Clinical Tests Of Vestibular Function Research Articles

The walking speed-dependency of gait variability in bilateral vestibulopathy and its association with clinical tests of vestibular function

Understanding balance and gait deficits in vestibulopathy may help improve clinical care and our knowledge of the vestibular contributions to balance. Here, we examined walking speed effects on gait variability in healthy adults and in adults with bilateral vestibulopathy (BVP). Forty-four people with BVP, 12 healthy young adults and 12 healthy older adults walked at 0.4 m/s to 1.6 m/s in 0.2 m/s increments on a dual belt, instrumented treadmill. Using motion capture and kinematic data, the means and coefficients of variation for step length, time, width and double support time were calculated. The BVP group also completed a video head impulse test and examinations of ocular and cervical vestibular evoked myogenic potentials and dynamic visual acuity. Walking speed significantly affected all gait parameters. Step length variability at slower speeds and step width variability at faster speeds were the most distinguishing parameters between the healthy participants and people with BVP, and among people with BVP with different locomotor capacities. Step width variability, specifically, indicated an apparent persistent importance of vestibular function at increasing speeds. Gait variability was not associated with the clinical vestibular tests. Our results indicate that gait variability at multiple walking speeds has potential as an assessment tool for vestibular interventions.

Vestibular migraine: An update on current understanding and future directions.

Vestibular migraine is among the most common causes of recurrent vertigo in the general population. Despite its prevalence and high impact on healthcare cost and utilization, it has remained an under-recognized condition with largely unknown pathophysiology. In the present article, we aim to provide an overview of the current understanding of vestibular migraine. We undertook a narrative literature review on the epidemiology, presentations, clinical and laboratory findings, pathophysiology, and treatments of vestibular migraine. Currently, the diagnosis of vestibular migraine relies solely on clinical symptoms since clinical tests of vestibular function are typically normal, or difficult to interpret based on inconsistent results reported in earlier studies. The challenges related to diagnosis of vestibular migraine lie in its relatively broad spectrum of manifestations, the absence of typical migraine headaches with vestibular symptoms, and its very recent definition as a distinct entity. Here, we highlight these challenges, discuss common vestibular symptoms and clinical presentations in vestibular migraine, and review the current aspects of its clinical diagnosis and evaluation. The concepts related to the pathophysiology and treatment of vestibular migraine are also discussed. Vestibular migraine is still underdiagnosed clinically. Future studies are needed to address the pathophysiological mechanisms and investigate effective treatment regimens.

The Gain-Time Constant Product Quantifies Total Vestibular Output in Bilateral Vestibular Loss.

Patients with inner ear damage associated with bilateral vestibular impairment often ask “how much damage do I have.” Although there are presently three clinical methods of measuring semicircular canal vestibular function; electronystagmography (ENG or VENG), rotatory chair and video head-impulse (VHIT) testing; none of these methods provides a method of measuring total vestibular output. Theory suggests that the slow cumulative eye position can be derived from the rotatory chair test by multiplying the high frequency gain by the time constant, or the “GainTc product.” In this retrospective study, we compared the GainTc in three groups, 30 normal subjects, 25 patients with surgically induced unilateral vestibular loss, and 24 patients with absent or nearly absent vestibular responses due to gentamicin exposure. We found that the GainTc product correlated better with remaining vestibular function than either the gain or the time constant alone. The fraction of remaining vestibular function was predicted by the equation R = (GainTc/11.3) – 0.6. We suggest that the GainTc product answers the question “how much damage do I have,” and is a better measure than other clinical tests of vestibular function.

The new vestibular stimuli: sound and vibration-anatomical, physiological and clinical evidence.

The classical view of the otoliths-as flat plates of fairly uniform receptors activated by linear acceleration dragging on otoconia and so deflecting the receptor hair bundles-has been replaced by new anatomical and physiological evidence which shows that the maculae are much more complex. There is anatomical spatial differentiation across the macula in terms of receptor types, hair bundle heights, stiffness and attachment to the overlying otolithic membrane. This anatomical spatial differentiation corresponds to the neural spatial differentiation of response dynamics from the receptors and afferents from different regions of the otolithic maculae. Specifically, receptors in a specialized band of cells, the striola, are predominantly type I receptors, with short, stiff hair bundles and looser attachment to the overlying otoconial membrane than extrastriolar receptors. At the striola the hair bundles project into holes in the otolithic membrane, allowing for fluid displacement to deflect the hair bundles and activate the cell. This review shows the anatomical and physiological evidence supporting the hypothesis that fluid displacement, generated by sound or vibration, deflects the short stiff hair bundles of type I receptors at the striola, resulting in neural activation of the irregular afferents innervating them. So these afferents are activated by sound or vibration and show phase-locking to individual cycles of the sound or vibration stimulus up to frequencies above 2000Hz, underpinning the use of sound and vibration for clinical tests of vestibular function.

Reliability and Diagnostic Accuracy of Clinical Tests of Vestibular Function for Children

Reliability and Diagnostic Accuracy of Clinical Tests of Vestibular Function for Children

Commentary on “Reliability and Diagnostic Accuracy of Clinical Tests of Vestibular Function for Children”

“How could I apply this information?” Clinicians can use the positive and negative likelihood ratios (LR+, LR−) provided in Table 5 to determine the likelihood that a specific child diagnosed with severe to profound sensorineural hearing loss (SNHL) has vestibular hypofunction (VH). We use the example of the 6-year-old child with SNHL in this study who did not undergo reference standard Vestibular Function Testing (VFT) yet had positive results on 4 clinical tests: (1) Head Thrust Test, (2) Dynamic Visual Acuity Test, (3) Modified Clinical Test of Sensory Interaction on Balance total score, and (4) Modified Emory Clinical Vestibular Chair Test with fixation removed. Her pretest probability for VH was 42%, on the basis of the fact that 8 of 19 children with SNHL in this study had VH as diagnosed by VFT. Using a nomogram1 and the LR+ from each clinical test (range, 2.84-5.87), her posttest probability of having VH as diagnosed by VFT would be approximately 65% to 82% (Figure 1). If each clinical test had been negative (LR− range, 0.14-0.38), her posttest probability of having VH as diagnosed by VFT would be approximately 8% to 20% (Figure 2). In this case, the use of a nomogram and the LR of each clinical test provided critical quantitative information that increased certainty that the child had VH to make appropriate referrals for reference standard VFT and determine the most appropriate intervention plan.Fig. 1: Using a nomogram to find the posttest probability of VH based on positive test results. Pretest probability = 42%. MCTSIB total +LR = 5.87, posttest probability = 82%. HTT +LR = 3.25, posttest probability = 70%. DVA +LR = 2.84, posttest probability = 65%. A positive result on each of these 3 clinical tests changes the probability of the child having VH from 42% (pretest) to 65% to 82% (posttest), depending on the test. DVA indicates Dynamic Visual Acuity; HTT, Head Thrust Test; LR, likelihood ratio; MCTSIB, Modified Clinical Test of Sensory Interaction on Balance.Fig. 2: Using a nomogram to find the posttest probability based on negative test results. Pretest probability = 42%. m-ECVCT-fixation removed − LR = 0.38, posttest probability = 20%. HTT − LR = 0.33, posttest probability = 18%. DVA − LR = 0.18, posttest probability = 10%. MCTSIB total − LR = 0.14, posttest probability = 8%. A negative result on each of these 4 clinical tests changes the probability of the child having VH from 42% (pretest) to 8% to 20% (posttest), depending on the test. DVA indicates Dynamic Visual Acuity; HTT, Head Thrust Test; LR, likelihood ratio; MCTSIB, Modified Clinical Test of Sensory Interaction on Balance; m-ECVCT, Modified Emory Clinical Vestibular Chair Test.“What should I be mindful about when applying this information?” Clinicians must be mindful that only 8 participants had VH as diagnosed by reference standard VFT and that the psychometric properties of the 5 clinical tests of vestibular function can only be generalized to 6- to 12-year-old children with severe to profound SNHL from chronic lesions. Furthermore, 13 of 20 participants with SNHL used cochlear implants, yet no mention was made as to whether these children had a higher incidence of VH or whether their implants were on or off during the clinical tests of vestibular function. Barabara Sargent, PT, PhD, PCS University of Southern California Los Angeles, California Jennifer Pate, PT, DPT Los Angeles Children's Hospital Los Angeles, California

Reliability and Diagnostic Accuracy of Clinical Tests of Vestibular Function for Children

To determine reliability, diagnostic values, and minimal detectable change scores, 90% confidence (MDC90) of pediatric clinical tests of vestibular function. Twenty children with severe to profound bilateral sensorineural hearing loss and 23 children with typical development, aged 6 to 12 years, participated. The Head Thrust Test, Emory Clinical Vestibular Chair Test, Bucket Test, Dynamic Visual Acuity, Modified Clinical Test of Sensory Interaction on Balance, and Sensory Organization Test were completed twice for reliability. Reference standard diagnostic tests were rotary chair and vestibular evoked myogenic potential. Reliability, sensitivity, specificity, predictive values, likelihood ratios, and MDC90 scores were calculated. Reliability ranged from an intraclass correlation coefficient of 0.73 to 0.95. Sensitivity, specificity, and predictive values, using cutoff scores for each test representing the largest area under the curve, ranged from 63% to 100%. The MDC90 for Dynamic Visual Acuity and Modified Clinical Test of Sensory Interaction on Balance were 8 optotypes and 16.75 seconds, respectively. Clinical tests can be used accurately to identify children with vestibular hypofunction.

Value of vestibular testing in young children with sensorineural hearing loss.

The mature vestibular system is responsible for stabilizing the position of the eyes, head, and body in space, and helps to maintain an upright stance. It is composed of 2 parts, each with different roles: (1) the vestibular-ocular system, responsible for visual stabilization; and (2) the vestibular-spinal system, which maintains the orientation of the body in space and contributes to the postural tone necessary for the acquisition of motor developmental milestones. Children with bilateral vestibular loss since birth or in childhood present with delayed gross motor development. These children stand and walk later than children without vestibular loss. However, the postural disturbances that result from isolated peripheral dysfunction are usually corrected by the time the children reach adolescence. Through a process of compensation, input from propioceptive, visual, and other sensory systems are substituted for the absent peripheral vestibular input. Thus, it is clear that the development of postural control is a multisystem process that does not depend solely on peripheral vestibular input, and children with a variety of sensory or central nervous system deficits may also exhibit delayed postural control. These deficits may be part of a constellation of manifestations of some forms of hereditary or acquired hearing loss, hence the importance of balance assessment in deaf children. Congenital SNHL, a wellrecognized risk factor for developmental delay, has been identified more commonly in early infancy since the advent of universal neonatal hearing screening. Although developmental delay must be monitored in various areas (eg, fine and gross motor skills, language acquisition, cognitive and psychological development), it is not unusual for some areas to be overlooked because of the relative importance that parents and caregivers place on language impairment. Since both the labyrinth and cochlea are in close anatomic relationship and may be susceptible to the same noxious or developmental factors, it is reasonable to presume that many deaf children have concomitant vestibular loss. Although the incidence of profound SNHL is estimated at 1 in 1000 live births, the incidence of vestibular loss is unknown. Published reports show that vestibular dysfunction is found in approximately 20% to 70% of children with hearing loss of different causes. Furthermore, the prevalence of vestibular tests showing abnormalities is higher in profound than in severe SNHL, in postnatally acquired cases (meningitis, labyrinthitis), in some forms of syndromic deafness (Usher, Waardenburg, and Pendred syndromes), and in children with labyrinthine dysplasia. In contrast, recessive inherited deafness is usually associated with normal vestibular function. Establishing the presence of vestibular dysfunction in children with SNHL is often difficult despite careful history taking and physical examination. Besides the obvious limitation of children when describing vestibular symptoms, there is a wide normal variation in posture acquisition; moreover, in older children, central compensation obscures the presence of vestibular loss. In addition, the relative contribution of a vestibular loss to postural delay is difficult to assess in the presence of deficits in other participating systems. Notwithstanding these limitations, age-specific bedside clinical examination can provide a qualitative assessment of vestibular function. The bedside vestibular examination of the young child includes evaluation of the tonic neck reflexes, vestibular-ocular reflex (VOR), gait, and posture. The Table, modified from Eviatar and Eviatar, outlines the most common clinical tests of vestibular function according to the child’s age. Laboratory tests can be used for quantitative assessment of the vestibular function in infants and children. Most clinically available tests evaluate the VOR because it is the most accessible arm of the vestibular system. The VOR generates shortlatency eye movements in response Simon Angeli, MD

Evaluation of vestibular and visual oculomotor function

The visual system interacts synergistically with the vestibular system. A normally functioning vestibulo-ocular reflex is necessary but not sufficient for optimum visual acuity during head motion. Studies of dynamic visual acuity, the acuity achieved during relative motion of visual targets or of the observer, indicate that motion of images on the retina markedly compromises vision. The vestibulo-ocular reflex normally provides a substantial measure of stabilization of the retina during head movements, but purely vestibular compensatory eye movements are not sufficiently precise for optimal vision under all circumstances. Other mechanisms, including visual tracking, motor preprogramming, prediction, and mental set, interact synergistically to optimize the gain (eye velocity divided by head velocity) of compensatory head movements. All of these mechanisms are limited in their capacity to produce effective visual-vestibular interaction at higher rotational frequencies and velocities. It is under these conditions that vestibular deficits give rise to symptoms of oscillopsia. Patients having vestibular lesions exploit mechanisms of visual-vestibular interaction to compensate by substitution for deficient vestibular function. Thus, for accurate topographic clinical diagnosis of vestibular lesions, testing conditions should isolate purely vestibular responses. This may be done by testing reflex eye movements during passively generated rotations in darkness, or perhaps by testing during other types of motion under conditions of extreme frequency and velocity sufficient to attenuate the effects of visual-vestibular interaction. This article reviews clinical tests of vestibular function in relation to synergistic interactions with vision. (OTOLARYNGOL HEAD NECK SURG 1995;112:16-35.)

Evaluation of vestibular and visual oculomotor function.

The visual system interacts synergistically with the vestibular system. A normally functioning vestibulo-ocular reflex is necessary but not sufficient for optimum visual acuity during head motion. Studies of dynamic visual acuity, the acuity achieved during relative motion of visual targets or of the observer, indicate that motion of images on the retina markedly compromises vision. The vestibulo-ocular reflex normally provides a substantial measure of stabilization of the retina during head movements, but purely vestibular compensatory eye movements are not sufficiently precise for optimal vision under all circumstances. Other mechanisms, including visual tracking, motor preprogramming, prediction, and mental set, interact synergistically to optimize the gain (eye velocity divided by head velocity) of compensatory head movements. All of these mechanisms are limited in their capacity to produce effective visual-vestibular interaction at higher rotational frequencies and velocities. It is under these conditions that vestibular deficits give rise to symptoms of oscillopsia. Patients having vestibular lesions exploit mechanisms of visual-vestibular interaction to compensate by substitution for deficient vestibular function. Thus, for accurate topographic clinical diagnosis of vestibular lesions, testing conditions should isolate purely vestibular responses. This may be done by testing reflex eye movements during passively generated rotations in darkness, or perhaps by testing during other types of motion under conditions of extreme frequency and velocity sufficient to attenuate the effects of visual-vestibular interaction. This article reviews clinical tests of vestibular function in relation to synergistic interactions with vision.