Tetrahydrobiopterin in dystonia: identification of abnormal metabolism and therapeutic trials.

The pteridine cofactor of tyrosine and tryptophan hydroxylases, tetrahydrobiopterin (BH4), is concentrated in the striatum and other sites of brain monoamine synthesis and is a regulatory factor in the rate-limiting step of catecholamine synthesis. CSF content was decreased in eight patients with dystonic disorders (mean, 13.0 +/- 0.8 pmol/ml CSF compared with 20.6 +/- 1.4 in age-matched normals). We gave several trials of synthetic BH4 intravenously to 10 dystonic patients with benefit for 2 subjects with diurnally fluctuating dystonia, 1 with hemidystonia and parkinsonism, and 1 with generalized torsion dystonia. The findings of biopterin abnormality and the observed clinical improvements may point to a role for the cofactor in the pathogenesis and, possibly, the treatment of some forms of primary dystonia.