Long lasting reduction of postural asymmetry by prism adaptation after right brain lesion without neglect

Abstract

Right brain damage (RBD) involves postural asymmetry and spatial frames disorders. In acute RBD patients, postural asymmetry is immediately reduced after one single session of prism adaptation (PA), without assessment of effects on spatial frames (Tilikete et al., 2001). To assess long-term effects of PA on posture and spatial frames in chronic RBD patients, without neglect. Six chronic RBD patients without neglect (mean delay: 45 months) were included. Each patient sustained 10 PA sessions of 20 minutes during 2 weeks. Outcome measures were: (i) posturographic analysis (mediolateral position of center of pressure (X cop ), (ii) subjective straight ahead (SSA) and perception of longitudinal body axis (LBA), (iii) the Scale for Controversive Pushing (SCP). Each parameter was assessed by 3 pre-tests and 3 post-tests (+2 h, Day + 3 and Day + 7). Moreover, the score of BBS, PASS, TUG and Barthel were measured. In pre-tests, all patients showed a shift of the X cop toward the right and a shift of SSA (4 toward the left and 2 toward the right). Four patients showed a shift of LBA (2 toward the right and 2 toward the left). The functional balance and the independence were decreased in all patients. In post-tests, results displayed (i) a significant reduction of mediolateral postural asymmetry at D + 7; (ii) a significant left deviation of SSA at D + 3 and enduring at D + 7; (iii) no significant modification of LBA and (iv) a significant increase of SCP at D + 3 and D + 7. Moreover, results showed a significant increase of PASS and BBS at D + 7. The mean curves of X cop and SSA between pre- and post-tests were similar. PA involves persistent reduction of postural asymmetry in RBD patients without neglect. These findings were obtained at a chronic stage. This new effect cannot be explained by reduction of spatial attentional shift. Improvement may be explained by a better calibration of extra-personal space frames used for posture, without effect on personal space frame. Findings argue in favour of a bottom-up effect of PA on mechanisms underlying spatial cognition.