Meniere’s in 2004

As printed in Hearing Health, volume 20:1, Spring 2004

By George A. Gates, M.D.

Meniere’s disease (MD) is the most common cause of recurring episodes of vertigo – a spinning dizziness that is often debilitating due to associated nausea, vomiting and imbalance. Also characterized by hearing loss, ear pressure and tinnitus, the illness affects approximately 615,000 people in the U.S., the vast majority between the ages of 40 and 60. People with MD are frequent visitors to physicians’ offices because of its chronic nature marked by repeated episodes of disruptive and unpredictable symptoms.

Much has been written about MD because it is so common and difficult to treat. Despite decades of clinical research, controversy remains about its cause, mechanism and treatment. What follows are my opinions, based on available evidence, about these important aspects of the disease.

What causes Meniere’s?
The sudden onset of symptoms in a previously well person suggests that an acquired disorder, such as a viral inner ear infection, may be the triggering event. The fact that symptoms come and go over a number of years infers that although the initial illness may have passed, the normal processes that regulate the internal environment of the inner ear remain affected.

Although unproven, the most widely held theory is that the mechanism that regulates inner ear fluid (endolymph) becomes damaged, leading to increased fluid volume over time. Treatments that likely reduce fluid volume, such as salt restriction and diuretic agents, commonly bring about improvement, results that seem to support this leading hypothesis.
About five percent of people with MD have a family history of similar symptoms, suggesting a hereditary component. But because these cases are relatively rare, we cannot say that it is an inherited disorder.

Also in a minority of cases, the disorder affects both ears, typically existing in one ear for years with symptoms then occurring much later in the other. Current evidence suggests that these individuals develop an autoimmune response that affects the second ear. Thus, this latter development, while leading to similar symptoms, may have a different cause and treatment.

How does it affect the body?
No matter the actual cause of MD, the mechanism of the disease is consistent as well as fairly well understood. It occurs in the inner ear and acts on both the balance (vestibular) and hearing (cochlear) centers. In each, sensory cells are bathed in endolymph, which is rich in potassium and vital to their function. Movement of the fluid in a healthy inner ear triggers signals that are sent to the brain and help us balance and hear.

Endolymph is surrounded by membranes that contain a second fluid (perilymph) that has almost no potassium. Keeping these two fluids in ionic balance and regulating their volumes is an essential function of supporting cells in a healthy inner ear. MD’s
onset appears to be related to increased endolymph volume. The resulting pressure leads to a range of symptoms with vertigo occurring when it affects the balance part of the inner ear.

Increased endolymph volume has been observed in inner ears removed posthumously from people with established MD. This evidence leads many researchers to suspect a blockage in the drainage of endolymph into the endolymphatic sac, a thin structure located behind the inner ear that can serve as an overflow reservoir. However, other considerations suggest that instead of a blockage affecting the flow from ear to sac, there might be an overproduction of endolymph that overloads the normal drainage mechanism.

Certainly the success of a low-salt diet in reducing buildup of bodily fluid and relieving symptoms in a majority of people with MD is in keeping with this theory of overproduction. Also bolstering this idea is recent research by Alec N. Salt, Ph.D., of the Cochlear Fluids Research Laboratory at Washington University in St. Louis, that indicates that endolymph can be “pumped” from the inner ear into the sac by alternating pressure applied to the ear. Study continues on the effect of this process on MD symptoms.

What treatments exist?
In the majority of cases, MD is self-limited, meaning that over several years, the vertigo attacks become less frequent and less severe. Over time, people with MD lose balance function in the affected ear, which has led to the concept that MD “burns itself out” by destroying the ear’s balance sensitivity. Many treatments for the illness “speed up” this process by deliberately removing the balance function of the affected ear. Fortunately, we can balance reasonably well with one ear after our body compensates for loss of vestibular function in the other.

Many people have hearing loss as well after several years of MD symptoms. Unfortunately, hearing with one ear has definite limitations. For some, a hearing aid is useful.

Since no specific antidote or cure for MD has been found, people with the disorder and their physicians struggle to find effective treatments to relieve symptoms. Many have been recommended over the years but most prove to be ineffective.

How can a treatment appear helpful in achieving relief when it is first introduced but fail to be convincing in the long term?

This is due to the episodic nature of the disease. MD tends to come in clusters of attacks and when a person is having numerous bad spells, any therapy may appear to help when, in reality, the improvement would have occurred anyway. In other words, good days follow bad days with or without treatment. It is not the fault of well-intentioned people who are desperate to find an effective treatment that the method of the moment becomes popular only to be discarded later. Only when a new alternative is compared to a control or placebo treatment can the true nature of the therapy be known.

Certain standard therapies do exist. Almost all patients newly diagnosed with MD receive recommendations about a low-salt diet, diuretic treatment and lifestyle adjustment (avoiding caffeine, alcohol, nicotine and stress). The overriding goal is to reduce the sodium level in the blood, which fluctuates with salt consumption and stress. Dyazide, a commonly prescribed diuretic, may also aid in achieving the desired result.

About 70 percent of people find they can keep their vertigo symptoms under reasonable control with this standard approach. They may still experience occasional bad days and use a vestibular suppressant drug, such as meclizine or diazepam, to help them feel better on such days. These drugs do not, however, affect MD’s underlying cause and/or mechanisms and are not useful to prevent attacks.

That leaves 30 percent of people whose vertigo is so frequent or so severe that it disrupts their life and for them, additional treatments are available. All have some degree of invasiveness and are generally categorized as either non-destructive or destructive to the inner ear.

Non-destructive options: The most commonly used approach in this category has been endolymphatic sac surgery, a low-risk procedure that does not harm the patient’s hearing and is completed on an outpatient basis. The bone over the sac is removed, allowing it to expand and handle more endolymph. This method provides vertigo control in approximately 75 percent of cases for the first six months and drops to about 50 percent thereafter. It seems to work better for people in the early stages of MD when hearing still fluctuates with attacks and when vestibular function remains normal.

The recently introduced Meniett device is another non-destructive surgical approach. Developed in Sweden, it is now manufactured in the U.S. by Medtronic Xomed and is being used as an alternative to sac surgery. The Meniett is a low-pressure pump that puts alternating low-intensity pressure pulses into the inner ear via a tube surgically placed in the eardrum. It is used three times a day indefinitely. Each treatment takes about five minutes and the portable device can be used anywhere below 8,000 feet elevation.

About 80 percent of patients I have treated at the University of Washington have had good to excellent success with the device. Half of them experience no vertigo while the others have only occasional mild spells. Twenty percent of people do not experience satisfactory relief from treatment with the Meniett and may then go on to invasive surgical therapy.
My colleagues at the University of Michigan, Duke University and Jacksonville Hearing Center have demonstrated in a recent study that participants using the Meniett showed improved vertigo control in comparison to those who used a placebo device. Further research is needed, however, to determine which people might be better served by sac surgery and which by the Meniett device.

Finally, although some practitioners prescribe corticosteroids (prednisone, decadron or methylprednisolone) to attempt to reduce the volume of endolymph and achieve symptom relief, there are no studies showing that they are effective. And because they have negative and lasting side effects, they are not currently indicated for use in controlling chronic MD.

Destructive therapy: The effectiveness of this type of approach is well-established. Simply put, vertigo stops once the balance part of the inner ear loses its function. This is done surgically by bisecting the vestibular (balance) nerve or by removing or destroying the labyrinth portion of the cochlea. The nerve section preserves hearing but is a “bigger” operation. A labyrinthectomy is an outpatient procedure but results in total and permanent hearing loss in the “bad” ear.

These considerations have led many to choose intratympanic (through the eardrum) injection of gentamicin (ITG) as an alternative. Gentamicin is an ototoxic antibiotic that will permanently damage inner ear hair cells. It is less toxic to hearing than to balance but the likelihood of some hearing loss exists.

Often one ITG stops vertigo permanently. However, some cases take multiple injections, increasing the risk of incurring hearing loss.

Meniere’s in the Future
Danish scientists made an intriguing discovery several years ago when they found that the endolymphatic sac produces a hormone (saccin) that seems to play a role in regulating the level of sodium in the bloodstream. However, this work has not yet been confirmed. If further investigations do support this possibility, chemicals could be developed to block saccin release in the affected ear, leading someday perhaps to a pill to conquer MD. Such a breakthrough could help remove a mighty disruption – as well as a hearing hazard – from the lives of many grateful people.

Dr. George A. Gates, director of the Virginia Merrill Bloedel Hearing Research Center, is professor of otolaryngology-head and neck surgery, epidemiology and speech and hearing sciences at the University of Washington and chief of otology/neurotology at University of Washington Medical Center in Seattle. He also gives generously of his time and energy to the Deafness Research Foundation as scientific/ medical director and a member of the executive committee.

Dr. Gates encourages readers to support further MD research through donations to DRF at www.drf.org or 202.289.5850.

Related Article:
Control Salt Intake & Tame MD