BACKGROUND: Although trihexyphenidyl has been used to treat both primary and secondary dystonia in children, previous studies have not investigated efficacy in secondary dystonia. We describe the results of a prospective, open-label, multi-center trial of high-dose trihexyphenidyl in children with secondary dystonia of the arms due to cerebral palsy.~METHODS: Twenty-six children age 4-15 years with cerebral palsy and dystonia that impairs function of the dominant upper extremity were enrolled. All children were given trihexyphenidyl at increasing doses over 9 weeks up to 0.75mg/kg/day. Trihexyphenidyl was subsequently tapered over 5 weeks. Visits occurred at baseline, 9 weeks, and 15 weeks. The primary outcome measure was the Melbourne assessment of upper extremity function, tested in the dominant arm.~RESULTS: Three children withdrew due to non-serious adverse events (chorea, drug rash, hyperactivity). 3 children reduced dosage due to non-serious adverse events. The 23 children who completed the study showed a significant improvement in arm function at 15 weeks (p=0.045) but not at 9 weeks. Post-hoc analysis showed that a subgroup (N=10) with hyperkinetic dystonia worsened at 9 weeks (p=0.04) but subsequently returned to baseline following taper of the medicine.~CONCLUSIONS: Trihexyphenidyl appears to be safe and effective for treatment of arm dystonia in children with cerebral palsy. Children with hyperkinetic dystonia may worsen. A larger randomized prospective trial is needed to confirm these results.
This study is an open-label trial of trihexyphenidyl in children with upper extremity dystonia due to cerebral palsy. It is hypothesized that trihexyphenidyl in doses up to 0.75mg/kg/day would be well-tolerated and show significant changes on the Melbourne scale of upper extremity function.