Test-retest reliability and response stability of gaze stabilization, postural sway, and dynamic balance tests in persons with multiple sclerosis and controls

Background: Psychometric properties of tests that assess the angular vestibulo-ocular reflex (aVOR) and vestibulospinal reflex function are currently unknown. This study investigated the test-retest reliability and response stability of gaze stabilization, postural sway, and dynamic balance measures in persons with multiple sclerosis (MS) and controls. Methods: Nineteen adults with MS and 14 controls performed passive horizontal head impulses, quiet standing, and dynamic balance tests on two separate occasions. Gaze stabilization measures included aVOR gain, number of compensatory saccades (CSs) per head rotation, CS latency, and gaze position error. Postural sway included sway amplitude and total sway path. Dynamic balance measure included the Functional Gait Assessment. Intraclass correlation coefficient, standard error of measurement (SEM, SEM%), and minimal detectable difference at 95% confidence level were calculated. Results: Test-retest reliability for aVOR gain, CSs per head rotation, and gaze position error was moderate and for each postural sway and dynamic balance measure was good. Low error (SEM, SEM%) for aVOR gain, CS latency, postural sway, and dynamic balance variables and low minimal detectable difference values for aVOR gain and Functional Gait Assessment scores were seen, suggestive of acceptable response stability. Conclusions: These results support the utility of some of the gaze and postural measures for examination and treatment efficacy purposes in people with MS.