Role of Audiologists in Vestibular and Balance Rehabilitation: Technical Report
ASHA Ad Hoc Committee on Vestibular Rehabilitation
About this Document
This technical report was prepared by the ASHA Ad Hoc Committee on Vestibular Rehabilitation and adopted by the ASHA Executive Board (EB 63-98) in November 1998. Members of the committee include Nancy P. Garrus; Eric B. Hecker; Kenneth G. Henry; Susan Herdman, PhD, PT, consultant; Neil T. Shepard, chair; Charles W. Stockwell; and Maureen E. Thompson, ex officio. Richard Nodar, vice president for professional practices in audiology, served as monitoring vice president.
The majority of patients with an acute balance disorder recover spontaneously with only symptomatic treatment from the medical community (Igarashi, 1984; Pfaltz, 1983). For reasons that are poorly understood, some of these patients develop chronic balance system problems requiring significant intervention from a variety of medical and surgical specialists to evaluate and manage their disorder.
Vertigo and balance disorders constitute a significant public health problem in the United States. It is estimated that the number of persons in the U.S. seeking medical care for disequilibrium or vertigo ranges as high as seven million per year. Approximately 30% of the U.S. population have experienced episodes of dizziness by age 65 (Roydhouse, 1974). There are indications that the incidence of balance disorders is increasing, particularly as the population ages (Herdman, 1994; Kroenke & Mangelsdorff, 1989). Another compelling issue is the increased incidence of falls with aging. Balance disorders and dizziness are important risk factors for falls in this population. Among community-dwelling elderly between ages 65 and 75 who do not report any major health problem or acute balance disorder, at least 25–35% report a significant fall annually. For persons more than 75 years old, those who report a significant fall at least once per year rises to 32–42%. The rates become significantly higher for those who have any type of impaired mobility including acute or chronic balance disturbances. Although most falls do not result in serious injury, 18.6 of 1,000 falls for those 60–65 years of age, and 55 of 1,000 falls for those more than 65 years require medical attention. It is estimated that falls are the leading cause of accidental death for those more than 65 years of age. Since it can be inferred from epidemiological studies that balance disorders increase the probability of an injurious fall, the management of balance disorders in the elderly population becomes a critical issue (Blake, Morgan, & Bendall, 1988; Tinetti, Speechlay, & Ginter, 1988).
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Vertigo or disequilibrium may persist due to poor central nervous system compensation after any acute injury to the vestibular system, even if there is no ongoing labyrinthine dysfunction. In addition, some patients will develop maladaptive postural control strategies that are destabilizing or bothersome in certain settings. These patients often benefit from a program of vestibular and balance rehabilitation. Such programs are most effective when customized to the needs of the individual patient. Typically, appropriately trained physical or occupational therapists supervise these programs. The use of exercises in the rehabilitation of patients with vestibular disorders dates back to the 1940s (Cawthorne, 1944). The justification and development of this management technique for this group of patients have been largely anecdotal. Recent work has refined the techniques and expanded the applicable patient population. The result is a firm documentation of the efficacy of the use of vestibular and balance rehabilitation programs for the management of patients with balance and dizziness complaints.
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The use of vestibular and balance retraining programs as a management strategy for the patient with balance disorders and/or dizziness is described in this technical report. In addition, the currently recognized knowledge and skills needed by an audiologist to (a) perform and interpret the assessment of balance disorders and (b) develop a treatment plan for vestibular and balance rehabilitation programs are delineated. The knowledge and skills outlined may not be all-inclusive, as the area of vestibular and balance rehabilitation is still evolving.
Clinical certification by the American Speech-Language-Hearing Association (ASHA) ensures that audiologists have met the entry-level education, knowledge, and experience requirements established by the Association for providing clinical services in the profession of audiology. In order to perform the clinical procedures in this technical report, audiologists typically possess knowledge and skills beyond those obtained in “entry level” education.
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Vestibular rehabilitation is a formulation of exercise activities, customized to the needs of the patient, based on movements of the head and/or eyes, or environmental visual movements that provoke symptoms of disequilibrium, vertigo, etc.; and functional deficits that involve static and dynamic balance, and/or gait activities. The formulation of the exercise activities is based on both animal and human experimentation involving basic scientific and controlled clinical studies. The exercise activities can include but are not limited to:
Habituation activities focused on specific planes of motion that are provocative for symptom production, or visual motion that provokes symptoms;
Canalith repositioning procedures (CRP) (various methods of specific movements of the head and body designed to reposition otoconia and/or other material from abnormal location in one of the semicircular canals back into the vestibule region) for benign paroxysmal positional vertigo (BPPV);
Vestibulo-ocular reflex (VOR) exercises that push the VOR system for maintenance of appropriate gain of the VOR or for increasing the VOR gain; and
A variety of gait and both static and dynamic balance activities.
The global goal of vestibular and balance therapy is to promote the system's natural central compensation process that reduces, and in some cases eliminates, symptoms for the patient with chronic dizziness and/or balance disorder. The process also involves techniques that can be useful in the reduction or elimination of symptoms for certain types of acute peripheral vestibular patients. Although most helpful for peripheral vestibular lesions with specific symptom presentations, the research to date suggests efficacy for a wide variety of lesion sites, with symptom presentation more critical than site-of-lesion for patient selection.
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Although the specific goals of a therapy program vary with the specific patient, the general goals of a vestibular and balance rehabilitation program are to:
Promote central vestibular system compensation process.
Reduce the patient's sensitivity to head, eye or visual motion activity that produces symptoms of vertigo, disequilibrium, unsteadiness etc.
Reduce risk for falls by improvement in static and dynamic balance, and gait activities.
Improve the maintenance of the compensation process via increased lifestyle activities associated with head and eye movements.
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Current knowledge about the process of central compensation for vestibular lesions suggests that avoidance of movements and body positions that provoke vertigo, as well as the traditional practice of prescribing vestibular suppressants for these patients, may be counterproductive. The stimulus for recovery from an acute vestibular lesion seems to be repeated exposure to the sensory conflicts produced by movement (habituation). Therefore, once the severe symptoms are resolved, the patient's medications should be discontinued and an informal program of increased activities that help toward recovery should be encouraged. For most individuals, recovery will be rapid and nearly complete. For some, the symptoms of vestibular dysfunction may persist. These patients with chronic balance disorders are candidates for formal programs of vestibular rehabilitation. Four features of the nervous system underlie the physiologic basis behind vestibular rehabilitation. These qualities, which collectively enhance the therapeutic effect of specific, customized exercise programs, are:
Adaptive plasticity of the central nervous system for balance system control. Examples of adaptive plasticity include modifications of postural control, the VOR, and the ocular control mechanisms for saccades. These activities take advantage of short-term central nervous system adaptation to produce a change in the automatic mapped response to a familiar stimulus (Zee, 1994). To accomplish this, repeated exposures to particular environmental conditions or specific stimuli are needed. This factor is exploited primarily for treating disorders of postural control and gait difficulties.
Central sensory substitution involves the nervous system's limited ability to substitute one sensory input (vision, vestibular or somatosensory/proprioception) for another one that is virtually absent. For example, vision may substitute for loss of cutaneous proprioceptive inputs in the plantar surface of the foot, or it may help control eye movements in patients with bilateral peripheral vestibular system paresis. Although many patients naturally use substitution, some may require specific targeted activities from a vestibular rehabilitation program to optimize this effect.
Tonic rebalancing of neural activity at the level of the vestibular nuclei, in response to a persistent asymmetry of input from the two sides of the peripheral vestibular system. This usually results from an acute peripheral system insult or an ablative surgical procedure. The acute (“static compensation”) phase of recovery should take place without active head movement exercises. However, some patients fail to progress through the chronic (“dynamic compensation”) phase and require a formalized program of head movement exercises to promote this process.
Habituation is a long-term reduction in a neurologic response to a particular noxious stimulus that is facilitated by repeated exposure to the stimulus. In the vestibular system, the unpleasant response is usually a vertiginous sensation, often associated with nausea, in response to certain head movements. Even with the mechanisms described in numbers 1–3 firmly in place and functioning properly, deficiencies in the overall compensation process may persist. If so, certain specific head movements, position changes, or motion in the visual environment may predictably provoke brief spells of vertigo or disequilibrium. To reduce or eliminate these undesirable responses to daily activity, habituation exercises are prescribed that repeatedly expose the patient to the stimuli that provoke the abnormal responses. When this process is complete, the changes appear to be long-lasting (Smith-Wheelock et al., 1991).
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The utility and success of vestibular rehabilitation programs appear to be population-specific. Generally patients with uncompensated or decompensated unilateral peripheral lesions have the best overall prognosis. The percentage of patients who dramatically or completely improve increases from 30% among those having a history of head injury at the onset of symptoms to better than 90% for those without head injury, provided they have good postural control and if their symptoms only occur with rapid head movement. A recent summary of many of the techniques and results is provided in Herdman (1997).
When patients have substantial loss of function in one or more systems responsible for balance function (vestibular, visual, somatosensory), prognosis for therapy success would be limited. However, this does not imply that treatment should be withheld in these patients. The impact of oscillopsia and deficits due to bilateral vestibular paresis may be reduced primarily from the repeated practice activities and to the extensive educational benefit of the therapy program.
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In a controlled study Norré (1987) demonstrated that patients with BPPV seem to benefit from habituation exercises . The active treatment group demonstrated a dramatically superior result when compared with a sham exercise group and a nontreated control group. He also studied the use of traditional vestibular suppressant therapy during habituation training, and noted that those on medications were approximately half as likely to achieve complete resolution of symptoms.
Horak and colleagues (1992) performed a controlled study comparing the benefits of a customized program of vestibular rehabilitation to two control groups. One group received medical therapy with meclizine or diazepam, and the other group performed a program of sham exercises, involving aerobic exercise and strength training. All three groups reported some subjective decreases in dizziness, with a dramatic benefit in the vestibular rehabilitation group. Posturography and other measures of balance ability documented a beneficial effect only in the vestibular exercise group.
Shepard and Telian (1995) completed a randomized trial comparing the efficacy of a customized vestibular and balance rehabilitation program with a generic program of vestibular exercises. The customized therapy group showed statistically significant resolution of spontaneous nystagmus and rotational chair asymmetries by the end of therapy, as well as significant reduction in motion sensitivity. They also had improved performance on clinical measures of static and dynamic balance ability. The only statistically significant change in the performance measures for the generic program was in static balance ability, probably reflecting the fact that one of the generic exercises was identical to one of the performance measures in this category. This study suggests that the level of vestibular compensation achieved in a customized program is far superior to the level that can be anticipated from a generic program, and justifies the expense required to involve a professional specifically trained in the treatment of patients with chronic vestibular symptoms.
Three other special applications of vestibular rehabilitation now each have controlled studies showing statistically significant improvement over a control group. The first is loosely referred to as a vestibular rehabilitation program since it is actually a single office treatment procedure for benign positional vertigo, the particle repositioning maneuver. This procedure has become popular within the last 5 years and will be discussed in more detail below. Lynn and colleagues (1995) randomized 36 patients with confirmed, unilateral BPPV, into a treatment group that went through a modified Epley procedure (Epley, 1992) or to a control group who underwent a sham procedure. Patients and the evaluating audiologist were blinded to the group assignments. At the 1-month follow-up, 89% of the treatment group and only 27% of the control group had negative Hallpike maneuvers, a highly significant difference. A controlled study of another particle repositioning maneuver compared a treatment group to no treatment and reported no significant difference in outcome (Blakely, 1994). This latter study cautioned that the natural history of BPPV is spontaneous resolution in many patients within the first 4–8 weeks.
Another area of study with a randomized control group involved therapy for gait in patients with significant bilateral peripheral vestibular system paresis (Krebs et al., 1993). This study, despite a small group of subjects, was able to demonstrate a statistically significant improvement in measures of gait performance in the treatment group compared to the control group.
A generic exercise program has been found to be useful in the postoperative care of patients after any surgical procedure that produces unilateral vestibular loss, such as vestibular nerve section, labyrinthectomy, or vestibular schwannoma resection (Shepard et al., 1993). The generic program is initiated as soon as the patient is out of intensive care. If the patient does not demonstrate significantly improved postural control and resolution of motion-provoked symptoms after 4 weeks, a customized program is instituted. Using this generic program (detailed in Shepard et al., 1993) over the last 3 years suggests that less than 5% of the postoperative patients will require a customized program. A recent randomized study (Herdman et al., 1995) was performed in patients following acoustic neuroma resection, with postoperative activities beginning on postoperative day three for both groups. The control group performed eye movement exercises and walking; the experimental group performed a series of activities designed to increase vestibulo-ocular reflex gain, including head and eye movements plus a walking program (a generic program). The authors were able to demonstrate a significantly superior improvement in postural control, as assessed by EquiTest®, in the experimental group. There was also significantly less subjective disequilibrium reported by postoperative days five and six in the experimental group.
The above review, though not meant to be exhaustive, does present an impressive and growing body of literature clearly demonstrating the statistically verifiable efficacy of this management technique in a wide variety of patients with balance disorders and/or dizziness.
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Outlined below are general and specific areas of knowledge and skills that help describe the area of development and administration of vestibular and balance rehabilitation programs. These are an adaptation of the areas outlined in a course, Vestibular Rehabilitation: A Competency-Based Course, which was sponsored by the University of Miami School of Medicine, Division of Physicial Therapy, for physical and occupational therapists. The course was directed by Susan J. Herdman, PhD, PT, who served as a consultant to this committee. The knowledge and skills outlined are not intended to be all inclusive but to provide an overview of the breadth of knowledge and skills in this interdisciplinary management of the patient with balance disorders and/or dizziness.
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A. General knowledge of the anatomy and physiology of the peripheral and central vestibular, visual and somatosensory/proprioceptive systems and their relative interactions.
B. Knowledge of various pathological processes that can affect the sensory and motor subsystems responsible for normal balance and equilibrium.
C. In addition to the requisite skills and knowledge necessary for the management of vestibular and balance rehabilitation, knowledge of other management techniques and when these might be used to include medical, surgical or dietary strategies for the patient with a balance disorder and/or dizziness.
D. Ability to determine candidacy for vestibular rehabilitation based on the patient's presenting history and symptoms supplemented by presenting signs (e.g., nystagmus), laboratory tests and functional assessment.
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A. The ability to interpret and integrate various laboratory studies for the purposes of diagnostic evaluation as well as to establish a baseline for outcome measures to assess the efficacy of rehabilitation and other management techniques. These tests may include but are not limited to: ENG including extensive oculomotor evaluation; rotational chair; head on body rotation; postural control assessment; audiological evaluation; electrocochleography; auditory brainstem evoked potentials.
B. Skill is needed with techniques for direct clinical examinations for diagnostic and rehabilitative assessments. These may include but not be limited to:
Oculomotor examinations with and without visual fixation (ocular alignment; spontaneous and gaze-holding nystagmus; ocular range of motion; vergence; pursuit and saccade eye movements; VOR cancellation; VOR to slow head rotation; VOR to head thrusts; head-shaking nystagmus; pressure-induced nystagmus; hyperventilation-induced nystagmus; dynamic visual acuity testing; vertebral artery compression test; Dix-Hallpike); and balance and gait evaluation (Romberg; tandem Romberg; modified Clinical Test for Sensory Interaction and Balance (CTSIB); Fukuda stepping test; single-legged stance; gait analysis; tandem walk; timed get up and go; functional reach test).
C. Knowledge of and ability to perform a clinical assessment of maneuvers that provoke symptoms. The tools may include but not be limited to:
Multiple rapid positioning inventories;
Dix-Hallpike maneuver to assess posterior and anterior canal benign paroxysmal positional vertigo (BPPV);
Side-lying test for BPPV; and
Roll test for horizontal canal BPPV.
D. Skill to utilize various objective and subjective disability and functional activity scales to determine activities of daily living restrictions and occupational capabilities.
E. Ability to assess the impact of general medical conditions and knowledge of specific conditions that might compromise or contraindicate a vestibular and balance rehabilitation program.
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A. Knowledge of the theory, rationale and procedures necessary to successfully distinguish between posterior, anterior and horizontal canal BPPV and between canalithiasis and cupulolithiasis; and skill to administer a canalith repositioning procedure on patients with BPPV of posterior, anterior or horizontal canal origin.
B. Knowledge of theory, rationale and procedures necessary to distinguish the need for adaptation and/or habituation exercises in the overall design of a vestibular and balance rehabilitation program. Determine the frequency of use and the level of difficulty needed based on a customized assessment of the specific patient.
C. Knowledge of theory, rationale and procedures necessary to determine the need for gait and balance exercise activities based on balance and gait assessment as part of the overall vestibular and balance rehabilitation program.
D. Knowledge of the interaction of the various therapy components as they relate to the symptoms of the patient to determine the ordering of use of the individual aspects of a therapy program. Given the program designed, determine the needed frequency of return visits and what criteria should be used to designate a termination point to the active therapy program. Development of outcome measures that reflect the efficacy of the vestibular and balance rehabilitation program for a given patient. Outcome measures need to be based on the knowledge of what measures are available and what validity they would carry given a particular patient and program design and specific goals established for the patient.
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