Inner Ear, Meniere Disease, Medical Treatment 

Evaluation and management of dizziness and vertigo can be one of the most difficult medical tasks. Sources of imbalance can range from simple conditions (eg, dehydration) to serious conditions (eg, brain tumors). CNS problems must be distinguished from circulation anomalies, chemical and hormonal imbalances, and peripheral inner ear disorders. Often, this distinction is not clear.

This article covers a form of peripheral inner ear disorders, specifically, endolymphatic hydrops and Ménière syndrome.

Endolymphatic hydrops refers to a condition of increased hydraulic pressure within the inner ear endolymphatic system. Excess pressure accumulation in the endolymph can cause a tetrad of symptoms: (1) fluctuating hearing loss, (2) occasional episodic vertigo (usually a spinning sensation, sometimes violent), (3) tinnitus or ringing in the ears (usually low-tone roaring), and (4) aural fullness (eg, pressure, discomfort, fullness sensation in the ears).

The term endolymphatic hydrops is often used synonymously with Ménière disease and Ménière syndrome. Ménière disease and Ménière syndrome are both believed to result from increased pressure within the endolymphatic system. However, Ménière disease is idiopathic, whereas Ménière syndrome can occur secondary to various processes interfering with normal production or resorption of endolymph (eg, endocrine abnormalities, trauma, electrolyte imbalance, autoimmune dysfunction, medications, parasitic infections, hyperlipidemia).

The distinction in nomenclature is similar to that of Bell palsy. When the source of facial paralysis is known, Bell palsy is not the diagnosis. Similarly, when the cause of vertigo is known, Ménière disease is not the diagnosis; the diagnosis is Ménière syndrome.

In other words, Ménière syndrome refers to endolymphatic hydrops caused by a specific condition (eg, thyroid hormone disease, inner ear inflammation due to syphilis). Ménière disease refers to endolymphatic hydrops with unknown etiology; it is the catch term for idiopathic endolymphatic hydrops.

Two fluids fill the chambers of the inner ear: endolymph and perilymph. These fluids are separated by thin membranes, which house the nervous tissue of hearing and balance. Fluctuations in pressure of these fluids stress these nerve-rich membranes and can cause hearing disturbance, ringing in the ears, vertigo, imbalance, and a pressure sensation in the ear.

More specifically, episodes of hydrops are probably caused by an increase in endolymphatic pressure that causes a break in the membrane separating the perilymph (a potassium-poor extracellular fluid) and the endolymph (a potassium-rich intracellular fluid). The resultant chemical mixture bathes the vestibular nerve receptors, leading to depolarization blockade and transient function loss. Sudden change in the vestibular nerve firing rate creates an acute vestibular imbalance, giving the sense of vertigo.

Physical distention caused by the increase in endolymphatic pressure leads to mechanical disturbance of the otolithic organs. Because the utricle and saccule are responsible for linear and translational motion detection, rather than angular and rotational acceleration, irritation of these organs may produce nonrotational vestibular symptoms.

This physical distention causes mechanical disturbance of the organ of Corti as well. Distortion of the basilar membrane and the inner and outer hair cells may cause hearing loss and tinnitus. Because the apex of the cochlea is wound much tighter than the base, the apex is more sensitive to pressure changes than is the base. This explains why hydrops affects low frequencies (located at the apex) more than high frequencies (located at the relatively wider base of the cochlea).

Symptoms improve after the membrane is repaired and normal sodium and potassium concentrations are restored.

Frequency

United States

Although probably underestimated, approximately 1,000 cases per 100,000 people occur. A familial predisposition seems to exist; approximately half of the patients have a notable family history of this disease.

Mortality/Morbidity

Although the disease itself is not fatal, significant morbidity can arise from various manifestations of the disease. Vertigo can cause devastating accidents and falls. Hearing loss is often progressive over time. Many patients are unable to continue working and are forced to claim disability.

Sex

Although sex-related rates are nearly equal, a slight female preponderance may exist, in the range of 50-65%.

Age

• In some studies, the mean age among treatment groups was 49-67 years.
• Ménière disease has been seen at almost all ages.
• Typical onset begins at early-to-middle adulthood.