OBJECTIVE: To report our experience with adult patients with spinal muscular atrophy (SMA), some of whom were treated with nusinersen. METHODS: We reviewed charts of adult patients with SMA seen in our neuromuscular clinic between 2017 and 2019 and noted their demographics, clinical characteristics, treatment, and side effects. RESULTS: Twenty-two patients were included. Nine had type 2 and 13 type 3 SMA. Median age was 36 years (range 20–71). Most could not walk unassisted. Ten patients had significant respiratory impairment necessitating ventilation and 2 had tracheostomy. Seventeen had severe scoliosis. Ten patients were treated with nusinersen for 6–24 months (median 12 months), 3 of whom required bone laminectomy for intrathecal access. One developed bowel and bladder incontinence following the procedure. In the treated group, on average, % Medical Research Council change was 2.5% at 12 months and 3.9% at 24 months. Most untreated patients remained stable; 3 had slightly declined. Five treated patients reported subjective improvement. Treatment side effects included post lumbar puncture headache in 5 patients, 2 of whom needed blood patch, and 1 bacterial meningitis requiring inpatient treatment. Three patients stopped treatment after 12–24 months due to lack of improvement, recurrent pneumonia, or proteinuria. CONCLUSION: Side effects of nusinersen can be serious. Whereas half of treated patients reported modest improvement in function, there were no significant objective changes, which may point largely to a placebo effect. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for some adult patients with SMA, nusinersen improves subjective function and causes serious adverse effects.