Trihexyphenidyl for dystonia in cerebral palsy

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Review question

Is trihexyphenidyl a helpful treatment for people with cerebral palsy who have a movement problem called dystonia?


Cerebral palsy is a common condition that covers a range of movement problems. One common movement problem is dystonia, which makes it difficult for people with cerebral palsy to control their movements. They have unwanted – and often painful and distressing – muscle contractions that they cannot control. The contractions reduce people’s ability to move, perform self-care activities, speak and participate in everyday activities.

Doctors often use medications to treat this difficult condition, including trihexyphenidyl. However, all the benefits and harms of prescribing trihexyphenidyl for individuals with cerebral palsy and dystonia are still unknown.

Study characteristics

In May 2017 we searched for all clinical trials that investigated the effectiveness of trihexyphenidyl for people with dystonic cerebral palsy. We included one Australian trial that involved 16 children (10 boys, 6 girls) with cerebral palsy and dystonia. They had an average age of nine years.

The children were divided into two different groups. Both groups took 12 weeks of trihexyphenidyl and 12 weeks of a placebo (something that looks the same as trihexyphenidyl but with no active ingredient), with a 4-week break in between during which they received neither. The only difference between the groups was that one group started with trihexyphenidyl and then had placebo, and the other group started with placebo and then had trihexyphenidyl.

Key results

We found no evidence that trihexyphenidyl was effective for reducing dystonia or improving upper arm function in children with cerebral palsy and dystonia. Trihexyphenidyl may be associated with an increased risk of side effects (agitation, constipation, dry mouth and poor sleep). There was some evidence that trihexyphenidyl may improve individual goals set by the child and family around improved participation in activities of daily living. The study did not measure pain or quality of life.

Quality of the evidence

We rated the quality of the evidence as low because the one study included a small number of children and there are no other studies to support the findings. Therefore, we are uncertain about the effectiveness of trihexyphenidyl in reducing dystonia or improving arm function and participation in everyday activities of people with cerebral palsy and dystonia.