Cerebrospinal fluid homovanillic acid and parkinsonism in Huntington's disease

In Huntington's disease (HD), normal or decreased levels of homovanillic acid (HVA) in cerebrospinal fluid (CSF) have been reported but have not been analyzed with respect to severity of parkinsonism, which in certain cases may be a predominant feature of the illness. We obtained CSF by lumbar puncture from four groups of nonmedicated subjects: (1) those with HD in the earliest stages of illness (n = 51), (2) those with parkinsonism, including idiopathic (n = 10) and atypical forms (n = 4), (3) those with nonparkinsonian movement disorders (n = 19), and (4) normal volunteers (n = 4). HVA was determined by high-pressure liquid chromatography with electrochemical detection, and motor signs were assessed in standardized fashion. The parkinsonian group had reduced levels of CSF HVA, but the other groups showed no significant differences. For those with HD, no correlation was found between HVA level and severity of parkinsonism, and there were no differences in HVA level between those subjects with (n = 14) or without (n = 37) prominent parkinsonism or between subjects whose age at illness onset was 30 years or less (n = 16) and those whose age at onset was over 30 (n = 35). Our findings indicate that in early, untreated HD, CSF HVA is in the normal range and does not correlate with the severity of parkinsonism. This observation supports neuropathological findings suggesting that parkinsonian features in HD are largely related to the loss of postsynaptic striatal dopamine receptors rather than to presynaptic nigral degeneration.