NEFL and proximal spinal muscular atrophy: From the biochemical point of view, evidence showed significant decreasing levels of markers of neurodegeneration like neurofilaments (NFL) in CSF of infantile-onset SMA during nusinersen treatment, suggesting a recovery in motor neuron damage, whereas in CSF and serum of adolescent and adult SMA it fails to act as a reliable marker of treatment response (Olsson et al. 2019; Winter et al. 2019).