Recently, combined CSF and plasma inflammatory markers have been proposed as an orthogonal biomarker to model prognosis in ALS, including plasma IFN-γ-induced protein 10, IL-5, and L-ferritin, as well as CSF IL-8, MCP-1, and IFN-γ plasma/CSF ratio.34 However, immunologic signals and other tissue-specific signals arising from the neuromuscular pathology seen in ALS may be underrepresented in CSF. This evidence concerns the gene CXCL8 and amyotrophic lateral sclerosis.