NEFL and amyotrophic lateral sclerosis: Taken together, we believe our observations reflect the release of NfL into the CSF from the degenerating CSTs in particular due to the abundance of neurofilaments in large axons and the highly soluble nature of NfL.18 There is undoubtedly a contribution from the concurrent degeneration of the CST within the spinal cord in ALS, which was not captured by the DTI in this study.