To analyze the effect of intrathecal nusinersen in spinal muscular atrophy type 2 and type 3.

Spinal muscular atrophy (SMA) is an autosomal recessive, neurodegenerative disease caused by the mutations in the survival motor neuron 1 (SMN1) gene. Nusinersen is the first approved disease-modifying therapy in spinal muscular atrophy (SMA).

Herein, we evaluate the clinical features and treatment responses of 35 patients out of 52, treated with nusinersen with SMA type 2 or type 3 who completed the first four loading doses. Patients were treated with intrathecal administration at day 1 (baseline), day 29, day 85, and day 274, depending on a scheme defined by Turkey Pharmaceuticals and Medical Devices Agency. The remaining 17 patients are still on the first three loading doses.

The mean age of onset was 5.30 ± 4.47 (between 10 months and 16 years), and 18 patients were female. Thirty-one patients were type 3, and four patients were type 2. The mean age  at the initial nusinersen dose was 26.32 ± 9.38 (between 13 and 47 years). Eighteen patients were ambulatory. Lumbar puncture was performed with X-Ray guidance in 5 patients due to severe scoliosis. The mean HMFSE score in the baseline visit was 31.28 ± 20.64 (between 0 and 60). In a mean duration of 573.22 ± 120.44 (between 299 and 770) days, HMFSE score was increased by 4.42 ± 3.32 (between 0 and 9) points. Increase in the HMFSE score was higher in type 3 patients compared to type 2 (2.25 vs. 4.70, p=0.04).

Our study provides one of the biggest type 2 and type three cohorts from Turkey. Functional improvement in our patients showed that nusinersen is effective in both types.