Other Surgery

Every year another operation or two is advocated for Meniere's disease. Many procedures for Meniere's disease have come and gone. The Cody tack operation, the Fick procedure, cryosurgery, and ultrasound proved less reliable than other methods.

7. Derebery MJ. Allergic and immunologic aspects of Meniere's disease. Otolaryngol Head Neck Surg 1996;114:360-365

8. Soliman AM. A subpopulation of Meniere's patients produce antibodies that bind to endolymphatic sac antigens. Am J Otol 1996;17:76-80

9. Blakley BW. Clinical forum: a review of intratympanic therapy. Am J Otol 1997;18:520-526

10. Grant IL, Welling DB. The treatment of hearing loss in Meniere's disease. Otolaryngol Clin North Am 1997;30: 1123-1144

11. Quaranta A, Onofri M, Sallustio V, Iurato S. Comparison of long-term hearing results after vestibular neurectomy, endolymphatic mastoid shunt, and medical therapy. Am J Otol 1997;18:444-448

12. Blakley BW, Barber HO, Tomlinson RD, et al. On the search for markers of poor vestibular compensation. Otolaryngol Head Neck Surg 1989;101:572-577

REFERENCES

Blakley—CHAPTER 46

Perhaps the most controversial subject in neurotology concerns the diagnosis and management of patients with Meniere's disease. There is uncertainty regarding not only the etiology and pathophysiology, but also the role of medical management, particularly because the precise cause is unknown, 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. Much of the 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 postmortem histopathologic 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 or the cochleovestibular nerve, or both. Beyond this basic description, the precise etiology of the problem remains to be clearly elucidated.

As a consequence, to manage Meniere's syndrome patients successfully, 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, management of these patients should be done with the mindset of a long-term chronic disorder, much like adult-onset diabetes mellitus, chronic pain, or hypertension. Although 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 simply have entered a remission phase.

Having stated that the exact etiology is unknown, what do we know of Meniere's disease? Meniere's disease is a clinical disorder associated with the histopathological finding of endolymphatic hydrops. Most of the hydropic distention found in postmortem specimens is seen in the cochlea and the saccule, although occasionally the utricle and the ampullae are involved. Other histopathologic features include ruptures or fistulae, collapse of membranes, and vestibular fibrosis. Minimal histopatho-logic changes are seen in the sensory epithelia, although the loss of ganglion and neuronal cells, inner and outer hair cells, and strial vascularity has been reported. Recognized causes of Meniere's syndrome include idiopathic, post-traumatic, postinfectious (i.e., delayed onset after a viral illness), late-stage syphilitic, and Cogan's syndrome or one of its variants.

One theory of Meniere's disease is that increased endolym-phatic pressure causes the symptoms as well as the histopatho-logic 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. This theory also suggests that 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. 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 endolym-phatic 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 in support of 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 this era of managed care with declining health care revenues, most clinicians are uncertain as to which studies are needed for proper evaluation of 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, and Romberg and gait tests. The otologic examination, although usually unremarkable, occasionally indicates 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 audiovestibular 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 raise the clinician's suspicion of bilateral dysfunction, but medical judgments 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 a magnetic resonance imaging (MRI) scan is much more definitive and should be obtained before any surgical procedure. Other studies indicated in the evaluation of Meniere's syndrome patients include syphilis screening tests, rheumatoid factor, sedimentation rate, antinuclear 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 autoimmune 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 47-1. A single episode of severe vertigo with hearing loss is classified as probable Meniere's dis-

TABLE 47-1

Diagnosis of Meniere's Disease

Certain Meniere's disease

Definite Meniere's disease, plus histopathologic confirmation

Definite Meniere's disease

Two or more definitive spontaneous episodes of vertigo < 20 min Audiometrically documented hearing loss on at least one occasion Tinnitus or aural fullness in the treated ear Other causes excluded

Probable Meniere's disease

One definitive episode of vertigo

Audiometrically documented hearing loss on at least one occasion Tinnitus or aural fullness in the treated ear Other causes excluded

Possible Meniere's disease

Episodic vertigo of the Meniere's type without documented hearing loss, or

Sensorineural hearing loss, fluctuating or fixed, with disequilibrium but without definitive episodes Other causes excluded ease, whereas multiple episodes of vertigo associated with hearing loss represent definite Meniere's disease.

Staging the disease currently depends on the severity of the hearing loss, as noted in Table 47-2. 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 representative of early, reversible disease (i.e., susceptible to remission). Stage 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; 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 use 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 antidiuretic hormone (ADH, or vasopressin [AVP]). One can only speculate whether 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

TABLE 47-2

Staging of Definite and Certain Meniere's Disease*

TABLE 47-2

Stage

Four-Tone Average (dB)

1

< 25

2

26-40

3

41-70

4

> 70

* Staging is based on the four-tone average (arithmetic mean rounded to the nearest whole number) of the pure-tone thresholds at 0.5, 1, 2, and 3 kHz of the worst audiogram during the interval 6 months before treatment. This is the same audiogram that is used as the baseline evaluation to determine hearing outcome from treatment. Staging should be applied only to cases of definite or certain Meniere's disease.

* Staging is based on the four-tone average (arithmetic mean rounded to the nearest whole number) of the pure-tone thresholds at 0.5, 1, 2, and 3 kHz of the worst audiogram during the interval 6 months before treatment. This is the same audiogram that is used as the baseline evaluation to determine hearing outcome from treatment. Staging should be applied only to cases of definite or certain Meniere's disease.

raise AVP levels. Simply stated, to keep AVP levels low, the most effective route would be a mild diuretic, a modest 2000-to 2500-mg salt diet, and plenty of water.

Vasodilator therapy is based on the belief that Meniere's disease is related to decreased blood flow in the inner ear. 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. Although 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 desensi-tization. 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 1 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. 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 recur. 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 2 to 3 years.

Few procedures in otologic surgery have been as controversial as endolymphatic sac surgery. Opinions vary from those who conclude the procedure is effective in more than 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; 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 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 ret-rosigmoid vestibular nerve section and gentamycin perfusion of the round window. Although 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 retrosig-moid 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, leading to 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 neurologic complication. Even so, ret-rosigmoid vestibular nerve section is appropriate in gentamicin failures, in patients who want a single definitive surgical procedure for control of the vertigo, and in patients who want to preserve their hearing if at all possible.

Destructive procedures, specifically transmastoid laby-rinthectomy, are used to destroy the entire vestibular end-organ to cure the vertigo. This procedure is appropriate in stage 4 disease and in cases for which 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 before 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. This has not been sufficiently reproducible to recommend as a treatment alternative.

SUGGESTED READINGS

Schwaber—CHAPTER 47

Arriaga MA, Goldman S. Hearing results of intratympanic steroid treatment of endolymphatic hydrops. Laryngoscope 1998;108(11 pt 1):1682-1685

Gibson WP, Arenberg IK. Pathophysiological theories in the etiology of Meniere's disease. Otolaryngol Clin North Am 1997;30(6): 961-967

Harner SG, Kasperbauer JL, et al. Transtympanic gentamicin for Meniere's syndrome. Laryngoscope 1998;108:1446-1449

Kerr AG, Toner JG. A new approach to surgery for Meniere's disease: talking about surgery. Clin Otolaryngol 1998;23:263-264 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;436:970-975

Pensak ML, Friedman RA. The role of endolymphatic mastoid shunt surgery in the managed care era. Am J Otol 1998; 19:337-340

Schwaber MK. Vestibular disorders. In: Hughes GB, Pensak ML, eds. Clinical Otology. 2nd Ed. New York: Thieme Medical Books, 1997;345-365

Takeda T. Computed radiographic measurement of the dimensions of the vestibular aqueduct in Meniere's disease. Acta Otolaryngol (Stockh) 1997(suppl);528:80-84

Thomsen J, Bonding P, Becker B, et al. 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;118: 769-773

No treatment has proved effective in reversing the pathophysiologic process of Meniere's disease. Further, no known treatment of Meniere's disease will consistently reverse the hearing loss or eliminate the aural fullness and tinnitus that often accompany this disorder. Most treatments are directed toward eliminating the often incapacitating symptom of vertigo with its associated vegetative symptoms (Fig. 48-1). It is axiomatic that before treating the symptoms of Meniere's disease, one must make the diagnosis. Most clinicians recognize the classic quadrad of fluctuating hearing, tinnitus, aural fullness, and incapacitating vertigo. The symptoms of Meniere's disease, however, are frequently evolutionary, and any one of the four symptoms may precede the others by months to years.1 A high index of suspicion and the judicious use of diagnostic aids such as electrocochleography and, when hearing loss is present, dehydration audiometry can facilitate early diagnosis when doubt exists.2 Treatment may then be instituted avoiding unnecessary delay and morbidity.

To complicate matters, some patients with the symptoms of Meniere's disease (Meniere's syndrome) will actually have a local, regional, or systemic cause for their symptoms.3 Failure to identify these causes may lead to inappropriate treatment and additional morbidity. Therefore, patients suffering the symptoms of Meniere's syndrome should be evaluated for inhalant and food allergies, immune disease, syphilis, cerebellopontine angle lesions, and demyelinating disease. If any of these disorders are identified, their treatment takes priority. If no underlying cause can be identified, or if auditory and vestibular symptoms persist despite specific successful treatment of an identified abnormality, the cause of the patient's symptoms is presumed to be idiopathic (Meniere's disease).

Histologic study of ears harvested from patients with Meniere's disease has demonstrated distention of Reissner's membrane into the vestibular scala, suggesting either overproduction of endolymph within the scala media of the cochlea or decreased absorption (endolymphatic hydrops).4 Most treatments have therefore been directed toward reducing endolymph volume pressure or bypassing the proposed pathophysiology of the disorder and directing treatment toward eliminating the symptoms of vertigo.

Treatment for the vertigo that often accompanies acute spells of Meniere's disease is designed to eliminate, or significantly reduce, this symptom and its associated nausea and vomiting. This objective is best accomplished using intravenous diazepam or droperidol if the patient can be carefully monitored. Promethazine hydrochloride (an antihistamine) in suppository form may be helpful in less controlled situations. Reassurance that the patient is not suffering a cerebrovascular accident or other life-threatening disease is essential if it is the initial attack and fluid repletion may be needed.5

Treatments used for the chronic condition of Meniere's disease with recurrent incapacitating vertigo basically fall into the two categories of invasive and noninvasive therapy. Nonin-vasive treatments directed toward reversing the pathophysio-logic process include low-salt diet (<2 g of sodium per day) and diuretics. Sodium causes fluid retention and has been implicated in the exacerbation of symptoms, presumably by increasing endolymphatic hydrops. It is hoped that low-salt diet and diuretics will have the opposite effect.6 It is proposed that some diuretics have a direct effect on ion transport in the stria vascu-laris and spiral ligament. Acetazolamide (a carbonic anhydrase inhibitor) and hydrochlorothiazide are commonly used. Acetazolamide appears somewhat more effective but also has a greater rebound effect when discontinued. Furosemide, a loop diuretic, may also be used but is more likely to require potassium supplementation.

Vasoconstriction has never been convincingly shown to contribute to the pathophysiology of Meniere's disease; therefore, vasodilators (e.g., niacin, histamine, papaverine hydrochloride, histamine analogues) probably do not play a role in its treatment. Other noninvasive treatments used theoretically to reverse the pathologic process, such as lipoflavonoid (proposed to improve microvascular integrity of the stria vascularis), also appear to play little role in altering the pathophysiology of this disease.7'8

Noninvasive treatments directed toward eliminating vertigo without addressing the inner ear disease process are legion. They include those treatments designed to produce temporary symptomatic relief and those designed to permanently ablate the vestibular neuroepithelium (e.g., streptomycin). Anticholin-ergic drugs are known to suppress activity within the vestibular system and, on occasion, reduce the vertigo associated with attacks of Meniere's disease. They also reduce peristalsis and gastric secretion, which helps reduce nausea and vomiting, and they inhibit sweat gland activity or diaphoresis. Scopo-lamine and probanthine are the two most commonly used drugs in this class. Occasionally, however, the side effects of these drugs, especially scopolamine, are worse than the symptoms of Meniere's disease, and the drugs may need to be discontinued.

Antihistamines, especially those with strong anticholiner-gic effects, also seem to reduce the severity of the vertigo spells by suppressing the activity within the central nervous system. The precise mechanisms, however, are not totally clear. Meclizine, a piperazine derivative, is the most commonly employed antihistamine, and the side effect of drowsiness is

Specific cause identified i

Symptoms of Meniere's syndrome +

Imaging, Hematology, allergy, serology, auditory and vestibular testing, etc.

Treat specific cause appropriately

End of treatment

Bilateral disease

Vertigo persists i

Consecutive endolymphatic sac decompression as needed and/or intramuscular streptomycin (tailored to patient's lifestyle, health, age, disease severity)

Vertigo terminated End of treatment

No specific cause identified (Meniere's disease)

Low salt-high water diet, diuretic, antihistamine, anticholinergics, and sympathomimetic amines (in various combinations tailored to patient's lifestyle, health, age, disease severity)

Vertigo terminated End of treatment

Unilateral disease

Serviceable hearing 1

Endolymphatic sac drainage procedure

Vertigo terminated

End of treatment

Vertigo persists

Middle cranial fossa, retrolabyrinthine, vestibular nerve section, or middle ear gentamicin (tailored to patient's lifestyle, health, age, and disease severity)

Nonserviceable hearing

Translabyrinthine vestibular nerve section, labyrinthectomy, or middle ear gentamicin (tailored to patient's lifestyle, health, age, and disease severity)

Vertigo terminated

Vestibular rehabilitation

End of treatment

Vertigo terminated i

Vestibular rehabilitation

End of Treatment

Figure 48-1 Treatment for the vertigo of Meniere's disease.

uncommon. Amitriptyline, a dibenzazepine derivative, has not only been used to treat depression but may also reduce vertigo through its anticholinergic action.

Sympathomimetic amines have long been used for suppression of vestibular symptoms. Amphetamines are notorious for substance abuse and are now under strict control by the Drug Enforcement Agency. The effects of ephedrine are similar to amphetamines but less pronounced. Ephedrine depolarizes and then blocks cells in the autonomic ganglia and appears to have the capacity of suppressing activity within the vestibular nuclei. It should be used judiciously in patients with hypertension.

Psychotropic drugs, such as the benzodiazepines, have been used to treat the vertigo of Meniere's disease. Benzodiazepines (diazepam, lorazepam, and clonazepam) either directly or indirectly enhance hyperpolarization and inhibition of neuronal firing. They are extremely effective in "crisis intervention" but their tendency to cause psychological and physical dependency argues against prolonged use.

Parenteral streptomycin has been used to ablate peripheral vestibular function in patients suffering vertigo secondary to bilateral Meniere's disease since the late 1940s.9 Streptomycin treatment is particularly useful when the offending ear is unclear and can often be titrated to eliminate vertigo while avoiding oscillopsia and further hearing loss.10 This treatment modality is an essential component of the therapeutic armamentarium for physicians treating patients with the vertigo of Meniere's disease.

Invasive therapy is reserved for patients who are not good candidates for or who fail noninvasive therapy. Invasive therapy can be chemical or mechanical. The most contemporary treatment is chemical and involves infusion of gentamicin into the inner ear either by intratympanic injection or the use of a microcatheter. Gentamicin is an aminoglycoside antibiotic that appears to be preferentially toxic to the vestibular hair cells; it may also be toxic to the dark cells of the inner ear. Treatment in therapeutic doses presumably ablates the peripheral vestibular end organ and may decrease endolymphatic hydrops by its action on the dark cells. It is primarily used for patients with unilateral Meniere's disease and carries the risk of sensorineural hearing loss. Although most investigators report a 70 to 90% success rate for control of vertigo with a 20 to 40% likelihood of additional hearing loss, the number of doses, concentration of drug, and total dose vary significantly between reports leaving the physician in a bit of a quandary regarding the best methodology.11 Streptomycin has been used in a similar manner but has fallen out of favor because of a perceived narrower therapeutic window and the difficulty in obtaining it.12

Steroids have also been placed in the middle ear of patients suffering Meniere's disease, presumably to reduce immune-mediated inflammation. Although evidence exists to support the association between immune-mediated inflammation and the symptoms of Meniere's disease, inflammation is conspicuously absent in histologic studies of temporal bones harvested from patients suffering from Meniere's disease. Data regarding intratympanic steroids for the treatment of Meniere's disease are inadequate, and personal experience is extremely inconclusive.13

Various agents have also been directly perfused through the inner ear by surgically fenestrating the horizontal semicircular canal. The results of this form of treatment have been extremely capricious and it has never gained widespread popularity. Although profusion of the horizontal semicircular canal with streptomycin appears to have some efficacy in ablating the peripheral vestibular end organ in treating the vertigo of Meniere's disease, the high incidence of associated hearing loss is unacceptable.

Of the invasive procedures used to eliminate the vertigo of Meniere's disease that are purely mechanical, there are those designed to ablate the end organ response and those designed to decompress the endolymphatic system. The ablative procedures are usually limited to patients with unilateral disease because of the risk of postoperative hearing loss and oscillopsia, and they include vestibular nerve section through either the middle cranial fossa, posterior cranial fossa, or retrolabyrinthine approach. These procedures eliminate vertigo in 85 to 90% of patients and complications such as sensorineural hearing loss, cerebrospinal fluid leak, facial nerve injury, and meningitis are uncommon, although sensorineural hearing loss can approach 15%. Translabyrinthine vestibular nerve section is extremely successful in ablating the peripheral vestibular response in the treatment of vertigo secondary to Meniere's disease when there is no useful hearing in the involved ear. Labyrinthectomy is similarly useful in elderly patients, as long-term ataxia seems less problematic than with translabyrinthine vestibular nerve section.14 All ablative therapy, whether invasive or noninvasive, is followed by vestibular rehabilitation in an effort to speed the patient's vestibular compensation.

Many procedures have been designed for mechanical decompression of the endolymphatic space, including the Fick procedure, the Cody tack, cryosurgery, ultrasound, and otic-periotic shunt. The one procedure that seems to have best survived the test of time despite controversy, however, is the endolymphatic sac drainage/decompression procedure.15 Since its description in 1927 by Portman16 the efficacy of endolymphatic sac surgery in the treatment of Meniere's disease has been questioned. The low complication rate and nondestructive nature of endolymphatic sac surgery, as well as the ability to perform the procedure on an outpatient basis, make it an attractive option for patients with serviceable hearing and incapacitating vertigo. However, the natural history of Meniere's disease, specifically the spontaneous remission rate and the high placebo effect seen in Meniere's patients, has provoked many to question the effectiveness of endolymphatic sac procedures.

Reported long-term vertigo control rates with endolymphatic sac surgery vary from 100% to 46% based on the 1985 American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) criteria.17'18 In general, most studies report vertigo control rates approaching 80%.19-22 These studies reported cure rates from endolymphatic sac surgery have been questioned, as spontaneous remission rates of vertigo in Meniere's disease have been reported to range from 30% to 71%.23,24 Silverstein et al.24 compared 50 patients who were candidates for surgery, but refused, with patients who underwent either endolymphatic sac surgery, vestibular nerve section, or labyrinthectomy. These investigators found that, at 2 years follow-up, 57% of patients who had not undergone surgery reported complete relief of vertigo, as compared with 40% of patients who had undergone sac surgery. Results at 7 years of follow-up showed about 70% relief in each group. By contrast, Filipo and Barbara23 found that only 30% of their nonsurgical Meniere's disease patients reported disappearance of vertigo at 2 years of follow-up.

In addition to the spontaneous remission rate of Meniere's disease, placebo effects must be considered in this patient population. The Danish study on sham surgery performed a prospective randomized double-blind evaluation of the effects of a simple cortical mastoidectomy versus endolymphatic sac surgery with shunt placement in 30 patients with Meniere's disease refractory to medical management. These investigators found no difference between the groups postoperatively in levels of nausea or vomiting, dizziness, aural fullness, tinnitus, and hearing. In this study, 73% of the group receiving endolymphatic sac surgery reported benefit from the operation versus 67% of the sham group.25 These patients have been followed now for more than 9 years without any change in their initial reported results.26

The results of the Danish sham study have been criticized by several groups, including independent statisticians.27'28 Pillsbury et al.27 analyzed the data reported in the Danish sham study and obtained different results. They noted significant differences between the sham groups and the endolymphatic sac surgery group with improved vertigo control rates, tinnitus levels, and low frequency hearing results for the group receiving sac surgery.

For obvious ethical reasons, repetition of the Danish study is not possible, but the effect of cortical mastoidectomy alone in controlling the vertigo of Meniere's disease has been evaluated. Kerr et al.29 studied the outcome of 14 patients with incapacitating vertigo who underwent cortical mastoidectomy before planned vestibular nerve section and found that 57% had achieved complete control of vertigo with mastoidectomy alone. The observed benefits of mastoidectomy alone observed in Thomsen and Kerr's studies may relate to effects produced by surgery alone, such as disturbances in blood flow, shock to the inner ear, and/or inflammation. Thus, cortical mastoidectomy probably should not be referred to as sham or placebo surgery.

Despite the obvious conflicting beliefs concerning the benefits of endolymphatic sac surgery in Meniere's disease, most otologists routinely perform the procedure. The nondestructive nature of the surgery, low complication rate, minimal morbidity, and ability to perform the procedure as an outpatient are obvious advantages over labyrinthectomy or vestibular nerve section. For these reasons, and with a success rate approaching 80%, endolymphatic sac surgery remains a valuable option for treating the vertigo of Meniere's disease.

REFERENCES

Meyerhoff and Jordan—CHAPTER 48

1. Paparella MM. Methods of diagnosis and treatment of Meniere's disease. Acta Otolarygol (Stockh) 1991;485(suppl): 108-119

2. Morrison AW, Moffat DA, O'Connor AF. Clinical usefulness of electrocochleography in Meniere's disease: an analysis of dehydrating agents. Otolaryngol Clin North Am 1980;13: 703-722

3. Rubin W, Brookler KH. Dizziness: etiologic approach to management. New York: Thieme Medical Publishers; 1991

4. Hallpike CE, Cairns H. Observations on the pathology of Meniere's syndrome. Jlaryngol Otol 1938;53:625-655

5. Blair RL. Medical management of vestibular dysfunction. Otolaryngol Clin North Am 1984;17:679-684

6. Furstenberg AC, Lashmet FH, Lathrop F. Meniere's symptom complex: medical treatment. Ann Otol Rhinol laryngol 1934;43:1035-1046

7. Williams HL, Maher FT, Corbin KB, et al. Eriodictyol glycoside in the treatment of Meniere's disease. Ann Otol Rhinol Laryngol 1963;72:1082-1101

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