Biogenic amines and pterins in cerebrospinal fluid: some pitfalls with interpretation

Abstract

The quantification of neurotransmitters or their metabolites in cerebrospinal fluid (CSF) can provide valuable clues for the detection of (often treatable) genetic disorders or their biosynthesis or salvage pathways. These analyses are technically demanding since the concentrations to be assessed are in the nanomolar range. To date, only a few laboratories worldwide offer these analyses. Since some metabolites are unstable at room temperature and sensitive to light or oxygen, special preparation of sampling tubes is helpful and the samples should be immediately frozen at the bedside. Furthermore, due to a craniocaudal gradient, a sampling protocol with numbered tubes should be adhered to. In addition to the technical difficulties, interpretation of the biochemical findings in lumbar CSF is much more complex than the interpretation of results in urine or blood. This article will focus on some pitfalls associated with the interpretation of analyses of dopamine, serotonin and pterin metabolites, and examines clinical data from pediatric patients to further illustrate those pitfalls.