Apart from a recent letter reporting a decrease of elevated tau and neurofilament light chain levels in an infant with SMA (9) and the description of the macroscopic condition of the CSF after lumbar puncture in adolescent and adult SMA patients (6), data regarding CSF parameters during nusinersen therapy are sparse and investigations of CSF cytology during nusinersen therapy are completely missing. This evidence concerns the gene MAPT and proximal spinal muscular atrophy.