MEASUREMENT OF IMPAIRED MUSCLE FUNCTION OF THE GASTROCNEMIUS, SOLEUS,AND TIBIALIS ANTERIOR MUSCLES IN SPASTIC HEMIPLEGIA - A PRELIMINARY-STUDY

Based on the results of several electrodiagnostic and biomechanical st udies, the following classification of muscle dysfunction in spastic h emiplegia is proposed: changes in muscle activation (excess symptoms, e.g., spasticity, and deficit symptoms, e.g., paresis); changes in mus cle stiffness; and changes in muscle length. The clinical significance of this classification is that different types of muscle dysfunction might require specific treatment. The authors have developed technique s to measure quantitatively each type of muscle dysfunction: free freq uency repetitive movement (FFRM) and torque angle diagram (TAD). Surfa ce EMGs of tibialis anterior, gastrocnemius, and soleus muscle are rec orded during active (FFRM) and passive (TAD) ankle movements. EMG data are converted to parameters for abnormal muscle activation (excess an d deficit symptoms). Parameters for muscle stiffness and muscle length are derived from the hysteresis curve of the TAD. This article descri bes the measurements and the results of a validation study. For the va lidation study, four hypotheses were formulated: 1) in nonimpaired con trol subjects, parameters expressing abnormal muscle activation are lo w; 2) in hemiplegic subjects, differences between the affected and the unaffected sides will be found for all types of parameters; 3) after local anaesthesia of the tibial nerve on the hemiplegic side, excess s ymptoms will decrease, while muscle stiffness remains unchanged; and 4 ) despite a uniform gait pattern, between-subject differences can be d etected with regard to muscle activation, stiffness, and length.