Longitudinal developmental profile of newborns and toddlers treated for spinal muscular atrophy

Spinal muscular atrophy (SMA) results from a loss-of-function mutation in the SMN1 gene. SMA patients suffer progressive motor disability, although no intellectual impairments have been described. Three drugs have been recently approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). These drugs result in longer life expectancy for SMA type 1 (SMA1) patients.

The objective of the study was to assess longitudinally the psychomotor development of patients with SMA1 treated after the symptom onset and of patients treated presymptomatically.

Longitudinal, monocentric, noninterventional, prospective study.

Our study included 11 SMA1 patients and seven presymptomatic SMA patients. The SMA1 patients were treated with an approved drug beginning after onset of symptoms; treatment for the presymptomatic patients was begun before symptom onset. They were longitudinally evaluated between September 2018 and January 2022 using the Bayley Scales of Infant and Toddler Development™ - Third Edition.

At each time point, all patients treated presymptomatically scored above those treated postsymptomatically on the motor scale. The cognitive scores of six of the seven patients treated presymptomatically were average; one patient was in the low average range. In the 11 postsymptomatically treated patients, four scored either in the low average or the abnormal range on the cognitive scale, but a positive trend was observed during the follow-up.

A significant proportion of patients treated postsymptomatically scored below average on cognitive and communicative scales, with most significant concerns raised about the age of 1 year. Our study indicates that intellectual development should be considered as an important outcome in treated SMA1 patients. Cognitive and communicative evaluations should be performed as part of standard of care, and guidance should be provided to parents for optimal stimulation.