Botulinum toxin (Dysport) treatment of the spastic gastrocnemius muscle in children with cerebral palsy: a randomized trial comparing two injection volumes

Objective: To compare the effect of equivalent doses in two different volumes of botulinum toxin type A (Dysport) on gastrocnemius spasticity. Design: Single-blind, randomized, controlled trial. Setting: Hospital rehabilitation department Subjects: Twenty-two children with spastic diplegic or quadriplegic cerebral palsy. Intervention: High (500 U/5 mL) and low (500 U/1 mL)-volume preparations of Dysport were injected into the gastrocnemius muscles, each child randomly receiving one preparation in the right and the other in the left leg. Main measures: Dynamic ankle joint range of motion (ROM), passive ROM of the ankle joint, modified Ashworth Scale scores, and the areas of the compound muscle action potential assessed before treatment and at four and eight weeks post treatment. Results: Both legs improved significantly, The mean (SD) improvements between baseline and the end of follow-up were 19.7 (10.83) degrees for dynamic ROM, 8.4 (9-19) degrees for passive ROM, -1.3 (0.6) for modified Ashworth Scale scores, and -9.4 (11.41) mV-ms for compound muscle action potential in the high-volume group; and 13.5 (10.45) degrees for dynamic ROM, 7.4 (7.88) for passive ROM, -0.9 (0.5) for modified Ashworth Scale scores, and -5.9 (7.50) mV-ms for areas of compound muscle action potential in the low-volume group. The high-volume preparation yielded significantly greater improvement in dynamic ROM (P < 0.001), muscle tone (P < 0.001), and lower compound muscle action potential area (P = 0.006). Conclusions: A high-volume preparation of Dysport is more effective than a low volume in reducing spasticity in the gastrocnemius muscle.