Predictive factors of hypertonia in the upper extremity of chronic stroke survivors

[Purpose] Muscle tone is known to predict the motor function of the upper extremity within 12 months after onset in stroke survivors. The aim of this study was to investigate whether motor function of the upper extremity can predict the risk of hypertonia in chronic stroke survivors, and to analyze the correlation between the two variables to determine the predictive validity. [Subjects and Methods] Forty-three chronic stroke survivors were assessed using the Modified Ashworth Scale (MAS) for elbow flexor tone, the Fugl-Meyer assessment of the upper extremity (FM-UE), and the Action Research Arm Test (ARAT) for upper extremity motor recovery and function. [Results] Elbow flexor tone (MAS≥1(+)) increased by 0.246 compared with the baseline muscle tone even at month 12 and appeared to negatively affect the motor function of the upper extremity. The cutoff value for predicting muscle tone (MAS≥1(+)) was 24 for FM-UE and 15.5 for ARAT. FM-UE had the biggest impact on elbow flexor tone (MAS≥1(+)), and the risk of elbow flexor hypertonia (MAS≥1(+)) increased 0.764-fold for a cutoff value of FM-UE≤24 compared with a cutoff value of FM-UE>24. [Conclusion] The results show that the most important variable for predicting muscle tone of the elbow flexor in stroke survivors is the FM assessment of the upper extremity.