DIFFERENTIAL DIAGNOSIS OF PERIPHERAL VESTIBULAR DISORDERS

Differential Diagnosis of Peripheral Vestibular Disorders

PART 3: Meniere’s Disease (Endolymphatic Hydrops)

Endolymphatic hydrops is the progressive retention of fluid in the endolymphatic space. There are many causes for endolymphatic hydrops and a predictable collection of symptoms results from endolymphatic hydrops. This collection of symptoms is termed Meniere’s syndrome. When no identifiable cause can be found for Meniere’s syndrome, it is termed Meniere’s Disease. So, Meniere’s disease is idiopathic Meniere’s Syndrome. Meniere’s can be seen in all age groups, but is relatively rare in the pediatric population and common in the 30-50 year old group.

Most patients present with unilateral disease but 30-50% will develop bilateral disease. The characteristic symptoms are unilateral aural fullness, fluctuating hearing loss, tinnitus and vertigo. Spontaneous remissions and exacerbations also characterize this disorder. Physical exam is typically normal. Work up should include a search for possible underlying causes. Most patients respond to treatment consisting of dietary changes and medical therapy. Less than 20% of patients will require surgical intervention.

Clinical presentation

Meniere’s disease is characterized by unilateral:

fluctuating hearing loss
tinnitus
aural fullness
vertigo

A typical Meniere’s attack will start with the sensation of unilateral aural fullness, which is often described like the feeling the ear gets during a URI or an airplane flight. Coincident with this is often a low pitch roaring tinnitus in the affected ear. Hearing loss will develop in the affected ear and then a spell of rotary vertigo will occur. The vertigo will typically last for 30 minutes to 4 hours. During the vertigo spell, the patient will frequently experience nausea, vomiting, and diaphoresis. After the vertigo spell, the hearing loss, tinnitus and aural fullness may resolve and the patient may experience disequilibrium that will last for several days. The patient will then have resolution of symptoms and is typically free of symptoms when visiting the physician.

A fairly rare, but disquieting symptom of Meniere’s disease is the drop attack or Otolithic Crisis of Tumarkin. In this situation the patient will suddenly lose all postural tone and drop to the floor without any warning. It can be distinguished from a cardiac event or stroke because there is no loss of consciousness during the drop attack and – although quite unsteady – immediately after falling to the floor the patient can often get right back up.

Pathophysiology

The pathophysiology of endolymphatic hydrops is felt to be most likely due to inadequate resorption of endolymph. The endolymphatic sac is purportedly the organ where endolymph is resorbed. Experimental disruption of the endolymphatic sac or blocking the endolymphatic duct, which leads to the sac, has been shown to result in endolymphatic hydrops. Progressive dilatation of the endolymphatic space will eventually result in intralabyrinthine membrane ruptures, which may be the cause of vertiginous spells and hearing loss. After these "ruptures", fluid equilibrium returns and the patient often has a quiescent period until endolymphatic pressure builds up again. Progressive destruction of intralabyrinthine structures results in what has been termed "burned out" Meniere’s.

Diagnosis

Patients with Meniere’s disease will typically have a normal physical exam unless they are seen during an acute attack. During an acute attack, your patient will be nauseated, diaphoretic and demonstrate nystagmus. The nystagmus is typically beating with the fast phase towards the normal ear. They will also note a feeling like the affected ear is block by wax or full of fluid in spite of a normal otoscopic exam. Audiometric examination will often demonstrate a low-frequency sensorineural hearing loss which may improve to normal once the attack has resolved.

The natural history of Meniere’s is one of remissions and exacerbations. Many will experience several years quiescent of any symptoms only to see return of symptoms. The natural history is also quite variable in that many patients will never progress beyond mild disease regardless of treatment and others will develop severe disease in spite of aggressive treatment. In the early onset of the disease, your patient may have only one or two of the classic symptoms, such as fullness and/or fluctuating hearing. As the disease progresses, the symptoms become more classic with the patient experiencing all of the classic symptoms – unilateral fluctuating hearing loss, tinnitus, aural fullness, and episodic vertigo.

As the disease progresses further, the fluctuating hearing loss will become a permanent hearing loss and the symptoms of tinnitus and aural fullness will become more constant than episodic. In "burned out" Meniere’s, the patients will have chronic dysequilibrium but no acute vertiginous episodes and they will typically have stable, moderate to severe hearing loss.

Diagnostic tests that are helpful in the evaluation of Meniere’s disease can be grouped into two categories – those helping to confirm Meniere’s disease and those helping to rule out other causes. In the category of helping to confirm Meniere’s disease are audiometry, electronystagmography (ENG), and electrocochleography (ECOG). None of these tests need to be done to make the diagnosis of Meniere’s disease, but the information derived from them can provide information about the severity of disease and sometimes help make the diagnosis.

Audiometry may be normal or demonstrate low-frequency sensorineural hearing loss. Repeat testing may show objective evidence of fluctuation of the hearing loss. ECOG is an electrophysiologic test done similar to evoked response testing, but one of the electrode is placed either on top of the ear drum itself or through the eardrum and on top of the promontory of the inner ear. The tracings that are measured represent the inner ear response to auditory stimuli. The important variable measured is the ratio of the amplitudes of the summating potential (SP) and the action potential. This is felt to be a fairly specific test but lacking somewhat in sensitivity. ENG may demonstrate normal findings, particularly in the early onset of disease, or a caloric weakness in the involved ear as the disease progresses. Additionally, spontaneous nystagmus may be noted if ENG testing is performed shortly after an acute vertiginous episode.

Among the tests that are useful in excluding causes for Meniere’s syndrome include auditory brainstem evoked responses (ABR), radiographic imaging, and blood tests. Computed tomography and ABR have been used as a screen for acoustic neuromas and cerebellopontine angle (CPA) tumors. However, a thin slice MRI with gadolinium contrast is currently the gold standard for anatomically evaluating this area for such lesions. Blood tests that may be useful include thyroid panel, syphilis serology, and an autoimmune panel.

In summary, the diagnosis of Meniere’s disease is made in a patient who has:

Characteristic history – unilateral fluctuating hearing loss, tinnitus, aural fullness, and episodic vertigo.
Supportive diagnostic tests – audiometry, ECOG, ENG
Exclusion of other causes by MRI and blood tests.

The differential diagnosis of Meniere’s syndrome is large. Entities, which are known causes of Meniere’s syndrome, include:

Trauma – acoustic trauma, temporal bone fracture, surgical trauma to the inner ear

Autoimmune – autoimmune inner ear disease, Cogan’s disease, Lupus

Infectious – chronic otitis media, syphilis, labyrinthitis (viral or bacterial)

Metabolic – otosclerosis, Paget’s disease, hyperlipidemia

Neoplastic – acoustic neuroma, leukemia,

Congenital/Developmental – Mondini’s dysplasia large vestibular aqueduct syndrome, congenital deafness, jugular bulb diverticulum

Endocrine – thyroid disease, diabetes

Idiopathic – perilymphatic fistula, Meniere’s disease

Treatment of Meniere’s disease can be categorized into a four step approach – dietary changes, medical therapy, conservative surgical therapy and ablative surgical therapy. Dietary changes include elimination of caffeine and reduction of sodium intake. Medical therapy usually includes control of any identified underlying medical problems (such as hypothyroidism or diabetes), maintenance diuretic therapy and PRN use of vestibular suppressant medication during acute spells.

Approximately 4 out of 5 patients will respond quite nicely to the above treatment. However, for those who have progressive disease in spite of maximal medical therapy, conservative surgical therapy may be employed – endolymphatic sac surgery or transtympanic steroid therapy. Ablative surgical therapy is usually reserved for the most severe cases that have failed all other treatments and includes transtympanic aminoglycosides, labyrinthectomy, or vestibular nerve section. Using this stepwise treatment approach, virtually all patients can be freed from vertiginous spells. Treatment is discussed more fully in a later chapter. A detailed review of Meniere’s disease was recently published in the Otolaryngology Clinics of North American.

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