Background: Two cerebrospinal fluid (CSF) biomarkers specific for neurodegeneration have recently emerged the neurofilament light (NfL, 68 kDa) and heavy (NfH, 190-210 kDa) chains. This study investigated whether the CSF NfH and NfL levels or their stoichionietric relationship changed over time in a neuroprotective treatment trial.Methods: Serial CSF samples (n =95) from 42 patients with multiple system atrophy (MSA), half randomized to treatment with recombinant human growth hormone (r-hGH) and the other half to placebo, were collected at baseline, 6 and 12 months. The concentration of CSF NfL and NfH was determined using standard ELISAs. Results: There was no consistent change in the levels of either protein over the 12 month period, or between treatment with active r-hGH versus placebo. The molar stoichiometry of CSF NfL:NfH was 4:1 (R=0.37, p=0.0002) and increased following treatment with r-hGH (p=0.03).Conclusion: These results indicate that CSF levels of both NfL and NfH on their own are not useful markets of disease progression in MSA, at least over a 12-month period. Future work is needed to elucidate whether the CSF stoichiometry and dynamics of Nf subunits in individual patients are a feature of the underlying pathology and of diagnostic or prognostic value. (C) 2008 Elsevier B.V. All rights reserved.