High dose botulinum toxin A for the treatment of lower extremity hypertonicity in children with cerebral palsy

The aim of this study was to determine the safety profile of high dose (15-25 units/kg) of botulinum toxin A (BTX-A) in children with cerebral palsy (CP) and increased lower extremity muscle tone. We performed a retrospective review of 929 patient encounters at the Movement Disorders Center at Washington University. A total of 261 patients (105 females; 156 males) were treated during these visits, ages 6 months to 21 years (mean 8y 4mo [SD 4y 8mo]). Ambulatory ability at the time of BTX-A injection was independent ambulation (36.4%, n=95), ambulation with a walker (27.6%, n=72), and non-ambulatory (31.8%, n=83). A few patients (4.2%, n=11) were able to ambulate with a cane or crutch at the time of injection. Participants were characterized according to BTX-A dose, CP etiology, motor involvement pattern, muscles injected, ambulatory ability, and use of oral tone medications. Follow-up records were searched for reported adverse events (AEs), with a mean time to AE assessment of 6.5 weeks (SD 3.38). The AE occurrence was determined for doses of 0 to 4.9 units/kg, 5 to 9.9 units/kg, 10 to 14.9 units/kg, 15 to 19.9 units/kg, and 20 to 25 units/kg. The overall AE occurrence was 4.2%. Standard doses of BTX-A had side-effect occurrences of 3.9% for 5 to 10 units/kg and 7.6% for 10 to 15 units/kg. Among higher doses (15-20 units/kg and 20-25 units/kg) the AE occurrence was 3.5% and 8.6% respectively. No patient developed botulism. AEs were randomly distributed across dosing groups, CP etiologies, clinical phenotypes, ambulatory status, and treatment duration. All doses were associated with a significant increase in passive range of motion using the Tardieu scale. We conclude that higher dose BTX-A is safe in children with a spectrum of CP phenotypes and are well tolerated over time.