eMedicine Specialties > Neurology > Neuro-otology

Endolymphatic Hydrops

Author: John C Li, MD, Private Practice in Otology and Neurotology; Medical Director, Balance Center
Coauthor(s): Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Contributor Information and Disclosures

Updated: Mar 12, 2009

Introduction

Background

Endolymphatic hydrops by definition refers to increased hydraulic pressure within the inner ear's endolymphatic system. This pressure accumulation causes the following tetrad of symptoms: (1) fluctuating hearing loss (sometimes good or bad); (2) episodic vertigo (can be violent); (3) tinnitus or ringing in the ears (usually low-tone roaring); and (4) aural fullness (pressure, discomfort, fullness sensation in the ears).

Evaluating and managing dizziness and vertigo can be extremely difficult.  The source of imbalance can range from easily treatable (eg, dehydration) to more ominous (eg, brain tumor). CNS problems need to be distinguished from circulation insufficiency, chemical and hormonal imbalances, and peripheral inner ear disorders. This distinction is often difficult. This article discusses peripheral inner ear disorders, specifically endolymphatic hydrops. Although it may be similar to articles on Ménière disease and syndrome, the focus will be the on pathophysiology of endolymphatic hydrops. (See eMedicine article Dizziness, Vertigo, and Imbalance for related information.)

Endolymphatic hydrops often is used synonymously with Ménière disease and Ménière syndrome, which are thought to result from increased pressure within the endolymphatic system.

Ménière disease is idiopathic, whereas Ménière syndrome is secondary to another disease process (eg, thyroid disease, inner ear inflammation due to syphilis). This distinction is analogous to that in Bell palsy. If the source of facial paralysis is known, the diagnosis is not Bell palsy. Similarly, if the cause of vertigo is known, the diagnosis cannot be Ménière disease. Ménière syndrome may be secondary to various processes that interfere with normal production or resorption of endolymph (eg, endocrine abnormalities, trauma, electrolyte imbalance, autoimmune dysfunction, medications, infections [especially parasitic], hyperlipidemia).

Pathophysiology

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

The physical distention caused by increased endolymphatic pressure also leads to a mechanical disturbance of the auditory and otolithic organs. Since the utricle and saccule are responsible for linear and translational motion detection (as opposed to angular and rotational acceleration), irritation of these organs may produce nonrotational vestibular symptoms.

The organ of Corti is disturbed mechanically. Distortion of the basilar membrane and the inner and outer hair cells may cause hearing loss and/or tinnitus. Since the apex of the cochlea is wound much tighter than the base, the apex is more sensitive to pressure changes than the base. This explains why hydrops preferentially affects low frequencies (at the apex) as opposed to high frequencies (at the relatively wider base). Symptoms improve after the membrane is repaired as sodium and potassium concentrations revert to normal.

Frequency

United States

Although probably underestimated, a prevalence of 1,000 cases per 100,000 population is a reasonable approximation. Familial predisposition may be a factor, since half of patients have a significant family history.

Mortality/Morbidity

Although the disease itself is not fatal, it can be associated with significant morbidity.

• Vertigo can cause accidents and falls, which can be devastating.
• Hearing loss often is progressive over time.
• Many patients can no longer work and are forced to claim disability.

Sex

The female-to-male ratio is 1.8:1.

Age

• The mean age among treatment groups in some studies ranged from 49-67 years.
• Ménière can be seen at almost all ages, but the typical onset begins at early to middle adulthood.

Clinical

History

The typical history involves episodic attacks of true whirling vertigo, which usually are preceded by a variable sense of ear pressure and fullness, decreased hearing, and a low-tone roaring tinnitus.

• The vertiginous attacks typically last minutes to hours, and often are associated with severe nausea and vomiting.
• After the acute attack, patients generally feel tired, unsteady, and nauseated for hours to days.
• The timing and frequency of attacks is variable. Some patients can regularly predict an attack while others note a completely random pattern. Attacks may be linked to dietary triggers, the menstrual cycle, or psychosocial stresses.
• Between episodes, some patients are completely symptom free. Many notice progressive deterioration of hearing and balance function with each successive attack.

Physical

Examination results vary, depending upon the phase of disease. During remission, physical examination findings may be completely normal, particularly if the patient is symptom free.

• During an acute attack, the patient has severe vertigo.
• Patients are often in significant distress. Many present to the physician's office clutching a bucket and towel with signs of recent vomiting.
• Patients are sometimes diaphoretic and pale.
• Vital signs may show elevated blood pressure, pulse, and respiration.
• Significant nystagmus may be present.
• Pneumo-otoscopy of the affected ear may elicit symptoms or cause nystagmus.
• The Romberg test generally shows significant instability and worsening when the eyes are closed.
• The Fukuda marching step test may show significant deviation (if the patient can stand with closed eyes).
• The Dix-Hallpike test result may be positive, indicating coexisting benign positional vertigo.
• Hearing usually is affected.
• The Weber tuning fork test usually lateralizes away from the affected ear.
• The Rinne test usually indicates that air conduction remains better than bone conduction.
• Complete neurologic evaluation is important. New-onset vertigo might be an early sign of stroke, migraine, or brainstem compression that may require emergent evaluation and care.

Causes

Based on semantics, Ménière disease is defined as idiopathic. In other words, if the cause is known, the disease process can no longer be called Ménière's disease.  However, since the root of the problem is elevated endolymphatic pressure, the causes of endolymphatic hydrops will be discussed.

• Several disorders may cause increased endolymph pressure, including metabolic disturbances, hormonal balance, trauma, and various infections.
• Autoimmune diseases, such as lupus and rheumatoid arthritis, may cause an inflammatory response within the labyrinth.
• Allergy also has been implicated in many patients with difficult to treat Meniere disease.
• Food triggers are also important factors in the generation of hydrops.

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