CSF monoamine metabolite levels in Alzheimer's and Parkinson's disease.

Levels of the monoamine metabolites homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured in lumbar CSF from 32 patients with a clinical diagnosis of Alzheimer's disease (AD) and from 21 patients with Parkinson's disease (PD). The baseline CSF metabolite values did not differ significantly between the two groups of patients, although HVA levels were lowest in patients with PD and in the more severely demented patients with AD. Levels of all three metabolites increased significantly in both patient groups during probenecid administration, but HVA levels were significantly higher in patients with AD than in patients with PD. Within the AD group, those with the most severe dementia had the greatest rise in MHPG levels. Alterations in monoamine metabolite levels in the CSF detected during probenecid administration aid in the differential diagnosis of neurodegenerative diseases such as AD.