Development of the "SMA NNE," a short neonatal neurological examination for newborns with spinal muscular atrophy

The advent of newborn screening for spinal muscular atrophy (SMA) has highlighted the need for easy, quick, clinical tools to be used in infants with SMA identified in the neonatal period. We propose a new short module developed using items from the Hammersmith Neonatal Neurological Examination (HNNE) and from a module developed for floppy infants, both previously used in newborns with SMA. The new module was developed by identifying and selecting the items that were more often found to have abnormal findings in SMA newborns. The proforma was designed by selecting 13 items and converting them into a format that would facilitate the interpretation of the results. The cohort included 25 infants. Based on HNNE and add-on module results, 13 were classified as asymptomatic, 5 as pauci-symptomatic, and 7 as symptomatic. All symptomatic infants showed abnormalities in posture, tone, tremors, and reflexes, along with reduced antigravity movements and abnormal breathing. Among pauci-symptomatic infants, all had abnormal reflexes, three also had tremors, and one showed mild hypotonia. There was excellent inter-observer reliability assessed using intra-class correlation coefficients with 95% confidence intervals (0.947) and full concordance with the original full-length forms.

Our findings support the use of the short form in clinical practice, especially when time or resources are limited. It can be used in multiple occasions, allowing to detect the onset of possible signs in asymptomatic infants and to follow their progression.

• Newborns with SMA identified by neonatal screening may show clinical signs at diagnosis. • These signs may be subtle and easily missed on standard neonatal examination.

• The new form includes a short examination that can reliably detect initial signs of SMA. • The new examination can be used to detect the onset and the progression of clinical signs.