Meniere's disease

Named for the French physician Prosper Meniere who first described the illness in 1861, Meniere's disease is an abnormality within the inner ear characterized by recurring vertigo (dizziness), hearing loss, and tinnitus (a roaring,buzzing or ringing sound in the ears). A fluid called endolymph moves in themembranous labyrinth or semicircular canals within the bony labyrinth insidethe inner ear. When the head or body moves, the endolymph moves, causing nerve receptors in the membranous labyrinth to send signals to the brain about the body's motion. A change in the volume of the endolymph fluid, or swellingor rupture of the membranous labyrinth, is thought to result in Meniere's disease symptoms.

The cause of Meniere's disease is unknown. However, scientists are studying several possible causes including noise pollution, viral infections, and otherbiological factors. Symptoms include severe dizziness or vertigo, tinnitus,hearing loss, and the sensation of pain or pressure in the affected ear. Symptoms appear suddenly, last up to several hours, and can occur as often as daily to as infrequently as once a year. A typical attack includes vertigo, tinnitus and hearing loss; however, some individuals with Meniere's disease may experience a single symptom, like an occasional bout of slight dizziness or periodic, intense ringing in the ear. Attacks of severe vertigo can force the sufferer to have to sit or lie down, and may be accompanied by headache, nausea, vomiting, or diarrhea. Hearing tends to recover between attacks, but becomes progressively worse over time.

Meniere's disease usually starts between the ages of 20 and 50 years and affects men and women in equal numbers. In most patients, only one ear is affected; but both ears are involved in about 15% of patients.

An estimated 3 to 5 million people in the United States have Meniere's disease, and almost 100,000 new cases are diagnosed each year. Diagnosis is based on medical history, physical examination, hearing and balance tests, and medical imaging with magnetic resonance imaging (MRI).

Several types of tests are used to diagnose the disease and to evaluate the extent of hearing loss. In patients with Meniere's disease, audiometric tests(hearing tests) usually indicate a sensory type of hearing loss in the affected ear. Speech discrimination or the ability to distinguish between words that sound alike is often diminished. In about 50% of patients, the balance function is reduced in the affected ear. An electronystagnograph (ENG) may be used to evaluate balance. Since the eyes and ears work together through the nervous system to coordinate balance, measurement of eye movements can be used totest the balance system. For this test, the patient is seated in a darkenedroom and recording electrodes, similar to those used with a heart monitor, are placed near the eyes. Warm and cool water or air are gently introduced intoeach ear canal, and eye movements are recorded.

Another test that may be used is an electrocochleograph (EcoG), which can measure increased inner ear fluid pressure.

There is no cure for Meniere's disease, but medication, surgery, and dietaryand behavioral changes, can help control or improve the symptoms. Symptoms may be treated with a variety of oral or injectable medications. Antihistamines, like diphenhydramine, meclizine, and cyclizine can be prescribed to sedatethe vestibular system. A barbiturate medication like pentobarbital may be used to completely sedate the patient and relieve the vertigo. Anticholinergic drugs, like atropine or scopolamine, can help minimize nausea and vomiting. Diazepam has been found to be particularly effective for relief of vertigo andnausea in Meniere's disease.

There have been some reports of successful control of vertigo after antibiotics (gentamicin or streptomycin) or a steroid medication (dexamethasone) are injected directly into the inner ear. This procedure is done in the doctor's office and is less expensive and less invasive than a surgical procedure.

Surgical procedures may be recommended if the vertigo attacks are frequent, severe, or disabling and cannot be controlled by other treatments. The most common surgical treatment is insertion of a small tube, or shunt, to drain someof the fluid from the canal. This treatment usually preserves hearing and controls vertigo in about one-half to two-thirds of cases, but it is not a permanent cure in all patients.

The vestibular nerve leads from the inner ear to the brain and is responsiblefor conducting nerve impulses related to balance. A vestibular neurectomy isa procedure where this nerve is cut so the distorted impulses causing dizziness no longer reach the brain. This procedure permanently cures the majorityof patients, and hearing is preserved in most cases. There is a slight risk that hearing or facial muscle control will be affected.

A labyrinthectomy is a surgical procedure in which the balance and hearing mechanism in the inner ear are destroyed on one side. This procedure is considered when the patient has poor hearing in the affected ear. Labyrinthectomy results in the highest rates of control of vertigo attacks; however, it also causes complete deafness in the affected ear.

Changes in diet and behavior are sometimes recommended. Eliminating caffeine,alcohol, and salt may relieve the frequency and intensity of attacks in somepeople with Meniere's disease. Reducing stress levels and eliminating tobacco use may also help.

Since the cause of Meniere's disease is unknown, there are no current strategies for its prevention. Research continues on the environmental and biological factors that may cause Meniere's disease or induce an attack, as well as onthe physiological components of the fluid and labyrinth system involved in hearing and balance. Preventive strategies and more effective treatment shouldbecome evident once these mechanisms are better understood.

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