The amplitude of distal compound motor action potential (CMAP) increased after 2 years of nusinersen (Spinraza®) treatment in pediatric patients with spinal muscular atrophy (SMA), according to a retrospective observational study published in the journal Pharmaceutics. This significantly correlated with the evolution of motor function in patients with SMA type 1.

“In treated SMA cases, the distal amplitude of the CMAP and motor functional scales are important prognostic factors, and early diagnosis and treatment are essential for a better outcome,” the study authors concluded.

The use of nusinersen and other disease-modifying treatments have changed the natural evolution of SMA and gave rise to new phenotypes.

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In the present study, a team of researchers evaluated the changes in clinical evolution and electrophysiology after 2 years of treatment with nusinersen in patients with SMA.

The team assessed CMAP on the ulnar nerve as well as the motor abilities of 34 patients with SMA who were being treated with nusinersen. Patients were 1 to 16 years of age.

The results showed that almost half (45%) of patients who had been able to sit unaided were able to sit, and a quarter of those who could sit were able to walk 2 years after nusinersen treatment.

In patients with SMA type 1 or 2, the age at which nusinersen treatment was started negatively correlated with treatment yield. This correlation was strong for patients with SMA type 1 and very strong for patients with SMA type 2. 

SMA is a rare autosomal recessive genetic disease caused by a mutation in the SMN1 gene. The disease is classified into different types based on the age of onset and severity of symptoms.

Nusinersen is an antisense oligonucleotide approved for the treatment of adults and children with SMA.


Axente M, Mirea A, Sporea C, et al. Clinical and electrophysiological changes in pediatric spinal muscular atrophy after 2 years of nusinersen treatment. Pharmaceutics. 2022;14(10):2074. doi:10.3390/pharmaceutics14102074