Bilateral Vestibulopathy

Timothy C. Hain, MD • Page last modified: April 3, 2023

See also: bilat_cause• bilat_prevent• Bilat_recent• bilat_vn• gentamicin_toxicity• ototoxic_drops• ototoxins • progressive_bilateral • regeneration • sensory_substitution

Additional Disclaimer: This material is not written for legal use, including trial testimony.

The illustration below shows what a person with bilateral vestibulopathy may see when driving over a bumpy road. Oscillopsia often occurs during walking (Freyss et al, 1988). Quick movements of the head are associated with transient visual blurring.

Bilateral vestibulopathy occurs when the balance portions of both inner ears are damaged. The symptoms typically include imbalance and visual disturbance. 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). We have recently reviewed the subject of bilateral vestibular loss (see Hain, Cherchi and Yacovino, 2018).

What Causes Bilateral Vestibulopathy ? (see also this page)

About 28/100,000 people in the US have bilateral vestibular loss (Ward et al, 2013). Actually, this paper counted people with oscillopsia, not bilateral loss, and one could argue that it over or undercounted. It probably overcounted -- see this page.

About one percent of all dizziness in the author's medical practice which specializes in dizziness is due to bilateral vestibulopathy. In many instances, bilateral vestibulopathy is due to exposure to an ototoxic medication (about 35%). Click here for a more detailed discussion of causes.

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. Other antibiotic ototoxins are streptomycin, tobramycin and vancomycin.

Bilateral vestibulopathy can also be due to infection (meningitis, about 10%), Meniere'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. Some causes accompanied by hearing loss may be due to auditory neuropathy. 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. 

Recently, the statistically rare co-occurance of cerebellar ataxia, neuropathy and vestibular areflexia (bilateral loss) has been assigned the acronym "CANVAS SYNDROME". In about a third of all cases no cause can be identified  for bilateral vestibular loss (Syms and House, 1997). We are not entirely sure where CANVAS belongs on the chart above -- probably a <10% slice of the idiopathics.

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 Bilateral Vestibulopathy Made?

A physician can make the diagnosis based on history, findings on physical examination, and the results of vestibular tests (ENG, VHIT, and rotatory chair) . The most important of these three is rotatory chair testing (see here), but VHIT will do if rotatory chair is not available. .

Regarding history, one should suspect bilateral loss when there is a combination of unsteadiness and decreased vision when the head is rotating (i.e. oscillopsia).

According to Janky et al (2018), in children "A referral for vestibular evaluation should be considered for children whose hearing loss is greater than 66 dB and particularly those who sit later than 7.25 months or walk later than 14.5 months or whose parents report concerns for gross motor development". So if we understand this correctly, if a child needs a cochlear implant and who was late to sit or walk, bilateral vestibular loss should be suspect. The number of children with bilateral loss is presumably far less than adults, as they are due to very rare conditions.

Bedside testing

On physical examination, the tandem Romberg test, the dynamic visual acuity test, and the ophthalmoscope tests are the three most helpful confirmatory tests. The ophthalmoscope test is particularly important as it is straightforward to perform and the results are not greatly affected by cooperation or lack of it. The horizontal head impulse test is favored by some authors (e.g. Weber et al, 2009). The cervico-ocular reflex is easy to check with a swivel chair and video-frenzel goggles, but it is variably increased. It is inconsistent and not a reliable sign (Schubert et al, 2004). We only do this test in severe bilaterals, and are not sure of its sensitivity ourselves.

Cervico-ocular reflex movie

Laboratory testing:

Nearly always, laboratory testing is needed to confirm bilateral loss. The options include Rotatory chair, Caloric testing, VHIT testing, VEMP testing, and other ear tests to exclude other disorders (such as Meniere's).

The Rotatory chair test is the "gold standard" test, but Caloric testing, and VHIT testing are a reasonable substitute. VEMP testing asseses something else. If only a single test is available, the vHIT test is the second best, and caloric third best. Rotatory chair testing is also the hardest to access, because the equipment is costly, but it is generally available in large metropolitan areas, and covered by health insurance. For example, in Chicago, it is done at Central Dupage Hospital and soon (as of 7/2023) will be available at UCM medicine (U. Chicago).. From an insurance coverage standpoint, often the VHIT has no coverage at all. Go figure. A very good quick test.. One wonders why health insurance companies don't cover health care ? VEMP testing is also often uncovered, although it has made it possible to diagnose SCD process in dizziness without a CT scan that incurs risk from radiation. Go figure again.

Hearing testing (audiogram) is necessary for most bilateral loss patients. High frequency audiometry is not diagnostic in the population at large because it is variable, but can be used to detect the start of ototoxicity (from the chance in the person's hearing). (Stevenson et al, 2022). ABR testing and otoacoustic emissions (OAE) may be considered in persons with hearing impairment to look for auditory neuropathy. This is so rare as to be almost nonexistent (in adults). OAE testing may be a little more efficient than high-frequency audiometry as it doesn't require cooperation and is a little faster. It is also an objective test that can detect the rare occurance of malingering of hearing loss.

Cause testing for bilateral vestibular loss

Diagnostic studies to attempt to establish the cause of bilateral vestibulopathy may be helpful. However it is rare that these are productive.

A test for syphilis (FTA), and an antibody tests (ANA, CRP) for autoimmune inner ear disease may be performed. If Cogan's is a possibility (generally recognized by rapid onset deafness), slit-lamp examination looking for uveitis is indicated. If hearing is normal, one doesn't need the slit-lamp exam.

Persons with very long standing bilateral loss accompanied by deafness may be diagnosed using temporal bone CT scan, which identifies Mondini.

Sarcoid: A chest X-ray and ACE test may be done if sarcoid is thought likely (almost never pans out). ACE blood testing is thought to be elevated in about 60% of patients with sarcoid. However, according to Kruit et al (2007), "given the gross inter-individual variation of ACE levels and the observations that population-based reference intervals for ACE have been acknowledged as being deceptive in terms of identifying abnormal values, the added value of ACE levels in the diagnosis and follow-up of sarcoidosis is still subject to debate". About half of the variability in ACE levels is caused by a major genetic quantitative trait locus. There may be insertions (I) or deletions (D), leading to the nomenclature of D, DD, I, II, and ID. ACE levels may be unerestimated in II individuals, and overestimated in DD individuals. (Kruit et al, 2007)

A Lyme titer may be obtained if there has been exposure (a tick bite in an endemic area). These tests are all very low yield. Although one might think that Lyme would be associated with bilateral loss, as it is another spirochete such as syphilis, as of 2016, there was only a single report (of a single patient).

Testing for a genetic cause of bilateral loss, CANVAS, is done in genetics labs -- one of these is at the University of Chicago. This makes the most sense if your bilateral loss is "idiopathic", and especially if you also are numb in your feet. We think this is worth doing.

How is Bilateral Vestibulopathy Treated ?

Treatment involves finding out the cause and treating it, if possible. Unfortunately, it is rare that the cause is identified.

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; Herdman 2007) are important to speed recovery and prevent setbacks.

There are a number of sensory substitution devices in development. None of these are presently practical. A full discussion can be found here.

In the future, we expect that treatment will be available to regrow inner ear hair cells. This is not practical yet (as of 2022).

There is also a recent development of galvanic stimulation devices -- electrical current appplied to the inner ear area. This is discussed in detail here.

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. Aspirin 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 suppressants. 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), Dramamine and phenergan.
• Antidepressants such as amitriptyline, 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 in the benzodiazepine family.
• 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. Certain bacteria, such as methacillin-resistant staphylococcus aureus (MRSA) are so difficult to treat that ototoxic medications may be required to save a persons life. Nevertheless, as medicine progresses, we expect that newer drugs such as Linezolid will provide reasonable alternatives.

Prognosis: How might bilateral vestibulopathy affect ones life ?

This is a condition which often causes some permanent impairment and 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, (2-5 years), most patients are substantially better. In the authors opinion, after 2 years, a small amount of improvement (10%) may still be possible. After 4 or 5 years, it is unlikely that any further improvement will occur, and in fact, objective testing (such as vHIT) generally never changes no matter how much practice and physical therapy is used. While a large repertoire of symptoms are reported, the core reasons for impairment are usually some mixture of imbalance and oscillopsia. (Lucieer et al, 2018)

Mechanisms for recovery: There are multiple reasons why people get better.

• Regeneration: At the present writing, most experts feel that regeneration does not account for any substantial amount of recovery. First, there is limited 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).
• Marginal cell recovery: Some recovery presumably occurs because marginal hair cells recover. If this occurs, it probably happens only in the first year.
• Plasticity: The brain can rewire itself to adapt to the new situation. This is a mechanism that probably occurs in all people, although with more effect and speed in younger persons. Behavioral adaptation, Another way to get accommodate to the new situation is for a person to change they way they do things. For example, if one is unsafe driving at night, then don't drive at night.
• Substitution: Recent experimental work suggests that high frequency vestibular-ocular responses to rotation recover (partially) via a pathway that does not require vestibular input (Wiest et al, 2001). Thus in time, oscillopsia should improve (we didn't say go back to normal) no matter how severe the vestibular deficit. According to Herdman et al (2007), "recovery" of visual acuity occurs in roughly 5 weeks. Practically, performance on the "dynamic illegible 'E' test" seems to recover substantially in all patients after 2 or more years, although in persons with severe bilateral loss, return to completely normal is very unlikely. All this being said, if one does "VHIT" testing - -which is high speed rotation of the head, there is no improvement even after 20 years. What this means is that there are probably some things -- like seeing while serving a tennis ball - -that are just not going to get better. We find that our patients appreciate

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. Impairment of other senses used for balance (such as vision or sensation from the feet) is associated with worsened balance and worsened prognosis.

In our experience, rotatory chair or vHIT testing done at 6 months following onset (preferably later) helps to establish prognosis by dividing individuals into three categories (see table above). One should wait to do this testing till at least 6 months have passed, at least in persons with aminoglycoside ototoxicity (gentamicin mainly), as vestibular loss can progress for months even after gentamicin is stopped. When using rotatory chair testing to attempt to establish long term prognosis, another test at about 2 years or later is recommended as recent data suggests that partially injured hair cells may recover in the interim. These comments are not absolute and there are occasional exceptions where people are seen who do better or worse than would be expected from their quantitative vestibular tests (i.e. rotatory chair or vHIT).

• Individuals with "mild" abnormalities on rotatory testing, are nearly always subjectively normal at one year. The scaling situation on vHIT testing is still being worked out.
• 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.
• Individuals with severe vestibular loss may still return to work, but again the job generally must not require good balance. Because persons with severe bilateral loss often never return to night driving, this must be considered when returning to work.

While balance is poorer than normal (Fujimoto et al, 2013), 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 more difficult than for persons with normal vestibular systems, but quite feasible, as the head can be steadied during reading.

Long-term -- do the symptoms ever go away ?

While crutches, canes, walkers and wheelchairs may be necessary in the first 3-6 months, appliances are rarely needed to get about by one year. The exception to this general rule are patients with severe loss, who also have other medical problems such as neuropathy or brain damage. After 2 years, many patients also have substantial improvement in their rotatory chair tests compared to those done at 3 months, attributed to a combination of adaptation (substitution), plasticity, and recovery of hair cells that were damaged but not killed.

After 20 years, most patients are functionally nearly normal for their age. Of course, "most" is not the same as "all", and there is substantial variability in outcome. To some extent this return to "normal" is related to aging of peers as normally vestibular function declines with age, and bilateral vestibular loss most often is diagnosed in persons in their 50's through 70's. 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. (Schubert et al, 2004)

People who get worse -- rarely, people with bilateral loss worsen rather than improve. See this page for more.

Lifestyle and occupational impact:

A change in life style may be needed adjust to reduced balance, and inability to see when the head is in motion. You will want to take precautions to avoid falls.  Symptoms are generally the worst in the first 6 months and get better from then on out. You will not be likely to need to use a wheelchair for your bilateral vestibular loss, or even a walker after two years, unless there is something wrong with you other than bilateral vestibular loss.

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. Adding night-lights and grab-bars is often helpful in the home. It is safer to live in a house where it is not necessary to climb stairs regularly. Uncarpeted basement stairs can be extremely dangerous. If you drive, it is safer to do it during daylight hours.

While it should be OK to walk and chew gum at the same time, it is not such a good idea to carry on a conversation while you are driving (this is multitasking).

Problems with thinking in bilateral vestibular loss:

Bilateral vestibulopathy is almost always an inner ear disease, not a brain disease. Thus thinking problems are generally far less salient than imbalance and oscillopsia. Nevertheless, 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 good vision, due to loss of vestibular input. Others call it "inability to multi-task", or "dual task interference". It is thought that in persons with bilateral vestibular loss, the ongoing extra effort needed to keep ones balance reduces the amount of attention that is available for other thinking tasks. Considerable evidence for this can be found in the literature (Andersson et al, 2003; Pellecchia, 2003; Redfern et al, 2003; Dobbeis et al, 2019). Persons with other vestibular disorders often complain of difficulty concentrating and mental fatigue (Yardley et al. 1998). Of course, symptoms scale with deficit, with severe bilateral loss patients having more substantial problems.

Research

Considerable research is ongoing regarding bilateral vestibular loss.

Presently efforts are ongoing to develop a vestibular prosthesis as well as other projects involving sensory substitution. There is also an emerging literature about noisy galvanic stimulation.

Another class of research involves mechanisms to stimulate regeneration of hair cells within the inner ear. We think that the regeneration projects are more likely to succeed than the prosthesis project, but we think that support of both of these is highly warranted.

Methods of preventing loss through protective agents and predicting susceptibility to gentamicin through genetic testing are also topics of interest.

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.

References: -- also see other ototoxicity references, not directly related to this page