Meniere's Disease
Description
Meniere's disease is a rare disorder of the inner ear. Our current understanding is that Meniere's disease involves a disturbance in the absorption of fluid in the inner ear. The result is that too much endolymph (fluid) accumulates. Because the inner ear is lined with a membranous labyrinth, the liquid can only expand a limited amount. The result is an increase in pressure in the inner ear, which damages the cochlea (auditory part of inner ear) in certain places.
Symptoms
Acute symptoms of Meniere's disease are characterized by a classic triad of symptoms. Dizziness: sudden attacks of rotational vertigo, often with nausea and vomiting. Hearing loss: fluctuating, unilateral hearing impairment during the vertigo attacks in the form of a sensorineural hearing loss. Tinnitus: ringing in the ears on the affected side.
The patient usually has nystagmus as an accompanying symptom. Due to the nystagmus, the patient cannot fix his gaze on a solid object, which increases his unsteadiness. In addition, vegetative symptoms such as tachycardia or sweating may occur.
In the intervals between Meniere's seizures, the patient does not suffer from vertigo.
In relation to hearing loss, a deterioration is often ascertained in the course of the disease: while at first the abilty to hear improves and completely recovers after the attacks, in cases of prolonged illness it is possible that the hearing is also reduced in the symptom-free periods, and even that deafness occurs.
Causes and Risks
The causes of Meniere's disease are not known. The disease occurs frequently in some families. Therefore it seems likely that there is a genetic predisposition for Meniere's disease. Perhaps certain anatomical features of the organs of equilibrium and hearing are inherited, for example small variations in their forms which might promote Meniere's disease. In rare cases, the disease appears after an injury to the inner ear. Other agents such as environmental factors (e.g. exposure to loud noise), viral infections or circulatory disorders are discussed as possible causes of Meniere's disease.
Examination and Diagnosis
A thorough survey of the patient's medical history and an exact description of the symptoms are an important basis for the diagnosis of Meniere's disease.
A diagnosis of Meniere's disease can be made if at least two spontaneous vertigo attacks at least 20 minutes long have occurred, if there is tinnitus either with or without a feeling of pressure in the ear, and if hearing loss can be demonstrated via audiometric tests. The diagnostic methods used include: electrocochleography, which tests the functioning of the hair cells of the ear, as well as the auditory nerve (increasing the compound action potential with hydrops); audiometry: positive recruitment in SISI test and Fowler test, glycerol test; Weber test: lateralization to the healthy side, BERA (Brainstem Evoked Response Audiometry).
To rule out an acoustic neuroma, an MRI examination can be carried out (using contrast-medium administration and T2 weighting).
Treatment
Since the cause of Meniere's disease is unknown, only the symptoms can be treated. A causal therapy for the disease does not exist. One distinguishes in therapy between treatment of acute attacks and the prevention of attacks. The therapy may involve specific drugs that are targeted at the symptoms, but can include also surgical procedures.
During an acute attack, antinauseant drugs can help against dizziness and antiemetic drugs against nausea. If the symptoms are very pronounced, the doctor may administer the agent as an infusion in a vein. With severe vomiting, the fluid and electrolyte loss must sometimes be compensated for with an infusion.
If attacks occur frequently and are a great burden, an interval treatment with drugs can be attempted. Agents such as betahistine should reduce the number of vertigo attacks. But here too, no definite therapeutic effect has been proved.
If other measures fail, the last resort for treatment of Meniere's disease must be considered: the partial disconnection of portions of the inner ear. The doctor administers a drug - an antibiotic (gentamicin) or a local anesthetic - through the tympanic membrane directly into the middle ear.
Dizziness can also be suppressed via surgery, by the doctor severing the vestibular nerve (which deals with balance). Because this method causes deafness in the affected ear, it can only be considered when there is already a complete loss of hearing. Alternatively, it is also possible to decrease pressure in the inner ear if the endolymphatic sac (saccule) is relieved via surgery (a so-called sacculotomy). This may allow the endolymph to be better reabsorbed.
Course and Prognosis
The course of Meniere's disease is very individual. It may involve just a single attack. In most cases, however, the attacks are repeated. Yet even after five years Meniere's disease may terminate spontaneously and never reappear. But in this case, the losses of hearing and balance incurred by then are generally permanent. The consequential damages of Meniere's disease attacks can range to complete deafness on the affected side. After five years' duration, the symptoms of the disease will in 50 percent of cases affect both sides.