Scientists Measure Major Developmental Milestones in Spinal Muscular Atrophy

Developmental milestones such as sitting unaided, rolling, crawling, standing or walking are rarely, or even partially, achieved by infants with type 1 spinal muscular atrophy (SMA), confirms a study published in the scientific journal Neuromuscular disorders.

Achieving these major developmental milestones would therefore constitute “robust outcomes in future interventional trials,” according to the authors of the study “Developmental milestones in type I spinal muscular atrophy.”

The team of researchers led by Eugenio Mercuri, MD, of Catholic University and Centro Clinico Nemo in Rome, retrospectively analyzed data from 33 infants, all of whom had a genetically and clinically confirmed diagnosis of type 1 SMA. The researchers evaluated the infants’ ability to sit unaided, roll, crawl, stand or walk. All infants achieved a score of zero out of four in this assessment.

A score of more than 0 was observed only in head control achieved by 13 infants, kicking, achieved by 15 infants, and hand grasp, achieved by 18 infants. In these items, the maximal score was one out of four, indicating only a partial achievement. Infants whose symptoms appeared after the age of six months preserved the score of one for longer compared to infants whose symptoms appeared before the age of six months. No infants in the study achieved a major milestone such as rolling over, or sitting unaided.

“Our results suggest that even when current standards of care are applied, developmental milestones are rarely even partially achieved,” the authors wrote.

Based on these confirmatory results, the authors concluded that in the future if infants with type 1 SMA achieve any of these milestones as a result of drug treatments, these could be attributed, with a strong probability, to the effect of the drug instead of as the result of high standards of care.

The authors also suggest that future studies investigating the association between milestone achievements and standards of care could help further clarify the variability of the condition.

SMA is a heritable disease caused by a mutation in the SMN1 gene, which results in a reduced amount of the SMN protein being produced. The severity of the condition depends on the amount of SMN protein the body can produce.