11 Revision Vestibular Surgery

Edwin M. Monsell

When the frequency and severity of episodic vertigo due to Meniere disease become disabling despite nonoperative measures, surgical treatments come into consideration (Table 11.1). Two things must be true before a person is a surgical candidate. First, the problem must be correctable by surgery. Second, the benefits must outweigh the risks. When patients are properly selected and counseled, and when the operation is properly performed, the surgeon has provided the best possible level of care. The results of some procedures, such as labyrinthectomy and selective vestibular nerve section, are predictable. The results of other procedures, such as endolymphatic sac operations and aminoglycoside treatments, are less predictable, though these procedures have other advantages.

Any procedure may fail to control vestibular symptoms. Determining what to do next may be the greatest of all clinical challenges to the otologist. This situation requires a thorough knowledge of vestibular physiology, pathophysiology, clinical assessment, psychological assessment, pharmacotherapy, counseling, and surgical technique. This chapter is an overview of some of the critical issues in revision vestibular surgery.

Meniere Disease

Definition and Clinical Features of Meniere Disease

Meniere disease is one of the most common vestibular disorders, and the one that most commonly results in the need for surgery. Meniere disease is defined as endolymphatic hydrops with the clinical manifestations of Meniere syndrome.¹ Meniere syndrome consists of recurrent, spontaneous vertigo, hearing loss, and tinnitus and/or aural fullness as defined by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS).¹ Definitive spells of vertigo in Meniere disease are rotational and last 20 minutes or longer. They are by definition accompanied by imbalance. Nausea and vomiting are common. Hearing loss is present in the ear with active disease.¹ Early in the course of the disease, hearing levels often fluctuate, especially in the low frequencies. The hearing loss tends to progress to threshold levels of 40 to 70 dB hearing level (HL); speech discrimination scores commonly fall to levels of 70 to 50%. Hearing usually does not worsen beyond these levels in Meniere disease.² Tinnitus in Meniere disease is typically described as a buzzing or roaring sound. The patient usually experiences a sense of fullness or pressure in the affected ear.

Table 11.1 Indications for Surgery or Intratympanic Gentamicin in Meniere Disease

In addition to these defining features of Meniere disease, patients may experience less typical symptoms, such as milder or shorter spells of vertigo. A more or less constant sense of dysequilibrium may occur after several years with the disease. In most of these cases, there is evidence of some permanent loss of vestibular function in the form of a reduced caloric response on the affected side, or testing of the vestibulo-ocular reflex may show abnormality in phase, gain, or asymmetry. Otolithic crises of Tumarkin (“drop” attacks) occur rarely. In these episodes, there is an apparent sudden collapse of vestibulospinal tone without loss of consciousness.3

The full clinical syndrome of classic Meniere disease is nearly always unilateral. It is not unusual for a patient to experience an occasional sense of fullness or tinnitus in the opposite ear without developing the full clinical syndrome. (See discussion of autoimmune inner ear disease, below.)

Disability in Meniere Disease

Spontaneous vertigo can become disabling when it occurs with such frequency and severity that the patient cannot work, drive, take care of a family, or make plans for travel. In general, disability occurs when definitive spells occur about once a month or more, especially if accompanied by nausea and vomiting. Such a person is locked into a state of constantly suffering through an episode, recovery from an episode, or anticipation of the next episode.

Disability can also result from sensations of imbalance and motion intolerance if they are constant and severe enough. Presumably, these symptoms arise from the damaged vestibular system and its interactions with vision, perception of space and movement, proprioception, and the autonomic nervous system. Malfunction of the vestibular system is associated with feelings of malaise, nausea, vomiting, headaches, and anxiety. In most cases, it is more appropriate to treat constant dysequilibrium by patient education, anxiolytic medication, and vestibular exercises than by surgery.

Treatment of Meniere Disease

Currently, there is no treatment that is acknowledged to reverse the natural history of the underlying endolymphatic hydrops or to improve hearing. Consequently, the goal of treatment in Meniere disease is relief of symptoms and preservation of useful hearing, when present. The elements of initial management include counseling, reassurance, diet, vestibular exercises for dysequilibrium (if present), diuretics, and vestibular suppressant medication for temporary symptomatic relief from attacks of vertigo. This management is sufficient for nearly all patients and is renewed if attacks of vertigo occur after surgical treatment.

Surgery for Meniere Disease

Surgery can reasonably be proposed to control the definitive spells of vertigo in Meniere disease when several conditions have been met (Tables 11.1, 11.2). First, to be a surgical candidate, a patient reaches a state of disability due to the frequency and severity of definitive spells (AAO-HNS functional level 4–6). It is not necessary or appropriate to offer surgery simply because a patient has the diagnosis of Meniere disease, because nonsurgical management is usually sufficient. Moreover, vestibular destructive procedures result in very troublesome dysequilibrium in 15% or more of patients.⁴ It is best not to offer surgery unless the patient is ready to accept the risk of substituting one disturbing symptom for another.

Second, it must be possible to identify the ear that is the source of the definitive attacks. The active ear is the ear with the hearing loss and/or caloric weakness. Occasionally, it may be difficult to be certain which one is the active ear.

Reading the Clinical Literature

The literature on Meniere disease is plagued by methodological problems. One of the most significant is the difficulty of identifying stable, verifiable clinical end points to measure. Meniere disease is primarily a subjective disorder. Although vertigo may precipitate a dangerous fall or traffic accident, Meniere disease is not in itself life threatening. Audiometry, vestibular laboratory tests, and imaging are useful in the assessment of patients, yet there is no standardized test with acceptable precision and accuracy that will confirm the diagnosis or indicate the status of the endolymphatic hydrops.

Table 11.2 Surgical Treatments for Meniere Disease, Including Intratympanic Gentamicin*

The symptoms of Meniere disease are particularly difficult to measure in a research setting, because patients vary enormously in the frequency, severity, and qualitative type of symptoms they experience. Emotional factors are highly prevalent, and the natural history of vestibular disorders is variable. Although the AAO-HNS has issued clinical research reporting guidelines,1 these guidelines are not always followed or interpreted uniformly.⁵ There is still a strong tendency for patients, and therefore some physicians, to consider any vestibular symptoms to be “vertigo.” Finally, there are many sources of investigator bias, principally case selection.

Of the many procedures that have been proposed for Meniere disease (Table 11.2), four continue to be widely used. These are the various endolymphatic sac procedures (decompression, shunts), selective vestibular nerve section, surgical labyrinthectomy, and intratympanic application of a vestibulotoxic antibiotic, usually gentamicin.

Torok reported that 60 to 80% of patients improve regardless of the treatment used, confounding an analysis of surgical outcomes.⁶ The phenomenon of regression to the mean, whereby patients present for care when they are at their worst and tend to recover spontaneously regardless of the treatment, must also be recognized. Another critical issue in surgery for Meniere disease has been the issue of the placebo, or nonspecific, effect, which has been studied mostly in relation to endolymphatic sac surgery.⁷

Surgery of the Endolymphatic Sac

Georges Portmann of Bordeaux, France, introduced endolymphatic sac (ELS) surgery in the 1920s. Portmann hypothesized that the sac has an important homeostatic function in the metabolism of the inner ear. ELS procedures consist of performing a mastoidectomy and exposing the endolymphatic sac. The sac exposure may be expanded by removing more of the bone over the posterior cranial fossa dura beyond the margins of the sac. Some authors have advocated probing the endolymphatic duct, performing the operation under electro-cochleographic control, and placement of various drains, shunts, or other devices. Often the surgery can be performed as an outpatient procedure, and local anesthesia is possible.

The results of ELS surgery vary from 50 to 90% complete control of definitive vertigo attacks (Table 11.3).^8,9 The variability seems to depend primarily on the criteria used to select patients for surgery, rather than on the technical skill of the surgeon or variables associated with the procedure itself. Realistically, 50 to 65% of patients will experience complete control of vertigo for a period of 1 to 2 years.⁸ These results will suffice for many patients.

Table 11.3 Results of Surgical Treatment and Intratympanic Gentamicin for Meniere Disease

ELS procedures have the highest rate of failure to control vertigo of the four major procedural treatments (Table 11.1). However, they also have the lowest rate of complications, including the lowest rate of hearing loss. Especially when simple decompression is performed, ELS surgery is a nondestructive, extracranial procedure and poses little risk to hearing or balance. It can be performed as an outpatient procedure under local or general anesthesia.

If vertigo recurs following ELS surgery, medical management is resumed. If the patient becomes disabled again, he or she should have a comprehensive reevaluation. If the sac procedure was initially successful, it is reasonable to repeat it; however, the patient and surgeon may prefer to proceed to more definitive treatment, such as one of the other four procedures (Table 11.1).

Surgical Labyrinthectomy

Surgical labyrinthectomy is a procedure that removes the vestibular sensory tissue of the inner ear and is intended to eliminate the sensory conflict between the dysfunction of the inner ear and the otherwise concordant input of the normal inner ear, vision, proprioception, and touch. The sensory epithelia can be avulsed through a transcanal approach¹⁰ or removed under direct vision through a transmastoid approach.¹¹ The expectation is that all vestibular function ceases in the operated ear, and all residual hearing is usually also lost.

Immediately following labyrinthectomy, patients experience a syndrome of acute unilateral vestibular loss, which consists of continuous vertigo, imbalance, and motion intolerance, all of which gradually cease as central nervous system (CNS) compensation occurs over 1 to 3 months. By 1 year nearly all patients after labyrinthectomy have compensated to the point where they have resumed all previous activities without significant impairment or disability. They typically will experience a mild sense of imbalance on sudden head movements, especially when tired or under stress.

Labyrinthectomy and translabyrinthine vestibular neurectomy are the gold standard for control of vertigo in Meniere disease. Complete control of definitive spells occurs in 95% of patients with classic Meniere disease (Table 11.3).^10,11 However, the diagnosis of vestibular disorders is often difficult. An uncommon cause of incomplete control of definitive spells is diagnostic error. The 5% rate of incomplete control of spells also reflects the problems of semantics and questionnaires in research design of some clinical studies.

Very troublesome and persistent dysequilibrium occurs in 15 to 50% of patients, presumably due to incomplete CNS compensation. Older patients may have more difficulty compensating. Often, postoperative testing confirms postural instability and/or abnormalities of the vestibuloocular reflex, though there are no reliable objective test indicators or tests for functional compensation. Infrequently, a patient may compensate satisfactorily initially but develop troublesome dysequilibrium later in life.

In some cases, patients are found to exhibit normal posture and gait examinations, suggesting that much postoperative dysequilibrium is subjective. Patients who receive prolonged disability compensation are less likely to get well. Persistent dysequilibrium is usually best treated by vestibular rehabilitation.

The incidence of incomplete labyrinthectomy when experienced surgeons use the transcanal approach has been shown to be as low as 5%.¹⁰ When appropriate, a transcanal labyrinthectomy could be revised with transmastoid labyrinthectomy or translabyrinthine vestibular neurectomy.

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