Parkinson's disease and dementia: clinical and neurochemical correlations.

In 38 old aged parkinsonian patients, two major subgroups could be established: one with predominant akinesia, rigidity, postural instability and accompanying cognitive impairment with intellectual deterioration correlated with duration of disease but not with age of onset and another with predominant tremor and relatively intact intellectual functions. The mean somatostatin-like immunoreactivity (SLI) level in the cerebrospinal fluid (CSF) was significantly lower in parkinsonian patients (21.4 +/- 8.1 fmol ml-1) compared to senile control patients (29.5 +/- 9.4 fmol ml-1). In contrast to senile dementia of Alzheimer's type SLI was not correlated with dementia scores but with motor disease progression. Homovanillic acid (HVA) significantly decreased only in patients without L-DOPA treatment. Correlations between SLI, HVA and 5-hydroxyindole acetic acid (5-HIAA) indicate a degeneration of multiple neuronal networks which includes somatostatinergic neurons.