Cytoskeletal proteins, including neurofilament proteins and tau, have been shown to be elevated in the CSF of patients with various neurodegenerative diseases. Interestingly, levels of phosphorylated neurofilament heavy subunit (pNfH) have been found to be significantly increased in the CSF of ALS patients as compared with healthy subjects, Alzheimer's disease patients or disease mimics Numerous inflammatory proteins, including cytokines and complement proteins, have been shown to be altered in ALS; complement proteins, including complement c3 (C3), have been found to be increased in the CSF of ALS patients.