Maintaining Trunk and Head Upright Optimizes Visual Vertical Measurement After Stroke

International audienceBackground. Visual vertical (VV) measurement provides information about spatial cognition and is now part of posturaldisorders assessment. Guidelines for clinical VV measurement after stroke remain to be established, especially regardingthe orientation settings for patients who do not sit upright. Objectives. We analyzed the need to control body orientationwhile patients estimate the VV. Methods. VV orientation and variability were assessed in 20 controls and 36 subacutepatients undergoing rehabilitation after a first hemisphere stroke, in 3 settings: body not maintained (trunk and head free),partially maintained (trunk maintained, head free), or maintained (trunk and head). VV was analyzed as a function of trunkand head tilt, also quantified. Results. Trunk and head orientations were independent. The ability to sit independently wasaffected by a tilted trunk. The setting had a strong effect on VV orientation and variability in patients with contralesionaltrunk tilt (n = 11; trunk orientation −18.4 ± 11.7°). The contralesional VV bias was severe and consistent under partiallymaintained (−8.4 ± 5.2°) and maintained (−7.8 ± 3.5°) settings, whereas various individual behaviors reduced the mean biasunder the nonmaintained setting (−3.6 ± 9.3°, P < .05). VV variability was lower under the maintained (1.5 ± 0.2°) thannonmaintained (3.7 ± 0.4°, P < .001) and partially maintained (3.6 ± 0.2°, P < .001) settings. In contrast, setting had no effectin patients with satisfactory postural control in sitting. Conclusion. Subject setting improves VV measurement in strokepatients with postural disorders. Maintaining the trunk upright enhances the validity of VV orientation, and maintainingthe head upright enhances the validity of within-subject variability. Measuring VV without any body maintaining is valid inpatients with satisfactory balance abilities