Objectives: We quantitatively examined the motor-imagery ability in stroke patients using a bimanual circle-line coordination task (BCT) and clarified the relationship between motor-imagery ability and motor function of hemiplegic upper limbs and the level of use of paralyzed limbs.
Methods: We enrolled 31 stroke patients. Tasks included unimanual-line (U-L)-drawing straight lines on the nonparalyzed side; bimanual circle-line (B-CL)-drawing straight lines with the nonparalyzed limb while drawing circles with the paralyzed limb; and imagery circle-line (I-CL)-drawing straight lines on the nonparalyzed side during imagery drawing on the paralyzed side, using a tablet personal computer. We calculated the ovalization index (OI) and motor-imagery ability (image OI). We used the Fugl-Meyer motor assessment (FMA), amount of use (AOU), and quality of motion (QOM) of the motor activity log (MAL) as the three variables for cluster analysis and performed mediation analysis.
Results: Clusters 1 (FMA <26 points) and 2 (FMA ≥26 points) were formed. In cluster 2, we found significant associations between image OI and FMA, AOU, and QOM. When AOU and QOM were mediated between image OI and FMA, we observed no significant direct association between image OI and FMA, and a significant indirect effect of AOU and QOM.
Interpretation: In stroke patients with moderate-to-mild movement disorder, image OI directly affects AOU of hemiplegic upper limbs and their QOM in daily life and indirectly influences the motor functions via those parameters.