General movement assessment in infants with inherited metabolic disorders

BACKGROUND: Several inherited metabolic disorders (IMD) are associated with neurodevelopmental problems, but clinically, the infants' neurological condition during their first months has not been well described. We aimed to describe infants' early motor repertoire, to identify specific atypical movements, and to determine its relation to outcome. STUDY DESIGN: Multi-centre cross-sectional retrospective study with prospectively collected videos. SUBJECTS: Twenty-five children with IMD at risk of central nervous system dysfunction. MEASURES: From videos taken until 20 weeks' post-term age, we performed Prechtl General Movements Assessment (GMA) and the revised motor optimality score (MOS-R). Descriptive data on neurodevelopmental outcome were retrospectively collected, and classified as normal or abnormal. RESULTS: Videos of writhing general movements were available in 13 of 25 infants. Four infants had normal, nine had poor repertoire general movements. At 9-20 weeks' post-term, 17 of 25 infants had normal and three had abnormal fidgety movements (FMs), and they were absent in three. In another two infants we observed a variant of FMs with high speed, small amplitude: so-called fidgety-like movements. Sixteen infants obtained a MOS-R below 23, without specific atypical movements or postures. A MOS-R below 23 was related to neurodevelopmental outcome, sensitivity 71% (95%-confidence-interval 44-90%) and specificity 80% (28-99.5%). CONCLUSION: The early motor repertoire in infants with IMD at high risk for adverse neurodevelopment is often atypical. Aberrant fidgety movements occurred in 24%, and a MOS-R below 23 in 64% of infants. Associations of GMA and MOS-R with development were moderate, because in this population outcomes may deteriorate over time.