Disturbances of spatial reference frame and postural asymmetry after a chronic stroke

Abstract

Asymmetrical postural behaviours are frequently observed after a stroke. They are due in part to the sensorimotor deficit, but could also be related to a disorder of the representation of the body in space. The objective was to determine whether the asymmetrical postural behaviours of chronic stroke patients are related to a disruption of the perception of spatial frame. Thirty chronic stroke patients (mean age 60.3 y ± 10, mean delay post-stroke 4.78 y ± 3) 15 patients with right brain damage (RDB) and 15 patients with left brain damage (LBD) and 20 healthy subjects participated in the study. Postural asymmetry was detected by the evaluation of body weight repartition on a force platform (weight body asymmetry) and was related to the longitudinal body axis (LBA) and the subjective straight ahead (SSA) (egocentric space representation) and also to the subjective visual vertical (SVV) (allocentric space representation) by means of a multivariate analysis of variance (MANOVA) which was adjusted with motor function and sensitivity as covariables. Both patients with RBD (35% ± 8) and LBD (39% ± 4) had a body weight asymmetry and there was still space misperception at this stage of recovery, especially in the RBD group. WBA was related to LBA when considering both patients with RDB and LDB ( P = 0.03). However, this relation was dependent on the side of the lesion ( P = 0.0006) with a stronger relation in the RBD group (58.26%). No relation with WBA was found neither with SSA ( P = 0.58) nor with SVV ( P = 0.47). This study pointed out a strong relationship between disturbance in the perception of the longitudinal body axis and postural asymmetry in chronic strokes, and predominantly within the RBD group. Whereas other spatial perturbations did not seem to be involved in this particular postural behaviour.