Anatomical correlates of proprioceptive impairments following acute stroke: a case series.

BACKGROUND Proprioception is the sensation of position and movement of our limbs and body in space. This sense is important for performing smooth coordinated movements and is impaired in approximately 50% of stroke survivors. In the present case series we wanted to determine how discrete stroke lesions to areas of the brain thought to be critical for somatosensation (thalamus, posterior limb of internal capsule, primary somatosensory cortex and posterior parietal cortex) would affect position sense and kinesthesia in the acute stages post-stroke. Given the known issues with standard clinical measures of proprioception (i.e. poor sensitivity and reliability) we used more modern quantitative robotic assessments to measure proprioception. METHODS Neuroimaging (MRI, n=10 or CT, n=2) was performed on 12 subjects 2-10 days post-stroke. Proprioception was assessed using a KINARM robot within the same time frame. Visually guided reaching was also assessed to allow us to compare and contrast proprioception with visuomotor performance. RESULTS AND CONCLUSIONS Proprioceptive impairments were observed in 7 of 12 subjects. Thalamic lesions (n=4) were associated with position sense (n=1) or position sense and kinesthesia (n=1) impairments. Posterior limb of the internal capsule lesions (n=4) were associated with primarily position sense (n=1) or kinesthesia (n=2) impairments. Lesions affecting primary somatosensory cortex and posterior parietal cortex (n=2) were associated with significant position sense and kinesthesia impairments. All subjects with damage to hypothesized structures displayed impairments with performance on the visually guided reaching task. Across the proprioceptive tasks, we saw that position sense and kinesthesia were impaired to differing degrees, suggesting a potential dissociation between these two components of proprioception.