The initially elevated CSF pNf‐H levels and their rapid decline during treatment with nusinersen in our SMA type 1 patients are in line with the results in plasma for pNf‐H in the SMA type 1 patients of the ENDEAR study and the report of initially high NfL and pNf‐H levels and their decrease with nusinersen treatment in one SMA type 1 infant.21 Here, NEFL is linked to spinal muscular atrophy, type 1.