This is a single center, 22-month observational study of nusinersen treatment in adult patients with spinal muscular atrophy (SMA). There will be a total of seven visits. Nusinersen is provided as standard of care and not considered research in this study. Information will be collected regarding the general health, and function including muscle strength of, as well as any positive and/or adverse events experienced by the study participants.

This is a single center, 22-month observational study of nusinersen treatment in adult patients with SMA. There will be a total of five visits. All subjects will be evaluated at a screening visit no more than four weeks before starting their standard of care nusinersen treatment to determine their eligibility for participation. Eligible patients will complete their standard induction intrathecal nusinersen treatment on day 1, 15, 29 and 60 followed by maintenance doses every four months. Subjects will be reevaluated after completing the loading doses at 2 months followed by every four-month evaluations for the total duration of the treatment of 22 months.

Currently, there is no data published on patients receiving this treatment over the age of 18. Without published data collected from research, it is difficult for adult patients to get approval from their insurance companies to receive this treatment. This study hopes to collect data, in order to make this treatment option easier for patients with SMA to access and in general learn how well nusinersen is working in adult patients with SMA overtime.

Inclusion Criteria:

1. Age 18 to 60 years
2. Genetic confirmation of 5q SMA documented by the homozygous deletion of both SMN1 genes on standard genetic tests for the disorder
3. SMN2 copy number of 3 or greater
4. Subjects must be able to walk thirty feet without assistance (i.e. no canes, walkers)
5. Interest in participating and the ability to meet the study requirements
6. Women of childbearing-age are required to be on birth control or abstain while participating in the research study

Exclusion Criteria:

1. Subjects with history of spinal disease that will interfere with the lumbar puncture procedure
2. Subjects with history of bacterial meningitis or encephalitis
3. Subjects with history of use of investigational drug treatment for SMA in the last six months, or plan on enrolling in any other treatment trial during the duration of this trial
4. History of treatment with gene therapy, stem cell or antisense oligonucleotide
5. Patients with co-morbid conditions that preclude travel, testing or study medications
6. Patients who are, in the investigator's opinion, mentally or legally incapacitated from providing informed consent for the study, or are otherwise unable to meet study requirements or cooperate reliably with study procedures, especially strength testing
7. Women who are pregnant or who intend to become pregnant while participating in the research study or who are breastfeeding

Adults with spinal muscular atrophy (SMA) as confirmed by clinical and genetic assessments.