Radiological Screening of Atlantoaxial Instability in Children with Trisomy 21: A Systematic Review and Evidence-Based Recommendations.

Background/Objectives: Atlantoaxial instability (AAI) affects approximately 20% of individuals with Trisomy 21. Radiological screening has been debated for decades due to its unclear clinical utility and lack of standardized diagnostic criteria. This systematic review evaluates the indications, efficacy, and clinical implications of radiological screening for AAI in children with Trisomy 21. Methods: Following the PRISMA guidelines, we conducted a systematic search in PubMed, Embase, and Google Scholar for studies published between 1990 and May 2024. Studies were included if they assessed AAI screening in pediatric Trisomy 21 populations, defined AAI radiologically, and reported at least two cases. We extracted the demographic data, study design, radiological criteria, screening recommendations, and biases from these studies. Results: Of the 537 identified studies, 8 met the inclusion criteria, encompassing 2536 children (mean age: 7 years). Five studies supported routine screening, while three opposed it. Studies varied significantly in their AAI definitions, using atlanto-dental interval (ADI) thresholds of 4 mm to 6 mm, the space available for cord (SAC), and the basion-axial interval (BAI). No study demonstrated a definitive correlation between radiological findings and neurological symptoms. Conclusions: Routine radiological screening for AAI in asymptomatic children with Trisomy 21 is not supported by consistent evidence. A selective screening approach, focusing on symptomatic patients or those engaging in high-risk activities, may be more appropriate. The standardization of radiological criteria and prospective studies are needed to refine screening recommendations.