Center of mass trajectories during turning in patients with Parkinson's disease with and without freezing of gait

Abstract

Background: Despite the strong relationship between freezing of gait (FOG) and turning in Parkinson's disease (PD), few studies have addressed specific postural characteristics during turning that might contribute to freezing. Methods: Thirty participants with PD (16 freezers, 14 non-freezers) (all tested OFF medication) and 14 healthy controls walked 5 meters and turned 180 degrees in a 3D gait laboratory. COM behavior was analyzed during four turning quadrants of 40 degrees between 10 degrees and 170 degrees pelvic rotation and during 40 degrees before actual FOG episodes. These pre-FOG segments were compared with similar turning sections in turns of freezers without FOG. Outcome parameters were turn time, COM distance, COM velocity, step width and the medial- and anterior COM position. Results: Turn time was increased in freezers compared to non-freezers (p = .000). No differences were found regarding COM distance and velocity during turning quadrants between groups and between freezers' pre-FOG segments and similar turning segments without FOG. Medial COM deviation was reduced in PD patients compared to controls (p = .004), but no differences were found between freezers and non-freezers. In turns with freezing, turn time increased (p = .005) and step width decreased (p = .025) pre-FOG. Freezers also showed a less medial (p = .020) and more anterior (p = .016) COM position pre-FOG compared to turning sections without FOG. Conclusions: Our results revealed no subgroup differences in COM behavior during uninterrupted turning. However, we found a reduced medial deviation, a forward COM shift and a decreased step width in freezers just before FOG episodes. These abnormalities may play a causal role, as they could hamper stability and fluent weight shifting necessary for continued stepping during turning. (C) 2015 Elsevier B.V. All rights reserved.