Meniere's disease - Audiology BSc

Ménière's Disease

Remit

This is a short description of Ménière's Disease. It outlines the pathology, symptoms and treatment of the disease.

For an in-depth treatment read: BMJ 1998;316:368-372 (31 January). Fortnightly review: Diagnosis and treatment of Ménière’s disease. Shakeel R Saeed.

Background

There are three main causes of vertigo: Benign Paroxysmal Positioning Vertigo (BPPV), Vestibular neuritis and Ménière's disease. They all provoke a spinning sensation and are caused by inner ear disease but that is about all they have in common.

Ménière's is a relapsing and remitting disease i.e. it shows episodic activity and periods of quiescence. Each spell is characteristic and to a variable degree disabling but the periods between attacks are typically problem free, at least in the early days of the disease.

In up to 40% of patients, both ears will be affected. It is commonest after the age of 40 and there is no sex difference.

To understand the disease better we must consider the normal physiology and then examine what happens in the disease. This will, in turn, help us to understand the symptom complex.

Normal Physiology

The normal physiology of the inner ear is covered in another tutorial. You should review this because it helps you to understand the genesis of the spinning sensation. However, a little more physiologic detail is required to understand Ménière's disease.

The organ of hearing and those of balance all lie within the endolymphatic space. This is the membrane bound space that is filled with endolymph. Endolymph is like intracellular fluid in composition - high in potassium and low in sodium. The diagram below shows the endolymphatic space in a very simplified form. In fact, in life, the hearing portion is a spiral shape and the balance portion is two cystic structures and three semicircular tubes. The endolymphatic space is yellow and the surrounding perilymph is blue.

The hearing and balance neuroepithelia are within a common space linked to the endolymphatic sac (ES). It is filled with endolymph (yellow here).

It is believed that the endolymph is produced in the stria vascularis of the cochlea and the dark cells of the balance portion. It is drawn towards the ES by osmotic flow.

The ES is critical in the normal homeostasis of the endolymph and can keep the volume of the endolymph constant even when production increases or decreases.

Pathophysiology

One theory of Ménière's disease has it that the function of the endolymphatic sac is impaired and that there is a relative build-up of endolymph within the endolymphatic space. This is sometimes referred to as endolymphatic hydrops.

Remember that the fluids around the endolymphatic space - perilymph - is low in potassium and high in sodium. Remember also that normal function of the delicate neuroepithelia of hearing and balance is dependent on ionic stability within the endolymph.

Now let us focus on the cochlea only. This spiral organ consists of a central endolymphatic space containing the hearing neuroepithelium. This is surrounded by the perilymph space.

This diagram is a cross section through one of the turns of the cochlea and show the neuroepithelium bearing endolymphatic space (scala media) surrounded by perilymph spaces (scalae vestibuli and tympani).

The endolymph is high in potassium and this is essential for normal hearing function.

In the following animation we can see one theory of the events that unravel during an episode of endolymphatic hydrops. You will see that the endolymphatic portion becomes progressively more distended and that finally it ruptures with admixture of endolymph with perilymph. This causes an ionic disequilibrium that causes stimulation and damage to the neuroepithelium of hearing - causing hearing loss and tinnitus.

Later the ionic disequilibrium spreads to include the balance portion of the endolymphatic sac and this, in turn, causes damage and vertigo.

(An alternate theory has it that it is the rupture that signals the end of the Ménière's attack. Much is uncertain in this disease!)

It is true that this is a simplification of the real cause but it does explain the sequence of symptoms in a typical Ménière's attack and is in keeping with histological evidence in patients known to have suffered with Ménière's Disease.

Once the membrane has healed the ionic distributions return to normal and the symptoms regress and finally stop.

This is what may be happening early in the disease course but with increasing time permanent damage occurs and hearing loss and tinnitus become a permanent feature - see below.

Symptoms

The triad of symptoms that characterise Ménière's Disease are: hearing loss, tinnitus and vertigo. To this triad is usually added 'aural pressure' but it's presence is variable.

In a typical attack the patient will describe a sensation of 'fullness' or 'pressure' in one ear. Some time later they will notice tinnitus and then hearing loss. These symptoms herald the onset of vertigo.

The vertigo lasts for hours and may be associated with nausea and vomiting. Eventually it eases off and the hearing loss and tinnitus disappear. The attack is over and the patient returns to normal.

This sequence recurs for years in some. With time the periods between attacks of vertigo are marred by persisting hearing loss and tinnitus in the affected ear. Eventually, as all function in the ear becomes progressively damaged, the attacks stop.

Investigation

As always a careful clinical history will give you the diagnosis in most cases of Ménière's Disease. However, there are a few essential investigations that are required:

1. Pure Tone Audiogram. This typically shows a fluctuating low frequency hearing loss. Later in the disease the hearing loss becomes permanent and progressive.

2. MRI of the posterior cranial fossa and Internal Acoustic Meatus. This is done to rule out acoustic neuroma.

3. FBC, Glucose, TFT are done to exclude systemic diseases.

The audiogram shows a low-frequency, left-sided sensorineural hearing loss.

Were one to plot hearing tests over time one would find that the thresholds improved and worsened at times. This is rare for any other cause of sensory loss.

Treatment

This is a very variable disease and, therefore, assessing the success of treatment is difficult. The list below summarises management:

Salt restriction.
Betahistine TID every day as prophylaxis.
Antiemetic during attacks only.
Surgery - conservative and destructive.

Betahistine (Serc) is the only medication that has any evidence of success in preventing attacks. This evidence is not very robust. Antiemetics are used only during attacks. For more information on the medication used in vertigo please click here.

Surgical options are divided into those that spare hearing function (conservative) and those that destroy it (destructive). The operation that is chosen depends to some extent on how much hearing the patient has left in their ear.

If the hearing is good then conservative options are tried:

Grommet. Nobody really knows why this works but it does in a large proportion of patients.
Intratympanic methylprednisolone injections. The drug is injected into the middle ear on two occasions.
Gentamicin instillation. Here gentamicin is instilled into the middle ear. It passes into the inner ear and destroys balance function while sparing hearing - mostly.
Saccus decompression. In this operation, the endolymphatic sac is opened to drain endolymph out.
Vestibular nerve section. While this aims to preserve hearing function it is nonetheless a major operation.

If hearing is very poor, or absent then one can consider labyrinthectomy. In this operation, the function of the inner ear is totally destroyed by drilling out the inner ear. It is a very effective operation but all hearing is lost from the ear.

In Primary Care, surgical options are not possible. However, a great deal can be done for patients with this condition:

1. Prescription and repeat prescription of Betahistine to prevent attacks and prochlorperazine to help during an attack

2. Psychological support - it is very important for some sufferers to know that there is someone who they can talk to about the condition

3. Advice on stress reduction (stress can be a trigger)

4. Advice on reducing salt

5. Referring to the local balance service (usually in the ENT Department)