Abstract
BACKGROUND: Atlantoaxial instability (AAI) and basilar invagination are potentially life-threatening complications in children with Down syndrome. When symptomatic, they may lead to progressive myelopathy, gait disturbance, and eventual quadriparesis. Surgical fixation is indicated in cases of neurological deterioration or radiographic evidence of significant instability. CASE DESCRIPTION: A 6-year-old female presented with Down syndrome and a history of complex congenital heart disease who presented with 10 months of progressive quadriparesis. Imaging revealed atlantoaxial subluxation with basilar invagination resulting in cervicomedullary compression. Surgery included an occiput-to-C4 posterior fusion, skipping C3 due to anatomical hypoplasia, performed under neuromonitoring and utilizing intraoperative imaging. Postoperative studies confirmed optimal location of instrumentation, and the patient exhibits continued neurological improvement. CONCLUSION: Early recognition and timely surgical intervention are critical to manage children with Down syndrome and cervical instability.