Generalised dystonia

When a patient presents with generalised dystonia, the first step is to find out whether the dystonia responds to a trial of levodopa. Levodopa-responsive dystonia is rare. It often presents with predominant leg dystonia with diurnal variation, and is more likely in children, adolescents and young adults. Consider levodopa-responsive dystonia in any child with a spastic diplegia. Diagnostic gene testing is available.

Refer all children with generalised dystonia for expert advice. If the child does have levodopa-responsive dystonia, low doses of levodopa may be adequate.

In adults with generalised dystonia, to test for levodopa responsiveness, use:

If the adult responds to levodopa, therapy is lifelong.

In a small proportion of patients (usually children), generalised dystonia is caused by a specific condition that can be treated. Investigate for Wilson disease, mitochondrial encephalomyopathies, lysosomal storage disorders (eg Niemann-Pick disease type C) and neuroacanthocytosis.

Pure dystonia with focal onset in childhood that becomes generalised over years is usually due to a deletion in the DYT1 gene.

If no cause for generalised dystonia is found, refer the patient for expert advice. First-line treatment for symptoms is an anticholinergic drug. Trihexyphenidyl (benzhexol) is effective—occasionally a child may need a dose as high as 60 mg daily, if tolerated. Pallidal deep brain stimulation is effective, especially in primary generalised dystonia, and clinical improvement is most evident after at least 6 months.