Head‐pelvis coupling is increased during turning in patients with Parkinson's disease and freezing of gait

Turning is the most important trigger for freezing of gait (FOG). The aim of this study was to investigate the relationship between impaired head‐pelvis rotation during turning and FOG. Head, trunk, and pelvic rotation were measured at onset and throughout a 180‐degree turn in 13 freezers and 14 nonfreezers (OFF medication). We also studied 14 controls at preferred and slow speed to investigate the influence of turn velocity on axial rotation. Location and duration of FOG episodes were defined during the turn. At turning onset, head rotation preceded thorax and pelvic rotation in all groups, but this craniocaudal sequence disappeared when FOG occurred. Maximum head‐pelvis separation was significantly greater in controls, compared to freezers and nonfreezers (35.4 versus 25.7 and 27.3 degrees; P < 0.01), but this finding was speed dependent. Timing of maximum head‐pelvis separation was delayed in freezers, compared to nonfreezers and controls, irrespective of turn velocity. This delay was correlated with increased neck rigidity (R = 0.62; P = 0.02) and worsened during FOG trials. FOG occurred more often at the end of the turn, when difference in rotation velocity between head and pelvis was greatest. Even after controlling for speed and disease severity, turning in freezers was characterized by delayed head rotation and a closer coupling between head and pelvis, especially in turns where FOG occurred. These changes may be attributed to delayed preparation for the change in walking direction and, as such, contribute to FOG. © 2013 Movement Disorder Society