Abstract
Proprioception is a critical component for motor functions and directly affects motor learning after neurological injuries. Conventional methods for its assessment are generally ordinal in nature and hence lack sensitivity. Robotic devices designed to promote sensorimotor learning can potentially provide quantitative precise, accurate, and reliable assessments of sensory impairments. In this paper, we investigate the clinical applicability and validity of using a planar 2 degrees of freedom robot to quantitatively assess proprioceptive deficits in post-stroke participants. Nine stroke survivors and nine healthy subjects participated in the study. Participants’ hand was passively moved to the target position guided by the H-Man robot (Criterion movement) and were asked to indicate during a second passive movement towards the same target (Matching movement) when they felt that they matched the target position. The assessment was carried out on a planar surface for movements in the forward and oblique directions in the contralateral and ipsilateral sides of the tested arm. The matching performance was evaluated in terms of error magnitude (absolute and signed) and its variability. Stroke patients showed higher variability in the estimation of the target position compared to the healthy participants. Further, an effect of target was found, with lower absolute errors in the contralateral side. Pairwise comparison between individual stroke participant and control participants showed significant proprioceptive deficits in two patients. The proposed assessment of passive joint position sense was inherently simple and all participants, regardless of motor impairment level, could complete it in less than 10 minutes. Therefore, the method can potentially be carried out to detect changes in proprioceptive deficits in clinical settings.
Highlights
The high demand for neurorehabilitation has stimulated interest for technology-assisted systems with the intention to decrease the therapist’s workload and to facilitate recovery at an affordable cost [1,2,3]
The method proposed in this work allows the assessment of joint position sense independently of the severity of motor impairments as the movement is fully assisted by the robotic device
We found a trend for stroke patients to identify the target position in a more variable fashion compared to the control group, which is consistent with previous results: Dukelow et al [21] and Leibowitz et al [52] found a high variance in repeated trials performance of stroke patients compared to healthy individuals
Summary
The high demand for neurorehabilitation has stimulated interest for technology-assisted systems with the intention to decrease the therapist’s workload and to facilitate recovery at an affordable cost [1,2,3]. Clinical studies with these setups have shown that robot-assisted therapy of the upper-extremity is at least as effective as conventional rehabilitation therapy in reducing motor impairments [3, 8, 9]. A limited amount of work has been done in evaluating somatosensory integrity, which plays a critical role in performing activities of daily living as known for the last few decades. Rothwell in the early 80’s studied manual motor function in a deafferented man with severe sensory loss and found that the subject could perform trained complex tasks even with sensory loss, but could not translate this skill to other similar activities due to limited learning—a potential consequence of lack of sensory feedback [10]. A clear understanding of somatosensory loss is critical for identification of individual’s specific therapy regimes
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