Developmental milestones in type I spinal muscular atrophy

Area of Science:

• Neurology
• Pediatrics
• Genetics

Background:

• Type I Spinal Muscular Atrophy (SMA) is a severe genetic neuromuscular disorder.
• Infants with Type I SMA typically do not achieve motor milestones like sitting unsupported.
• Understanding the natural history of developmental milestones is crucial for evaluating therapeutic interventions.

Purpose of the Study:

• To longitudinally assess developmental milestones in infants with Type I SMA.
• To evaluate the achievement of motor milestones using the Hammersmith Infant Neurological Examination (HINE).
• To establish baseline data for future interventional trials in Type I SMA.

Main Methods:

• Retrospective, multicentric study design.
• Inclusion of 33 infants diagnosed with Type I SMA.
• Longitudinal assessment of developmental milestones via the HINE.

Main Results:

• All patients scored 0/4 on items assessing sitting, rolling, crawling, standing, and walking.
• Partial achievement (1/4) was observed in head control (n=13), kicking (n=15), and hand grasp (n=18).
• Infants with symptom onset after 6 months showed longer preservation of partial scores compared to those with earlier onset.

Conclusions:

• Developmental milestones are rarely achieved, even partially, in the natural history of Type I SMA infants.
• Major milestones like independent sitting or rolling over were not achieved by any infant.
• These findings underscore the limited efficacy of current standards of care in promoting motor development and identify key outcomes for future trials.