The focus of this article is on the role of vestibular rehabilitation in the remediation of postural and gaze instability in individuals with peripheral vestibular deficits. Although vestibular rehabilitation does not cure the organic disease that produces the balance disorder, it improves mobility, prevents falls, and overall has a positive impact on the quality of life for the patient.
Dizziness is among the most prevalent complaints for which people seek medical help and is the number one reason for a physician visit for individuals aged more than 75 years. Although dizziness can be caused by many different medical conditions, it is estimated that as many as half of cases are due to vestibular disorders. Uncompensated vestibular hypofunction results in postural instability, visual blurring, and subjective complaints of imbalance. These serious problems result in decreased activity level, avoidance or modification of driving with resultant diminished independence, limited social interactions, and increased isolation.
Studies have shown that the incidence of falls is greater in persons with vestibular hypofunction when compared with healthy individuals of the same age living in the community. The potential consequences of a fall include physical harm and loss of independence as well as social embarrassment. The costs of fall-related injuries in older adults are substantial. In the United States alone, it is estimated that annual direct and indirect costs of fall-related injuries will reach $54.9 billion by the year 2020. The psychologic consequences of falls in younger adults have not been studied; however, among older adults who have fallen, nearly half are fearful of falling again, and up to one quarter restrict activities in an attempt to avoid another fall.
Evidence is beginning to accumulate that the use of vestibular rehabilitation is a critical component in improving postural stability and gaze stability and in decreasing subjective complaints of disequilibrium and oscillopsia (perception of visual blurring) for patients with peripheral vestibular loss. Although these studies differ in the specific details of vestibular rehabilitation, common elements include vestibular adaptation and substitution exercises, balance and gait activities, and general conditioning. The focus of this article is on the role of vestibular rehabilitation in the remediation of postural and gaze instability in individuals with peripheral vestibular deficits. Although vestibular rehabilitation does not cure the organic disease that produces the balance disorder, it improves mobility, prevents falls, and overall has a positive impact on the quality of life for the patient.
Mechanisms of recovery
The goals of vestibular rehabilitation are to reduce subjective symptoms, to improve gaze and postural stability (particularly during head movements), and to return the individual to normal activities, including regular physical activity, driving, and work. Vestibular rehabilitation includes exercises to habituate symptoms such as head movement provoked dizziness, exercises to promote vestibular adaptation and substitution, exercises to improve balance and dynamic postural control, and exercises to improve general conditioning.
Compensation for the loss of vestibular function is a process of recovery, with the desired outcome being a return to normal function. Compensation occurs in response to permanent vestibular damage and not to fluctuations in function, such as occurs during the episodic spells of Meniere’s disease.
Habituation
One mechanism of compensation is habituation. Habituation refers to the long lasting attenuation of a response to a provocative stimulus brought about by repeated exposure to the provocative stimulus. Habituation exercises are chosen based on particular movements that provoke symptoms in the individual. The Motion Sensitivity Quotient is a standardized assessment in which the patient rates the intensity and duration of dizziness following each of a series of 16 position changes. Habituation as a treatment approach involves systematically provoking symptoms by having the individual perform several repetitions of two to three of the movements or position changes that caused mild-to-moderate symptoms. This systematic repetition of provocative movements leads to a reduction in symptoms. This treatment approach was found to be effective in reducing disability in a group of patients with peripheral and central vestibular deficits. Overall, 82% of the patients reported an improvement in symptoms. Among those with peripheral vestibular deficits, 90% achieved successful outcomes defined as having symptoms that minimally interfered with activities at discharge from rehabilitation. This approach was less successful in individuals with central vestibular disorders as a result of head injury and least successful in individuals with bilateral vestibular hypofunction. For that reason, habituation exercises are not advocated in the treatment of bilateral vestibular loss.
Adaptation
A second mechanism of recovery is adaptation. Adaptation refers to the potential for the remaining vestibular system to adjust its output according to the demands placed on it. Adaptation refers to long-term change in the neuronal response with the goal of reducing symptoms and normalizing gaze and postural stability. A critical signal to induce adaptation is retinal slip during head movements. The adaptation exercises involve head movement while maintaining focus on a target which may be stationary or moving ( Fig. 1 ). Typical progression of adaptation exercises involves increased velocity of head movement, movement of the target and head, target placement in a distracting visual pattern, and maintenance of a challenging posture. Table 1 presents a sample progression of vestibular adaptation and substitution exercises. Adaptation exercises alone have been found to reduce symptoms of disequilibrium and to improve balance while walking in individuals who are post surgery for resection of acoustic neuroma.
| Time Period | Exercise | Duration | Frequency | Total Time a |
|---|---|---|---|---|
| Week 1 |
|
|
| 20 |
| Week 2 |
|
|
| 40 |
| Week 3 |
|
|
| 50 |
| Week 4 |
|
|
| 40 |
| Week 5 |
|
|
| 40 |
| Week 6 |
|
|
| 55 |
Substitution
A third mechanism of recovery is substitution. The goal is to substitute alternative strategies for missing vestibular function. Potential substitution for the vestibulo-ocular reflex (VOR) includes the cervical ocular reflex, use of smooth pursuit eye movements, and central preprogramming of eye movements. Substitution for the vestibulospinal reflex includes the use of visual, somatosensory cues, or both to maintain stability. Substitution exercises specifically attempt to facilitate the use of alternative strategies rather than teaching the specific strategies. For example, during a remembered target exercise, the individual attempts to maintain eye position on a target with the eyes closed, potentially facilitating use of the cervical ocular reflex. During active eye-head exercise, a large eye movement to a target is made before the head moving to face the target, potentially facilitating the use of preprogrammed eye movements.
In addition to exercises specifically geared to the vestibular system, balance exercises under challenging sensory and dynamic conditions are typically included as part of vestibular rehabilitation. Static exercises include balancing under conditions of altered visual and somatosensory input. The tasks are made more challenging by progressively narrowing the base of support. Dynamic conditions challenge high level balance and include walking with head turns, walking with quick turns to the right or left, or performing a secondary task while walking such as tossing a ball to a partner or performing a cognitive task while walking.
Many individuals with vestibular hypofunction limit regular physical activities. Although general conditioning alone does not reduce symptoms or improve postural stability, including physical activity is an important element of rehabilitation. The authors recommend that every patient start a progressive walking program, ideally outside, and increase to 20 to 30 minutes on a daily basis.
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