Is spastic muscle echo intensity related to the response to botulinum toxin type a in patients with stroke? A cohort study

OBJECTIVE: To investigate the relationship between gastrocnemius muscle echo intensity and response to botulinum toxin type A (BoNT-A) in patients with spastic equinus foot resulting from stroke. DESIGN: Cohort study. SETTING: University hospital. PARTICIPANTS: Adult patients (N=56) with spastic equinus foot resulting from stroke scheduled to receive BoNT-A injection into the gastrocnemius muscle. INTERVENTIONS: All patients were injected with BoNT-A (abobotulinumtoxinA) into the gastrocnemius muscle with an ultrasonography-guided, multisite injection technique. The toxin dose was 250U for the gastrocnemius medialis and 250U for the gastrocnemius lateralis (dilution 500U/2mL) in each patient. All patients were evaluated before and 4 weeks after BoNT-A injection. MAIN OUTCOME MEASURES: Spastic gastrocnemius muscle echo intensity visually graded with the Heckmatt scale. Clinical assessment of the spastic gastrocnemius with the Modified Ashworth Scale, Tardieu Scale, and ankle passive range of motion. RESULTS: Postintervention testing at 4 weeks showed overall significant improvements in the clinical assessment of the spastic gastrocnemius muscle. No significant change was observed in the echo muscle intensity of the spastic gastrocnemius after BoNT-A injection. Post hoc comparisons showed that all clinical outcomes were significantly better in those patients with echo muscle intensity of the spastic gastrocnemius graded II on the Heckmatt scale than those with grades III (P<.001) and IV (P<.001) after botulinum toxin injection. CONCLUSIONS: These findings support the hypothesis that patients with higher spastic muscle echo intensity have a reduced response to BoNT-A.