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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Anne L. van Daalen ()
Elise J. Padmos ()
Sarah B. Zandvliet ()
Carel G.M. Meskers ()
Gert Kwakkel ()
Erwin E.H. van Wegen ()

Abstract:
An important consequence of stroke is postural instability, associated balance problems and falling. Adequate standing balance performance is related to perception of spatiotemporal margins relative to stability boundaries at the support surface. Boundary relevant measures are altered in neurologic patients compared to healthy individuals, however they have never been assessed in patients with a stroke. Objectives: Primary objective was to examine differences in boundary relevant measures between stroke patients and healthy controls. Secondary we studied the relationship between boundary relevant and traditional posturographic measures. Methods: In 24 chronic patients and 10 healthy age-matched individuals ground reaction forces were measured during quiet stance. Posturographic time-to-boundary (TtB) measures (mean TtB, TtB variability, TtB temporal distance (TD) and TD variability and CoP measurements (range, sway, path) in two conditions (eyes open, eyes closed) were calculated. Results: Stroke patients had a significantly lower mean TtB compared to healthy individuals in medio-lateral (ML) direction (mean(m)=7.89s (standard deviation (sd)=1.06) vs. m=16.49s, (sd=1.64), resp. p<0.01), and a significantly lower ML TtB variability (m=1.31s (sd=0.16) vs. m=2.52s (sd=0.24), resp. p<0.01). While no difference was found in anterior-posterior (AP) direction for mean TtB (stroke m=2.52 (sd=0.41) vs. healthy m=3.43s (sd=0.63), p=0.23), and TtB variability (stroke m=0.45s (sd=0.07) vs. healthy m=0.57s (sd=0.11), p=0.38). No significant differences were found for mean TD or TD variability for both directions. CoP sway and range in both directions and CoP path were significantly higher for stroke patients compared to healthy individuals. A significant negative correlation was found between mean TtB and CoP sway in ML direction (t=-0.66, p<0.01) and between mean TtB and CoP range in ML direction (t=-0.67, p<0.01) in stroke patients. Conclusion: Boundary relevant measures are altered in the chronic phase after stroke. Separate AP and ML TtB measures provide additional directional information. Lower mean ML TtB in stroke patients indicate lower spatio-temporal stability margins, likely related to the hemiparesis or balance asymmetry. Boundary relevant measures could contain critical information concerning the postural control system.