Objective: Evaluate the motor development of infants with spinal muscular atrophy (SMA) identified by newborn screening (NBS) and treated with a disease modifying drug before significant symptom onset using the Alberta Infant Motor Scale (AIMS).
Background: Infants with SMA identified by NBS may be treated before onset of significant motor symptoms. With early treatment, new phenotypes of SMA are emerging and previous outcome measures for infants with SMA may not fully capture the impact of the disease or treatment. The AIMS is an outcome measure for infants 0-18.5 months that involves observation in different positions. The AIMS includes a norm referenced percentile chart.
Methods: A physical therapist with experience assessing individuals with SMA administered the AIMS and standard of care measures (CHOP-INTEND, HINE-2, and WHO motor milestones) during routine clinical evaluations on infants with SMA diagnosed via NBS. The subject’s age, SMN2 copy number, treatment type, AIMS raw and percentile score, behavioral state, and time taken to complete were recorded.
Results: Infants with 2 or 3 copies of SMN2 identified by NBS were included. The AIMS took </= 10 minutes and was assessed concurrently with the CHOP-INTEND. Both the CHOP-INTEND and the raw AIMS scores improved over time. Norm referenced AIMS scores were below the 50th percentile at majority of assessments, although, those with 3 copies of SMN2 scored more frequently at 50th percentile.
Conclusion: The AIMS appears to adequately track motor development in infants with SMA identified by NBS and treated with a disease modifying therapy. While infants may score highly when assessed using the CHOP-INTEND, the AIMS scores generally showed slower than normal motor development. The AIMS can be assessed alongside the CHOP-INTEND and may supplement scores for weaker infants. It may also provide a bridge between the CHOP-INTEND and other measures not easily assessed in young infants.