Vestibular rehabilitation: rationale and indications.

Treatment options of the patient with dizziness include medication, rehabilitation with physical therapy, surgery, counseling, and reassurance. Here the authors discuss vestibular rehabilitation for patients with benign paroxysmal positional vertigo (BPPV), unilateral vestibular loss or hypofunction, and bilateral vestibular loss/hypofunction. They describe the different mechanisms for recovery with vestibular rehabilitation, the exercises that are used, and which ones are best. An exhaustive literature review on clinical outcomes with the best research publications for BPPV, unilateral vestibular loss/hypofunction, and bilateral vestibular loss/hypofunction is presented. For BPPV, the authors also summarize the evidence-based review practice parameters published in Neurology by Fife et al. (2008) and review all relevant articles published since then.

Dizziness and vertigo: emergencies and management.

The cause of dizziness in patients seen in the emergency room can usually be determined by a focused evaluation that consists of identifying three key features in the history and five key elements of the clinical examination. This article discusses the most common causes of dizziness, how to use this approach, and management of these cases in the emergency room.

A Prototype Head-Motion Monitoring System for In-Home Vestibular Rehabilitation Therapy.

This work reports the use of a head-motion monitoring system to record patient head movements while completing in-home exercises for vestibular rehabilitation therapy. Based upon a dual-axis gyroscope (yaw and pitch, ± 500-degrees/sec maximum), angular head rotations were measured and stored via an on-board memory card. The system enabled the clinician to document exercises at home. Several measurements were recorded in one patient with unilateral vestibular hypofunction: The total time of exercise for the week (118 minutes) was documented and compared with expected weekly exercise time (140 minutes). For gaze stabilization exercises, execution time of 60 sec was expected, and observed times ranged from 75-100 sec. An absence of rest periods between each exercise instead of the recommended one minute rest period was observed. Maximum yaw head velocities from approximately 100-350 degrees/sec were detected. A second subject provided feedback concerning the ease of use of the HAMMS device. This pilot study demonstrates, for the first time, the capability to capture the head-motion "signature" of a patient while completing vestibular rehabilitation exercises in the home and to extract exercise regime parameters and monitor patient adherence. This emerging technology has the potential to greatly improve rehabilitation outcomes for individuals completing in-home gaze stabilization exercises.

Efficacy of gaze stability exercises in older adults with dizziness.

BACKGROUND AND PURPOSE: The purpose of this study was to determine whether the addition of gaze stability exercises to balance rehabilitation would lead to greater improvements of symptoms and postural stability in older adults with normal vestibular function who reported dizziness. METHODS: Participants who were referred to outpatient physical therapy for dizziness were randomly assigned to the gaze stabilization (GS) group (n = 20) or control (CON) group (n = 19). Dizziness was defined as symptoms of unsteadiness, spinning, a sense of movement, or lightheadedness. Participants were evaluated at baseline and discharge on symptoms, balance confidence, visual acuity during head movement, balance, and gait measures. The GS group performed vestibular adaptation and substitution exercises designed to improve gaze stability, and the CON group performed placebo eye exercises designed to be vestibular neutral. In addition, both groups performed balance and gait exercises. RESULTS: There were no baseline differences (P > .05) between the GS and CON groups in age, sex, affect, physical activity level, or any outcome measures. Both groups improved significantly in all outcome measures with the exception of perceived disequilibrium. However, there was a significant interaction for fall risk as measured by Dynamic Gait Index (P = .026) such that the GS group demonstrated a significantly greater reduction in fall risk compared with the CON group (90% of the GS group demonstrated a clinically significant improvement in fall risk versus 50% of the CON group). DISCUSSION AND CONCLUSIONS: This study provides evidence that in older adults with symptoms of dizziness and no documented vestibular deficits, the addition of vestibular-specific gaze stability exercises to standard balance rehabilitation results in greater reduction in fall risk.

Nystagmus during attacks of vestibular migraine: an aid in diagnosis.

INTRODUCTION: An estimated one-fourth to one-third of patients with migraine will experience vertigo associated with their migraine attacks. Vestibular migraine frequently presents as a diagnostic challenge as objective neurological findings consistent with this entity have not been well described. OBJECTIVE: The aim of this study is to characterize eye movements of patients presenting with nystagmus during attacks of migrainous vertigo. DESIGN: A retrospective study of 26 patients presenting with nystagmus during an acute vestibular migraine was performed. All patients were examined while symptomatic during a migraine spell, and also while asymptomatic. All patients underwent tests of vestibular function with either bithermal water caloric or rotary chair electronystagmography. RESULTS: The most common patient was a female of perimenopausal age. Spontaneous nystagmus was seen in 19% of patients and nystagmus provoked by horizontal headshaking was seen in 35%. Nystagmus could be provoked with positional testing in 100% of symptomatic patients with fixation blocked. The positional nystagmus most commonly was sustained, of low velocity, and could be horizontal, vertical or torsional. Bithermal water caloric or rotary chair tests obtained during symptom-free intervals were normal in all patients. CONCLUSIONS: Although nystagmus characteristics are quite variable during vestibular migraine, the finding on examination of low-velocity, sustained nystagmus with positional testing in a young to middle-aged adult patient presenting with vertigo, nausea and headache is highly suggestive of vestibular migraine as long as the nystagmus dissipates when the patient is free of symptoms.

Oculomotor strategies and their effect on reducing gaze position error.

OBJECTIVE: Vestibular adaptation exercises have been shown to improve gaze stability during active head rotation in individuals with vestibular hypofunction. Little is known, however, of the types of eye movements used during passive head rotation and their effect on gaze stability in individuals with vestibular hypofunction. The primary purpose of this study was to determine differences in oculomotor strategies and their effect on stabilizing gaze during ipsilesional passive and active head rotations in vestibular hypofunction. PATIENTS: Subjects with unilateral (n = 4) and bilateral (n = 3) vestibular hypofunction and healthy subjects (n = 4) based on bithermal caloric and rotational chair testing. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE: Head and eye velocity and position data measured with scleral search coil. RESULTS: Subjects with unilateral and bilateral vestibular hypofunction generated 3 types of gaze-stabilizing eye movements with ipsilesional head impulses: slow vestibular ocular reflex, compensatory, and corrective saccades. The types of eye movements generated during active and passive head impulses were highly individualized. Gaze position error was reduced when compensatory saccades were recruited as part of the gaze-stabilizing strategy. CONCLUSION: Rehabilitation for individuals with vestibular hypofunction should identify individuals' unique gaze stability preferences and attempt to facilitate compensatory saccades.

Dizziness.

Dizziness is an imprecise term used to describe various symptoms, each of which has a different pathophysiologic mechanism and significance. In 80% of outpatients presenting with dizziness, it is severe enough to require medical intervention. This article describes causes, assessment, and management of dizziness.

The reliability of the Vestibular Autorotation Test (VAT) in patients with dizziness.

OBJECTIVE: To establish intrarater and interrater reliability of the Vestibular Autorotation Test (VAT) (Western Systems Research Inc., Pasadena, CA) in a clinical sample of individuals reporting dizziness. STUDY DESIGN: Ninety-eight patients with reports of dizziness referred for vestibular function testing performed repeated trials of horizontal VAT. A subsample of 49 individuals repeated the test for a second rater. RESULTS: Approximately 66% of subjects were unable to meet the performance criterion of six consecutive trials where data was displayed at frequencies > or =3.9 Hz with coherence values held constant trial to trial. There was a good level of intrarater reliability for gain independent of the effects of practice (intraclass correlation coefficient [ICC] = 0.78 [95% confidence interval [CI]: 0.69-0.87] to 0.95 [(95% CI: 0.93-0.97]). A significant difference in intrarater reliability was found when the first three trials were compared to the last three trials for phase (ICC ranged from 0.04 [95% CI: 0.00-0.31] to 0.96 [95% CI: 0.93-0.97]) and asymmetry (ICC ranged from 0.39 [95% CI: 0.17-0.56] to 0.73 [95% CI: 0.32-0.81]) particularly at frequencies > or =4.3 Hz. Interrater reliability was good to excellent across all variables at frequencies < or =3.9 Hz. CONCLUSIONS: Many patients had difficulty performing the VAT. The reliability estimates for phase and asymmetry, but not gain, were significantly affected by practice. Careful attention to patient preparation, instruction, and test monitoring including sufficient patient practice before data collection are likely to be critical factors to ensure quality data.

Screening for vestibular disorders: a study of clinicians' compliance with recommended practices.

BACKGROUND: Dizziness and vertigo are very common patient complaints encountered by clinicians in both primary as well as specialty care in otolaryngology and neurology. Vestibular impairment is an underlying cause in as many as 45% of people complaining of dizziness. Most causes of vestibular impairment can be effectively treated; however, the diagnosis is frequently missed. The aim of this study was to examine clinical assessments used by providers in evaluating dizzy patients in outpatient clinics and the emergency department. MATERIAL/METHODS: Computerized medical records of all patients receiving an ICD-9 diagnosis code for dizziness, including benign paroxysmal positional vertigo, Meniere's disease, and vestibular hypofunction over a six-month period at the Atlanta VA Medical Center were reviewed. RESULTS: 476 patients were identified and of these, 157 patients were included. Over two-thirds of providers (69%) used the patient's description of the dizziness for identifying the cause; however, significant variability was evident across disciplines, ranging from 84% of audiologists asking for a description of the dizziness to only 33% of geriatricians asking. 89% of providers did not evaluate a patient for BPPV by examining for positional nystagmus. Primary care clinicians referred 22% of dizzy patients to a specialist (neurotologist), geriatricians referred 17%, and emergency physicians referred only 16%. CONCLUSIONS: Dizzy patients were not routinely screened for vestibular impairment based on available recommended practices, likely contributing to underdiagnosis and treatment. Results indicate a need for effective dissemination of guidelines to improve health care quality, increase awareness of medical risks, and enhance patient access to appropriate treatment.

Horizontal saccade disconjugacy in strabismic monkeys.

PURPOSE: Previous studies have shown that binocular coordination during saccadic eye movement is affected in humans with large strabismus. The purpose of this study was to examine the conjugacy of saccadic eye movements in monkeys with sensory strabismus. METHODS: The authors recorded binocular eye movements in four strabismic monkeys and one unaffected monkey. Strabismus was induced by first occluding one eye for 24 hours, switching the occluder to the fellow eye for the next 24 hours, and repeating this pattern of daily alternating monocular occlusion for the first 4 to 6 months of life. Horizontal saccades were measured during monocular viewing when the animals were 2 to 3 years of age. RESULTS: Horizontal saccade testing during monocular viewing showed that the amplitude of saccades in the nonviewing eye was usually different from that in the viewing eye (saccade disconjugacy). The amount of saccade disconjugacy varied among animals as a function of the degree of ocular misalignment as measured in primary gaze. Saccade disconjugacy also increased with eccentric orbital positions of the nonviewing eye. If the saccade disconjugacy was large, there was an immediate postsaccadic drift for less than 200 ms. The control animal showed none of these effects. CONCLUSIONS: As do humans with large strabismus, strabismic monkey display disconjugate saccadic eye movements. Saccade disconjugacy varies with orbital position and increases as a function of ocular misalignment as measured in primary gaze. This type of sensory-induced strabismus serves as a useful animal model to investigate the neural or mechanical factors responsible for saccade disconjugacy observed in humans with strabismus.

Recovery of dynamic visual acuity in bilateral vestibular hypofunction.

OBJECTIVE: To determine the effect of vestibular exercises on the recovery of visual acuity during head movement in patients with bilateral vestibular hypofunction (BVH). DESIGN: Prospective, randomized, double-blinded study. SETTING: Outpatient clinic, academic setting. PATIENTS: Thirteen patients with BVH, aged 47 to 73 years. INTERVENTION: One group (8 patients) performed vestibular exercises designed to enhance remaining vestibular function, and the other (5 patients) performed placebo exercises. MAIN OUTCOME MEASURES: Measurements of dynamic visual acuity (DVA) during predictable head movements using a computerized test; measurement of intensity of oscillopsia using a visual analog scale. RESULTS: As a group, patients who performed vestibular exercises showed a significant improvement in DVA (P = .001), whereas those performing placebo exercises did not (P = .07). Only type of exercise (ie, vestibular vs placebo) was significantly correlated with change in DVA. Other factors examined, including age, time from onset, initial DVA, and complaints of oscillopsia and disequilibrium, were not significantly correlated with change in DVA. Change in oscillopsia did not correlate with change in DVA. CONCLUSIONS: Use of vestibular exercises is the main factor involved in recovery of DVA in patients with BVH. We theorize that exercises may foster the use of centrally programmed eye movements that could substitute for the vestibulo-ocular reflex. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00411216.

Incomitance in monkeys with strabismus.

PURPOSE: Rhesus monkeys reared with restricted visual environment during their first few months of life develop large ocular misalignment (strabismus). The purpose of this study was to describe 'A and V' patterns and DVD in these animals during fixation and eye movements and suggest that this form of rearing produces animals that are suitable model to study the mechanisms that might cause 'A/V' pattern incomitant strabismus and dissociated vertical deviation (DVD) in humans. METHODS: Eye movements were recorded during fixation, smooth-pursuit and saccades using binocular search coils in one monkey with esotropia, three monkeys with exotropia and one normal monkey. RESULTS: 1) Monkeys reared with Alternating Monocular Occlusion or Binocular deprivation (tarsal plates intact) showed both horizontal and vertical misalignment during monocular and binocular viewing. 2) Large 'A' patterns were evident in 2 out of 3 exotropes while a 'V' pattern was observed in the esotrope. 3) Similar 'A/V' patterns were observed with either eye viewing and during fixation or eye movements. 4) The vertical misalignment, which consisted of the non-viewing eye being higher than the fixating eye, appeared to constitute a DVD. CONCLUSION: Visual sensory deprivation methods that induce large strabismus also induce 'A/V' patterns and DVD similar to certain types of human strabismus. The source of pattern strabismus could be central, i.e., altered innervation to extraocular muscles from motor nuclei, or peripheral, i.e., altered location of extraocular muscle pulleys.

Latent nystagmus: vestibular nystagmus with a twist.

BACKGROUND: Latent nystagmus is a horizontal binocular oscillation that is evoked by unequal visual input to the 2 eyes. It develops primarily in humans with congenital esotropia. OBJECTIVE: To investigate the interrelationship between latent and peripheral vestibular nystagmus and their corollary neuroanatomical pathways. METHODS: Examination of subcortical neuroanatomical pathways producing latent nystagmus and review of the neurophysiological mechanisms by which they become activated in congenital esotropia. RESULTS: The vestibular nucleus presides over motion input from the eyes and labyrinths. Latent nystagmus corresponds to the optokinetic component of ocular rotation that is driven monocularly by nasal optic flow during a turning movement of the body in lateral-eyed animals. Congenital esotropia alters visual pathway development from the visual cortex to subcortical centers that project to the vestibular nucleus, allowing this primitive subcortical motion detection system to generate latent nystagmus under conditions of monocular fixation. CONCLUSIONS: Latent nystagmus is the ocular counterpart of peripheral vestibular nystagmus. Its clinical expression in humans proclaims the evolutionary function of the eyes as sensory balance organs.

Cervico-ocular reflex in normal subjects and patients with unilateral vestibular hypofunction.

OBJECTIVE: To determine whether the cervico-ocular reflex contributes to gaze stability in patients with unilateral vestibular hypofunction. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS: Patients with unilateral vestibular hypofunction (n = 3) before and after vestibular rehabilitation and healthy subjects (n = 7). INTERVENTIONS: Vestibular rehabilitation. MAIN OUTCOME MEASURES: We measured the cervico-ocular reflex in patients with unilateral vestibular hypofunction before and after vestibular rehabilitation and in healthy subjects. To measure the cervico-ocular reflex, we recorded eye movements with a scleral search coil while the trunk moved at 0.3, 1.0, and 1.5 Hz beneath a stabilized head. To determine whether the head was truly stabilized, we measured head movement using a search coil. RESULTS: We found no evidence of cervico-ocular reflex in any of the seven healthy subjects or in two of the patients with unilateral vestibular hypofunction. In one patient with chronic unilateral vestibular hypofunction, the cervico-ocular reflex was present before vestibular rehabilitation only for leftward trunk rotation (relative head rotation toward the intact side). After 5 weeks of placebo exercises, there was no change in the cervico-ocular reflex. After an additional 5 weeks that included vestibular exercises, cervico-ocular reflex gain for leftward trunk rotation had increased threefold. In addition, there was now evidence of a cervico-ocular reflex for rightward trunk rotation, potentially compensating for the vestibular deficit. CONCLUSION: The cervico-ocular reflex appears to be a highly inconsistent mechanism. The change of the cervico-ocular reflex in one patient after vestibular exercises suggests that the cervico-ocular reflex may be adaptable in some patients.

Optimizing the sensitivity of the head thrust test for identifying vestibular hypofunction.

BACKGROUND AND PURPOSE: The head thrust test (HTT) is used to assess the vestibulo-ocular reflex. Sensitivity and specificity for diagnosing unilateral vestibular hypofunction (UVH) in patients following vestibular ablation is excellent (100%), although sensitivity is lower (35%-39%) for patients with nonsurgically induced UVH. The variability of the test results may be from moving the subject's head outside the plane of the lateral semicircular canals as well as using a head thrust of predictable timing and direction. The purpose of this study was to examine sensitivity and specificity of the horizontal HTT in identifying patients with UVH and bilateral vestibular hypofunction (BVH) when the head was flexed 30 degrees in attempt to induce acceleration primarily in the lateral semicircular canal and the head was moved unpredictably. SUBJECTS: The medical records of 176 people with and without vestibular dysfunction (n=79 with UVH, n=32 with BVH, and n=65 with nonvestibular dizziness) were studied. METHODS: Data were retrospectively tabulated from a de-identified database (ie, with health information stripped of all identifiers). RESULTS: Sensitivity of the HTT for identifying vestibular hypofunction was 71% for UVH and 84% for BVH. Specificity was 82%. DISCUSSION AND CONCLUSION: Ensuring the head is pitched 30 degrees down and thrust with an unpredictable timing and direction appears to improve sensitivity of the HTT.

Conjugate adaptation of saccadic gain in non-human primates with strabismus.

In this study, we have used the double-step paradigm to test saccadic gain adaptation during monocular viewing in one normal monkey, two monkeys with exotropia, and one monkey with esotropia. In this paradigm, the target for the saccade is displaced during the saccade, resulting in a consistent visual error. Studies in normal humans and monkeys have shown that the brain responds to this consistent visual error by gradually changing saccade gain. Using this technique, we were able to elicit adaptation in both the viewing eye and the nonviewing eye in the normal monkey and in monkeys with strabismus. The rate of adaptation was not significantly different in the viewing and nonviewing eyes in the normal and strabismic monkeys. The magnitude of adaptation as calculated by a percentage change in gain was also not significantly different in the viewing and the nonviewing eyes in the normal and strabismic monkeys. Our data show that animals with strabismus retain the ability to elicit a conjugate adaptation of saccades using this mechanism. We also suggest that the double-step paradigm elicits a conjugate adaptation of saccades whether the animal is viewing monocularly (our studies) or binocularly (data published in literature).

Role of the dorsolateral pontine nucleus in visual-vestibular behavior.

Visual-vestibular behavior depends on signals traveling in climbing and mossy fiber pathways. Our study examined the role of the dorsolateral pontine nucleus (DLPN), a major component of the cortico-ponto-cerebellar mossy fiber pathway. DLPN neurons discharge in relation to smooth pursuit and during visual stimulation, indicating a potential role in visually guided motor learning in the vestibulo-ocular reflex (VOR). We used unilateral muscimol injections to determine the potential role of the DLPN in short-term VOR gain adaptation. Preinjection adaptation of VOR gain was achieved by sinusoidal rotation (0.2 Hz, 30 degrees /s) for 2 h while the monkey viewed a stationary visual surround through either magnifying (x2) or minifying (x0.5) lenses. VOR gain increases (23-32%) or decreases (22-48%) as measured in complete darkness (VORd) were achieved. Following DLPN inactivation, initial acceleration of ipsilateral smooth-pursuit was reduced by 35-68%, and steady state gain was reduced by 32-61%. Furthermore, the monkey's ability to cancel the VOR was impaired. In contrast to these significant deficits in ipsilesional smooth pursuit, the VOR during lens viewing was similar to that measured in preinjection control experiments. Similarly, following 2 h of adaptation, VORd gain adaptation was indistinguishable from control adaptation values for either ipsilesional or contralesional directions of head rotation. Our results suggest that visual error signals for short-term adaptation of the VOR are derived from sources other than the DLPN, such as those from the accessory optic system.

Recovery of dynamic visual acuity in unilateral vestibular hypofunction.

OBJECTIVE: To determine the effect of vestibular exercises on the recovery of visual acuity during head movement in patients with unilateral vestibular hypofunction. STUDY DESIGN: Prospective, randomized, double-blind study. SETTING: Ambulatory referral center. PATIENTS: Twenty-one patients with unilateral vestibular hypofunction, aged 20 to 86 years. INTERVENTION: One group (13 patients) performed vestibular exercises designed to enhance the vestibulo-ocular reflex, and the other group (8 patients) performed placebo exercises. The placebo group was switched to vestibular exercises after 4 weeks. OUTCOME MEASURES: Measurements of dynamic visual acuity (DVA) during predictable (DVA-predictable) and unpredictable (DVA-unpredictable) head movements by means of a computerized test and measurement of intensity of oscillopsia by means of a visual analog scale. RESULTS: As a group, patients who performed vestibular exercises showed a significant improvement in DVA-predictable (P<.001) and DVA-unpredictable (P<.001), while those performing placebo exercises did not (P =.07). On the basis of stepwise regression analysis, the leading factor contributing to improvement was vestibular exercises. This reached significance for DVA-predictable (P =.009) but not DVA-unpredictable (P =.11). Other factors examined included age, time from onset, initial DVA, oscillopsia, and duration of treatment. Changes in oscillopsia did not correlate with DVA-predictable or DVA-unpredictable. CONCLUSIONS: Use of vestibular exercises is the main factor involved in recovery of DVA-predictable and DVA-unpredictable in patients with unilateral vestibular hypofunction. Exercises may foster the use of centrally programmed eye movements that could substitute for the vestibulo-ocular reflex. The DVA-predictable would benefit more from this than would DVA-unpredictable.

Dizziness.

There are several causes of dizziness, each of which requires a different form of management. Virtually all causes of dizziness can be treated with medication, diet, or physical therapy. This article discusses the most common causes of dizziness and management. Case examples are used extensively.