Observational Evaluation of Muscle Echointensity and EMG Insertional Activity in Poststroke Spasticity

Introduction/aims: When spasticity occurs after a stroke, peripheral changes in spastic muscle architecture may develop. The primary objective was to determine if an association exists between spastic muscle echointensity (EI) measured by the Modified Heckmatt Scale (MHS) and changes in insertional activity detected by electromyography (EMG). The secondary aim was to investigate whether these changes are due to the effects of botulinum neurotoxin (BoNT). Methods: A total of 55 patients with poststroke spasticity were enrolled from three outpatient spasticity clinics. Muscle EI and needle EMG insertional activity were assessed for 8 muscles in each subject. Chi-square tests or Fisher's exact tests for categorical variables were used to evaluate the association between muscle EI and EMG insertional activity, as well as the association between BoNT exposure and muscle changes. Results: For MHS Grade 1-2 muscles, 91.7% had normal insertional activity compared to 46.4% of MHS Grade 3-4 muscles (p < 0.001). In muscles with abnormal insertional activity, reduced or absent insertional activity was seen in 67.3% of MHS 3-4 muscles compared to only 16.7% for MHS 1-2 muscles, while increased insertional activity was seen in 32.7% of MHS 3-4 muscles and 83.3% of MHS graded 1-2 muscles. Exposure to BoNT did not impact the observed association between MHS and abnormal EMG insertional activity. Discussion: Increased EI is associated with abnormal EMG insertional activity. Exposure to BoNT does not explain the observed EI and EMG changes. Further research is needed to elucidate the significance and causes of muscle architectural and electromyographical transformation in poststroke spasticity.