We administered tetrahydrobiopterin (BH4) to 4 patients with progressive dystonia with diurnal variation (PDDV). One patient improved clinically. Deficient CSF concentrations of HVA and 5-HIAA were unchanged despite marked elevation of CSF biopterin concentration. Variable effectiveness of BH4 in PDDV may reflect reduced number or function of biopterin-metabolizing neurons or variable entry of BH4 into these neurons.
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Fink et al. (1989) studied this question.