Differential loss of position sense and kinesthesia in sub-acute stroke.

Position sense and kinesthesia are thought to be independent sub-modalities of proprioception, based on neuromuscular recordings in the periphery. However, little evidence has demonstrated separation in the central nervous system (CNS). Stroke provides an interesting model to examine this dissociation in the CNS due to the heterogeneity of lesion locations and high incidence of proprioceptive impairment. Here, we aimed to determine if position sense and kinesthesia are behaviorally dissociable in a stroke patient model, and if behavioral dissociations in proprioception corresponded to different stroke lesion damage. Position sense and kinesthesia were assessed in subjects with unilateral stroke (N = 285) using two robotic tasks: Position Matching (PM) and Kinesthetic Matching (KIN). Without vision, the robot moved the subjects' stroke-affected arm and they mirror-matched perceived location (PM) or movement (KIN) with their opposite arm. Fifty-two percent of subjects had deficits in both PM and KIN, 22% had impairments in only one sub-modality (7% PM only, 15% KIN only). These subjects tended to have smaller lesions (internal capsule, basal ganglia, insula) compared to those with larger lesions affecting both sub-modalities. Overall, we observed separation of proprioceptive sub-modalities in a large number of stroke subjects, and that lesion load impacted the pattern of proprioceptive impairment.