Botulinum A toxin produces selective and reversible
chemodenervation that can be employed to balance muscle forces across joints in children with
cerebral palsy (CP). Currently, there are two commercially available
botulinum A toxin formulations (
BOTOX) and
Dysport). The amount of
botulinum A toxin required depends upon the number of muscles that are targeted, and the size of the patient. In order to achieve adequate
chemodenervation with
botulinum A toxin, the following conditions must be met: (i) a sufficient number of units of toxin must be injected in order to neutralize neuromuscular junction (NMJ) activity; (ii) an appropriate
drug volume is required in order to optimize the delivery of the toxin to the NMJs; and (iii) localization of the injecting needle through the fascia of the target muscle is necessary. Localization of the injection may be facilitated by active electromyography, ultrasonography, palpation of the muscle belly, and/or use of anatomic landmarks.
Botulinum A toxin injections are indicated for use in pediatric patients with CP to: (i) improve motor function by balancing muscle forces across joints; (ii) improve health-related quality of life by decreasing spasticity and/or decreasing caregiver burden; (iii) decrease
pain from spasticity; (iv) enhance self-esteem by diminishing inappropriate motor responses; and (v) provide a presurgical diagnostic tool. Following
intramuscular injections of
botulinum A toxin, short-term benefits of reduced spasticity are observed in approximately 70-82% of children. The intermediate term (1-2 years) efficacy rate is approximately 50%. The most common
deformity treated with toxin
injections in pediatric patients with CP is equinus
foot deformity. However, efficacy of toxin
injections for the management of crouched gait, pelvic flexion
contracture, cervical spasticity, seating difficulties, and upper extremity
deformity also has been documented. In addition, toxin
injections have been shown to manage painful
muscle spasticity associated with surgery or application of casts and painful cervical spasticity with or without
dystonia. Toxin
injections can also be used as a diagnostic tool to determine the appropriateness of other interventions by observing the muscle response to the injection in order to gain additional information for the development of a treatment plan.
Botulinum A toxin, when used in appropriate doses, is well tolerated.