Long-Term Effects of Different Number of Botulinum Toxin Injections Into the Gastrocnemius Muscle on Function and Muscle Morphology in Children With Cerebral Palsy.

[BACKGROUND] Botulinum toxin (BoNT) injections are used to reduce spasticity, and sometimes repeated injections are required. The aim of this study is to investigate the effects of the number of BoNT injections into the gastrocnemius muscle on function, muscle morphology, muscle stiffness, and muscle vascularization in children with cerebral palsy (CP).

[METHODS] The study included 22 children with spastic-type CP aged five to 13 years who had previously received one, two, or three BoNT injections into the gastrocnemius muscle. A total of 29 gastrocnemius muscles were evaluated. Gastrocnemius muscle morphology was examined by ultrasonography, muscle stiffness by shear wave ultrasound elastography, and muscle vascularization by superb microvascular imaging. The functional status of the children was evaluated by the Gross Motor Function Measurement, the Timed-Up-and-Go Test, the Squat Test, the Vertical Jumping Test, and the Sit-and-Reach Test.

[RESULTS] In the motor functions and muscle morphology values were similar in all three groups (P > 0.05). Muscle stiffness values were higher (P = 0.035) and vascularization values were lower (P = 0.03) in the group that received three injections compared with the groups that received one injection. There was a moderate positive correlation of the number of BoNTs with muscle stiffness (P < 0.05, r = 0.454) and a moderate negative correlation with muscle vascularization (P < 0.05, r = -0.497).

[CONCLUSIONS] Repeated BoNT applications have no effect on motor functions and muscle morphology in children with CP, whereas BoNT injections administered three times increase muscle stiffness and decrease vascularization.