A Silent Threat: Acute Respiratory Failure and Os Odontoideum in a Child With Down's Syndrome.

We report the case of a 6-year-old boy with Down syndrome who developed acute neurological deterioration and respiratory distress secondary to non-traumatic os odontoideum. Although the patient had a history of global developmental delay, he exhibited atypical and progressive gross motor regression, prompting further evaluation. Cervical spine MRI revealed severe cranio-cervical junction stenosis with significant upper cervical cord compression and myelomalacia. CT angiography confirmed marked atlantoaxial dislocation due to an anteriorly displaced os odontoideum and a hypoplastic odontoid peg. The patient was placed on the priority surgical list and discharged home. Three weeks post-discharge, he presented to the ED in respiratory arrest and was admitted to the paediatric ICU (PICU). Urgent occipito-cervical (C0-C5) fusion and C1 posterior arch decompression surgery were performed to maximize the possibility of respiratory improvement. Postoperatively, he required prolonged supportive care, including supplemental oxygen and halo vest immobilisation. He was discharged nearly three months later with full neurological recovery and stable respiratory function. This case underscores the critical importance of early recognition of cervical spine instability in patients with Down syndrome and os odontoideum to prevent severe spinal cord compression and life-threatening complications, while also highlighting the potential for favorable outcomes with timely surgical intervention.