The independence of deficits in position sense and visually guided reaching following stroke

Abstract

Background: Several studies have found correlations between proprioception and visuomotor function during stroke recovery, however two more recent studies have found no correlation. Unfortunately, most of the studies to date have been conducted with clinical assessments of sensation that are observer-based and have poor reliability. We have recently developed new tests to assess position sense and motor function using robotic technology. The present study was conducted to reassess the relationship between position sense and upper limb movement following stroke.

Methods: We assessed position sense and motor performance of 100 inpatient stroke rehabilitation subjects and 231 non-disabled controls. All subjects completed quantitative assessments of position sense (arm-position matching task) and motor performance (visually-guided reaching task) using the KINARM robotic device. Subjects also completed clinical assessments including handedness, vision, Purdue Pegboard, Chedoke-McMaster Stroke Assessment-Impairment Inventory and Functional Independence Measure (FIM). Neuroimaging documented lesion localization. Fisher's exact probability tests were used to determine the relationship between performances on the arm-position matching and visually-guided reaching task. Pearson's correlations were conducted to determine the relationship between robotically measured parameters and clinical assessments.

Results: Performance by individual subjects on the matching and reaching tasks was statistically independent (Fisher's test, P<0.01). However, performance on the matching and reaching tasks both exhibited relationships with abilities in daily activities as measured by the FIM. Performance on the reaching task also displayed strong relationships with other clinical measures of motor impairment.

Conclusions: Our data support the concept that position sense deficits are functionally relevant and point to the importance of assessing proprioceptive and motor impairments independently when planning treatment strategies.

Figure 1

Exemplar control subject data.A) Arm-position matching task as seen from above. On the left, the positions of the robotically moved hand are filled symbols; positions of the actively moved hand are open symbols. Ellipses represent 1 standard deviation. B) Passive (robotically moved) hand positions have been mirrored onto those of the active hand for visualization purposes. C) Individual hand paths for movements to each of the eight targets in the visually guided reaching task. D) Velocity profiles for hand paths from the centre to the rightward target.

Figure 2

Exemplar data from subjects with stroke. Data are presented in the left column for position matching, and the middle and right hand columns for visually guided reaching movements. A &B) Two subjects with stroke who performed within normal limits on both tasks. C &D) Two subjects with stroke who performed outside the normal range on the matching task, but were normal on the reaching task. E &F) Two subjects with stroke who performed normally on the matching task, but were abnormal on the reaching task. G &H) Two subjects with stroke who performed abnormally on both tasks.

Figure 3

A) Scatter plot of matching parameters Variability (Var_xy) vs Systematic Shift (Shift_xy). Grey shading represents normal control performance on each parameter. Tick marks indicate regions where normal performance can vary due to each subject’s age, gender, and/or active arm. Circles: subjects with stroke who perform normally on both parameters. Diamonds: subjects with stroke who perform abnormally on both parameters. Squares: subjects with stroke who perform abnormally on Var_xy only. Triangles: subjects with stroke who perform abnormally on Shift_xy only. B) Scatter plot of reaching parameters Movement Time (MT) versus Initial Direction Error (IDE). Shading and symbols similar to above. C) Scatter plot of reaching parameter MT versus position matching parameter Var_xy. Shading and symbols similar to above.