SMN2 and proximal spinal muscular atrophy: Intrathecal administration of Nusinersen (IONIS-SMNRx), an 18-mer AON in 2’-O-2-methoxyethyl (MOE) phosphorothioate chemistry that targets the intronic splicing silencer N1 element (ISS-N1) in intron 7 of SMN2 gene, in severe SMA infant is now in phase III clinical trials with encouraging data in safety and clinical outcome measurement from the previous phase I clinical trial [17].