Endolymphatic Hydrops

Endolymphatic hydrops is a disorder of the inner ear caused by an excessive buildup of fluid that affects both hearing and balance, leading to symptoms like dizziness, hearing loss, and ringing in the ears.

Table of contents

• What is Endolymphatic Hydrops?
• Types of Endolymphatic Hydrops
• Associated Anatomy
• Causes
• Symptoms
• Diagnosis
• Treatment and Management
• Relationship with Ménière’s Disease

What is Endolymphatic Hydrops?

Endolymphatic hydrops is a disorder of the inner ear that results from an excessive buildup of a fluid called endolymph, which fills the hearing and balance structures of the inner ear^[1]. Endolymph is a special fluid that contains salts such as sodium, potassium, chloride, and other substances called electrolytes. This fluid is critical to the function of all sensory cells in the inner ear^[2].

When endolymph moves or shifts, it triggers sensory hair cells inside your ear to release signals that your brain can understand as sound or information about your body’s position^[3]. In a normal inner ear, the endolymph is maintained at a constant volume and with specific concentrations of electrolytes. This allows the sensory cells of the inner ear to function normally^[5].

When the inner ear is damaged by disease or injury, the volume and composition of endolymph fluid can change. This creates a condition where the structures bounding the endolymphatic space become distended or swollen, which is referred to as endolymphatic hydrops^[2]. In the cochlea (the snail-shaped hearing organ), hydrops typically appears as a distension of a membrane called Reissner’s membrane^[6].

• Inner ear
• Cochlea
• Endolymphatic sac
• Utricle
• Saccule
• Semicircular canals

Types of Endolymphatic Hydrops

Endolymphatic hydrops is classified into two main types based on whether the cause is known or unknown^[1].

Primary endolymphatic hydrops (also called idiopathic endolymphatic hydrops) occurs for no known reason. The word “idiopathic” means that the cause cannot be identified. This type is commonly known as Ménière’s disease. When the source of the problem is known, the diagnosis cannot be Ménière’s disease^[4].

Secondary endolymphatic hydrops occurs in response to a specific event or underlying condition. For example, it can follow head trauma or ear surgery, and it can occur with other inner ear disorders, allergies, or conditions that affect the whole body such as diabetes or autoimmune disorders^[5]. Secondary hydrops may also result from infection, degeneration of the inner ear, dehydration and loss of electrolytes, or in extremely rare cases, a benign tumor such as an endolymphatic sac tumor^[2].

cochlear hydrops, idiopathic endolymphatic hydrops

How Endolymph Works in the Inner Ear

Endolymph fills a network of ducts within your inner ear called the membranous labyrinth. This includes structures that are essential for hearing (the cochlear duct) and an intricate pathway of organs that sense movement, including the utricle, saccule, and three semicircular canals^[3].

The most important ingredient in endolymph fluid is potassium. When endolymph shifts, it releases potassium ions that activate the hair receptor cells to send nerve signals. These signals eventually reach your brain and allow you to hear sounds and maintain your balance^[3].

In an inner ear affected by hydrops, the normal controls that maintain fluid volume and composition are believed to be lost or damaged. This may cause the volume and concentration of the endolymph to fluctuate in response to changes in the body’s circulatory fluids and electrolytes^[5].

Causes

In many cases, the exact cause of endolymphatic hydrops is not clear^[2]. However, researchers believe that the condition stems from abnormal fluctuations in the endolymph fluid. These abnormalities may be related to problems in how the fluid is produced or absorbed within the inner ear^[1].

When an increase in endolymphatic volume occurs in the inner ear, it can cause a temporary leak in the membrane separating two different types of inner ear fluids. The mixing of these fluids can lead to a temporary electrical blockade and loss of sensory function. The sudden change in nerve signals results in a disturbance in how the brain processes information, leading to acute sensations of imbalance^[2].

Several conditions and events may contribute to the development of secondary endolymphatic hydrops, including trauma such as a blow to the head, infection, allergies, dehydration and loss of electrolytes, or conditions like autoimmune disorders^[2]. Spinal trauma earlier in life may also be a potential cause. A connection may exist between a neck trauma (such as a fall or auto accident) earlier in life and the onset of endolymphatic hydrops. The onset of symptoms may occur months to years after the injury^[19].

Symptoms

The symptoms of endolymphatic hydrops include a feeling of pressure or fullness in the ears, hearing loss, tinnitus (ringing or other noise in the ears), and balance problems^[2]. More specifically, symptoms can include:

• A feeling of fullness, pressure, or discomfort in one or both ears^[1]
• Fluctuating hearing loss, often affecting the ability to hear lower pitches^[1]
• Tinnitus, which may sound like ringing, roaring, machines whirring, or the whooshing noise you hear when holding a seashell up to your ear^[7]
• Dizziness and problems with balance^[1]
• Vertigo (a spinning sensation where you feel as if the world is spinning around you when you’re standing still)^[7]
• Nausea and vomiting, which can accompany vertigo episodes^[7]
• Hearing “double” or distorted sounds^[21]
• Sensitivity to loud noises^[21]
• Pain in the ear that does not go away despite taking pain relievers^[21]

Individuals who have endolymphatic hydrops strong enough to trigger severe symptoms do not always develop full Ménière’s disease^[2]. The symptoms can vary from person to person in how they present and how severe they become^[21].

Diagnosis

Endolymphatic hydrops is often diagnosed clinically by a specialist called an ENT (ear, nose, and throat doctor, also known as an otolaryngologist). The diagnosis is based on a patient’s medical history, their symptoms, and the results of tests and investigations^[1].

The clinical diagnosis may be strengthened by the results of certain tests. For example, certain abnormalities in a test called electrocochleography (which tests the response of the eighth cranial nerve to clicks or tones presented to the ear) or audiometry (which tests hearing function) may support a hydrops diagnosis^[5].

New research has shown that a special type of imaging test called MRI (magnetic resonance imaging) with contrast in the inner ear can give a definitive diagnosis of endolymphatic hydrops. This test uses a technique called delayed intravenous contrast-enhanced MRI, which allows doctors to see the endolymphatic space and identify whether hydrops is present^[2][11]. However, this imaging approach is not commonly used because clinical diagnosis based on symptoms and patient history is often accurate^[5].

After death, hydrops can be confirmed using examination of the petrous bone (part of the skull that contains the inner ear structures), although this method can sometimes be affected by how the tissue is prepared^[2].

Treatment and Management

Treatment of endolymphatic hydrops aims to reduce the frequency and intensity of symptoms, manage acute attacks, prevent damage to hearing and balance, and maintain quality of life^[5][16]. If the hydrops is secondary to another condition, the first-line management is to diagnose and treat that underlying disease (such as thyroid disease or an autoimmune disorder)^[4].

Lifestyle and Dietary Changes

Making changes to your diet and daily habits can help manage symptoms. These include:

• Reducing caffeine and alcohol intake, as these substances may worsen symptoms^[1][2]
• Staying well hydrated at all times^[1][2]
• Eating a balanced diet with lower salt and sugar intake. Keeping a strict, consistent low-sodium diet can help relieve the pressure on the nerve to the brain^[1][21]
• Making lifestyle changes and using stress-reduction techniques, as stress can cause inflammation^[1][16]

Medications

Several types of medications may be prescribed to help control symptoms:

• Medications to control dizziness, nausea, and vomiting during acute attacks^[1]
• Diuretics (water pills) to help reduce fluid buildup^[1][9]
• Corticosteroids (anti-inflammatory medications) given orally or injected directly into the ear^[2][9]
• A medication called acetazolamide, which has been shown in some studies to help reverse hydrops^[11]

Medications that decrease symptoms (such as meclizine, prochlorperazine, diazepam, lorazepam) are called vestibulosuppressants. These work by dulling the brain’s response to balance signals. However, frequent and long-term use of these medications is not recommended, as they can lead to poor balance function over time^[9].

Vestibular Rehabilitation

Vestibular rehabilitation, also called balance retraining, can help with problems with balance. This therapy involves carefully practicing movements that make you dizzy. Over time, the brain learns to cope with these movements and balance improves. This retraining can reduce dizziness and imbalance between major attacks^[1][16].

Surgical Treatments

In severe cases where conservative treatments have not been effective, a doctor may recommend surgery to relieve symptoms. Surgical procedures can include steroid injections into the ear, shunts to help drain excess fluid, or procedures that reduce the function of the affected inner ear structures^[1][9].

Relationship with Ménière’s Disease

Endolymphatic hydrops and Ménière’s disease are often used as interchangeable terms, but there are important distinctions^[1]. People diagnosed with Ménière’s disease are thought to have endolymphatic hydrops. However, not all people diagnosed with endolymphatic hydrops have Ménière’s disease^[1].

Ménière’s disease is, by definition, idiopathic, meaning the cause is unknown. When the cause of vertigo and related symptoms is known, the diagnosis is not Ménière’s disease but rather Ménière’s syndrome or secondary endolymphatic hydrops^[4]. This distinction in naming is similar to other medical conditions where knowing the underlying cause changes the diagnosis.

It is well-established that endolymphatic hydrops plays a role in Ménière’s disease, even though the precise role is not fully understood and the presence of hydrops in the ear does not always result in symptoms of the disease^[6].