Peripheral vestibular disorders

What are peripheral vestibular disorders? How are they treated?

1. Labyrinthitis or vestibular neuronitis

This is caused by inflammation from viral influence or possibly microvascular ischemia or compromise, is common.

Patients have acute or gradual onset of vertigo, disequilibrium, and nausea and may have other vasovagal signs.

They are likely to have decreased responses to bithermal caloric testing and low-frequency rotational tests of the VOR in darkness, impaired balance, impaired sense of the visual vertical, or they may sit with the head tilted to one side chronically.

Patients tend to seek medical care when they have difficulty reading, doing chores around the house, exercising, driving, or have had falls. In the acute phase, use of steroids such as methylprednisolone may be useful.

Medications are not useful in patients with chronic symptoms. Meclizine and scopolamine are widely used but are not very effective and the sedative effects can be disabling.

The current standard of care is to refer these patients for vestibular rehabilitation exercises, which use head movements to increase the patient’s tolerance for movement and decrease vertigo gradually over 1 to 4 weeks. In addition, balance therapy exercises may be indicated.

Since many patients need specific instructions and coaching, as well as advice about how to function while they are having symptoms, these patients are best referred to occupational therapy or physical therapy with a trained therapist.

2. Ménière’s disease (endolymphatic hydrops)

This condition is well known but not as common. It is characterized by fluctuating but progressive, low-frequency sensorineural hearing loss, tinnitus, fullness in the affected ear, and a sudden, unprovoked episode of vertigo lasting minutes to hours.

It is thought to be caused by a buildup of endolymph that is not resorbed normally. These patients have normal balance and minimal or no vertigo in between Ménière’s attack so that by the time they arrive at the clinic their vestibular function often appears to be normal.

The disorder itself may cause BPPV or labyrinthitis. The first line of treatment is dietary modification with a low-sodium diet.

Since many patients may not understand the concept of using no salt at all or may have difficulty meal planning, counseling with a nurse, occupational therapist, or dietician may be useful. If dietary management alone is not therapeutic, the patient should be managed with diuretics, such as hydrochlorothiazide.

Antiemetics, such as promethazine, may also be useful. In most cases, patients may function well on such a regimen.

Some patients progress to profound hearing loss and attacks of vertigo so intense that they cannot function. In those cases, treatment with intratympanic gentamicin may be used to destroy the hair cells of the affected vestibular labyrinth.

This procedure should be performed by an otoneurologist or neurotologist who has had subspecialty training and has experience with this disorder. After gentamicin injections the patient may still have some residual vertigo. These patients often do well with vestibular rehabilitation for vertigo habituation exercises. 

Several surgical procedures are available although, with the advent of gentamicin treatment, these procedures have become less widely used, mostly as a last resort if the patient fails gentamicin injections.

Endolymphatic sac surgery is controversial and is no longer widely used. Similarly, endolymphatic shunts were widely used in the past but are now rarely performed. Vestibular labyrinthectomy can be performed but vestibular nerve section may be preferred as the less complex procedure that is likely to be just as reliable.

These procedures often result in chronic vertigo and disequilibrium.

Patients who fail to compensate completely after surgical procedures should be referred for vestibular rehabilitation.

3. Bilateral vestibular impairment or loss

This disorder is rare but can occur.

It is most often due to the use of aminoglycosides or due to autoimmune disorders, but it may be idiopathic or may be related to meningitis or polyneuropathy.

Typical autoimmune disorders that can cause bilateral vestibular loss are rheumatoid arthritis, systemic lupus erythematosus, Cogan’s syndrome, and Sjögren’s syndrome.

Patients present with disequilibrium and oscillopsia and may have had falls. They may also have vertigo if some vestibular function remains. 

Depending on the pathophysiology, some patients may benefit from use of corticosteroids. When suspected of autoimmune disorders patients should be referred to rheumatology.

Patients with bilateral vestibular loss may benefit from vestibular rehabilitation for balance exercises, vertigo habituation if vertigo is present, and from functional skills training.

4. Acoustic neuroma, a schwannoma of the vestibular nerve

This condition is rare.

It is often diagnosed with magnetic resonance imaging (MRI) when the patient has unexplained hearing loss. These tumors grow slowly, over many years. Therefore, older patients may benefit from watchful waiting.

Treatment with medication and rehabilitation is not effective.

Two surgical procedures are available: (1) surgical resection of the tumor or (2) stereotactic radioablation (gamma knife).

Although gamma knife is reputed to spare residual hearing, it may not spare hearing in individual cases. With a small tumor a surgical resection may be able to spare hearing in some cases depending on the approach.

After surgery some patients compensate well within 2 months. Other patients may benefit from vestibular rehabilitation if they are still symptomatic after the acute phase of recovery.

5. Perilymph fistulas

This disorder is rare. They occur when the bony semicircular canal of the anterior semicircular canal, or the oval or round window of the middle ear, has been breached.

Superior canal dehiscence (SCD) occurs when the arcuate eminence, which contains the superior semicircular canal, erodes over time, presumably due to minute changes in intracranial pressure over the course of a lifetime as the individual coughs or strains.

These patients complain of vertigo elicited by loud sounds and may even have nystagmus (Tullio’s phenomenon).

Sometimes these patients speak very softly because the sound of their own voices elicits vertigo. The clinical diagnostic test for SCD is the cervical vestibular evoked myogenic potential.

The follow-up in suspected SCD is computed tomography (CT) scan in the plan of the anterior semicircular canal. The treatment is surgical intervention to patch the area. Other types of fistulas are rare and are most often caused by head trauma.

They can also be caused by otic barotrauma from diving accidents.

Diagnosis, although difficult, may be aided with the use of computerized dynamic posturography (computerized Romberg testing) in the condition with eyes closed and movable support surface given with and without a puff of air to the impaired ear to observe for increased postural sway.

The surgical intervention involves middle ear exploration and patching if necessary.