Reliable and valid robot-assisted assessments of hand proprioceptive, motor and sensorimotor impairments after stroke

Abstract Background: Neurological injuries such as stroke often differentially impair hand motor and somatosensory function, as well as the interplay between the two, which leads to limitations in performing activities of daily living. However, it is challenging to identify which specific aspects of sensorimotor function are impaired based on conventional clinical assessments that are often insensitive and subjective. In this work we propose and validate a set of robot-assisted assessments aiming at disentangling hand proprioceptive from motor impairments, and capturing their interrelation (sensorimotor impairments). Methods: For this purpose, a battery of five complementary assessment tasks was implemented on a one degree-of-freedom end-effector robotic platform acting on the index finger metacarpophalangeal joint. Specifically, proprioceptive impairments were assessed using a position matching paradigm. Fast target reaching, range of motion and maximum fingertip force tasks characterized motor function deficits. Finally, sensorimotor impairments were assessed using a dexterous trajectory following task. Clinical feasibility (duration), reliability (intra-class correlation coefficient ICC, smallest real difference SRD) and validity (Kruskal-Wallis test, Spearman correlations rho) of these tasks were evaluated with 36 sub-acute stroke subjects and 31 age-matched neurologically intact controls. Results: Eighty-three percent of stroke survivors with varied impairment severity (mild to severe) could complete all robotic tasks (duration: 0.7, SRD<30%), as well as discriminant validity, as indicated by significant differences (p-value<0.001) between stroke and control subjects on all metrics extracted from the robotic tasks. Concurrent validity was shown through moderate to strong correlations (rho=0.4-0.8) between the robotic outcome measures and clinical scales. Finally, robotic tasks targeting different deficits were not strongly correlated, thereby presenting complementary information about a patient’s impairment profile. Conclusions: The proposed robot-assisted assessments provide a clinically feasible, reliable, and valid approach to distinctly characterize impairments in hand proprioceptive and motor function, along with the interaction between the two. This opens new avenues to help unravel the contributions of unique aspects of sensorimotor function in post-stroke recovery, as well as to contribute to future developments towards personalized, assessment-driven therapies.