 to 15% of patients. Recently, some clinicians have recommended gentamicin perfusion as the surgical treatment of choice in Meniere's disease, using retrosigmoid vestibular nerve section only in cases of gentamicin failure.

Retrosigmoid vestibular nerve section also has a role in the surgical management of Meniere's disease. Its advantages include a more complete deafferentation of the vestibular nerve and therefore much less postoperative unsteadiness and only rare episodic vertigo. Also cochlear function can be more certainly preserved with this approach. The disadvantages of this procedure are its higher cost, the patient's loss of gainful employment during recovery, and because it is an intracranial procedure, the risk of severe neurological complication. Even so, retrosigmoid vestibular nerve section is appropriate in gentamicin failures, in patients that want a single definitive surgical procedure for control of the vertigo, and in patients that want to preserve their hearing if at all possible.

Destructive procedures, specifically transmastoid labyrinthectomy are used to destroy the entire vestibular end organ to cure the vertigo. This procedure is appropriate in Stage 4 disease, and in cases where other surgical treatments have failed. Episodic vertigo can be controlled in more than 90% of patients undergoing this procedure, although this may reflect the careful selection used prior to this procedure. The major disadvantage of this procedure is total hearing loss, although several clinicians have reported hearing preservation in some cases in which the laser was used to seal the canals prior to the bony exenteration. At this writing, this has not been sufficiently reproducible to recommend as a treatment alternative.

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References

1. Arriaga MA, Goldman S. Hearing results of intratympanic steroid treatment of endolymphatic hydrops. Laryngoscope 1998 Nov; 108 (11 Pt 1): 1682-5.
2. Gibson WP. Pathophysiological theories in the etiology of Meniere's disease. Otolaryngol Clin North Am, 1997 Dec.
3. Harner SG, Kasperbauer JL, et al. Transtympanic Gentamicin for Meniere's Syndrome. Laryngoscope 1998 Oct; 108: 1446-9.
4. Kerr AG, Toner JG. A new approach to surgery for Meniere's disease: talking about surgery. Clin Otolaryngol 1998 Jun; 23(3):263-4.
5. Kumagami H, Loewenheim H, Beitz E, et al. The effect of anti-diuretic hormone on the endolymphatic sac of the inner ear. Pflugers Arch 1998 Nov; 436(6):970-5.
6. Pensak ML, Friedman RA. The role of endolymphatic mastoid shunt surgery in the managed care era. Am J Otol 1998 May; 19(3):337-40.
7. Schwaber MK. "Vestibular Disorders". Clinical Otology 2nd Edition. Hughes GB and Pensak ML, ed. Thieme Medical Books, 345-65, 1997.
8. Takeda T. Computed radiographic measurement of the dimensions of the vestibular aqueduct in Meniere's disease. Acta Otolaryngol Suppl (Stockh), 1997.
9. Thomsen J, Bonding P, Becker B, Stage J, Tos M. The non-specific effect of endolymphatic sac surgery in treatment of Meniere's disease: a prospective, randomized controlled study comparing "classic" endolymphatic sac surgery with the insertion of a ventilating tube in the tympanic membrane. Acta Otolaryngol (Stockh) 1998 Nov; 118(6):769-73.

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