A short guide to vestibular testing and rehabilitation
By Richard E. Gans
COMMON ACRONYMS
BPPV Benign Paroxysmal Positional Vertigo
CRM Canalith Repositioning Maneuver
ENG Electronystagmography
SLM Semont Liberatory Maneuver
VNG Videonystagmography
VOR Vestibulo-ocular reflex
VOG Video-Oculography
VRT Vestibular Rehabilitation Therapy
implemented Gans Repositioning Maneuver (GRM).
1 There seems to be increasing interest recently in vestibular testing and treatment. How do you account for this?
I believe it is consumer driven. There’s an old adage that dizzy patients don’t get better; they simply go to different doctors. The average patient with a condition as simple to diagnose as Benign Positional Paroxysmal Vertigo (BPPV) seeks medical attention from an average of 4.5 physicians before getting a diagnosis.1
Unlike persons with hearing loss, the dizzy patient does not present with denial and projection. Often, the diagnosis is simple and straightforward; however, until recently, vestibular testing was often an afterthought. Another factor is the advent of the Internet, which enables consumers to access information on a variety of topics, including dizziness and balance dysfunctions and treatment options.
2 Are third-party payers covering vestibular testing?
Yes, and that’s a good point. Another reason for increased interest is medical economics. After headache and backache, dizziness ranks as the third most common complaint heard in physician’s offices for all age groups.2 And, among patients 70 years or older, dizziness is the number one complaint. This suggests that third-party payers, Medicare, and frustrated healthcare professionals are constantly being challenged by patients who present with chronic symptoms that are radiographically negative, who are not candidates for surgery, and who have not responded to pharmacologic management. I believe that this has also created increased interest.
3 What are the most common causes of vestibular problems?
By far the most common cause of vertigo is BPPV. It is estimated that by age 70, 50% of all people will experience BPPV.3 BPPV does not occur exclusively in the elderly; it is also very common in younger individuals. BPPV is most often seen following an inner ear involvement such as vestibular neuronitis, labyrinthitis, or Meniere’s disease.4 It may be observed in any age group after even mild head trauma. Among younger folks, the most common cause of vestibular involvement is vestibular neuronitis. This is a viral inflammation of the vestibular portion of cranial nerve VIII. It has also been linked to seasonal air-borne allergies, as well as having a close relationship with the herpes simplex B virus.
4 Do vestibular disorders also cause hearing loss?
Vestibular neuronitis causes no hearing loss, which is one of several factors differentiating it from Meniere’s disease and labyrinthitis, which have a hearing loss component. Gans Labyrinthitis is an infection of the fluid of the inner ear and may be caused by either bacterial or viral involvement. Labyrinthitis patients tend to be more acutely ill than vestibular neuronitis or even Meniere’s patients, and may need weeks to recover from the illness. Although Meniere’s disease gets a lot of attention, investigators and clinicians are re-thinking the diagnosis of Meniere’s in females who also present with a history of migraines. The literature suggests that what we previously believed to be vestibular Meniere’s may, in fact, be a form of migraine equivalent.
5 I’m not familiar with the term “migraine equivalent.” What is it, and how does it relate to vestibular problems?
Reclassification by the International Headache Society indicates that migraine with auras can mimic a variety of vestibular problems such as vestibular neuritis or Meniere’s. Vertigo, hearing loss, and tinnitus are several auras listed by that organization.5 An aura is defined as a focal neurological dysfunction affecting sensory perceptions. Migraine auras may be caused by vasoconstriction of blood flow to the ear or the brainstem or be due to neurochemical problems related to serotonin levels that affect the neural synapse. Many migrainous patients develop symptoms of phonophobia and photophobia as part of their attack. Frequently these patients do not have the acute headache, but rather aura ymptoms, making diagnosis more complicated. Migraine can cause permanent hearing loss and vestibulopathy.6
6 In general, are there common histories or symptoms with vestibular patients?
The hallmark of the vestibular patient is usually an indelible memory of at least one (often the first) occurrence of an acute attack of vertigo. This often was accompanied by nausea and emesis. Over time, as patients move from the acute to the chronic phase (if they have a stabilized condition), their symptoms may be provoked or exacerbated by quick head movements, moving visual stimuli, change in head or body position, or increased motion sensitivity. We have also noticed that patients who report a lifelong and often familial history of motion sensitivity may be predisposed not to compensate following a vestibular disorder as easily or completely as others with the condition.
7 What are the most helpful tests for evaluating the vestibular patient?
It really depends on the nature of the problem. There is no instrumentation that provides a definitive diagnosis of BPPV. The diagnosis is made by the clinician’s observation of the rotatory-torsional nystagmus created by the positioning used to elicit the patient’s symptoms. However, infrared video-oculography, the latest and my personal preference for assessment, does not necessarily provide a quantifiable or template type of response. In reality, the best piece of instrumentation is the one between the clinician’s ears. VNG or videonystagmography (perhaps better termed “video-oculography” because we are looking at video of all eye movement) has been a great advance. We are no longer dependent on a vertical and horizontal axis graph from which to extrapolate what we believe is happening beneath closed eyelids. A good example is BPPV, which produces predominantly a rotatory-torsional nystagmus. In traditional corneo-retinal potential recording, as with ENG, the horizontal recording showed a right-beating nystagmus and, in the vertical channel, an upbeat nystagmus. This was really the upward rotation that occurs with a posterior canal BPPV. However, the technologic limitation of the corneo-retinal potential type recording made it unable to provide a true representation of what was occurring. Over the years, ENG, and now VNG, were considered the primary tests of the vestibular function. They have their own limitations, however. For example, the caloric test, which is considered the barometer of labyrinthine function, tests the horizontal canal only at its lowest frequency sensitivity, around .003 Hz. To use an audiologic analogy, this is like performing hearing testing only at an ultralow frequency and then trying to
extrapolate from that the hearing acuity of the patient through the important mid to- high speech frequencies. Similarly, it is quite possible to have a mid-to-high-frequency vestibulopathy that would not be revealed through a caloric weakness.
8 That sounds like a problem. So, how do we test for a high-frequency vestibular problem?
Most patients with uncompensated vestibulopathy complain of gaze-stabilization problems with head movement.
A rotary chair is helpful, but is limited to a sinusoidal harmonic movement of about 1.25 Hz. The vestibulo-ocular reflex (VOR) really begins at under 2 Hz. Thus, even a sophisticated rotary chair does not provide evaluation of the entire spectrum of vestibular sensitivity. A vestibular dysfunction due to an uncompensated loss or hypofunction causes abnormal VOR gain and/or phase. The result is oscillopsia, which is an inability to maintain focused vision with head movement. It can also occur in patients with a condition of neurologic origin who have a spontaneous nystagmus. So the oscillopsia is present even without head movement.
9 Let’s go back to BPPV. Is the incidence higher in patients with other ear pathology?
Absolutely, particularly in younger individuals. We have now come to think of BPPV as an indication to look for other
problems within the cochleovestibular system. There is a possibility that the otolith degeneration in the utricle, whether it is vascular or viral, may have a more ominous underlying cause than merely the individual’s difficulty with the electrochemical calcium absorption of excessive otoconia in the posterior canal. That’s why, even with a patient who is referred to us for treatment of BPPV, we like to have a complete auditory, vestibular, and electrophysiologic evaluation to ensure that nothing has been missed.
10 Are there different types of BPPV?
Yes, several. The good news is that approximately 95% of patients experiencing BPPV will have a posterior canal involvement. The posterior canal is the one most likely to catch the degenerated otoconia from the utricle because of its anatomic position. The posterior canal somewhat resembles a trap drain below your kitchen sink. However, sometimes there is a horizontal canal involvement. This is fairly rare (occurring approximately 5% of the time), and when a patient does have a horizontal canal BPPV, it is usually due to migration during a Canalith Repositioning Maneuver (CRM). Anterior canal BPPV is very rare. In our practice, in treating over 1200 BPPV patients, we’ve seen it perhaps a half-dozen times. The other consideration is whether the BPPV is of the cupulolithiasis or the canalithiasis form. The theory of cupulolithiasis is that the otoconia debris adheres to the cupula and causes an abnormal shearing of the hair cells due to the additional weight. Over the past decade, since the publication by Parnes and McClure,7 we now see that most patients with BPPV have a canalithiasis variant. The debris is free-floating and moves easily through the long process of the posterior canal rather than adhering to the cupula.
11 Slow down a moment. Posterior or horizontal canal? Cupulolithiasis or canalithiasis? How do you differentiate the various forms of BPPV?
In most cases it’s fairly straightforward. The predominantly rotatory torsional nystagmus created by BPPV is not suppressed by vision and can be seen in patients by direct visual observation. However, the recent introduction of infrared video-oculography has been invaluable in allowing us to see the nystagmus clearly and to videotape it for additional review.
The semicircular canals innervate the corresponding intra-ocular eye muscles. The vertical canal involvement results in vertical eye movement, and the horizontal canals produce horizontal eye movement.
That is why the posterior canal form of BPPV causes a rotatory-torsional nystagmus with an upward bounce. Conversely, anterior canal BPPV causes a downward bounce. Horizontal canal BPPV produces a linear horizontal form of nystagmus with a fast phase occurring toward the affected undermost ear. This occurs when the patient is placed in a lateral position. With this in mind, the cupulolithiasis variant with repetition will not fatigue because the debris remains adhered to the cupula until it is released through a Liberatory-type maneuver. The canalithiasis will decrease in severity, both in subjective vertigo and in the strength and intensity of nystagmus with repetition.
12 If BPPV comes in different forms, then do the treatments for this disorder also vary?
Yes. Canalithiasis is the most common variant of BPPV, and may be treated successfully with all of the Canalith Repositioning/Liberatory maneuvers or modifications. The most commonly utilized CRM is the one reported by Herman et al. in 1993.8. This is a single-treatment process our clinic has used (with some minor modification) with great success. Semont’s Liberatory Maneuver (SLM) has also been found highly efficacious for this form of BPPV.9
Recently, we have developed a treatment combining the Canalith Repositioning (CRP) and Liberatory maneuvers.
The great advantage we see in our new method is that it avoids the patient’s having to be hyper-extended. Unlike the
SLM, which requires the patient to be moved in one sweeping action from one lateral position to another in a 180° arc,
we simply have the patient roll from one side to the opposite side, as one does when rolling over in bed. We have treated 115 patients, and the outcomes have been as good as they were with our previously treated 1000+ CRP and LM patients. Cupulolithiasis, because of the adherence of the otoconia to the cupula, has been thought to depend on some additional inertia, requiring the patient to be moved somewhat more briskly. This is why the SLM has been determined to be the most efficacious treatment for this variant. However, our recent experience with 115 patients suggests that, rather than the brisk lateral 180° arc movement of the SLM, a simple side-to-side head movement when the patient is placed in a secondary position may be sufficient.
13 Do most patients have BPPV in only one ear?
Yes, Our experience suggests that 90% or more of patients present a unilateral condition. However, we have seen an increased incidence of bilateral BPPV in patients whose condition is secondary to head trauma. Also, it is not uncommon for a patient to have a right-ear BPPV, have it successfully treated, and then return 2 years later with
a left-ear BPPV.
14 What do you do if the patient has BPPV in both ears?
In the past, I have treated one ear at a time, with a 1-week interval between treatments. This gave the patient ample opportunity for the first affected ear to be treated along with some recovery time. When the patient returned for the follow-up visit, I would make sure that the first ear treated was clear, then recheck the other ear. If that ear was still positive, we would proceed to treat it. I recently treated a 92-year-old female in-patient in our day hospital program.
Her unrelated but lifelong motion intolerance resulted in acute nausea and emesis. She was sedated with 0.5 mg of Ativan so she could better tolerate the treatment procedure. The attending physician asked if it would be possible to treat both ears the same day to spare the patient from undergoing a second sedation. I treated her with a repositioning maneuver in the right ear, and immediately treated the left ear without waiting the customary week’s interval. She was rechecked a week later and was clear in both ears. She is still doing fine and is participating in a wellness program.
15 Are your results with BPPV patients always that successful?
In general, the results have been consistently good for all treatment methods. When we look at our 1200 patients, we
observe little or no difference among the outcomes of the three treatment methods we have been using over the past 10 years. Our data indicate that, on average, approximately 1.3 treatments are required, whether we use CRM, SLM, or the recently implemented Gans Repositioning Maneuver (GRM).
We have found that 80% of our patients require only one treatment to be successfully cleared. Approximately 17%
of patients need a second treatment, and only 3% need three or more treatments. We have followed 376 patients over a
7-year period looking at recurrence rates. While we have found no differences in treatment efficacy, we did see a variation in the recurrence rates in patients treated with the SLM versus those treated with the CRM.10 We have not had any horizontal canal migration with either the SLM or GRM. The only horizontal canal migrations we have found have been related to a Canalith Repositioning Maneuver. This is likely the result of the patient’s head being moved from Position 1 to Position 2. If the patient’s head is lifted too high or if the patient tries to assist the clinician, it seems to make migration more likely.
16 Is vestibular rehabilitation appropriate for all patients with vestibular problems?
Since the original articles by Cawthorne11 and Cooksey12 in the 1940s, there have been scores of articles demonstrating the efficacy of vestibular rehabilitation. Over the past decade, we have become more sophisticated in the application of such therapy. It is most suitable for patients who present with stabilized but uncompensated vestibular problems subsequent to some type of labyrinthine event such as vestibular neuronitis, labyrinthitis, or labyrinthine concussion. It is also ideal for many patients who were treated with Gentamicin for intractable Meniere’s disease or have had acoustic neuroma surgery. It is not suitable for patients in the throes of an active disease process who require pharmacologic or surgical management.
17 From a physiologic standpoint, exactly how does vestibular rehabilitation work?
Vestibular rehabilitation has some resemblance to tinnitus retraining treatment, as it is based on neurophysiologic programming. At the level of the brainstem and cerebellum, we are asking the central vestibular pathways to recognize the asymmetry of the impaired peripheral vestibular systems, and then to reset the vestibular ocular reflex (VOR) gain. This is accomplished through adaptation and habituation. Adaptation can best be described as an accommodation of the central nervous system to the disparity between the signals. Habituation results in a reduction of the severity or noxious aspect of the stimulus, also through the central nervous system’s repeated exposure to it. I like the term “diagnosis-based strategies.”13 Rather than merely treating the patient’s symptoms, one applies a specific set of protocols based on the underlying physiologic and functional problems. Others have referred to this as individualized or programmatic therapy.14
18 What is your thought process in determining treatment plans for vestibular rehabilitation?
I am a firm believer in the use of clinical pathways and critical decision analysis protocols. (Figures 1 and 2.) It is like using a road map to plan a trip. If you want to arrive at your destination in the most efficient manner possible, you must understand all the routes and alternatives available. The thought process begins with an understanding of the physiologic dysfunction presented by the patient. Then, as the process continues, we apply diagnosis-based strategies to address the treatment of BPPV, uncompensated unilateral vestibular dysfunction (with or without a concomitant balance problem), as well as bilateral vestibular dysfunction or other multifactorial involvements. Our role in treating the multifactorial patient is to help the physical therapist understand if there is sufficient peripheral vestibular function to use substitution protocols. Upon completion of the treatment, we also have an array of outcome measurements indicating the efficacy of the treatment.
19 How does the audiologist working with the vestibular patient fit into the healthcare ommunity?
The answer varies somewhat from practice to practice. At our clinic, we enjoy an outstanding working relationship with both physicians and physical therapists.
Our role is to serve as a resource to the medical and rehabilitation community in appropriate triage and management for
the vestibular patient. More than 400 physicians, including otolaryngologists and neurotologists, regularly use our diagnostic and treatment services. Most (75%) of our patients come to us through medical referrals. Often, patients have already undergone comprehensive radiographic, blood work, cardiology, and neurology studies, which makes our job much easier.
Figure 1. Positive vestibular history and symptoms begin the clinical pathway process for testing and treatment triage.
Figure 2. Test results differentiate vestibular from non-vestibular patients. Diagnosis-based strategies then may be applied to each type of vestibular dysfunction.