Beyond "low tone". What do the General Movements Assessment and Motor Optimality Score tell us about infants with developmental central hypotonia? A scoping review.

Developmental central hypotonia is a broad clinical term describing low muscle tone secondary to non-degenerative brain impairment. Because there is no widely implemented, standardized way to quantify hypotonia in young children, and low tone is still judged largely through subjective clinical examination, early motor phenotyping remains challenging. We conducted a scoping review to map how Prechtl's General Movements Assessment (GMA) and the Motor Optimality Score-Revised (MOS-R) have been used in infants with developmental central hypotonia aged <5 months corrected age. PubMed, Scopus, ProQuest, Web of Science and the Cochrane Library were searched from inception to November 2025. Included studies assessed preterm or term infants with developmental central hypotonia using GMA and/or MOS-R. Fourteen studies met inclusion criteria, covering 12 diagnoses and etiologies (including Cornelia de Lange syndrome, hypotonic cerebral palsy, Cri du chat syndrome, Down syndrome, Prader-Willi syndrome, Smith-Magenis syndrome, and West syndrome). Across conditions, spontaneous motor behavior showed a consistent pattern: reduced variability and complexity, a below-age-expected repertoire, and atypical posture, with predominantly slow or monotonous movement character. Atypical fidgety patterns were frequent, although fidgety movements could still be present in infants diagnosed with Down syndrome or Prader-Willi syndrome. Evidence was limited and heterogeneous, with most studies small and descriptive. GMA and MOS-R are feasible, reliable tools to assess early motor phenotypes in developmental central hypotonia and may strengthen detection and surveillance pathways. Prospective longitudinal studies should standardize MOS-R subdomain reporting and evaluate clinical utility by examining associations with later functional and hypotonia trajectories, and responsiveness to early intervention.