Meniere disease or endolymphatic hydrops is an idiopathic inner ear disorder characterized by attacks of vertigo, fluctuating hearing loss, tinnitus, and aural fullness. The incidence of Meniere disease ranges from 10 to 150 cases per 100,000 persons each year. There is no gender bias and patients typically present in the fifth decade of life. A new diagnosis of Meniere disease in someone younger than age 20 or older than age 70 is unusual. There is no right or left ear predilection for the disease.
The cause of Meniere disease remains elusive and has been attributed to anatomic, infectious, immunologic, and allergic factors. The focus of most studies has been the endolymphatic duct and sac based on the basic premise that there is increased endolymphatic fluid owing to impaired reabsorption of endolymphatic fluid in the endolymphatic duct and sac. Histopathological studies have shown blockage in the longitudinal flow of endolymph in the endolymphatic duct, the endolymphatic sinuses, the utricular ducts, the saccular ducts, and the ductus reuniens. Studies have reported that the endolymphatic sacs in patients with Meniere disease are smaller, have less absorptive tubular epithelium, and have increased perisaccular fibrosis. Results of a blinded control study, however, did not show any difference in the connective tissue or fibrosis surrounding the endolymphatic sac in patients with Meniere disease. The vestibular duct has also been shown to be smaller in patients with Meniere disease. Recent studies have shown a decrease in Type II vestibular hair cells in cases of Meniere disease. The role and significance of the decrease in these Type II hair cells are currently not known. The endolymphatic sac has been shown to be important in inner ear metabolic homeostasis. The endolymphatic sac secretes glycoprotein conjugates in response to osmotic challenges, and preliminary studies have shown an alteration in glycoprotein metabolism in Meniere disease. There has been no conclusive proof of an infectious agent related to this disease.
The roles of allergy and immunology in Meniere disease are under active investigation. The “seat” of immunity in the inner ear may be the endolymphatic sac, which is able to process antigens and mount a local antibody response. The endolymphatic sac may be vulnerable to immunologic injury because of the hyperosmolarity of its contents and the fenestrations in its vasculature. These two properties increase the risk of immune complex deposition and injury. IgG deposition is seen in the endolymphatic sacs of patients undergoing shunt procedures of the endolymphatic sac. Patients with Meniere disease also have elevated IgM complexes and C1q component of complement, and low levels of IgA complexes in their serum. These patients have also shown vulnerability to autoimmune (cytotoxic) reactions. Thirty percent of patients with Meniere disease had autoantibodies to an inner ear antigen by Western blot analysis. The response of some patients to steroid therapy and the increased rate of expression of certain HLA antigens (eg, A3, Cw7, B7, and DR2) in patients with Meniere disease support the presence of an underlying immune mechanism.
A similar argument may be made regarding Meniere disease and allergy. A significant percentage (50%) of affected patients have concomitant inhalant or food allergies (or both), and treating these allergies with immunotherapy and diet modification has improved the manifestations of their allergies and Meniere disease.
The role of genetic influences in the pathogenesis in Meniere disease is also being elucidated. Mutation in the COCH gene is associated with Meniere disease. The family of water channels (AQPs) and ion channels have also been implicated.
Meniere disease occurs as episodic attacks lasting for hours. The four symptoms and signs include (1) a unilateral, fluctuating sensorineural hearing loss (often involving low frequencies); (2) vertigo that lasts minutes to hours; (3) a constant or intermittent tinnitus typically increasing in intensity before or during the vertiginous attack; and (4) aural fullness. The acute attack is also associated with nausea and vomiting and, following the acute attack, patients feel exhausted for a few days. Table 56–3 shows the diagnostic scale for Meniere disease created by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology–Head and Neck Surgery. As emphasized in the diagnostic scale, the diagnosis of Meniere disease is based on the longitudinal course of the disease rather than on a single attack.
Table 56–3. Diagnostic Scale for Meniere Disease of the AAO-HNSa |Favorite Table|Download (.pdf)
Table 56–3. Diagnostic Scale for Meniere Disease of the AAO-HNSa
- Certain Meniere Disease
- Definitive Meniere's disease, plus histopathological confirmation
- Definitive Meniere Disease
- Two or more episodes of vertigo of at least 20 minutes
- Audiometrically documented hearing loss on at least one occasion
- Tinnitus and aural fullness
- Probable Meniere Disease
- One definite episode of vertigo
- Audiometrically documented hearing loss on at least one occasion
- Tinnitus and aural fullness
- Possible Meniere Disease
- Episodic vertigo without documented hearing loss
- Sensorineural hearing loss, fluctuating or fixed, with disequilibrium, but without definitive episodes
Meniere disease is a clinical diagnosis. The diagnostic evaluation primarily includes audiometry and a fluorescent treponemal antibody absorption (FTA-ABS) test to rule out syphilis. FTA-ABS testing is mandatory in any patient given the diagnosis of an idiopathic disease, because syphilis may perfectly imitate Meniere disease. Electrophysiologic studies, other serologic studies, and imaging are obtained as needed. The role of allergy testing continues to be defined. Initially, autoimmune ear disease may be clinically indistinguishable from Meniere disease.
The distinguishing characteristics of an autoimmune ear disease include a more aggressive course and early bilateral involvement. Autoimmune serologic tests may also be helpful. There is no diagnostic test for Meniere disease.
MRI with gadolinium contrast allows the exclusion of retrocochlear pathology, such as a vestibular neuroma, and should be considered in all patients with asymmetric hearing loss.
Audiologic assessment initially shows a low-frequency or a low- and high-frequency (inverted V) sensorineural hearing loss. As the disease progresses, there is a flat sensorineural hearing loss. A glycerol dehydration test involves measuring serial pure-tone thresholds and discrimination scores during diuresis. The diagnosis of Meniere disease is supported if there is improvement in the patient's hearing. The test is positive in only 50% of patients suspected to have the disease and is not routinely performed in the US.
Electrocochleography (ECOG) measures the sound-evoked electrical potentials from the inner ear. The three phenomena measured from the external canal (tympanic membrane) or on the promontory in response to clicks include (1) the cochlear microphonic, (2) the summating potential, and (3) the action potential. The endolymphatic hydrops of Meniere disease causes a larger summating potential and so the ratio of the summating potential to the action potential (SP/AP) is elevated. ECOG lacks the specificity or sensitivity to reliably use the SP/AP ratio to consistently diagnose Meniere disease or predict the clinical course.
ENG with caloric testing shows peripheral vestibular dysfunction. The caloric response decreases during the first decade of the disease and usually stabilizes at 50% of normal function.
Vestibular-Evoked Myogenic Potential (VEMP) Testing
VEMP is a vestibulo-collic reflex whose afferent limb arises from acoustically sensitive cells in the saccule, with signals conducted via the inferior vestibular nerve. VEMP is a biphasic, short-latency response recorded from the tonically contracted sternocleidomastoid muscle in response to loud auditory clicks or tones. VEMPs may be diminished or absent in patients with early and late Meniere disease, vestibular neuritis, BPPV, and vestibular schwannoma. On the other hand, the threshold for VEMPs may be lower in cases of superior canal dehiscence and perilymphatic fistula.
In addition to the vestibular system, dizziness may be caused by poor vision, decreased proprioception (diabetes mellitus), cardiovascular insufficiency, cerebellar or brainstem strokes, neurological conditions (eg, migraines, multiple sclerosis), metabolic disorders, and the side effects of medications (see Table 56–2).
Since the introduction of aminoglycoside therapy in 1948, no significant conceptual advances have been made in the treatment of Meniere disease. The current treatments focus on relieving vertigo without further injuring the patient's hearing. Hearing may be temporarily improved or stabilized by the current treatments, but the hearing does not have long-term stability.
Dietary Modifications and Vestibular Suppressants
The primary management of Meniere disease involves a sodium-restricted diet (≤2000 mg/d) and diuretics (eg, diazide). In a crossover placebo study of diazide, it was shown that diuretics seem to improve vestibular complaints but have no effect on hearing or tinnitus. Some patients benefit from dietary restrictions on caffeine, nicotine, alcohol, and foods containing theophylline (eg, chocolate). Acute attacks are managed with vestibular suppressants (eg, meclizine and diazepam [Valium]) and antiemetic medications (eg, prochlorperazine [Compazine] suppository). Most patients are controlled with conservative management.
Medically refractory patients with or without serviceable hearing may benefit from intratympanic gentamicin therapy. Intratympanic gentamicin is absorbed into the inner ear primarily via the round window and selectively damages the vestibular hair cells relative to the cochlear hair cells. Gentamicin may also decrease endolymph production by affecting dark cells in the stria vascularis. Intratympanic gentamicin has nearly a 90% vertigo control rate with a follow-up of at least 2 years; the extent of hearing loss depends on the protocol for gentamicin delivery. A variety of treatment protocols (daily, biweekly, weekly, or monthly injections) using fixed-dose or titration end-point regimens exist but a few trends are present. Treatments are stopped if there is persistent hearing loss. Vertigo control is nearly always obtained if vestibular function is ablated. However, the risk of hearing loss increases as the total dose and frequency of gentamicin injections are increased. Current protocols are reducing the dose and frequency of injections to decrease hearing loss and still obtain vertigo control. Vertigo control can be obtained with some residual vestibular function, and this residual function may be useful if patients develop bilateral Meniere disease. Recent studies with monthly injections have shown a nearly 90% vertigo control with a 17% (<10 dB) hearing loss.
Acute exacerbation of Meniere disease may respond to a short burst of oral steroids. Intratympanic steroids have also been used to treat active disease and avoid the systemic complications associated with oral steroids.
Occasionally, patients who fail medical and gentamicin treatment may require surgical intervention. Endolymphatic sac surgery and vestibular nerve sections preserve hearing while labyrinthectomy ablates hearing.
Endolymphatic Sac Surgery
The role of endolymphatic sac surgery in the management of Meniere disease remains controversial. One double-blinded, placebo-controlled comparison of the endolymphatic mastoid shunt versus a simple cortical mastoidectomy showed no benefit of the sac surgery. A 9-year follow-up showed a 70% control of vertigo in both surgical groups. Re-analysis of the study suggested a greater benefit in the group who had endolymphatic sac surgery, and a recent study with a 5-year follow-up showed an 88% functional level 1 or 2 response after an endolymphatic mastoid shunt operation. Endolymphatic sac surgery involves a mastoidectomy and locating the endolymphatic sac on the posterior fossa dura (Figure 56–3A). The sac is medial to the sigmoid sinus and inferior to the posterior semicircular canal. The endolymphatic sac is also located along an imaginary line (Donaldson line) in the plane of the horizontal semicircular canal. The endolymphatic sac may be decompressed or have a shunt placed that communicates into the subarachnoid space or mastoid cavity. Endolymphatic shunt surgery provides a nondestructive option for patients who fail medical or aminoglycoside therapy and have good hearing.
(A) Endolymphatic sac surgery. The sac surgery involves a mastoidectomy and identifying it within the posterior fossa dura. (B) Vestibular nerve section. Illustration shows a vestibular neurectomy via the posterior fossa craniotomy. LSCC, lateral semicircular canal; PSCC, posterior semicircular canal; SSCC, superior semicircular canal; ES, endolymphatic sac; PFD, posterior fossa dura; JB, jugular bulb; 7, facial nerve or cranial nerve 7; FI, flocculus; 8, audiovestibular nerve or cranial nerve 8; C, cochlear division of the audiovestibular nerve; V, vestibular division of the audiovestibular nerve; 5, trigeminal nerve or cranial nerve 5; Ch, choroid plexus.
A vestibular nerve section provides a definitive treatment of unilateral Meniere disease in patients with serviceable hearing. Ninety-five percent of patients achieve vertigo control, and hearing is preserved in more than 95% of patients. The vestibular neurectomy may be approached via a retrosigmoidal or middle fossa approach (Figure 56–3B). The risk to the facial nerve is <1% in the retrosigmoidal approach and <5% in the middle fossa approach. The patients are acutely vertiginous and have nystagmus (fast phase away from the operated ear) for a few days until central compensation takes effect.
A transmastoid labyrinthectomy with fenestration of the bony semicircular canals and vestibule and removal of the membranous neuroepithelium provides control of vertigo in nearly all patients with unilateral Meniere disease and poor hearing. The rate of control may decline in 10 years owing to the development of vertebral-basilar insufficiency (aging), poorer vision, and the development of Meniere disease in the contralateral ear. The complete loss of unilateral vestibular function due to the labyrinthectomy leads to unsteadiness in up to 30% of patients.
Meniere disease is characterized by remissions and exacerbations, making it difficult to predict the future behavior of the disease in any individual patient based on the patient's own history, diagnostic evaluations, or epidemiologic profiles. The initial manifestation may be vertigo or hearing loss, but within 1 year of onset, the typical syndrome–attacks of vertigo, tinnitus, fluctuating hearing loss, and aural fullness–is present. Longitudinal studies have shown that after 10–20 years, the vertigo attacks subside in most patients and the hearing loss stabilizes to a moderate to severe level (50 dB). Meniere disease is usually a unilateral disease, and the risk of developing this disease in the contralateral ear appears to be linear with time. Of the patients, 25–45% may develop disease in the contralateral ear.
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is efficacious in controlling vertigo while preserving hearing.)