Interferon (IFN) scores higher than 2 SD of the mean IFN scores of the controls were denoted as positive IFN signatures. Repeated samples were averaged and the mean value was used to determine the interferon signature. ISG values and interferon scores were plotted logarithmically and analyzed with parametric testing (t tests for two groups and ANOVA for more than 2 groups). Spearman rank correlation was used to compare age and CSF and serum interferon activity.