Robot-aided Assessment and Associated Brain Lesions of Impaired Ankle Proprioception in Chronic Stroke

Abstract

Abstract Background Impaired ankle proprioception strongly predicts balance dysfunction in chronic stroke. However, only sparse data on ankle position sense and no systematic data on ankle motion sense dysfunction in stroke are available. Moreover, the lesion sites underlying impaired ankle proprioception have not been comprehensively delineated. Using robotic technology, this study quantified ankle proprioceptive deficits post-stroke and determined the associated brain lesions. Methods Twelve adults with chronic stroke and 13 neurotypical adults participated. A robot passively plantarflexed a participant’s ankle to two distinct positions or at two distinct velocities. Participants subsequently indicated which of the two movements was further/faster. Based on the stimulus-response data, psychometric just-noticeable-difference (JND) thresholds and intervals of uncertainty (IU) were derived as measures on proprioceptive bias and precision. To determine group differences, Welch’s t-test and the Wilcoxon-Mann-Whitney test were performed for the JND threshold and IU, respectively. Voxel-based lesion subtraction analysis identified the brain lesions associated with observed proprioceptive deficits in adults with stroke. Results 83% of adults with stroke exhibited abnormalities in either position or motion sense, or both. JND and IU measures were significantly elevated compared to the control group (Position sense: + 77% in JND, + 148% in IU; Motion sense: +153% in JND, + 78% in IU). Lesions in the parietal, frontal, and temporoparietal regions were associated with deficits in both senses, lesions in the medial/lateral occipital cortex were exclusively linked to impaired position sense, and temporal pole lesions were associated with impaired motion sense. Conclusions This is the first study to document the prevalence and magnitude of ankle position and motion sense impairment in adults with chronic stroke. Proprioceptive dysfunction was characterized by elevated JND thresholds and increased uncertainty in perceiving ankle position/motion. Associated cortical lesions for both proprioceptive senses were largely overlapping, but temporal pole lesions were independently linked to motion sense dysfunction.