Professor University of Maryland School of Medicine, United States
Introduction: Stroke is a leading cause of long-term disability globally, affecting millions of individuals each year. One significant area of impairment post-stroke is proprioception, the sense of body position and movement. Proprioceptive deficits can greatly impact sensory-motor coordination and rehabilitation outcomes, decreasing the quality of life. Despite the importance of proprioception, the specific effects of stroke on finger proprioception remain poorly understood.
Materials and
Methods: A modified Hand of Hope (HoH) hand robot with a LabView control program was used to assess proprioceptive acuity in stroke survivors (n=14) compared to healthy controls (n=10). Participants were instructed to close their eyes and press a handheld switch using the other hand when a HoH-controlled slow movement was felt, while also indicating which digit was moved and its movement direction (flexion or extension). The experiment consisted of 20 trials with a set randomized sequence of different digits and directions for each participant. Digits 1, 2, 3, 4 and 5 refer to the thumb, index finger, middle finger, ring finger and pinky finger, respectively. Data was analyzed using MATLAB for the digit movement driven by the linear actuators of the HoH from the initial position to the position when the handheld switch was pressed (Figure 1). A 3-way repeated measures (2 X 5 X 2) ANOVA was used to analyze the result with 3 independent factors of group (Stroke and Healthy), digit (1 to 5), and direction (flexion and extension).
Results, Conclusions, and Discussions: The results show a significant difference between groups [F(1, 168) = 62.453, p<.001] meaning the stroke group had lower proprioceptive acuity than the healthy group. There was also a significant difference in direction [F(1, 168) = 52.276, p<.001], where the stroke group displayed higher proprioceptive acuity in the outward direction than the inward direction (Figure 2). However, there was no significant difference across the five digits within the stroke group [F(4, 168) = .189, p =.994].
Through further analysis, a pairwise comparison of group and direction revealed a significant group difference in direction at each digit, including significant differences at Digit 1 Flexion (p = .001), Digit 2 Flexion (p = .004), Digit 2 Extension (p = .007), Digit 3 Flexion (p < .001), Digit 4 Flexion (p = .029), and Digit 5 Flexion (p < .001). A pairwise comparison of proprioceptive acuity within groups between digits (p = .913) revealed there was no significant difference, meaning that both the stroke and healthy group's proprioceptive acuity were similar across all digits. Another pairwise comparison of proprioceptive acuity in different directions across digits (p = .884) revealed there was no significant difference, indicating that there was insignificant sensitivity to flexion versus extension between the different digits.
These results suggest that stroke-related sensorimotor impairment including muscle spasticity and paralysis may contribute to heightened sensitivity towards extension movements. The significant interaction between group and direction highlights the importance of considering specific movement deficits in proprioceptive rehabilitation. Furthermore, although there was no significant difference across different digits, the overall lower proprioceptive acuity in the stroke group suggests a generalized deficit affecting all fingers uniformly. Tailoring rehabilitation to address these deficits could enhance proprioceptive function and improve functional outcomes in stroke survivors.
