“…Postural instability is one of the major symptoms of Parkinson's disease, and the instability in the control of upright stance and posture in PD often results in falling (Bloem et al, 2001;Wood et al, 2002;Grimbergen et al, 2004;Bloem et al, 2006). Several studies reported that postural sway patterns during quiet stance in PD patients are different compared to those of healthy elderly subjects, with PD patients displaying larger lateral excursion compared with anteroposterior excursion (Mitchell et al, 1995;Morris et al, 2000;Van Wegen et al, 2001; Van der Burg et al, 2006).…”