Atlas of pathophysiology, 2 Edition

Part II - Disorders

Sensory Disorders

Meniere's disease

Ménière's disease, a labyrinthine dysfunction also known as endolymphatic hydrops, causes severe vertigo, sensorineural hearing loss, and tinnitus.

Age Alert

Ménière's disease usually affects adults between ages 30 and 60, men slightly more often than women. It rarely occurs in children.

Usually, only one ear is involved. After multiple attacks over several years, residual tinnitus and hearing loss can be incapacitating.

Causes

Unknown

Possible associations

·   Positive family history

·   Immune disorder

·   Migraine headaches

·   Middle ear infection

·   Head trauma

·   Autonomic nervous system dysfunction

·   Premenstrual edema

Pathophysiology

Ménière's disease may result from overproduction or decreased absorption of endolymph—the fluid contained in the labyrinth of the ear. Accumulated endolymph dilates the saccule and cochlear duct. Dilation of the endolymphatic system occurs and the Reissner membrane often tears. When rupture of the membrane causes endolymph to escape into the perilymph, the symptoms of Ménière's occurs.

Signs and symptoms

·   Sudden, severe spinning, whirling vertigo, lasting from 10 minutes to several hours, because of increased endolymph (attacks may occur several times a year, or remissions may last as long as several years)

·   Tinnitus caused by altered firing of sensory auditory neurons; possibly, residual tinnitus between attacks

·   Hearing impairment due to sensorineural loss:

§  hearing possibly normal between attacks

§  repeated attacks possible progressive cause of permanent hearing loss

·   Feeling of fullness or blockage in the ear before an attack, a result of changing sensitivity of pressure receptors

·   Severe nausea, vomiting, sweating, and pallor during an acute attack because of autonomic dysfunction

·   Nystagmus due to asymmetry and intensity of impulses reaching the brain stem

·   Loss of balance and falling to the affected side due to vertigo

Diagnostic test results

·   Audiometric testing shows a sensorineural hearing loss and loss of discrimination and recruitment.

·   Electronystagmography reveals normal or reduced vestibular response on the affected side.

·   Cold caloric testing shows impairment of oculovestibular reflex.

·   Electrocochleography reveals increased ratio of summating potential to action potential.

·   Brain stem-evoked response audiometry test evaluates for acoustic neuroma, brain tumor, and vascular lesions in the brain stem.

·   Computed tomography scan and magnetic resonance imaging detects acoustic neuroma as a cause of symptoms.

Treatment

During an acute attack

·   Lying down to minimize head movement

·   Avoiding sudden movements and glaring lights to reduce dizziness

·   Promethazine or prochlorperazine to relieve nausea and vomiting

·   Atropine to control an attack by reducing autonomic nervous system function

·   Dimenhydrinate to control vertigo and nausea

·   Central nervous system depressants, such as lorazepam or diazepam, to reduce excitability of vestibular nuclei

·   Antihistamines, such as meclizine or diphenhydramine, to reduce dizziness and vomiting

Long-term management

·   Diuretics, such as triamterene or acetazolamide, to reduce endolymph pressure

·   Betahistine, to alleviate vertigo, hearing loss, and tinnitus

·   Vasodilators, to dilate blood vessels supplying the inner ear

·   Sodium restriction, to reduce endolymphatic hydrops

·   Antihistamines or mild sedatives, to prevent attacks

·   Systemic streptomycin, to produce chemical ablation of the sensory neuroepithelium of the inner ear and thereby control vertigo in patients with bilateral disease for whom no other treatment can be considered

Disease that persists despite medical treatment or produces incapacitating vertigo

·   Endolymphatic drainage and shunt placement, to reduce pressure on the hair cells of the cochlea and prevent further sensorineural hearing loss

·   Vestibular nerve resection in patients with intact hearing, to reduce vertigo and prevent further hearing loss

·   Labyrinthectomy to relieve vertigo in patients with incapacitating symptoms and poor or no hearing (destruction of the cochlea results in a total loss of hearing in the affected ear)

·   Cochlear implantation, to improve hearing in patients with profound deafness

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MÉNIÈRE'S DISEASE

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