Background: Somatosensory impairment of the hand persists in 50% of stroke survivors and is associated with reduced arm function. Stroke survivors may not use their arm in real life despite motor recovery. Aim: to examine relationships between quantitative, discriminative measures of somatosensation (touch discrimination, wrist proprioception and object recognition), sensorimotor function and arm use.
Methods: Path Analysis methodology was used to explore causal relationships between somatosensation and arm use, inclusive of sensorimotor function, at a single timepoint.
Results: Participants had somatosensory impairment of the hand (n=44) in at least one modality. Tactile object recognition showed a moderate to good correlation with arm use (motor activity log, r=0.55) and the action research arm test (ARAT, r=0.63). Path analysis findings: 1. Three somatosensory variables predicted 33% of the variance in arm use. Object recognition had a direct effect on arm use (β=0.61, p=0.004). 2. Three somatosensory variables predicted 45% of the variance in sensorimotor function (ARAT). Object recognition had a direct effect on ARAT (β=0.71, p=0.002). Texture discrimination (β=0.38, p=0.002) and wrist proprioception (β=-.22, p=0.004) had indirect effects on ARAT. 3. Somatosensory variables and ARAT together predicted 66% of the variance in arm use. A significant total effect was found for both the ARAT (β=0.77, p=0.002) and object recognition (β=0.61, p=0.004) on arm use.
Conclusion: Sensorimotor function together with object recognition, a complex, integrative measure of sensation, had substantial total effects on arm use. This study highlights the significant yet underexplored role of somatosensation, particularly object recognition, in arm use after stroke.