Tilted 3D visual scenes - A new therapy approach for pusher syndrome

Hemiparetic stroke patients with 'pusher syndrome' use their non-paretic extremities to push towards their paralyzed side and actively resist external posture correction. The disorder is associated with a distorted perception of postural vertical combined with a maintained, or little deviating perception of visual upright. With the aim of reducing this mismatch, and thus reducing pushing behavior, we manipulated the orientation of visual input in a virtual reality setup. We presented healthy subjects and an acute stroke patient with severe pusher syndrome a 3D visual scene that was either upright or tilted in roll plane by 20{degrees}. By moving the sitting participants in roll plane to the left and right, we assessed the occurrence of active pushing behavior, namely the active resistance to external posture manipulation. With the 3D visual scene oriented upright, the patient with pusher syndrome showed the typical active resistance against tilts towards the ipsilesional side. He used his non-paretic arm to block the examiner's attempt to move the body axis towards that side. With the visual scene tilted to the ipsiversive left, his pathological resistance was significantly reduced. Statistically, the tolerated body tilt angles no longer differed from those of healthy controls. We conclude that even short presentations of tilted 3D visual input can reduce pusher symptoms. The technique provides potential for a new treatment method of pusher syndrome and offers a simple, straightforward approach that can be effortlessly integrated in clinical practice.