Oral Communication

Reliability study of the Visual Vertical in subacute stroke

Mrs Céline PISCICELLIa, Mr Julien BARRAb, Dr Patrice DAVOINEc, Dr Anne CHRISPINc, Prof Sylvie NADEAUd, Prof Dominic PÉRENNOUe

a CHU Grenoble, MPR neurologique & Laboratoire de Psychologie et NeuroCognition, b Laboratoire Vision Action Cognition, c CHU Grenoble, MPR Neurologique, d École de réadaptation, Université de Montréal & Centre de recherche interdisciplinaire en réadaptation (CRIR), e CHU de Grenoble, MPR neurologique & Laboratoire de Psychologie et NeuroCognition

Objectives: Visual vertical (VV) has been being increasingly used as a routine clinical assessment to identify alteration of verticality perception as a possible cause of postural disorders after stroke. This study aims to determine if the reliability of VV is sufficient to support a wide clinical use in neuro-rehabilitation for stroke patients monitoring. We assessed the inter-and intra-raters reliability and the inter-trials reliability.

Methods: In a first study, 20 subacute stroke patients in neuro-rehabilitation unit were tested after a first hemispheric stroke. To evaluate the inter-rater reliability, VV was assessed the same day by 2 examiners whose degrees of expertise differed. The second examiner repeated the test the next day in order to investigate intra-rater reliability. VV orientation (mean, primary criterion) and uncertainty (standard deviation, secondary criterion) were calculated over 10 trials. Their reliability was quantified by the intraclass correlation coefficient [ICC], Bland-Altman plots and the minimal detectable change (MDC).The concordance between two examiners was quantified by Cohen's kappa coefficients (κ). In a second study, inter-trials reliability was assessed in 117 subacute stroke patients by ICC and SEM.

Results: In study 1, regarding VV orientation, inter-and intra-rater reliability were excellent (ICC=0.979 and 0.982).The Bland-Altman plots and the MDC revealed a difference inferior to 2° between two tests. The concordance between two assessments for the diagnosis of abnormal VV orientation was absolute for the same examiner (κ=1;p<0.05) and excellent between two examiners (κ=0.92;p<0.05).As for VV uncertainty the intra-rater reliability was satisfactory (ICC=0.836) but the inter-rater reliability poor (ICC=0.211). In study 2, a high inter-trials reliability required a minimum of 8 trials (ICC=0.909; SEM=1.18°) for patients with contralesional VV bias, whereas a minimum of 6 and 10 trials were required for patients with ipsilesional VV bias (ICC=0.896; SEM=0.96) and patients with normal VV perception (ICC=0.728; SEM=1.13) respectively.

Conclusion: The orientation of the visual vertical is a highly reliable criterion, which may be used both in research and routine clinical practice. VV orientation can be adequately assessed with 6 to 10 trials in subacute stroke patients. Ten trials are recommended when comparison between sub-groups of patients having divers VV biased perception is intended.

Keywords : Spatial cognition, psychometric properties, verticality perception, rehabilitation