Introduction and Symptomatology
John J. Zappia, MD
Michigan Ear Institute
Prosper Meniere was the first to report a group of patients with episodic vertigo attacks in 1861. His name has been associated with the disorder described below since that time. Formally, Meniere’s disease is characterized by (1) unilateral sensorineural hearing loss, typically fluctuating and predominantly in the lower frequencies, (2) tinnitus, constant or intermittent with the hearing loss typically increasing in intensity before or during the vertiginous attacks and, (3) attacks of vertigo lasting minutes to hours with irregular intervals, and accompanied by nausea and vomitting. A sense of fullness in the ear is also experienced. The fluctuations in hearing often accompany the vertigo attacks. The patient is generally left exhausted and unstable for the subsequent one to three days after an acute vertigo attack. The tinnitus and fullness are generally constant, but frequently increase in severity just preceding, or during the attack.
One difficulty in the diagnosis, and an issue of controversy, is that the auditory and vestibular symptoms may not develop simultaneously, and in many patients the full complement of symptoms never develop. For the diagnosis of Meniere’s disease to be applicable, all of the symptoms in the first paragraph must be present. Subsequent terms have been created to attempt to categorize these possibilities. Meniere’s variant, vestibular Meniere’s, cochlear Meniere’s and other terms have been applied to those with only a portion of the symptomatology. Endolymphatic hydrops is probably a more useful way of describing the disorder because it identifies the underlying problem (see below), with the understanding that there can be various manifestations and degrees of severity of the disease.
Meniere’s disease is characterized by exacerbations and remissions making it impossible to predict the future behavior of any individual patient. After a number of years, in many patients, the vertigo symptoms subside and the hearing loss stabibizes at a moderate to severe level. This pattern of “burning out” occurs in a large number but by no means all patients.
The average age of onset of symptoms is in the 40’s but it can occur at any time in one’s life. The occurence of the disease in children, although, is somewhat uncommon. The risk of developing the desease in the opposite ear is estimated to be as high as 30%. Most believe that the second will usually become symptomatic within 2-5 years of the onset of symptoms in the first ear.
Pathogenesis
The inner ear contains two separate fluid comparments. One contains a fluid designated perilymph and the second innermost compartment contains a fluid called endolymph. In Meniere’s disease there is too much pressure and fluid within the endolymphatic space. The exact reason for the excess pressure is unknown. It is known that endolymph is produced by special cells in the inner ear and that the fluid ultimately drains out of the inner ear into the cerebrospinal fluid through the endolymphatic duct and sac. An obvious and fundamental thought in this disorder is that there either excess production of endolymph by the specialized cells or there is reduced or impaired resorption by the endolymphatic sac. Either or both problem will lead to excess fluid. Although there has been much research the answer is not known.
Genetic and hereditary factors may be a part of Meniere’s disease. There appears to be a significantly higher incidence of Meniere’s disease in family members with the disease. Also the size and shape of some of the inner ear structures such as the endolymphatic sac and the vestibular aqueduct (the bony tunnel that the endolymphatic duct passes through) are different.
Testing
Diagnosis can frequently be made by historical information and physical examination but several tests can be useful in not only establishing the diagnosis but also in eliminating other possible disorders. Standard audiometric testing will show the characteristic hearing loss when the patient is experiencing aural symptoms. Basic and complete balance tests such as electronystagmography (ENG) typically are abnormal but can show a variety of abnormalities.
There are two tests that are somewhat specific for Meniere’s disease or endolymphatic hydrops. The first test, the glycerol dehydration test, involves the subject ingesting glycerol or mannitol (dehydrating agents) and observing for a change in symptoms and a measurable change (improvement) in hearing. The second specific test is electrocochleography (ECoG). In this test electrical information is recorded from the inner ear as sound is presented. Normal patients have a characteristic shaped electrical response and in Meniere’s disease this response is altered.
Treatment
Although many medical treatments have been used and discussed the most accepted treatment involves dietary modification and the use of diuretics. Restricting salt intake decreases the amount of water the body and ultimately the inner ear retains. Other foods such as caffeine and nicotine are stimulants that induce the faulty inner ear to become more active. Diuretics such as Dyazide, Lasix and hydrochlorothiazide activate the kidneys to excrete more salt leading to elimination of some of the salt in the inner ear. Many other medications have been utilized. Vasodilators such as papaverine and niacin(also a vitmamin), the natural substance histamine, various herbal remedies, allergy therapy, steriods, antihistamines and others have been used.
Symptomatic treatment can be extremely helpful. Medications such as Antivert (meclizine) and Valium (Diazepam) can reduce the severity of the vertigo when it occurs. Anti-emetics (anti-nausea) medications can sometimes be useful.
In patients where it has not been possible to control the vertigo generated by the affected ear, certain antibiotics (aminoglycosides) can be used to weaken the inner ear so that it is incapable of generating dizziness. One of these aminoglycosides, gentamicin, has been used to affect the inner ear directly. It can be placed in the middle ear (behind the eardrum) and be allowed to diffuse into the inner ear where it generally destroys some or all of the balance cells in the one ear. In patients with Meniere’ disease in both ears, a similar medication (streptomycin) can be given intramuscularly and will have an effect on both ears.
For those people with persistent dizzy symptoms in whom medications have not been successful, or who have special situations (i.e. bus driver), there are several surgical options. Surgery of the endolymphatic sac can be very successful in patients who have active fluctuations of hearing. This suggests that the problem in the inner ear is reversible if the pressure problem can be reversed. Incidently, some patients have permanent damage to the inner ear from the pressure problem so that even if the pressure problem is reversed the inner ear will not function normally. This procedure is performed through an incision immediately behind the ear. After removal of some of the mastoid bone the endolymphatic sac is identified and decompressed and/or opened to enhance its function. This is an outpatient procedure.
The remaining two procedures, vestibular neurectomy and labyrinthectomy, are ways of eliminating the balance function of the faulty inner ear. It is known that a person will function much better with one normal balance system alone than with one normal and one faulty system. In patients who have very poor hearing in the affected ear a labyrinthectomy is a very successful option. The incision and approach are the same as in the endolymphatic sac surgery except that instead of carefully preserving the inner ear it is completely removed. The change from having two balance systems to having one balance system alone does require a recovery or “compensation” period. It takes the brain a period of weeks to figure out that only one system is active and that it is no longer receiving information from the faulty system which it had come to expect. The second procedure, the vestibular neurectomy, is an good option if the hearing is good in the ear with the failing balance system. In this surgical procedure, the balance nerve (vestibular nerve) is cut between the inner ear and the brain. The inner ear is completely preserved but the faulty balance information is not able to reach the brain and cause the vertigo. Like the labyrinthectomy, this procedure requires a recovery period while the brain “figures out” the new situation.
Meniere’s disease is a complex disorder. In each person, the symptoms are variable in their severity, scope and longevity. In some people it will be a trivial event whereas in others it will be a lifelong limitation. Research continues in this unusual problem.