Spinal muscular atrophy (SMA) is the most common genetic cause of infantile death caused by mutations in the SMN1 gene. Nusinersen (Spinraza), an antisense-based drug with the 2′-methoxyethoxy (2′MOE) chemistry approved by the FDA in 2016, brought antisense drugs into the spotlight. Antisense-mediated exon inclusion targeting SMN2 leads to SMN protein expression. Although effective, 2′MOE has weaknesses such as the inability to cross the blood-brain barrier and the high cost of treatment. To investigate new chemistries of antisense oligonucleotides (ASOs), SMA mouse models can serve as an important source. Here we will describe methods to test the efficacy of ASOs, such as phosphorodiamidate morpholino oligomers (PMOs), in a severe SMA mouse model. We demonstrate that PMOs given by intra-cerebroventricular (ICV) route efficiently Increase SMN levels in a severe SMA mouse model in vivo.