What Is Delayed Endolymphatic Hydrops?

Delayed endolymphatic hydrops (DEH) is an inner ear disorder that typically appears years after a person has already experienced a profound hearing loss in one ear. The term delayed is used because the defining symptoms usually do not emerge until a long interval, sometimes decades, after the original hearing damage.

Like classic Meniere's disease, delayed endolymphatic hydrops is associated with an excess of endolymphatic fluid inside the membranous labyrinth of the inner ear. This condition is known as endolymphatic hydrops. When pressure builds within the affected labyrinth, it can produce severe vertigo attacks, usually without causing any further deterioration of the hearing that was already lost.

Many clinicians regard DEH as a special subtype of Meniere's disease rather than a completely separate disorder. The relationship between Meniere's disease and delayed endolymphatic hydrops is close, but the two conditions differ in their sequence of symptoms. In Meniere's disease, fluctuating hearing loss, tinnitus, a feeling of fullness in the ear, and episodic vertigo generally occur together from early on. In DEH, a single profound hearing loss event happens first, and only much later do vertigo attacks appear.

What Causes the Original Hearing Loss?

Diverse insults can lead to the initial severe hearing loss that precedes delayed endolymphatic hydrops. Common causes include:

• Sudden sensorineural hearing loss
• Viral labyrinthitis, as may occur with mumps or measles
• Head trauma affecting the temporal bone
• Surgery or infection of the inner ear
• Idiopathic cases where no exact cause can be identified

After the initial injury, the ear remains profoundly deaf or severely impaired. A person may adapt well to using their other ear. Years later, without any new hearing loss, episodic vertigo begins. This delay can make it difficult for the person to connect the original hearing problem with the new balance symptoms.

Types of Delayed Endolymphatic Hydrops

Two main patterns of DEH are recognised:

• Ipsilateral DEH: The vertigo attacks arise from the same ear that already has the profound hearing loss. This is more common.
• Contralateral DEH: The vertigo attacks appear to come from the opposite, previously hearing ear. In this form, the better-hearing ear may begin to show fluctuating hearing loss, tinnitus, and fullness, resembling a typical Meniere's disease pattern in the only useful ear.

Determining which ear is responsible for the vertigo is important because treatment is directed at the offending labyrinth.

Symptoms of DEH

The hallmark symptom of delayed endolymphatic hydrops is recurring episodes of vertigo that develop after a period of established unilateral profound hearing loss. An individual attack may include:

• Spinning or rotational vertigo that lasts minutes to hours
• Nausea and vomiting
• Sweating and pallor
• Unsteadiness between attacks

In ipsilateral DEH, there is usually no new change in hearing, and tinnitus or aural fullness may or may not accompany the vertigo episodes. In contralateral DEH, the formerly healthy ear can develop fluctuating hearing, roaring tinnitus, and pressure sensations that migrate as the disease progresses. Because the only functional ear may become involved, contralateral DEH presents a greater clinical challenge.

How Is DEH Diagnosed?

A diagnosis of delayed endolymphatic hydrops is largely clinical. The essential features are a documented history of severe to profound unilateral hearing loss, followed by recurrent spontaneous vertigo episodes that develop later, and no identifiable alternative explanation for the attacks.

Testing generally includes:

• Audiometry to confirm the pattern and severity of the hearing loss and to monitor the healthy ear
• Vestibular testing, such as videonystagmography or caloric irrigation, to evaluate the balance function of each ear
• Electrocochleography in selected cases, which may support the presence of endolymphatic hydrops
• Imaging with MRI after the administration of contrast material in order to exclude a tumour at the inner ear or nerve, such as a vestibular schwannoma

Treatment and Management

Treatment options for delayed endolymphatic hydrops resemble those used for Meniere's disease. The main goals are to reduce the frequency and severity of vertigo and to preserve any usable hearing in the remaining functional ear.

Conservative Measures

• Dietary changes, including a lower sodium intake, to help regulate inner ear fluid volume
• Reducing caffeine and alcohol consumption
• Vestibular rehabilitation to improve balance and compensate for the damaged labyrinth

Medical Treatment

Diuretic medications may be used to lower fluid pressure in the inner ear. Medications to suppress vertigo, such as vestibular suppressants, can relieve symptoms during an acute attack, although they are not intended for long-term daily use. Betahistine is offered in some regions, although evidence for its benefit is variable.

Ablative and Surgical Approaches

When medical treatment fails and the vertigo is disabling, more invasive procedures are considered. These include:

• Intratympanic corticosteroid injections to reduce inflammation and hydrops
• Intratympanic gentamicin, which selectively damages the vestibular hair cells to reduce vertigo
• Endolymphatic sac decompression
• Total labyrinthectomy, which can be very effective if the affected ear has no usable hearing

Because a person with ipsilateral DEH has already lost hearing in the offending ear, the threshold for a destructive procedure may be lower than in typical Meniere's disease. In contralateral DEH, however, treatment is more conservative because damage to the only hearing ear must be avoided.

Prognosis

The natural course of delayed endolymphatic hydrops is highly variable. Some individuals experience only a few attacks, while others have frequent vertigo for months or years. Episodes often become less severe with time, and spontaneous remission can occur. Ipsilateral DEH is generally easier to manage because the affected ear has no useful hearing, meaning that ablative treatments can be used more freely. Contralateral DEH requires a more cautious approach over a longer period.