Conclusions: Post-treatment D2R appears to have a paradoxical behaviour in B phenotype. Post-treatment GABAVT increase suggests GABA-dopa co-release. Study of CSF synaptic proteins may help understanding pathophysiological mechanisms in these disorders. Background: Homovanillic acid (HVA) is the main catabolic product of dopamine. Decreased cerebrospinal fluid (CSF) HVA values may be related to dopamine deficiency, but also in secondary HVA alterations. We have analysed biogenic amines and other biomarkers in CSF samples collected from neuropediatric patients. We aimed to study the association between CSF HVA and other biogenic amines and different neurological diseases. Methods: Samples from 1,386 subjects were analysed by HPLCelectrochemical detection. Subjects were classified in three groups according to HVA values compared to age-related reference value: low, normal or high levels.