Progressive Bilateral Vestibular Loss (PBVL)

Timothy C. Hain, MD Page last modified: February 16, 2023

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

This page is to discuss a very rare situation - -progressive bilateral vestibular loss. Bilateral Vestibular Loss is a rare condition - -Ward reported that it affects about 28/100,000, but this number doesn't seem to us to be very reliable. This suggests that progressive bilateral vestibular loss must be even rarer. We have reviewed bilateral vestibular loss in an article in Frontiers in Neurology -- see here.

We have seen many patients with bilateral vestibulopathy (generally not progressive), over about 30 years. The figure below shows data from a 176 patient subset of our entire database compiled in 2014. This data is being actively updated and does not include all of our patients, as this is a big project. These are all patients referred for clinical diagnosis. It does not include patients referred through medicolegal review activity.

Pie

As can easily be seen, the majority of cases are "idiopathic", and the second largest group are aminoglycoside ototoxicity (i.e. gentamicin+tobramycin+streptomycin).

Most of these patients are "one-offs" and idiopathic.

In recent years, a new quick test for bilateral vestibular damage has become available, the VHIT test. This is a reasonable method of detecting severe vestibular damage on one or both sides. It works best for the lateral semicircular canal (there are three semicircular canals), and cannot be trusted for the other "vertical" canals. We hope that this will improve.

Because it has been possible in recent years (i.e. 2016 on) to rapidly diagnose severe vestibular damage, we now are able to follow people over time, and have found a few people in whom both ears are getting worse -- i.e. they have progressive bilateral vestibular loss.

Example of PBVL:

A man in his 30's complained of oscillopsia (seeing the world move when the head is turned). Vestibular testing at that time documented very substantial vestibular loss -- his rotatory chair test showed poor gain and increased phase at all frequencies. There was no question at all that he has partial bilateral loss. Hearing was almost normal, with no changes over several years. cVEMP testing was normal.

Progression of bilateral loss
Initial VHIT Second VHIT
First VHIT test -- patient had oscillopsia. Second VHIT done 6 months later

The two VHIT tests done above show worsening, in both ears, over 6 months. (they look a little different due to a software change, but they are the same device.

Another case example is here.

Differential Diagnosis

Progressive bilateral vestibular loss is a small subset of the already rare patients with bilateral vestibular damage. It seems likely that more of these patients will be seen due to improved technology (i.e. VHIT).

Practically, about half of cases with bilateral vestibular loss are undiagnosed, and to our knowledge, few have attempted to reason about progressive bilateral vestibular loss. One would expect that there are patients with vestibular hair cell disease (such as aminoglycoside ototoxicity), patients with nerve disease (such as bilateral vestibular neuritis), and patients with brainstem disease (such as Wernicke's).

Lets consider specific causes: (see also a more general discussion of bilateral loss causes)

Aminoglycoside ototoxicity:

One might reasonably consider ototoxicity from aminoglycosides (easily identified from exposure history). Toxicity from aminoglycosides is "over" within 2 years -- people experience damage, and recover as much as is practical.

Genetic causes of bilateral vestibular loss:

Jen (2009) reviewed a tiny collection of families with inherited bilateral vestibulopathy with normal hearing. These included 3 dutch patients reported by Verhagen and colleagues(1987), the 3 families reported by Baloh (see above), and a Swedish family reported in 2003 by Brandtberg. In the Swedish family, most had normal VEMPs (implying that it may actually have been bilateral vestibular neuritis).

There are other progressive genetic disorders, usually involving both hearing and vestibular, or vestibular and cerebellar. For an example of the latter, there are several spinocerebellar atrophy genetic variants. Other cerebellar syndromes with bilateral vestibular loss such as SCA-3 (Machado Joseph), SCA-7, and Friedreich ataxia have overlapping symptoms. The CANVAS syndrome may be inherited (another one with cerebellar disturbance). However, purely sensory syndromes that affect dorsal root ganglia can cause ataxia.

There is a rare variant of inherited bilateral vestibular loss that begins with migraine and episodic vertigo. This syndrome responds to acetazolamide (Baloh et al, 1994). We have found a few of these in our own practice. It is presumably reportedly dominantly inherited. Thus, hard to miss in a family.

Autoimmune disorders:

Autoimmune ear disorders including bilateral Meniere's (progressive bilateral is rarely encountered). Little is understood about these. Once Meniere's is excluded, it generally is not even known if they are hair-cell or nerve disease. As a general rule though, if a person has purely vestibular damage (i.e. normal hearing, reduced vestibular function on one or both sides), it is probably not going to be autoimmune in origin, because autoimmune diseases attack the entire inner ear -- both hearing and vestibular function. If a person has bilateral vestibular loss alone, an autoimmune mechanism is very unlikely, even in the face of having a clear cut autoimmune disease (such as Rheumatoid arthritis).

A potential connection in this situation is that patients on immune suppressant medications (common in RA and other autoimmune disorders), it may reduce the persons ability to ward off viral damage to the vestibular nerve, such as from the herpes family of viruses as well as from Zoster (the chicken-pox virus). This may explain the connection between pure bilateral vestibular loss and autoimmune conditions. If this idea is correct, then increasing the intensity of immune suppressants in these patients would be unlikely to help.

Vestibular Nerve disease:

In theory, there might be chronic and progressive vestibular inflammation (i.e. bilateral vestibular neuritis -- difficult to be sure lacking autopsy data),

Dorsal root ganglion disorders that also affect the vestibular system such as the CANVAS syndrome.

Practically, it is extremely rare to encounter both progressive deafness and bilateral vestibular loss. Occasionally this occurs post bacterial meningitis -- ossification of the labyrinth is fairly quick. Another rare context is Cogan's syndrome, where again the labyrinth is obliterated. There are few hereditary disorders with known mutations where this occurs.

Clinical Approach to PBVL

Diagnostically, it seems reasonable to attempt to determine what exactly is getting worse (i.e. horizontal canals are tested with VHIT, otoliths are tested with cVEMP and oVEMP, and hearing is tested with audiometry and OAE). When there is reasonable suspicion for inflammation, a sed-rate, and autoimmune panel seem reasonable. Other blood tests are routine but rarely productive (such as for sarcoid or syphilis).

What we don't think is reasonable as diagnostic testing:

  • MRI scans (other than the first one)
  • CT scans of the temporal bone (unless there is known ear disease impairing hearing).
  • Blood testing for cancer
  • Genetic testing unless there is a reasonable suspicion of a particular familial disorder.
  • Cardiac testing of any kind

Treatment of PBVL

Therapeutically, patients should be referred for vestibular PT, or at least encouraged to perform vestibular exercises. Eventually everyone should be doing home exercise programs.

Trials of medication including steroids, antivirals seem reasonable. These are unproven treatments and one must consider the side effects.

Investigational approaches for progressive bilateral vestibular loss.

Eventually, treatments that regenerate inner ear hair cells may be useful for patients who have vestibular hair cell disease. Patients with aminoglycoside toxicity might benefit. Patients with bilateral nerve disease would naturally not improve.

Treatments that involve implantation of stimulators of the vestibular nerve might work for aminoglycoside ototoxicity. For vestibular nerve damage, it would also likely fail, because if the nerve is damaged, it will not conduct information to the brainstem.

 

References