There is compelling evidence that specific exercises are effective in ameliorating the symptomatic and functional problems associated with certain vestibular disorders. There is also evidence that these exercises are not universally effective, some patients do not benefit from these exercises, and furthermore that there are several vestibular disorders for which the use of exercise is not appropriate. This review will explore some of the evidence published in 2011 and 2012 on the application of vestibular rehabilitation therapy. New and promising treatment approaches will also be discussed. Some research published prior to 2011 has been included to provide the necessary background for the review.
EXERCISES FOR PATIENTS WITH VESTIBULAR HYPOFUNCTION
People with unilateral and bilateral vestibular hypofunction typically have subjective complaints of dizziness and dysequilibrium, motion sensitivity, oscillopsia – visual blurring or jumping of the environment during head movement, as well as gait ataxia and imbalance, especially with head movements. Different exercise approaches have been proposed to address these different problems. Habituation exercises are designed to decrease symptoms by systematically provoking those symptoms [1–4]. Adaptation exercises are based on inducing long-term changes in the neuronal response of the vestibular system to a specific error signal – retinal slip. The goals of these exercises are to decrease visual blurring during head movement, improve postural stability, and decrease symptoms. The exercises consist of repeated head movements while fixating a small stationary target or a target moving in the opposite direction of the head movements performed with progressively greater challenges (, pp. 314–315). The third traditional exercise approach, substitution, has patients perform exercises that foster the substitution of alternative strategies to replace the lost or compromised vestibular function. The goal of these exercises, such as performing eye and head movements between two or more targets and the remembered target exercises in which visual fixation is maintained during a head movement performed with eyes closed, is to improve gaze stability during head movement (, pp. 311, 315–316). Finally, most vestibular rehabilitation programs include balance and gait exercises, especially while walking or performing other activities.
Evidence supporting the use of vestibular rehabilitation exercises in the treatment of patients with vestibular hypofunction
A Cochrane Review in 2011 on vestibular rehabilitation added six studies to the 21 identified in the 2007 review . Exercises used in these articles include habituation, adaptation, and substitution. These studies compared vestibular rehabilitation therapy for patients with unilateral peripheral vestibular hypofunction to sham treatments, no treatment, and other forms of vestibular rehabilitation therapy. The patients in all studies were either community dwelling or in-patients following surgery who had been community dwelling prior to admission to the hospital. The authors concluded:
- There is moderate to strong evidence that vestibular rehabilitation therapy is both well tolerated and effective for patients with unilateral vestibular hypofunction (UVH) or loss.
- There is moderate evidence that vestibular rehabilitation therapy is an effective treatment of patients during the acute period after resection of vestibular schwannoma or after vestibular neuritis.
- Improvements have been reported in dizziness, gait and balance, activities of daily living, vision during head movements, and quality of life.
- There is moderate evidence that these improvements are sustained for months after the rehabilitation process ends.
Moving force platform exercise approaches in the treatment of patients with vestibular hypofunction
Several studies have examined whether training balance on force platforms has an added benefit to the more traditional vestibular exercises. Nardone et al.  compared postural control and subjective scores of stability in patients performing Cawthorne–Cooksey habituation exercises and patients performing balance training on an oscillating force platform. Both forms of exercise resulted in improved balance and in decreases in the subjective rating of dysequilibrium. Winkler and Esses  noted that the use of exercises incorporating platform perturbation with changes in foot position and in visual cues and habituation and gaze stabilization exercises resulted in greater improvement than habituation and gaze stabilization exercises alone. Another study compared the effect of computerized dynamic posturography and treatment using optokinetic stimulation in patients with chronic UVH . Both groups improved in the overall posturography score but there were differences noted in the performance based on which sensory cues were altered. Finally, a study by Marioni et al.  demonstrated that gaze stability and weight shifting exercises with biofeedback resulted in improved stability compared to no treatment.
Are different treatment approaches equally effective for vestibular hypofunction?
Only one study has compared habituation and gaze stabilization exercises in the treatment of patients with UVH . This study had a small number of participants (n = 7) and therefore the results should be considered as preliminary. Furthermore, the study did not include gait and balance outcome measures. Nevertheless, in this randomized comparison study patients were treated with either habituation exercises or gaze stabilization exercises (adaptation and substitution exercises). Both groups improved in measures of handicap, motion sensitivity, and visual acuity during head movement [computerized dynamic visual acuity (DVA)]. These findings were unanticipated because while habituation exercises are designed to reduce symptoms, they theoretically should not result in an improved DVA. Similarly, gaze stabilization exercises are expected to improve DVA but not necessarily reduce symptoms, although this has been shown in at least one previous study . The author suggests that the important factor for successful outcome for patients with UVH may be the inclusion of head movements in the exercises.
It is possible that treatment efficacy is not only dependent on matching the exercise appropriately to the patient's problems but also is dependent on the characteristics of the individual patient.
Are there factors that can be identified that are associated with who will and who will not show improvement?
Herdman et al. [13▪▪] examined data from 209 patients with UVH, all of whom had been treated with similar courses of vestibular adaptation, substitution, and balance and gait exercises. As with numerous other studies, the results documented that whereas most patients improve with a course of vestibular exercises, some patients do not improve or improve in only certain areas (Table 1). This prognostic study examined the relationship between patient characteristics, pretreatment measures of subjective complaints, and physical function and treatment outcome. The strength of the relationships between patient characteristics, initial subjective complaints, and initial physical function with outcome measures was determined using bivariate correlation analysis. Factors or groups of factors that influenced recovery were determined using regression analysis. The primary findings of the study were:
- In agreement with previous studies, age did not affect which patients would improve . However, the current study showed that older patients walked more slowly and had poorer visual acuity during head movement than did younger patients at discharge. This was expected because there is a naturally occurring decrement in gait speed and in DVA with age. Older patients were also more likely to remain at risk for falls than were younger patients. This may reflect slow gait speed as that is a component of scoring in the Dynamic Gait Index (DGI) test or it may indicate a lesser degree of recovery in older patients.
- Time from onset was not related to any outcome, supporting the use of these exercises in patients regardless of chronicity. Patients in this study had a mean time from onset of 14.5 months (range 1 week to 12 years; median 5.0 months).
- The presence of different comorbidities did not affect whether or not improvement occurred. The exception was the presence of anxiety and/or depression.
- Several patterns were identified in which multiple factors accounted for significant percentages of recovery of some of the outcome measures.
- Poor subjective complaint outcome: Patients with a high percentage of time symptoms interfered with activities (%TSI) at discharge were those who had anxiety and/or depression and who had a high %TSI at the time of the initial assessment. These two factors together accounted for 83.7% (R 2 = 0.837) of the outcome. Similarly, patients who rated their disability as high at discharge had higher %TSI initially, worse disability scores initially, and poor DVA score initially. These three factors accounted for 47.8% (R 2 = 0.478) of the disability score at discharge.
- Slow gait speed at discharge: Patients who walked more slowly at discharge had slower gait speed initially and were older. Approximately 55% of gait speed at discharge was accounted for by those two factors.
- Fall risk: Patients had lower (poorer) fall risk scores at discharge, as measured by the DGI test, if they had a history of falls, had poor fall risk scores initially, and were older. These three factors accounted for 42.5% of DGI at discharge. Interestingly, initial DVA score, which has previously been show to predict fall risk at discharge, was not a significant factor .
The results of this study provide guidelines that therapists and other clinicians can use to develop expectations for recovery. More research is needed, however, to determine other factors that may explain treatment outcome such as psychological factors including coping mechanisms and personality traits that may affect recovery. The identification of factors that influence recovery should lead to different and more effective treatment protocols.
‘Vestibular rehabilitation’ for patients with nonvestibular dizziness
The use of the some of the vestibular rehabilitation exercises appears to have benefits in people with nonvestibular imbalance and dizziness. A randomized placebo controlled trial studied older people with nonvestibular dizziness who performed a 6-week course of either balance exercises or balance exercises and gaze stabilization exercises . They found that both groups improved in all outcome measures; however, the group that performed the gaze stabilization exercises had a significantly greater improvement in fall risk compared to the balance exercises only group.
Although there is insufficient evidence at this time to determine the benefits of the use of exercises in the virtual reality environment, the possibilities are promising. For example, virtual reality environments can be used to help patients who have difficulty maintaining balance while walking in a busy visual environment. Gaming paradigms are also being used in the treatment of patients with vestibular hypofunction . Another anticipated intervention for patients with vestibular loss is the development of implantable vestibular prostheses . These prosthetic devices will require the therapist to re-examine which vestibular exercises will be most effective.
VESTIBULAR REHABILITATION OF PATIENTS WITH BENIGN PAROXYSMAL POSITIONAL VERTIGO
Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo due to a peripheral vestibular disorder. It is especially common in older persons, making it important that physicians screen for this disorder considering our growing older population.
Treatment of posterior semi-circular canal benign paroxysmal positional vertigo
The effectiveness of exercises for the most common form of BPPV, posterior semi-circular canal canalithiasis, is supported by a Cochrane review and other systematic reviews. A Cochrane review noted that the canalith repositioning maneuver (CRM) was both well tolerated and effective as a treatment for posterior canal BPPV  and a systematic review by Helminski et al.  similarly concluded that the canalith repositioning procedure is more effective than sham treatments in managing posterior semi-circular canal canalithiasis. Furthermore, both the American Academy of Neurology and the American Association of Otolaryngology and Head and Neck Surgery published practice guidelines and concluded that the CRM was an effective treatment for posterior canal BPPV [21,22].
The original canalith repositioning procedure included detailed post-treatment instructions, such as the patient was to remain upright for 48 h after the treatment. Numerous studies suggested that these post-treatment instructions are unnecessary. A 2012 Cochrane review, based on nine papers, concluded that although there was a statistically significant improvement in outcome when the post-treatment instructions were used, the difference was so small that the use of these post-treatment restrictions was optional .
Although strong evidence supports the use of the CRM for the treatment of posterior semi-circular canal BPPV (PC-BPPV), there has been little evidence supporting the use of an alternative treatment, the Liberatory (Semont) maneuver. Fortunately, two recent, randomized, placebo-controlled, double-blinded studies reported a significantly greater percentage of remission following using the Liberatory maneuver (86.8 and 84% remission, respectively) compared to the sham treatment groups (0 and 14% remission, respectively) [24▪▪,25▪▪].
Advances in the treatment of horizontal semi-circular canal benign paroxysmal positional vertigo
One of the difficulties of successfully treating patients with horizontal semi-circular canal BPPV (HC-BPPV) has been the determination of which side is the affected side. Historically, in the canalithiasis form the affected side is the most symptomatic side, and in the cupulolithiasis form the affected side is the least symptomatic side. In 2006, the ‘bow and lean test’ (BLT) was proposed as an addition to the roll test to identify the affected side in HSC-BPPV . In the BLT, the roll test is performed first to determine whether the BPPV is canalithiasis or cupulolithiasis based on the duration of the nystagmus. The BLT is then performed to determine the affected side by observing the direction of the nystagmus in the bow and lean positions. Lee et al.  found that the use of the BLT with the roll test increases treatment efficacy from 67.4 to 83.1% for the canalithiasis form of HC-BPPV and from 61.1 to 74.7% for the cupulolithiasis form of HC-BPPV.
For the most part, evidence of treatment efficacy for treatment of HC-BPPV canalithiasis has been weak, with no control groups or with control groups consisting of patients who refused treatment or who could not be treated. Recently a randomized study examined 170 consecutive patients with HC-BPPV canalithiasis . The authors reported that both the roll treatment and the Gufoni maneuver resulted in a higher remission rate (69.1 and 60.9%, respectively) than a sham treatment (35.4%) on the initial day of treatment. At 1 month after treatment, treatment efficacy for both the roll and the Gufoni treatment group was still significantly better than the sham treatment group. Another study compared the Gufoni maneuver to a modification of the Gufoni maneuver in which patients moved to the sidelying position in stages rather than in a single rapid movement . Treatment of the modified Gufoni resulted in a similar rate of remission (93%) as treatment with the original Gufoni maneuver (88%). However, the modified Gufoni resulted in only a 2% conversion to PC-BPPV compared to a 16% rate for the original Gufoni maneuver .
A final note
For better or worse the treatment of BPPV has moved into cyberspace. Kerber et al. [30▪] noted that in 2011 there were 33 videos on YouTube that demonstrated the CRM. The ‘good’ news is that the video with the most ‘hits’ (over 800 000) was one that accurately demonstrated the CRM. The ‘bad’ news is that 36% of the videos were considered by the authors to inaccurately demonstrate the treatment. The ease of access to videos on YouTube may enable patients to review treatments that they perform at home. However, access to inaccurate information may delay appropriate treatment and recovery.
Although there is an increasing body of knowledge supporting the use of vestibular exercises, there are certain important questions that remain unanswered. First, we do not understand the mechanisms underlying the improvement that occurs with various treatment approaches for patients with vestibular hypofunction. Identifying the underlying mechanisms should lead to the development of better treatment approaches. We do not know why some patients with vestibular hypofunction do not improve with a course of vestibular exercises. Although we have strong evidence for treatments for PC-BPPV, and some evidence that supports certain treatments for HC-BPPV, we do not have similar evidence for treatment of anterior canal BPPV nor for multiple-canal BPPV.
Conflicts of interest
The author has no financial conflict of interest with material presented in this paper. The author is the primary author on one of the studies discussed in this paper. This work was not sponsored by any funding agency, organization or person. The author is an investigator on a grant pending review through the Veterans Administration that will study patients with vestibular hypofunction.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
- ▪ of special interest
- ▪▪ of outstanding interest
Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 107).
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