Unresponsiveness to L-DOPA in parkinsonian patients: a study of homovanillic acid concentration in the cerebrospinal fluid.

In this study, concentrations of homovanillic acid (HVA), a principal metabolite of dopamine (DA), in the cerebrospinal fluid (CSF) were measured in 17 patients with Parkinson's disease (PD) who had been effectively treated with L-DOPA and in 8 patients clinically diagnosed as having striatonigral degeneration (SND) and for whom treatment with L-DOPA had proved ineffective. L-DOPA administration, consisting of a daily dosage of 600 mg plus 150 mg aromatic L-amino acid decarboxylase inhibitor was continued in all cases for at least 3 months. In the PD group, the HVA value was 511.6 +/- 196.5 pmol/ml and in the SND group, 144.9 +/- 83.4 pmol/ml. This remarkably low value for the SND group suggests that there may exist severe disorders in the uptake and decarboxylation of exogenous L-DOPA.