Meniere's disease is characterized by spontaneous attacks of vertigo, fluctuating sensor neural hearing loss, aural pressure, and tinnitus. Meniere's disease is one of the clinically significant diseases because it has serious implications for the affected person. Unanticipated attacks that keep repeating will disrupt the patient's daily life; it can even bother the patient's professional career.
Meniere's disease is a disorder of the inner ear that results in symptoms of episodic vertigo, tinnitus, hearing loss, and aural pressure. Clinically, fluctuating sensor neural hearing loss tends to be resistant to treatment (progressive), but the symptoms of episodic vertigo are usually quite responsive to treatment.
Meniere's disease occurs approximately 50 to 200 per 100,000 adults and is most common in between 40 and 60 years old. Several studies have suggested that the prevalence of Meniere's disease is slightly higher in women than in men, with a reported female: male ratio in the United States of 1.89: 1.30. Hypothesis shows that the main cause of this female predominance was because there was a mixture of patients who had vestibular migraine which the symptoms are similar with Meniere's disease. In some Meniere's disease patients, the symptoms of decreased hearing function are the most significant symptoms.
The course of Meniere's disease is generally variable, and the development of cochlear and vestibular symptoms may take years in individual patients. Cochlear symptoms may also occur in between vertigo episodes. The episodes of vertigo are usually much more common in the first few years of the disease. Hearing loss and vestibular hypo function show a great variability among patients, making its phenotyping difficult. Taxonomy of Meniere's disease subtypes is needed to help categorize individuals who manifest what may be incomplete phenotypes. Moreover, subsets of patients have been described who develop bilateral sensor neural hearing loss (SNHL) and other comorbidities such as migraine, benign paroxysmal positional vertigo (BPPV) and systemic autoimmune diseases, further complicating the diagnosis and management.
Several efforts have been made in the past to define and have a consensus diagnosis for Meniere's disease. The Japanese Society for Equilibrium Research proposed clinical criteria for diagnosis of Meniere's disease in 1974. The American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) developed the guidelines for diagnosis of Meniere's disease in 1972, which was then revised in 1985 and again in 1995.9 Since then, these guidelines have been widely used in clinical research, nearly all studies published are based on these guidelines. International Classification of Vestibular Disorders (ICVD) has classified Meniere's disease into 2 basic categories: definite Meniere's disease and probable Meniere's disease.
Several lines of epidemiological evidence support a genetic contribution in Meniere's disease, including (a) the higher prevalence observed in the European population over other ethnicities and (b) a strong familial aggregation found in Europeans and South Koreans.
Two genes for the immune response have been associated with the development of hearing loss in Meniere's disease. In a separate study, the common variant rs11096955 in the TLR10 gene also influenced the development of sensorineural hearing loss in patients with bilateral Meniere's disease. The MIF gene mediates the production of proinflammatory cytokines and increases autoimmune-mediated nerve inflammation.
Additional evidence for genetic contribution is also supported by a study conducted in four families with Meniere's disease with an autoimmune background. The autoimmune mechanism involved in this disease is still uncertain. There are several hypotheses have been proposed to explain the development of autoimmune responses in the inner ear: (a) a cross-reaction due to shared epitopes between inner ear proteins and microbial proteins, such as cochlin, (b) collateral damage due to persistent levels of cytokines and chemokines that can trigger the reaction delayed immunity, possibly explaining the relapsing remitting course of Meniere's disease, (c) intolerance to inner ear antigens, and (d) immunogenetic factors leading to a persistent inflammatory.
Attacks of episodic vertigo can be explained by two theories. The first is the rupture theory which states that an increase in pressure within the scala media results in the rupture of Reissner's membrane. Endolymph and perilymph will come together which in turn causes vertigo attacks. This theory is based on historical histological specimens of individuals with Meniere's disease.
The second theory is the drainage theory. Drainage theory suggests that excess endolymph at the scala media will eventually flow rapidly from the cochlear duct, saccule and into the endolymphatic sinus. Once the capacity of the endolymphatic sinus is reached, the valve that separates the utricle and sinus is breached and the endolymph overflows into the utricle, stretching the crest of the semicircular canal causing vertigo. Furthermore, if there is blockage of the endolymphatic duct or Bast valve which is responsible for the drainage function, it can cause endolymphatic hydrops. Endolymphatic hydrops can also result from overproduction of endolymph which can make damage to the organs of the corti.
Symptoms of Meniere's disease are episodic vertigo, tinnitus, hearing loss, and aural pressure. The vertigo is typically rotatory, makes the patient feeling weak and may be accompanied by nausea, vomiting and the less common symptom is diarrhea. Vertigo usually lasts more than 20 minutes but rarely exceeds four hours and rarely has more than one attack within 24 hours. Between attacks, the balance function subjectively returns to normal. Hearing loss, tinnitus symptoms and aural pressure are fluctuating. There are three stages in Meniere's disease:
Stage one- Dominant symptom in the stage one is the attack of vertigo and usually occurs with severe intensity. Hearing levels fluctuate, but recover to normal levels between attacks. Tinnitus and aural pressure often improve or disappear between attacks, with hearing function and balance tests often normal.
Stage two- There continues to be repeated episodes of vertigo. Hearing may still fluctuate but not fully recover to normal levels. Tinnitus and aural pressure usually don't completely disappear between attacks.
Stage three-The patient may also experience a Tumarkin drop attack, in where the patient suddenly falls without warning, without loss of consciousness and without neurological symptoms but this is rare. Hearing level remains poor (threshold around 60 dBHL).
The patient diagnosis is done as per the ICVD classification. It is to be remembered that Meniere's disease is more of a clinical diagnosis as none of the available investigations are diagnostic.
Initial management is with dietary alterations. This is a long-established practice, although the evidence base is limited. Sodium restriction is proposed to help by reducing endolymphatic pressure and is defined as <2000 mg/day. Dietary restrictions to sodium have been shown to be efficacious in reducing the frequency and severity of vertigo attacks, and caffeine restriction is likely also beneficial. Increasing oral water intake (35 mL/kg/day) has also been shown to have some benefit, particularly in terms of vertigo and hearing. Dietary modifications can often be difficult for patients to manage alone, though input from a dietician improves outcomes and compliance. Because of the overlapping clinical symptoms between vestibular migraine and Meniere's, some patients benefit from further lifestyle modifications such as healthy sleep patterns and reducing migraine precipitants such as dark chocolate and alcohol.
Betahistine has long been used for Meniere's. Precisely why the histamine analogue helps is unknown, though it may improve labyrinthine circulation. A Cochrane review suggests benefit from betahistine in reducing vertigo and is generally well tolerated.8
Thiazides are frequently used as medical management of endolymphatic hydrops, with the same rationale as the above dietary modifications. A Cochrane review found no studies of sufficient quality to meet the inclusion criteria. Given the potential side effects of electrolyte disturbance and renal dysfunction, it is therefore not usually commenced in primary care.
The vertigo caused by Meniere's disease can cause disruption to driving, and patients are therefore obliged to notify the Driver and Vehicle Licensing Agency (DVLA). Should a patient neglect to inform the DVLA, and the clinician responsible for their care has reason to believe they are still driving, and then it is the clinician's responsibility to report this.
In the otolaryngologists' clinic, patients may undergo further management for their symptoms. This may include injection of steroid or gentamicin into the middle ear. In the most debilitating of cases, surgical options such as endolymphatic sac surgery or selective vestibular nerve section may be considered.
