Dataset Information

VOR Gain Is Related to Compensatory Saccades in Healthy Older Adults.

ABSTRACT:

Objective

Vestibulo-ocular reflex (VOR) gain is well-suited for identifying rotational vestibular dysfunction, but may miss partial progressive decline in age-related vestibular function. Since compensatory saccades might provide an alternative method for identifying subtle vestibular decline, we describe the relationship between VOR gain and compensatory saccades in healthy older adults.

Methods

Horizontal VOR gain was measured in 243 subjects age 60 and older from the Baltimore Longitudinal Study of Aging using video head impulse testing (HIT). Saccades in each HIT were identified as either "compensatory" or "compensatory back-up," i.e., same or opposite direction as the VOR response respectively. Saccades were also classified as "covert" (occurring during head movement) and "overt" (occurring after head movement). The relationship between VOR gain and percentage of HITs with saccades, as well as the relationship between VOR gain and saccade latency and amplitude, were evaluated using regression analyses adjusting for age, gender, and race.

Results

In adjusted analyses, the percentage of HITs with compensatory saccades increased 4.5% for every 0.1 decrease in VOR gain (p < 0.0001). Overt compensatory saccade amplitude decreased 0.6° (p < 0.005) and latency increased 90 ms (p < 0.001) for every 0.1 increase in VOR gain. Covert back-up compensatory saccade amplitude increased 0.4° for every 0.1 increase in VOR gain.

Conclusion

We observed significant relationships between VOR gain and compensatory saccades in healthy older adults. Lower VOR gain was associated with larger amplitude, shorter latency compensatory saccades. Compensatory saccades reflect underlying rotational vestibular hypofunction, and may be particularly useful at identifying partial vestibular deficits as occur in aging adults.

SUBMITTER: Anson ER

PROVIDER: S-EPMC4919329 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

VOR Gain Is Related to Compensatory Saccades in Healthy Older Adults.

Anson Eric R ER Bigelow Robin T RT Carey John P JP Xue Qian-Li QL Studenski Stephanie S Schubert Michael C MC Agrawal Yuri Y

Frontiers in aging neuroscience 20160624

<h4>Objective</h4>Vestibulo-ocular reflex (VOR) gain is well-suited for identifying rotational vestibular dysfunction, but may miss partial progressive decline in age-related vestibular function. Since compensatory saccades might provide an alternative method for identifying subtle vestibular decline, we describe the relationship between VOR gain and compensatory saccades in healthy older adults.<h4>Methods</h4>Horizontal VOR gain was measured in 243 subjects age 60 and older from the Baltimore ...[more]

PMID: 27445793

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Project description:Background/hypothesisThe video Head Impulse Test (vHIT) is now widely used to test the function of each of the six semicircular canals individually by measuring the eye rotation response to an abrupt head rotation in the plane of the canal. The main measure of canal adequacy is the ratio of the eye movement response to the head movement stimulus, i.e., the gain of the vestibulo-ocular reflex (VOR). However, there is a need for normative data about how VOR gain is affected by age and also by head velocity, to allow the response of any particular patient to be compared to the responses of healthy subjects in their age range. In this study, we determined for all six semicircular canals, normative values of VOR gain, for each canal across a range of head velocities, for healthy subjects in each decade of life.Study designThe VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89.MethodsThe compensatory eye movement response to a small, unpredictable, abrupt head rotation (head impulse) was measured by the ICS impulse prototype system. The same operator delivered every impulse to every subject.ResultsVestibulo-ocular reflex gain decreased at high head velocities, but was largely unaffected by age into the 80- to 89-year age group. There were some small but systematic differences between the two directions of head rotation, which appear to be largely due to the fact that in this study only the right eye was measured. The results are considered in relation to recent evidence about the effect of age on VOR performance.ConclusionThese normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss. VOR gain, as measured directly by the eye movement response to head rotation, seems largely unaffected by aging.

Project description:Gaze stability exercises are a critical component of vestibular rehabilitation for individuals with vestibular hypofunction and many studies reveal the rehabilitation improves functional performance. However, few studies have examined the vestibular physiologic mechanisms (semicircular canal; otolith) responsible for such recovery after patients with vestibular hypofunction complete gaze and gait stability exercises. The purpose of this study was to compare behavioral outcome measures (i.e., visual acuity during head rotation) with physiological measures (i.e., gain of the vestibulo-ocular reflex) of gaze stability following a progressive vestibular rehabilitation program in patients following unilateral vestibular deafferentation surgery (UVD). We recruited n = 43 patients (n = 18 female, mean 52 ± 13 years, range 23-80 years) after unilateral deafferentation from vestibular schwannoma; n = 38 (25 female, mean 46.9 ± 15.9 years, range 22-77 years) age-matched healthy controls for dynamic visual acuity testing, and another n = 28 (14 female, age 45 ± 17, range 20-77 years) healthy controls for video head impulse testing. Data presented is from n = 19 patients (14 female, mean 48.9 ± 14.7 years) with UVD who completed a baseline assessment ~6 weeks after surgery, 5 weeks of vestibular physical therapy and a final measurement. As a group, subjective and fall risk measures improved with a meaningful clinical relevance. Dynamic visual acuity (DVA) during active head rotation improved [mean ipsilesional 38.57% ± 26.32 (n = 15/19)]; mean contralesional 39.96% ± 22.62 (n = 12/19), though not uniformly. However, as a group passive yaw VOR gain (mean ipsilesional pre 0.44 ± 0.18 vs. post 0.44 ± 0.15; mean contralesional pre 0.81 ± 0.19 vs. post 0.85 ± 0.09) did not show any change (p ≥ 0.4) after rehabilitation. The velocity of the overt compensatory saccades during ipsilesional head impulses were reduced after rehabilitation; no other metric of oculomotor function changed (p ≥ 0.4). Preserved utricular function was correlated with improved yaw DVA and preserved saccular function was correlated with improved pitch DVA. Our results suggest that 5 weeks of vestibular rehabilitation using gaze and gait stability exercises improves both subjective and behavioral performance despite absent change in VOR gain in a majority of patients, and that residual otolith function appears correlated with such change.

Project description:Compensatory strategies (behavioral/environmental modifications) can reduce the difficulties of performing daily living activities, fear of falling, and mortality risk. However, individuals vary in their readiness to use strategies. We examined characteristics associated with readiness to use compensatory strategies, the extent to which level of readiness changed from participation in an intervention (Advancing Better Living for Elders (ABLE)) providing compensatory strategies, and factors predictive of change in readiness level.Data from a randomized trial were used. Participants were 148 older adults assigned to the ABLE intervention designed to enhance daily function through compensatory strategy use. Baseline measures included demographic characteristics, functional difficulty level, presence/absence of depressive symptoms, compensatory strategy use, and social support. At initial (2 weeks from baseline) and final (6 months) ABLE sessions, interventionists rated readiness (1 = precontemplation; 2 = contemplation; 3 = preparation; 4 = action/maintenance) of participants to use strategies. Ordinal logistic regression was used to identify baseline characteristics associated with initial readiness rating. A McNemar-Bowker test of symmetry was used to describe change in readiness, and binary logistic regression was used to identify baseline predictors of change in readiness (from initial to final intervention session).At the initial intervention session, 70.3% (N = 104) scored in pre-action (precontemplation/contemplation, preparation), and 29.7% (N = 44) in action/maintenance. Depressive symptomatology (?2(2) = 9.08, p = 0.011) and low compensatory strategy use (F(2, 147) = 8.44, p = 0.001) at baseline were associated with lower readiness levels at initial ABLE session. By final ABLE session, most participants demonstrated greater readiness: 72% (N = 105) in action/maintenance, 28% (N = 41) in pre-action (two participants dropped out). A significant baseline predictor of positive change in readiness (from initial to final session) was higher social support levels (b = 0.10, SE = 0.05, Wald = 4.98, p = 0.026).Whereas presence of depressive symptomatology and lower use of compensatory strategies at baseline were associated with lower readiness at initial intervention session, neither predicted change in readiness level. Thus, mood and prior compensatory strategy use do not effect enhancements in readiness to use strategies provided in an intervention. Baseline social support was the strongest predictor of change in readiness suggesting that interventions may need to involve older adults' social networks to enhance acceptability of compensatory strategy use.

Dataset Information

VOR Gain Is Related to Compensatory Saccades in Healthy Older Adults.

Objective

Methods

Results

Conclusion

Publications

VOR Gain Is Related to Compensatory Saccades in Healthy Older Adults.

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