Leg orientation as a clinical sign for pusher syndrome

Abstract

Background: Effective control of (upright) body posture requires a proper representation of body orientation. Stroke patients with pusher syndrome were shown to suffer from severely disturbed perception of own body orientation. They experience their body as oriented 'upright' when actually tilted by nearly 20 degrees to the ipsilesional side. Thus, it can be expected that postural control mechanisms are impaired accordingly in these patients. Our aim was to investigate pusher patients' spontaneous postural responses of the non-paretic leg and of the head during passive body tilt.

Methods: A sideways tilting motion was applied to the trunk of the subject in the roll plane. Stroke patients with pusher syndrome were compared to stroke patients not showing pushing behaviour, patients with acute unilateral vestibular loss, and non brain damaged subjects.

Results: Compared to all groups without pushing behaviour, the non-paretic leg of the pusher patients showed a constant ipsiversive tilt across the whole tilt range for an amount which was observed in the non-pusher subjects when they were tilted for about 15 degrees into the ipsiversive direction.

Conclusion: The observation that patients with acute unilateral vestibular loss showed no alterations of leg posture indicates that disturbed vestibular afferences alone are not responsible for the disordered leg responses seen in pusher patients. Our results may suggest that in pusher patients a representation of body orientation is disturbed that drives both conscious perception of body orientation and spontaneous postural adjustment of the non-paretic leg in the roll plane. The investigation of the pusher patients' leg-to-trunk orientation thus could serve as an additional bedside tool to detect pusher syndrome in acute stroke patients.

Figure 1

Pusher patient with right hemisphere stroke and left-sided hemiparesis during three tilt positions within one experimental body tilt cycle (open eyes condition). One can easily see that the patient with pusher syndrome exhibits a constant ipsiversive tilt (with respect to trunk orientation) of his non-paretic leg when sitting upright. This inclined leg position was kept throughout the whole tilt cycle. The read lines represent the longitudinal axes of the respective body segments. (The patient does not show pushing behaviour on this series of photos because he was required to hold his arms in his lap and was not able to touch the floor with his feet.)

Figure 2

Mean leg orientation as a function of trunk orientation for each subject of all four groups over the whole tilt cycle. Each thin line represents the performance of a single individual, averaged across five tilt cycles and both viewing conditions. The broken thick line indicates each group's averaged linear regression derived from all individuals' regression parameters. Positive values indicate orientation into the ipsiversive/right direction; negative values indicate orientation into the contraversive/left direction.

Figure 3

(A) Mean leg-to-trunk orientation of all four subject groups for both directions of body tilt and both viewing conditions. Positive values indicate a relative orientation of the leg into the ipsiversive/right direction; negative values into the contraversive/left direction. (B) Mean head-to-trunk orientation of all four subject groups for both directions of body tilt and both viewing conditions. Error bars indicate standard deviations; asterisks indicate significant differences with p < 0.05.