Abstract
BackgroundThe visual vertical (VV) consists of repeated adjustments of a luminous rod to the earth vertical. How many trials are required to reach consistency in this measure? This question has never been addressed despite the widespread clinical use of the measurement in stroke rehabilitation.MethodsVV perception was assessed (10 trials) in 117 patients undergoing rehabilitation after a first hemisphere stroke. The intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated for each patient category: with contralesional VV bias (n = 48), ipsilesional VV bias (n = 17) and normal VV (n = 52).ResultsFor patients with VV biases, 6 trials were required to reach high inter-trial reliability (contralesional: ICC = 0.9, SEM = 1.36°; ipsilesional: ICC = 0.896, SEM = 0.96°). For patients with normal VV, a minimum of 10 trials was required (ICC = 0.728, SEM = 1.13°). A set of 6 trials correctly classified 96 % of patients.ConclusionsIn the literature, 10 is the most frequently used number of trials used to assess VV orientation. Our study shows that 10 trials are required to adequately measure VV orientation in non-selected subacute stroke patients. For complex protocols imposing a decrease in the number of trials in each condition, 6 trials are needed to identify VV biases in most patients.
Highlights
The visual vertical (VV) consists of repeated adjustments of a luminous rod to the earth vertical
The measurement consists of repeated adjustments of a luminous rod to the earth vertical in darkness from which the mean orientation perceived as vertical (VV orientation) is calculated [1,2,3,4,5,6,7]
The number of adjustments, usually even [1,2,3,4,5,6,7, 11, 12], counterbalances the leftward and rightward initial tilt to reduce the effect of the initial tilt position of the rod on VV measurement [13]
Summary
The visual vertical (VV) consists of repeated adjustments of a luminous rod to the earth vertical. Ipsilesional VV biases are less frequent (about 10 % of patients after hemisphere stroke) and smaller in magnitude [2, 3], and In estimating these alterations in VV perception, the number of adjustments reported in the published studies varies from 2 [5] to 30 trials [10]. Studies of stroke patients assessing VV with more than 10 trials are few [10, 12] because these patients often present high fatigability and limited attentional resources, which may compromise or limit clinical assessments This situation is true for subacute stroke patients in neuro-rehabilitation units, where a reliable measure of Piscicelli et al BMC Neurology (2015) 15:215
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