Abstract
Proprioceptive deficits negatively affect postural control but their precise contribution to postural instability in Parkinson’s disease (PD) is unclear. We investigated if proprioceptive manipulations differentially affect balance, measured by force plates, during quiet standing in 13 PD patients and 13 age-matched controls with a history of falls. Perceived limits of stability (LoS) were derived from the differences between maximal center of pressure (CoP) displacement in anterior–posterior (AP) and medio-lateral (ML) direction during a maximal leaning task. Task conditions comprised standing with eyes open (EO) and eyes closed (EC): (1) on a stable surface; (2) an unstable surface; and (3) with Achilles tendon vibration. CoP displacements were calculated as a percentage of their respective LoS. Perceived LoS did not differ between groups. PD patients showed greater ML CoP displacement than elderly fallers (EF) across all conditions (p = 0.043) and tended to have higher postural sway in relation to the LoS (p = 0.050). Both groups performed worse on an unstable surface and during tendon vibration compared to standing on a stable surface with EO and even more so with EC. Both PD and EF had more AP sway in all conditions with EC compared to EO (p < 0.001) and showed increased CoP displacements when relying on proprioception only compared to standing with normal sensory input. This implies a similar role of the proprioceptive system in postural control in fallers with and without PD. PD fallers showed higher ML sway after sensory manipulations, as a result of which these values approached their perceived LoS more closely than in EF. We conclude that despite a similar fall history, PD patients showed more ML instability than EF, irrespective of sensory manipulation, but had a similar reliance on ankle proprioception. Hence, we recommend that rehabilitation and fall prevention for PD should focus on motor rather than on sensory aspects.
Highlights
Falls are a major problem in the elderly population
This study investigated the impact of proprioceptive manipulations on postural control in patients with Parkinson’s disease (PD) and healthy people with a history of falls
Comparing a group of PD patients with elderly fallers (EF), instead of elderly non-fallers allowed identifying both general aspects of postural imbalance and additional Parkinsonspecific components
Summary
Falls are a major problem in the elderly population. Approximately 30% of community-dwelling elderly over 65 years of age experience at least one fall per year and this amount increases up to 50% by the age of 80 (Tinetti and Williams, 1997). The integrity of these systems declines (Horak, 2006; Muir et al, 2013), resulting in sensory impairments and gait and balance disturbances (Dozza et al, 2005; Cho et al, 2012). Quiet standing predominantly depends on somatosensory processing, with proprioception, or the sense of body movement and spatial orientation, as a vital component. Disrupting proprioception during quiet standing on a movable surface was shown to increase body sway in the elderly and subjects with sensory polyneuropathy (Horak et al, 2002; Speers et al, 2002; Goble et al, 2011). Standing on a foam surface reduces the Frontiers in Human Neuroscience www.frontiersin.org
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