Local Copy Bilateral Vestibulopathy

NOTICE: This is a local copy, for continued access and backup, of an article authored by Timothy C. Hain, MD, last revised 7/2002. You are encouraged to read the original material. The original http://www.tchain.com/otoneurllogy/disorders/bilat/bilat.html at this T.C. Chain site

BILATERAL VESTIBULAR LOSS

Bilateral Vestibulopathy

Timothy C. Hain, MD

Bilateral vestibulopathy occurs when the balance portions of both inner ears are damaged. The symptoms typically include imbalance and visual symptoms. The imbalance is worse in the dark, or in situations where footing is uncertain.

Spinning vertigo is unusual. The visual symptoms, called '' oscillopsia'' , only occur when the head is moving (J.C., 1952). The illustration to the right shows what a person with bilateral vestibulopathy may see when driving over a bumpy road. Oscillopsia is often common during walking (Freyss et al, 1988).

Quick movements of the head are associated with transient visual blurring.

What causes Bilateral Vestibulopathy ?

About 1% of all dizziness in the author's practice is due to Bilateral Vestibulopathy.

In many instances, bilateral vestibulopathy is due to exposure to an ototoxic medication (about 50%). Gentamicin is an antibiotic medication and gentamicin toxicity is the most common single known cause of bilateral vestibulopathy, accounting for 15-50% of all cases. Ototoxicity can also be due to infection (meningitis, about 10%), Ménière's disease, sarcoidosis, bilateral ear surgery such as for certain forms of acoustic neuroma or bilateral vestibular neuritis, congenital disorders with deafness such as the Mondini malformation, and very rarely, from disorders of the immune system. One rare familial form is associated with migraine. Advanced age is another risk factor as normally vestibular ganglion cell counts decrease with age so that by the age of 80 years, about 50% of vestibular neurons remain. In about a third of all cases no cause can be identified for bilateral vestibular loss (Syms and House, 1997).

There is also accumulating evidence that free radical generation plays an important role in ototoxicity. This information is the basis of experimental treatments to prevent ototoxicity.

How is the Diagnosis of Bialteral Vestibulopathy Made?

Rotatory Chair ENG caloric responses

Mild Increased phase, steeper than normal slope to gain vs. frequency plot Normal and symmetric. Total response >= 20.

Moderate Increased phase, steep slope, gain greater than 0.2 at highest frequencies Total response between 0 and 10

Severe No response at all frequencies except (possibly) highest (0.64 Hz) No response to usual temperatures as well as ice water

(These categories are based on testing done at the author's institution, and might not be applicable to other protocols at other institutions). Pathologic correlation is minimal for these categories -- but recent data suggests that '' severe'' losses are associated with roughly an 80% or more loss of hair cells.

A physician can make the diagnosis based on history, findings on physical examination, and the results of vestibular tests (rotatory chair) . On physical examination, the tandem Romberg test, the dynamic visual acuity test, and the ophthalmoscope tests are the three most helpful confirmatory tests. The opthalmoscope test is particularly important as it is straightforward to perform and the results are not greatly affected by cooperation or lack of it. The rotatory chair test is essential to document the characteristic reduced responses to motion of both ears and also in assessing compensation and the partial recovery that nearly always occurs over time. Rotatory chair testing generally improves with time -- high frequency gain eventually becomes normal or nearly so, several years after exposure. Recovery at high frequencies is felt to be related to non-vestibular sensory input, and does not necessarily correlate with severity of vestibular injury. Low frequency responses (e.g. < .04 Hz) may remain depressed. Optokinetic afternystagmus is abolished in significant bilateral vestibular loss

Moving platform posturography is always abnormal, but it is not specific (i.e. many other disorders also impair posturograpy). Allum and others recently concluded that diagnosis of bilateral vestibular loss using posturography is best achieved using measure of trunk control following pure toe-up rotational perturbations under eyes-closed conditions (Allum et al, 2001). This is not a paradigm that is routinely available.

Based on rotatory chair testing in our laboratory, patients are divided into three groups: mild, moderate, and severe (see table above). These categories have prognostic significance (see later). Other diagnostic studies may be helpful.

Hearing testing (audiogram) is necessary.

A test for syphilis (FTA), and an antibody test (ANA) for autoimmune inner ear disease may be performed. A chest X-ray and ACE test may be done if sarcoid is thought likely, and a Lyme titer may be obtained if there has been exposure (a tick bite in an endemic area).

How is Bilateral Vestibulopathy Treated ?

Treatment involves finding out the cause and treating it, if possible. If the damage has already been done, then the focus of treatment is upon avoidance of vestibular suppressants and ototoxins (see following) , and vestibular rehabilitation (Krebs, 1991) are important to speed recovery and prevent setbacks. We recommend that you tell health care workers that you are can't take drugs that end in '' mycin'' , because of possible '' reaction'' .

This will keep you from contact with the most common ototoxins. Asprin and nonsteroidal anti-inflammatory drugs can affect hearing. It may be prudent to avoid these drugs, or at least large doses of them. Antihistamines (like Antivert (meclizine) or Dramamine) and benzodiazepines (Valium-like drugs like Klonopin, Xanax, and Ativan) are temporary vestibular supressants. While they won't permanently harm you, typically they make imbalance temporarily worse. A list of the most common problem medication follows:

Potential problem medications for patients with bilateral loss (the most common ones)

Agents that can cause temporary worsening of dizziness or hearing symptoms are generally vestibular suppressants.

Antihistamines such as meclizine (Antivert) and phenergan.
Antidepressants such as amitryptyline, especially tricyclic type antidepressants.
Aspirin or NSAIDS (drugs like ibuprofen and naproxen) in large doses
Diazepam (Valium), alprazolam (Xanax), lorazepam (Ativan), klonazepam (Klonopin) and related drugs
Verapamil and other calcium channel blockers
In general, any drug that is commonly used to make vertigo better, will likely make the symptoms of bilateral loss worse.
Agents that can cause permanent or temporary worsening of dizziness or hearing
Cis-Platinum (a chemotherapy drug) and other platinum based drugs.
Gentamicin and other '' mycin'' antibiotics, including large doses of erythromycin (although this is actually in a different group than Gentamicin)
Furosemide (Lasix) and ethacrynic acid (Edecrin) loop diuretics
Quinine and related drugs (they usually have a '' quin'' in their name).

These medications need not be avoided at all costs but reasonable judgment should be exercised. Medications that cause only temporary unsteadiness (i.e. meclizine), may still be useful in some situations. Medications that are ototoxic (such as gentamicin), may still be useful in cases of bilateral vestibular loss when there is no reasonable alternative or when the damage done is already so extensive that there is nothing more to lose.

Prognosis: How might bilateral vestibulopathy affect my life ?

This is a condition which realistically often causes some permanent disability.

In patients with gentamicin induced ototoxicity, the symptoms generally peak at 3 months from the last dose of gentamicin. In the long run however, (5 years), most patients are substantially better. There are multiple reasons why people get better. First, there is evidence that the damaged vestibular hair cells in the inner ear can regenerate, although the extent to which this occurs and the degree to which they are functional is not presently clear (Forge et al, 1993; Warchol et al, 1993). Birds and reptiles seem to regenerate much better than do humans (Cotanche and Lee, 1994; Forge et al, 1993). Some recovery presumably occurs because marginal hair cells recover, because the brain rewires itself to adapt to the new situation (plasticity), and because people change they way they do things to adjust to their situation.

One can predict prognosis based on the amount of damage done initially, modified by other factors such as age, and other medical problems. Gillespie and Minor (1999) reported that recovery is related to various factors, including of course, severity of lesion. In our experience, rotatory chair testing done at 6 months following onset (or later) helps to establish prognosis by dividing individuals into three categories. Individuals with '' mild'' abnormalities on rotatory testing, are nearly always subjectively normal at one year. Individuals with moderate vestibular loss are usually able to continue to work productively, with some modifications in their behavior. For example, most people with moderate or severe loss never return to driving at night. In situations where there is complete or near-complete loss of vestibular function, vision and balance usually remain impaired permanently, but nevertheless, most individuals do return to work, especially if their job does not require good head/eye coordination or balance. Frequently job modification or accommodation occurs.

While balance is poorer than normal, given that normal vision and sensation in the feet and ankles is present, most patients with bilateral loss appear, at least on casual inspection, to have normal gait. Falls are more frequent in persons with bilateral vestibulopathy (Herdman et al, 2000). Reading is generally a more difficult than for persons with normal vestibular systems, but quite feasible, as the head can be steadied during reading. Many people with bilateral vestibulopathy complain of a mild confusion or '' brain fog'' , which is attributed to the increased attention needed to maintain balance and vision.

This reduces the amount of attention that is available for other thinking tasks.

While crutches, canes, walkers and wheelchairs may be necessary in the first 3 months, appliances are rarely needed to get about by one year. After 20 years, most patients have returned to near normal for their age. To some extent this return to '' normal'' is related to aging of peers as normally vestibular function declines with age. Other aspects of recovery involve use of other senses such as neck position sensors (the COR or cervico-ocular reflex), vision, and compensation through prediction.

You will want to change your life style to adjust to your reduced balance, and inability to see when your head is in motion. You will want to take precautions to avoid falls. You may need to change your occupation if your present one requires good balance, and an ability to see while the head is in motion.

For example, it would not be safe to continue as a truck driver, construction worker, or a roofer if you developed a significant bilateral vestibulopathy.

A job where you work at a desk is usually a good choice.

Research

Considerable research is ongoing regarding bilateral loss. Presently efforts are ongoing to develop a vestibular prosthesis (ARO abstracts 743-747, 2001) as well as mechanisms to stimulate regeneration of hair cells within the inner ear. Both of these projects seem likely to be successful within 10 years. Methods of preventing loss through protective agents and predicting susceptibility to gentamicin through genetic testing are also currently hot topics.

The author of this pamphlet maintains a database of a well studied group of about 100 persons with bilateral loss, most of whom are willing to participate in research projects. Researchers are invited to contact him for potential collaborations.

Help with research efforts is much needed to speed progress in this disorder.

You may wish to volunteer to be a research subject, to contribute funds for research efforts aimed at treating or preventing ototoxicity, or to contribute your inner ear in the event of your death. Donations of the inner ear of individuals with gentamicin toxicity are sorely needed by the National Temporal Bone Bank as no usable specimens presently exist in the collection (Tsuji et al, 1999).

	Rotatory Chair	ENG caloric responses
Mild	Increased phase, steeper than normal slope to gain vs. frequency plot	Normal and symmetric. Total response >= 20.
Moderate	Increased phase, steep slope, gain greater than 0.2 at highest frequencies	Total response between 0 and 10
Severe	No response at all frequencies except (possibly) highest (0.64 Hz)	No response to usual temperatures as well as ice water