Maintaining Trunk and Head Upright Optimizes Visual Vertical Measurement After Stroke

Background. Visual vertical (VV) measurement provides information about spatial cognition and is now part of postural disorders assessment. Guidelines for clinical VV measurement after stroke remain to be established, especially regarding the orientation settings for patients who do not sit upright. Objectives. We analyzed the need to control body orientation while patients estimate the VV. Methods. VV orientation and variability were assessed in 20 controls and 36 subacute patients 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 trunk and head tilt, also quantified. Results. Trunk and head orientations were independent. The ability to sit independently was affected by a tilted trunk. The setting had a strong effect on VV orientation and variability in patients with contralesional trunk tilt (n = 11; trunk orientation -18.4 +/- 11.7 degrees). The contralesional VV bias was severe and consistent under partially maintained (-8.4 +/- 5.2 degrees) and maintained (-7.8 +/- 3.5 degrees) settings, whereas various individual behaviors reduced the mean bias under the nonmaintained setting (-3.6 +/- 9.3 degrees, P < .05). VV variability was lower under the maintained (1.5 +/- 0.2 degrees) than nonmaintained (3.7 +/- 0.4 degrees, P < .001) and partially maintained (3.6 +/- 0.2 degrees, P < .001) settings. In contrast, setting had no effect in patients with satisfactory postural control in sitting. Conclusion. Subject setting improves VV measurement in stroke patients with postural disorders. Maintaining the trunk upright enhances the validity of VV orientation, and maintaining the head upright enhances the validity of within-subject variability. Measuring VV without any body maintaining is valid in patients with satisfactory balance abilities.