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Prospective study of spinal muscular atrophy before age 6 years. DCN/SMA Group
S T Iannaccone1, R H Browne, F J Samaha
1Department of Neurology, University of Texas Southwestern Medical Center, Dallas 75235-8897.
Insights
Spinal muscular atrophy (SMA) is a common childhood neuromuscular disorder. This study found improved motor function and acquired milestones in children with SMA, challenging the notion of a universally progressive course.
Area of Science:
- Neurology
- Pediatrics
- Genetics
Background:
- Spinal muscular atrophy (SMA) is a prevalent childhood neuromuscular disorder with a historically high mortality rate.
- The condition is typically characterized by progressive muscle weakness and functional loss due to motor neuron degeneration.
- Clinical expectations often focus on high mortality and respiratory failure risks in affected children.
Purpose of the Study:
- To investigate the natural history of spinal muscular atrophy (SMA) in young children.
- To document muscle function, acquired milestones, and disease progression in a cohort of pediatric SMA patients.
- To provide a more nuanced understanding of SMA's course beyond the commonly perceived progressive trajectory.
Main Methods:
- A multicenter collaborative study examined 58 children aged 6 years and younger with SMA.
- Muscle function was assessed using a standardized, reliable protocol at regular intervals.
- Data collection occurred between January 1987 and April 1992.
Main Results:
- Tongue fasciculations were observed in 56% of patients, and facial weakness in 22%.
- Persistent deep tendon reflexes were noted in one patient.
- Improved motor function and the acquisition of new developmental milestones were documented during the study period.
Conclusions:
- The findings suggest that spinal muscular atrophy (SMA) may not always follow a uniformly progressive course in young children.
- Documented improvements in motor function and acquired milestones challenge traditional views of SMA's natural history.
- This research contributes to a better understanding of SMA's variability and potential for functional gains.
Abstract:
Spinal muscular atrophy (SMA) is a common neuromuscular disorder of childhood, associated with a high mortality rate during the first 2 years of life. Most practitioners expect patients with SMA to follow a progressive course with loss of muscle strength and function over 2-10 years. Counselling sessions with parents frequently emphasize the high mortality rate and risk for respiratory failure. The progressive nature of SMA has been attributed to the loss of motor neurons. Fifty-eight children, ages 6 years and younger, were examined between January, 1987, and April, 1992, as part of a large, multicenter collaborative study of SMA. Muscle function was evaluated at regular intervals using a standardized protocol that was demonstrated to be reliable. We determined a prevalence of 56% for tongue fasciculations, a prevalence of 22% for facial weakness, and persistent deep tendon reflexes in one patient. Improved motor function and acquired milestones during the study were documented. This work should contribute toward a better understanding of the natural history of SMA.