Abstract W P138: Hand Asymmetries in the Control of Grasp Force Post-Stroke

Abstract

Background and Purpose: Stroke survivors have difficulty overcoming deficits associated with grasping ability that differ for their right and left hand. However, grasp force deficits unique to each hand are not clearly characterized. The purpose of this study was to determine right and left hand differences in control of grasp force for individuals who were right handed pre-stroke. Methods: Twenty-one participants (13 with left hemispheric & 8 with right hemispheric stroke) completed clinical assessments and performed hand-grasp tasks using Instrumented Strain Gauges embedded with force sensors. Pre / post stroke hand preference scores were obtained using the self-reported Edinburgh Handedness Inventory (EHI). A right and left hand Reference Force (RF) was based on 20% of the right and left maximum grasp force. The Matching Force (MF) was performed by the opposite hand. Visual feedback represented by a horizontal line on a computer monitor displayed the 20% RF. MF, performed without visual feedback, indicated whether the participant overshot or undershot the RF and was quantified as the Constant Error. Results: EHI scores for right hemispheric stroke patients were 0.86 / 1.00 pre, and 0.92 / 1.00 post stroke, indicating greater right hand use post stroke. EHI scores for left hemispheric stroke patients were 0.91 / 1.00 pre, and 0.59 / 1.00 post stroke, indicating less right hand use and greater left hand use post stroke. The ANOVA showed a significant three-way interaction for matching hand *reference hand* affected side F(2, 38) =4.42, p < 0.05) for constant error. Right hemispheric stroke patients showed left hand MF undershoots for right hand RF (p < 0.05). Left hemispheric stroke patients showed right hand MF undershoots for left hand RF (p < 0.05). Conclusions: Shifts in handedness scores and asymmetries in force matching performance were dependent on lesion location. From a clinical perspective, stroke survivors may not be aware of how hand differences in the control of grasp force influence their ability to perform everyday tasks despite knowing that one hand may be weaker than the other. This suggests using a lesion-side specific treatment technique to improve awareness and function when performing unimanual and bimanual hand-grasp tasks.